2021 |
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Wilbrandt, Ulrich; Alia, Najib; John, Volker Optimal control of buoyancy-driven liquid steel stirring modeled with single-phase Navier--Stokes equations Journal Article Journal of Mathematics in Industry, 11 (1), pp. 10, 2021, ISBN: 2190-5983. @article{najiblast, title = {Optimal control of buoyancy-driven liquid steel stirring modeled with single-phase Navier--Stokes equations}, author = {Ulrich Wilbrandt and Najib Alia and Volker John}, url = {https://doi.org/10.1186/s13362-021-00106-7}, doi = {10.1186/s13362-021-00106-7}, isbn = {2190-5983}, year = {2021}, date = {2021-01-01}, journal = {Journal of Mathematics in Industry}, volume = {11}, number = {1}, pages = {10}, abstract = {Gas stirring is an important process used in secondary metallurgy. It allows to homogenize the temperature and the chemical composition of the liquid steel and to remove inclusions which can be detrimental for the end-product quality. In this process, argon gas is injected from two nozzles at the bottom of the vessel and rises by buoyancy through the liquid steel thereby causing stirring, i.e., a mixing of the bath. The gas flow rates and the positions of the nozzles are two important control parameters in practice. A continuous optimization approach is pursued to find optimal values for these control variables. The effect of the gas appears as a volume force in the single-phase incompressible Navier--Stokes equations. Turbulence is modeled with the Smagorinsky Large Eddy Simulation (LES) model. An objective functional based on the vorticity is used to describe the mixing in the liquid bath. Optimized configurations are compared with a default one whose design is based on a setup from industrial practice.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Gas stirring is an important process used in secondary metallurgy. It allows to homogenize the temperature and the chemical composition of the liquid steel and to remove inclusions which can be detrimental for the end-product quality. In this process, argon gas is injected from two nozzles at the bottom of the vessel and rises by buoyancy through the liquid steel thereby causing stirring, i.e., a mixing of the bath. The gas flow rates and the positions of the nozzles are two important control parameters in practice. A continuous optimization approach is pursued to find optimal values for these control variables. The effect of the gas appears as a volume force in the single-phase incompressible Navier--Stokes equations. Turbulence is modeled with the Smagorinsky Large Eddy Simulation (LES) model. An objective functional based on the vorticity is used to describe the mixing in the liquid bath. Optimized configurations are compared with a default one whose design is based on a setup from industrial practice. | |
2020 |
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Arenas, Manuel J; Hömberg, Dietmar; Lasarzik, Robert; Mikkonen, Pertti; Petzold, Thomas Modelling and simulation of flame cutting for steel plates with solid phases and melting Journal Article Journal of Mathematics in Industry, 10 (18), 2020. @article{Arenas2020, title = {Modelling and simulation of flame cutting for steel plates with solid phases and melting}, author = {Manuel J Arenas and Dietmar H\"{o}mberg and Robert Lasarzik and Pertti Mikkonen and Thomas Petzold}, doi = {10.1186/s13362-020-00086-0}, year = {2020}, date = {2020-06-24}, journal = {Journal of Mathematics in Industry}, volume = {10}, number = {18}, publisher = {Springer Science and Business Media LLC}, keywords = {}, pubstate = {published}, tppubtype = {article} } | |
2019 |
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Ramasetti, Eshwar Kumar ; Visuri, Ville-Valtteri ; Sulasalmi, Petri ; Kärnä, Aki ; Fabritius, Timo Numerical study of multiphase flows in a ladle for different closure models Conference Proceedings of the 11th Pacific Symposium on Flow Visualization and Image Processing , http://jultika.oulu.fi/Record/nbnfi-fe2019082225151, 2019. @conference{EshwarConference, title = {Numerical study of multiphase flows in a ladle for different closure models}, author = {Ramasetti, Eshwar Kumar and Visuri, Ville-Valtteri and Sulasalmi, Petri and K\"{a}rn\"{a}, Aki and Fabritius, Timo}, url = {http://jultika.oulu.fi/Record/nbnfi-fe2019082225151}, doi = {PSFVIP11-019}, year = {2019}, date = {2019-08-22}, booktitle = {Proceedings of the 11th Pacific Symposium on Flow Visualization and Image Processing }, address = {http://jultika.oulu.fi/Record/nbnfi-fe2019082225151}, abstract = {Computational Fluid Dynamics (CFD) modelling is increasingly being used for studying various metallurgical processes. In secondary steelmaking, gas stirring is used in ladles to enhance the mixing of the steel. This work aims at numerical study to investigate the effect of different closure models on of the flow analysis in a two-phase gas-stirred ladle. The study represents a cylindrical geometry, in which liquid Wood’s metal represents the liquid metal phase and nitrogen gas is injected through nozzle located centrically or eccentrically at the bottom of the vessel. Three-dimensional CFD simulations were carried out using the commercial software package ANSYS FLUENT using Euler-Euler multi-phase model. To study the influence of turbulence models on the accuracy of the CFD analysis, three different models Standard k-ε, k-ω and Reynolds Stress Model (RSM) were employed. Furthermore, four different gas flow rates (100, 200, 500 and 800 cm3/s) were used for studying the effect of gas flow rates on the flow velocities. The simulation results were compared with the available experimental data of the liquid velocity profiles, volume fraction of gas and turbulent kinetic energy at different heights in the ladle. The RSM model showed a good accuracy of results when compared to experimental results, but it requires more computational time when compared to other turbulence models. The simulation results using the liquid Wood’s metal/nitrogen system were compared to water/air and liquid steel/argon systems to check the effect of material properties on the flow velocities in the ladle. The results provide useful guidelines for numerical modelling of fluid flows in steelmaking ladles and suggest that the RSM turbulence model is better suited for studying gas injection in metallurgical ladles than k-ε or k-ω models.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } Computational Fluid Dynamics (CFD) modelling is increasingly being used for studying various metallurgical processes. In secondary steelmaking, gas stirring is used in ladles to enhance the mixing of the steel. This work aims at numerical study to investigate the effect of different closure models on of the flow analysis in a two-phase gas-stirred ladle. The study represents a cylindrical geometry, in which liquid Wood’s metal represents the liquid metal phase and nitrogen gas is injected through nozzle located centrically or eccentrically at the bottom of the vessel. Three-dimensional CFD simulations were carried out using the commercial software package ANSYS FLUENT using Euler-Euler multi-phase model. To study the influence of turbulence models on the accuracy of the CFD analysis, three different models Standard k-ε, k-ω and Reynolds Stress Model (RSM) were employed. Furthermore, four different gas flow rates (100, 200, 500 and 800 cm3/s) were used for studying the effect of gas flow rates on the flow velocities. The simulation results were compared with the available experimental data of the liquid velocity profiles, volume fraction of gas and turbulent kinetic energy at different heights in the ladle. The RSM model showed a good accuracy of results when compared to experimental results, but it requires more computational time when compared to other turbulence models. The simulation results using the liquid Wood’s metal/nitrogen system were compared to water/air and liquid steel/argon systems to check the effect of material properties on the flow velocities in the ladle. The results provide useful guidelines for numerical modelling of fluid flows in steelmaking ladles and suggest that the RSM turbulence model is better suited for studying gas injection in metallurgical ladles than k-ε or k-ω models. | |
Kaijalainen, A; Seppälä, O; Javaheri, V; Pohjonen, A; Porter, D; Kömi, J Comparison between experimental data and a cellular automata simulation of martensite formation during cooling Journal Article Journal of Physics: Conference Series, 1270 , pp. 012035, 2019. @article{Kaijalainen_2019, title = {Comparison between experimental data and a cellular automata simulation of martensite formation during cooling}, author = {A Kaijalainen and O Sepp\"{a}l\"{a} and V Javaheri and A Pohjonen and D Porter and J K\"{o}mi}, url = {https://doi.org/10.1088%2F1742-6596%2F1270%2F1%2F012035}, doi = {10.1088/1742-6596/1270/1/012035}, year = {2019}, date = {2019-08-01}, journal = {Journal of Physics: Conference Series}, volume = {1270}, pages = {012035}, publisher = {IOP Publishing}, abstract = {Computer simulations of steel microstructural development provide a powerful tool, which can form the basis of mechanical property predictions. However, in order to create detailed understanding of the factors affecting the properties, the model should predict microstructural evolution during cooling. The present study compares the results of cellular automata simulations with experimental data for two distinct austenite conditions, recrystallized and deformed. Detailed microstructural features were studied using a laser scanning confocal microscope, FESEM and FESEM-EBSD. The two-dimensional cellular automata (CA) model for simulating the formation of lath martensite was parameterized using fitted Johnson-Mehl-Avrami-Kolmogorov and Koistinen-Marburger equations. The parent austenite microstructure for the CA model was determined from the final martensitic microstructure using austenite grain reconstructions based on the use of MATLAB software and the MTEX toolbox. The results of this cellular automata simulation can be used to estimate the shapes and sizes of martensite blocks, which offers new possibilities for the qualitative estimation of the mechanical properties of high-strength steels formed from recrystallized or deformed austenite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Computer simulations of steel microstructural development provide a powerful tool, which can form the basis of mechanical property predictions. However, in order to create detailed understanding of the factors affecting the properties, the model should predict microstructural evolution during cooling. The present study compares the results of cellular automata simulations with experimental data for two distinct austenite conditions, recrystallized and deformed. Detailed microstructural features were studied using a laser scanning confocal microscope, FESEM and FESEM-EBSD. The two-dimensional cellular automata (CA) model for simulating the formation of lath martensite was parameterized using fitted Johnson-Mehl-Avrami-Kolmogorov and Koistinen-Marburger equations. The parent austenite microstructure for the CA model was determined from the final martensitic microstructure using austenite grain reconstructions based on the use of MATLAB software and the MTEX toolbox. The results of this cellular automata simulation can be used to estimate the shapes and sizes of martensite blocks, which offers new possibilities for the qualitative estimation of the mechanical properties of high-strength steels formed from recrystallized or deformed austenite. | |
Javaheri, Vahid; Khodaei, Nasseh; Nyo, Tun Tun; Porter, David A Induction Hardening of a 0.40 % C Novel Microalloyed Steel: Effects of Heating Rate on the Prior Austenite Grain Size Inproceedings THERMEC 2018, pp. 64–70, Trans Tech Publications, 2019. @inproceedings{javaheri2018e, title = {Induction Hardening of a 0.40 % C Novel Microalloyed Steel: Effects of Heating Rate on the Prior Austenite Grain Size}, author = {Vahid Javaheri and Nasseh Khodaei and Tun Tun Nyo and David A Porter}, doi = {10.4028/www.scientific.net/MSF.941.64}, year = {2019}, date = {2019-01-01}, booktitle = {THERMEC 2018}, volume = {941}, pages = {64--70}, publisher = {Trans Tech Publications}, series = {Materials Science Forum}, abstract = {This work explores the effect of heating rate on the prior austenite grain size and hardness of a thermomechanically processed novel niobium-microalloyed 0.40 % carbon low-alloyed steel intended for use in induction hardened slurry pipelines. The aim was to identify the heating rates that lead to the maximum hardness, for high wear resistance, and minimum prior austenite grain size, for high toughness. For this purpose, a Gleeble 3800 machine has been employed to simulate the induction hardening process and provide dilatometric phase transformation data. The prior austenite grain structure has been reconstructed from the EBSD results using a MatlabR script supplemented with MTEX texture and crystallography analyses. Heating rates ranged from 1 to 50 \^{A}°C/s and the cooling rate was 50 \^{A}°C/s. The results show that the prior austenite grain size greatly depended on the heating rate: compared to the lower heating rates, the maximum heating rate of 50 C/s produces remarkably fine prior austenite grains and a fine final martensitic microstructure after quenching. In addition, a relation between the heating rate and the deviation from equilibrium temperature has been established.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } This work explores the effect of heating rate on the prior austenite grain size and hardness of a thermomechanically processed novel niobium-microalloyed 0.40 % carbon low-alloyed steel intended for use in induction hardened slurry pipelines. The aim was to identify the heating rates that lead to the maximum hardness, for high wear resistance, and minimum prior austenite grain size, for high toughness. For this purpose, a Gleeble 3800 machine has been employed to simulate the induction hardening process and provide dilatometric phase transformation data. The prior austenite grain structure has been reconstructed from the EBSD results using a MatlabR script supplemented with MTEX texture and crystallography analyses. Heating rates ranged from 1 to 50 °C/s and the cooling rate was 50 °C/s. The results show that the prior austenite grain size greatly depended on the heating rate: compared to the lower heating rates, the maximum heating rate of 50 C/s produces remarkably fine prior austenite grains and a fine final martensitic microstructure after quenching. In addition, a relation between the heating rate and the deviation from equilibrium temperature has been established. | |
Javaheri, Vahid; Kolli, Satish; Grande, Bjørnar; Porter, David Insight into the induction hardening behavior of a new 0.40% C microalloyed steel: Effects of initial microstructure and thermal cycles Journal Article Materials Characterization, 149 , pp. 165 - 183, 2019, ISSN: 1044-5803. @article{JAVAHERI2019165, title = {Insight into the induction hardening behavior of a new 0.40% C microalloyed steel: Effects of initial microstructure and thermal cycles}, author = {Vahid Javaheri and Satish Kolli and Bj\ornar Grande and David Porter}, url = {http://www.sciencedirect.com/science/article/pii/S1044580318333606}, doi = {https://doi.org/10.1016/j.matchar.2019.01.029}, issn = {1044-5803}, year = {2019}, date = {2019-01-01}, journal = {Materials Characterization}, volume = {149}, pages = {165 - 183}, abstract = {The induction hardening behavior of a new, hot-rolled 0.4 wt% carbon steel with the two different starting microstructures of upper and lower bainite has been simulated using a Gleeble 3800. The effect of heating rate in the range 1\textendash500 °C/s on austenite grain size distribution has been rationalized. Dilatometry together with Scanning Electron Microscopy combined with Electron Backscatter Diffraction analyses and thermodynamic simulations provide insight into the austenite formation mechanisms that operate at different heating rates. Two main mechanisms of austenite formation during re-austenitization were identified: diffusional and diffusionless (massive). At conventional (1\textendash5 °C/s) and fast (10\textendash50 °C/s) heating rates the austenite formation mechanism and kinetics are controlled by diffusion, whereas at ultrafast heating rates (100\textendash500 °C/s) the formation of austenite starts by diffusion control, but is later overtaken by a massive transformation mechanism. Comprehensive thermodynamic descriptions of the influence of cementite on austenite formation are discussed. The finest austenite grain size and the highest final hardness are achieved with a lower bainite starting microstructure processed with a heating rate of 50 °C/s to an austenitization temperature of 850 °C followed by cooling at 60 °C/s.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The induction hardening behavior of a new, hot-rolled 0.4 wt% carbon steel with the two different starting microstructures of upper and lower bainite has been simulated using a Gleeble 3800. The effect of heating rate in the range 1–500 °C/s on austenite grain size distribution has been rationalized. Dilatometry together with Scanning Electron Microscopy combined with Electron Backscatter Diffraction analyses and thermodynamic simulations provide insight into the austenite formation mechanisms that operate at different heating rates. Two main mechanisms of austenite formation during re-austenitization were identified: diffusional and diffusionless (massive). At conventional (1–5 °C/s) and fast (10–50 °C/s) heating rates the austenite formation mechanism and kinetics are controlled by diffusion, whereas at ultrafast heating rates (100–500 °C/s) the formation of austenite starts by diffusion control, but is later overtaken by a massive transformation mechanism. Comprehensive thermodynamic descriptions of the influence of cementite on austenite formation are discussed. The finest austenite grain size and the highest final hardness are achieved with a lower bainite starting microstructure processed with a heating rate of 50 °C/s to an austenitization temperature of 850 °C followed by cooling at 60 °C/s. | |
Ramasetti, Eshwar Kumar; Visuri, Ville-Valtteri; Sulasalmi, Petri; Mattila, Riku; Fabritius, Timo Modeling of the Effect of the Gas Flow Rate on the Fluid Flow and Open-Eye Formation in a Water Model of a Steelmaking Ladle Journal Article steel research international, 90 (2), pp. 1800365, 2019. @article{doi:10.1002/srin.201800365, title = {Modeling of the Effect of the Gas Flow Rate on the Fluid Flow and Open-Eye Formation in a Water Model of a Steelmaking Ladle}, author = {Eshwar Kumar Ramasetti and Ville-Valtteri Visuri and Petri Sulasalmi and Riku Mattila and Timo Fabritius}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/srin.201800365}, doi = {10.1002/srin.201800365}, year = {2019}, date = {2019-01-01}, journal = {steel research international}, volume = {90}, number = {2}, pages = {1800365}, abstract = {In ladle metallurgy of steelmaking, the role of gas injection into the metal bath is been studied to a great extent as it improves the quality of steel. The size of the open-eye is associated with higher emulsification of top slag, which intensifies metal\textendashslag reactions, and information about the position and size of the open-eye is important for effective alloying practice. Moreover, the open-eye has an effect on the energy balance since it increases heat losses. In this work, experimental measurements and numerical simulations are performed to study the effect gas flow rate on the formation of the open-eye in a steelmaking ladle. A one-fifth scale water model is constructed for studying gas injection with single and dual plug configurations. For the numerical modeling, the Multiphase Volume of Fluid (VOF) model is used for simulating the system including the behavior of the slag layer. The physical modeling results show that the open-eye area changes from 9.22 to 198.34 cm2 when the gas flow rate varies from 0.75 to 15 SLM using a single plug. The effect of the number of plugs on the open-eye area for the same range of flow rates mentioned above is also studied. The two open-eye areas generated due to the gas injected through the dual plugs change from 37.59 to 231.1 cm2 when the gas flow rate is increased from 0.75 to 7.5 SLM for each plug in the physical modeling. The numerical simulation results of the open-eye area are found to be in good agreement with the experimental data obtained from the water model. During the gas stirring process, the slag layer is deformed such that the thickness of the slag becomes thick near to the wall and thin near the slag eye at high gas flow rates. In dual plug system, the two open-eyes tends to merge and form a huge open-eye at high flow rates that suits for better alloying purposes. The high-flow velocity near the surface, which could damage the ladle refractory, tends to be reduced in dual plug system when compared to single plug system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In ladle metallurgy of steelmaking, the role of gas injection into the metal bath is been studied to a great extent as it improves the quality of steel. The size of the open-eye is associated with higher emulsification of top slag, which intensifies metal–slag reactions, and information about the position and size of the open-eye is important for effective alloying practice. Moreover, the open-eye has an effect on the energy balance since it increases heat losses. In this work, experimental measurements and numerical simulations are performed to study the effect gas flow rate on the formation of the open-eye in a steelmaking ladle. A one-fifth scale water model is constructed for studying gas injection with single and dual plug configurations. For the numerical modeling, the Multiphase Volume of Fluid (VOF) model is used for simulating the system including the behavior of the slag layer. The physical modeling results show that the open-eye area changes from 9.22 to 198.34 cm2 when the gas flow rate varies from 0.75 to 15 SLM using a single plug. The effect of the number of plugs on the open-eye area for the same range of flow rates mentioned above is also studied. The two open-eye areas generated due to the gas injected through the dual plugs change from 37.59 to 231.1 cm2 when the gas flow rate is increased from 0.75 to 7.5 SLM for each plug in the physical modeling. The numerical simulation results of the open-eye area are found to be in good agreement with the experimental data obtained from the water model. During the gas stirring process, the slag layer is deformed such that the thickness of the slag becomes thick near to the wall and thin near the slag eye at high gas flow rates. In dual plug system, the two open-eyes tends to merge and form a huge open-eye at high flow rates that suits for better alloying purposes. The high-flow velocity near the surface, which could damage the ladle refractory, tends to be reduced in dual plug system when compared to single plug system. | |
Ramasetti, Eshwar Kumar; Visuri, Ville-Valtteri; Sulasalmi, Petri; Palovaara, Tuomas; Gupta, Avishek Kumar; Fabritius, Timo Physical and CFD Modeling of the Effect of Top Layer Properties on the Formation of Open-Eye in Gas-Stirred Ladles With Single and Dual-Plugs Journal Article steel research international, 90 (8), pp. 1900088, 2019. @article{EshwarPhysicalb, title = {Physical and CFD Modeling of the Effect of Top Layer Properties on the Formation of Open-Eye in Gas-Stirred Ladles With Single and Dual-Plugs}, author = {Eshwar Kumar Ramasetti and Ville-Valtteri Visuri and Petri Sulasalmi and Tuomas Palovaara and Avishek Kumar Gupta and Timo Fabritius}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/srin.201900088}, doi = {10.1002/srin.201900088}, year = {2019}, date = {2019-01-01}, journal = {steel research international}, volume = {90}, number = {8}, pages = {1900088}, abstract = {In secondary steelmaking, the optimal size and position of open-eye is important for effective alloying practice. In the current work, the effect of the top layer thickness and density on the formation of open-eye in a gas stirred ladle was investigated. A one-fifth scale water model of 150-ton ladle was established with single and dual plug configurations for the physical modeling measurements. Air, water and three different oils were used to simulate the argon, liquid steel and slag in the water model, respectively. A transient Computational Fluid Dynamics (CFD) model based on Eulerian Volume of Fluid (VOF) approach was developed for numerical modeling of the fluid flow behavior. The physical modeling results show that the relative open-eye area decreases from 46.7 to 5.6% when top layer thickness was increased from 0.75 to 7.5\^{a}cm using a gas flow rate of 7.5\^{a}NL\^{a}min\^{a}1. The effect of the number of plugs on the open-eye area for the same range of top layer thickness mentioned above was also studied. The relative open-eye area generated due to the gas injection through the dual plugs decreased from 49.9 to 5.8%. To study the effect of top layer properties, rapeseed oil, castor oil and paraffin oil were employed for studying the effect of density and dynamic viscosity on the open-eye formation. The results revealed that a larger open-eye is formed when the density is increased. Furthermore, it was found out that the density of the upper phase dominates the open-eye formation while dynamic viscosity has only minor effect. The results obtained from numerical simulations and physical modeling were found to be in good agreement.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In secondary steelmaking, the optimal size and position of open-eye is important for effective alloying practice. In the current work, the effect of the top layer thickness and density on the formation of open-eye in a gas stirred ladle was investigated. A one-fifth scale water model of 150-ton ladle was established with single and dual plug configurations for the physical modeling measurements. Air, water and three different oils were used to simulate the argon, liquid steel and slag in the water model, respectively. A transient Computational Fluid Dynamics (CFD) model based on Eulerian Volume of Fluid (VOF) approach was developed for numerical modeling of the fluid flow behavior. The physical modeling results show that the relative open-eye area decreases from 46.7 to 5.6% when top layer thickness was increased from 0.75 to 7.5âcm using a gas flow rate of 7.5âNLâminâ1. The effect of the number of plugs on the open-eye area for the same range of top layer thickness mentioned above was also studied. The relative open-eye area generated due to the gas injection through the dual plugs decreased from 49.9 to 5.8%. To study the effect of top layer properties, rapeseed oil, castor oil and paraffin oil were employed for studying the effect of density and dynamic viscosity on the open-eye formation. The results revealed that a larger open-eye is formed when the density is increased. Furthermore, it was found out that the density of the upper phase dominates the open-eye formation while dynamic viscosity has only minor effect. The results obtained from numerical simulations and physical modeling were found to be in good agreement. | |
Ramasetti, Eshwar Kumar; Visuri, Ville-Valtteri; Sulasalmi, Petri; Fabritius, Timo; Saatio, Tommi; Li, Mingming; Shao, Lei Numerical Modeling of Open-Eye Formation and Mixing Time in Argon Stirred Industrial Ladle Journal Article Metals, 9 (8), 2019, ISSN: 2075-4701. @article{EshwarNumerical, title = {Numerical Modeling of Open-Eye Formation and Mixing Time in Argon Stirred Industrial Ladle}, author = {Eshwar Kumar Ramasetti and Ville-Valtteri Visuri and Petri Sulasalmi and Timo Fabritius and Tommi Saatio and Mingming Li and Lei Shao}, url = {https://www.mdpi.com/2075-4701/9/8/829}, doi = {10.3390/met9080829}, issn = {2075-4701}, year = {2019}, date = {2019-01-01}, journal = {Metals}, volume = {9}, number = {8}, abstract = {In secondary metallurgy, argon gas stirring and alloying of elements are very important in determining the quality of steel. Argon gas is injected through the nozzle located at the bottom of the ladle into the molten steel bath; this gas breaks up into gas bubbles, rising upwards and breaking the slag layer at high gas flow rates, creating an open-eye. Alloy elements are added to the molten steel through the open-eye to attain the desired steel composition. In this work, experiments were conducted to investigate the effect of argon gas flow rate on the open-eye size and mixing time. An Eulerian volume of fluid (VOF) approach was employed to simulate the argon/steel/slag interface in the ladle, while a species transport model was used to calculate the mixing time of the nickel alloy. The simulation results showed that the time-averaged value of the open-eye area changed from 0.66 to 2.36 m2 when the flow rate of argon was varied from 100 to 500 NL/min. The mixing time (95% criterion) of tracer addition into the metal bath decreased from 139 s to 96 s, when the argon flow rate was increased from 100 to 500 NL/min. The model validation was verified by comparing with measured experimental results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In secondary metallurgy, argon gas stirring and alloying of elements are very important in determining the quality of steel. Argon gas is injected through the nozzle located at the bottom of the ladle into the molten steel bath; this gas breaks up into gas bubbles, rising upwards and breaking the slag layer at high gas flow rates, creating an open-eye. Alloy elements are added to the molten steel through the open-eye to attain the desired steel composition. In this work, experiments were conducted to investigate the effect of argon gas flow rate on the open-eye size and mixing time. An Eulerian volume of fluid (VOF) approach was employed to simulate the argon/steel/slag interface in the ladle, while a species transport model was used to calculate the mixing time of the nickel alloy. The simulation results showed that the time-averaged value of the open-eye area changed from 0.66 to 2.36 m2 when the flow rate of argon was varied from 100 to 500 NL/min. The mixing time (95% criterion) of tracer addition into the metal bath decreased from 139 s to 96 s, when the argon flow rate was increased from 100 to 500 NL/min. The model validation was verified by comparing with measured experimental results. | |
Ramasetti, Eshwar Kumar; Visuri, Ville-Valtteri; Sulasalmi, Petri; Fabritius, Timo; Savolainen, Jari; Li, Mingming; Shao, Lei Numerical Modelling of the Influence of Argon Flow Rate and Slag Layer Height on Open-Eye Formation in a 150 Ton Steelmaking Ladle Journal Article Metals, 9 (10), 2019, ISSN: 2075-4701. @article{met9101048, title = {Numerical Modelling of the Influence of Argon Flow Rate and Slag Layer Height on Open-Eye Formation in a 150 Ton Steelmaking Ladle}, author = {Eshwar Kumar Ramasetti and Ville-Valtteri Visuri and Petri Sulasalmi and Timo Fabritius and Jari Savolainen and Mingming Li and Lei Shao}, url = {https://www.mdpi.com/2075-4701/9/10/1048}, doi = {10.3390/met9101048}, issn = {2075-4701}, year = {2019}, date = {2019-01-01}, journal = {Metals}, volume = {9}, number = {10}, abstract = {A transient computational fluid dynamics (CFD) modelling approach was used to study the complex multi-phase flow in an argon-stirred industrial scale ladle with a nominal capacity of 150 tons. During the stirring process, when gas was injected through the porous plug from the bottom into the steel bath, it breaks up into bubbles and infringes the slag layer creating an open-eye. The volume of fluid model was used to investigate the open-eye formation process in the simulations. In the numerical simulations, the open-eye area changed from 0.7 to 2.24 m2 with the increment of argon flow rate from 200 to 500 NL/min for slag layer thickness of 40 cm. Furthermore, the influence of slag layer height on the open-eye area was investigated. An argon flow rate of 200 NL/min was able to break the slag layer for slag layer height of 40 cm, and the open-eye formation was not possible for the same flow rate when the slag layer height was elevated from 40 to 55 cm. The numerical simulation results were validated against industrial measurements carried out at Outokumpu Stainless located in Tornio, Finland. The numerical simulation results of dynamics and time-averages of the slag area showed a good agreement when compared to the industrial measurements. To conclude, it is necessary to define gas flow rate based on the slag layer height to have an open-eye suitable for alloying.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A transient computational fluid dynamics (CFD) modelling approach was used to study the complex multi-phase flow in an argon-stirred industrial scale ladle with a nominal capacity of 150 tons. During the stirring process, when gas was injected through the porous plug from the bottom into the steel bath, it breaks up into bubbles and infringes the slag layer creating an open-eye. The volume of fluid model was used to investigate the open-eye formation process in the simulations. In the numerical simulations, the open-eye area changed from 0.7 to 2.24 m2 with the increment of argon flow rate from 200 to 500 NL/min for slag layer thickness of 40 cm. Furthermore, the influence of slag layer height on the open-eye area was investigated. An argon flow rate of 200 NL/min was able to break the slag layer for slag layer height of 40 cm, and the open-eye formation was not possible for the same flow rate when the slag layer height was elevated from 40 to 55 cm. The numerical simulation results were validated against industrial measurements carried out at Outokumpu Stainless located in Tornio, Finland. The numerical simulation results of dynamics and time-averages of the slag area showed a good agreement when compared to the industrial measurements. To conclude, it is necessary to define gas flow rate based on the slag layer height to have an open-eye suitable for alloying. | |
Javaheri, Vahid; Pohjonen, Aarne; Asperheim, John Inge; Ivanov, Dmitry; Porter, David Physically based modeling, characterization and design of an induction hardening process for a new slurry pipeline steel Journal Article Materials & Design, 182 , pp. 108047, 2019, ISSN: 0264-1275. @article{JAVAHERI2019108047, title = {Physically based modeling, characterization and design of an induction hardening process for a new slurry pipeline steel}, author = {Vahid Javaheri and Aarne Pohjonen and John Inge Asperheim and Dmitry Ivanov and David Porter}, url = {http://www.sciencedirect.com/science/article/pii/S026412751930485X}, doi = {https://doi.org/10.1016/j.matdes.2019.108047}, issn = {0264-1275}, year = {2019}, date = {2019-01-01}, journal = {Materials & Design}, volume = {182}, pages = {108047}, abstract = {Numerical and Gleeble experimental data are combined to predict potential microstructure and hardness profiles through the wall thickness of an induction hardened slurry transportation pipe made of a recently developed 0.4\^{a}¯wt% C, Nb-microalloyed steel. The calculated thermal history of various positions through the wall thickness of an industrial pipe (400\^{a}¯mm diameter, 10\^{a}¯mm thick) were combined with a model that predicts the phase transformations, microstructures and final hardness values on heating and cooling along arbitrary thermal cycles. The accuracy of the hardness profile predictions was verified by experimental data, i.e. reproducing the thermal cycles on a Gleeble thermomechanical simulator. The results indicated that the approach should be a feasible way to optimize induction heating and cooling parameters to obtain desired hardness profiles through the wall thickness.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Numerical and Gleeble experimental data are combined to predict potential microstructure and hardness profiles through the wall thickness of an induction hardened slurry transportation pipe made of a recently developed 0.4â¯wt% C, Nb-microalloyed steel. The calculated thermal history of various positions through the wall thickness of an industrial pipe (400â¯mm diameter, 10â¯mm thick) were combined with a model that predicts the phase transformations, microstructures and final hardness values on heating and cooling along arbitrary thermal cycles. The accuracy of the hardness profile predictions was verified by experimental data, i.e. reproducing the thermal cycles on a Gleeble thermomechanical simulator. The results indicated that the approach should be a feasible way to optimize induction heating and cooling parameters to obtain desired hardness profiles through the wall thickness. | |
Kolli, Satish; Ohligschläger, Thomas; Porter, David Quantitative Prediction of Sensitization in Austenitic Stainless Steel Accounting for Multicomponent Thermodynamic and Mass Balance Effects Journal Article ISIJ International, 59 (7), pp. 1330-1336, 2019. @article{SatishKolli2019ISIJINT-2018-715, title = {Quantitative Prediction of Sensitization in Austenitic Stainless Steel Accounting for Multicomponent Thermodynamic and Mass Balance Effects}, author = {Satish Kolli and Thomas Ohligschl\"{a}ger and David Porter}, doi = {10.2355/isijinternational.ISIJINT-2018-715}, year = {2019}, date = {2019-01-01}, journal = {ISIJ International}, volume = {59}, number = {7}, pages = {1330-1336}, keywords = {}, pubstate = {published}, tppubtype = {article} } | |
Kolli, Satish; Ohligschläger, Thomas; Kömi, Jukka; Porter, David Sensitization and Self-healing in Austenitic Stainless Steel: Quantitative Prediction Considering Carbide Nucleation and Growth Journal Article ISIJ International, advpub , 2019. @article{SatishKolli2019ISIJINT-2019-264, title = {Sensitization and Self-healing in Austenitic Stainless Steel: Quantitative Prediction Considering Carbide Nucleation and Growth}, author = {Satish Kolli and Thomas Ohligschl\"{a}ger and Jukka K\"{o}mi and David Porter}, doi = {10.2355/isijinternational.ISIJINT-2019-264}, year = {2019}, date = {2019-01-01}, journal = {ISIJ International}, volume = {advpub}, keywords = {}, pubstate = {published}, tppubtype = {article} } | |
Kolli, Satish; Ferancova, Adriana; Porter, David; Kömi, Jukka Study of Intergranular Corrosion in Austenitic Stainless Steels Using Electrochemical Impedance Spectroscopy Journal Article International Journal of Materials and Metallurgical Engineering, 13 (4), pp. 165 - 168, 2019, ISSN: eISSN: 1307-6892. @article{satish3, title = {Study of Intergranular Corrosion in Austenitic Stainless Steels Using Electrochemical Impedance Spectroscopy}, author = {Satish Kolli and Adriana Ferancova and David Porter and Jukka K\"{o}mi}, url = {https://publications.waset.org/vol/148}, issn = {eISSN: 1307-6892}, year = {2019}, date = {2019-01-01}, journal = {International Journal of Materials and Metallurgical Engineering}, volume = {13}, number = {4}, pages = {165 - 168}, publisher = {World Academy of Science, Engineering and Technology}, abstract = {Electrochemical impedance spectroscopy (EIS) has been used to detect sensitization in austenitic stainless steels that are heat treated in the temperature regime 600-820 °C to produce different degrees of sensitization in the material. The tests were conducted at five different DC potentials in the transpassive region. The quantitative determination of degree of sensitization has been done using double loop electrochemical potentiokinetic reactivation tests (DL-EPR). The correlation between EIS Nyquist diagrams and DL-EPR degree of sensitization values has been studied. The EIS technique can be used as a qualitative tool in determining the intergranular corrosion in austenitic stainless steels that are heat treated at a given temperature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrochemical impedance spectroscopy (EIS) has been used to detect sensitization in austenitic stainless steels that are heat treated in the temperature regime 600-820 °C to produce different degrees of sensitization in the material. The tests were conducted at five different DC potentials in the transpassive region. The quantitative determination of degree of sensitization has been done using double loop electrochemical potentiokinetic reactivation tests (DL-EPR). The correlation between EIS Nyquist diagrams and DL-EPR degree of sensitization values has been studied. The EIS technique can be used as a qualitative tool in determining the intergranular corrosion in austenitic stainless steels that are heat treated at a given temperature. | |
Alia, Najib; John, Volker; Ollila, Seppo Revisiting the single-phase flow model for liquid steel ladle stirred by gas Journal Article 67 , pp. 549 - 556, 2019, ISSN: 0307-904X. @article{ALIA2019549, title = {Revisiting the single-phase flow model for liquid steel ladle stirred by gas}, author = {Najib Alia and Volker John and Seppo Ollila}, url = {http://www.sciencedirect.com/science/article/pii/S0307904X18305328}, doi = {https://doi.org/10.1016/j.apm.2018.11.005}, issn = {0307-904X}, year = {2019}, date = {2019-01-01}, volume = {67}, pages = {549 - 556}, abstract = {Ladle stirring is an important step of the steelmaking process to homogenize the temperature and the chemical composition of the\^{A} liquid steel and to remove inclusions before casting. Gas is injected from the bottom of the bath to induce a turbulent flow of the\^{A} liquid steel. Multiphase modeling of ladle stirring can become computationally expensive, especially when used within optimal flow control problems. This note focuses therefore on single-phase flow models. It aims at improving the existing models from the literature. Simulations in a 2d axial-symmetrical configuration, as well as in a real 3d laboratory-scale ladle, are performed. The results obtained with the present model are in a relative good agreement with experimental data and suggest that it can be used as an efficient model in optimal flow control problems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ladle stirring is an important step of the steelmaking process to homogenize the temperature and the chemical composition of the liquid steel and to remove inclusions before casting. Gas is injected from the bottom of the bath to induce a turbulent flow of the liquid steel. Multiphase modeling of ladle stirring can become computationally expensive, especially when used within optimal flow control problems. This note focuses therefore on single-phase flow models. It aims at improving the existing models from the literature. Simulations in a 2d axial-symmetrical configuration, as well as in a real 3d laboratory-scale ladle, are performed. The results obtained with the present model are in a relative good agreement with experimental data and suggest that it can be used as an efficient model in optimal flow control problems. | |
Alia, Najib; Pylvänäinen, Mika; Visuri, Ville-Valtteri; John, Volker; Ollila, Seppo Vibrations of a laboratory-scale gas-stirred ladle with two eccentric nozzles and multiple sensors Journal Article Journal of Iron and Steel Research International, 26 (10), pp. 1031–1040, 2019, ISSN: 2210-3988. @article{Alia2019e, title = {Vibrations of a laboratory-scale gas-stirred ladle with two eccentric nozzles and multiple sensors}, author = {Najib Alia and Mika Pylv\"{a}n\"{a}inen and Ville-Valtteri Visuri and Volker John and Seppo Ollila}, url = {https://doi.org/10.1007/s42243-019-00241-x}, doi = {10.1007/s42243-019-00241-x}, issn = {2210-3988}, year = {2019}, date = {2019-01-01}, journal = {Journal of Iron and Steel Research International}, volume = {26}, number = {10}, pages = {1031--1040}, abstract = {During ladle stirring, a gas is injected into the steel bath to generate a mixing of the liquid steel. The optimal process control requires a reliable measurement of the stirring intensity, for which the induced ladle wall vibrations have proved to be a potential indicator. An experimental cold water ladle with two eccentric nozzles and eight mono-axial accelerometers was thus investigated to measure the vibrations. The effect of the sensors' positions with respect to the gas plugs on the vibration intensity was analyzed, and experimental data on several points of the ladle were collected for future numerical simulations. It is shown that the vibration root-mean-square values depend not only on process parameters, such as gas flow rate, water, and oil heights, but also on the radial and axial positions of the sensors. The vibration intensity is clearly higher, close to the gas plumes, than in the opposite side. If one of the nozzles is clogged, the vibration intensity close to the clogged nozzle drops drastically (-36to -59%), while the vibrations close to the normal operating nozzle are hardly affected. Based on these results, guidelines are provided for an optimized vibration-based stirring.}, keywords = {}, pubstate = {published}, tppubtype = {article} } During ladle stirring, a gas is injected into the steel bath to generate a mixing of the liquid steel. The optimal process control requires a reliable measurement of the stirring intensity, for which the induced ladle wall vibrations have proved to be a potential indicator. An experimental cold water ladle with two eccentric nozzles and eight mono-axial accelerometers was thus investigated to measure the vibrations. The effect of the sensors' positions with respect to the gas plugs on the vibration intensity was analyzed, and experimental data on several points of the ladle were collected for future numerical simulations. It is shown that the vibration root-mean-square values depend not only on process parameters, such as gas flow rate, water, and oil heights, but also on the radial and axial positions of the sensors. The vibration intensity is clearly higher, close to the gas plumes, than in the opposite side. If one of the nozzles is clogged, the vibration intensity close to the clogged nozzle drops drastically (-36to -59%), while the vibrations close to the normal operating nozzle are hardly affected. Based on these results, guidelines are provided for an optimized vibration-based stirring. | |
Babu, Shashank Ramesh; Jaskari, Matias; Järvenpää, Antti; Porter, David The Effect of Hot-Mounting on the Microstructure of an As-Quenched Auto-Tempered Low-Carbon Martensitic Steel Journal Article Metals, 9 (5), 2019, ISSN: 2075-4701. @article{shashankb, title = {The Effect of Hot-Mounting on the Microstructure of an As-Quenched Auto-Tempered Low-Carbon Martensitic Steel}, author = {Shashank Ramesh Babu and Matias Jaskari and Antti J\"{a}rvenp\"{a}\"{a} and David Porter}, url = {https://www.mdpi.com/2075-4701/9/5/550}, doi = {10.3390/met9050550}, issn = {2075-4701}, year = {2019}, date = {2019-01-01}, journal = {Metals}, volume = {9}, number = {5}, abstract = {The effect of hot-mounting for metallographic studies of as-quenched low-carbon martensitic steels has been studied. Hot-mounting is typically carried out at 150–200 °C, i.e., a low-temperature tempering regime. Cold- and hot-mounted specimens from an as-quenched low-carbon auto-tempered steel were examined using a scanning electron microscope and their hardness levels were also compared. It was found that hot-mounting causes additional tempering that manifests as the appearance of new precipitates in those regions that are free of auto-tempered cementite. The observations were rationalized using DICTRA simulations to calculate the potential growth of cementite. Hot-mounting was also shown to cause a small but statistically significant increase in the hardness of the martensite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of hot-mounting for metallographic studies of as-quenched low-carbon martensitic steels has been studied. Hot-mounting is typically carried out at 150–200 °C, i.e., a low-temperature tempering regime. Cold- and hot-mounted specimens from an as-quenched low-carbon auto-tempered steel were examined using a scanning electron microscope and their hardness levels were also compared. It was found that hot-mounting causes additional tempering that manifests as the appearance of new precipitates in those regions that are free of auto-tempered cementite. The observations were rationalized using DICTRA simulations to calculate the potential growth of cementite. Hot-mounting was also shown to cause a small but statistically significant increase in the hardness of the martensite. | |
Babu, Shashank Ramesh; Nyyssönen, Tuomo; Jaskari, Matias; Järvenpää, Antti; Davis, Thomas Paul; Pallaspuro, Sakari; Kömi, Jukka; Porter, David Observations on the Relationship between Crystal Orientation and the Level of Auto-Tempering in an As-Quenched Martensitic Steel Journal Article Metals, 9 (12), 2019, ISSN: 2075-4701. @article{met9121255, title = {Observations on the Relationship between Crystal Orientation and the Level of Auto-Tempering in an As-Quenched Martensitic Steel}, author = { Shashank Ramesh Babu and Tuomo Nyyss\"{o}nen and Matias Jaskari and Antti J\"{a}rvenp\"{a}\"{a} and Thomas Paul Davis and Sakari Pallaspuro and Jukka K\"{o}mi and David Porter}, url = {https://www.mdpi.com/2075-4701/9/12/1255}, doi = {10.3390/met9121255}, issn = {2075-4701}, year = {2019}, date = {2019-01-01}, journal = {Metals}, volume = {9}, number = {12}, abstract = {Auto-tempering is a feature of the technologically important as-quenched low-carbon martensitic steels. The focus of this paper is on the morphology of the martensite and the orientation of the last forming untempered regions in relation to the earlier formed auto-tempered martensite in both small and large austenite grains. A low-carbon martensitic steel plate was austenitized for 24 h and quenched to room temperature. The resulting microstructure was characterized using electron microscopy and electron back scattered diffraction (EBSD) imaging. It was found that all the untempered regions in the martensitic microstructure were oriented with the plane normals 100 close to the thickness, or normal, direction of the plates. Variant analysis revealed that the untempered regions and the auto-tempered regions are part of the same packet.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Auto-tempering is a feature of the technologically important as-quenched low-carbon martensitic steels. The focus of this paper is on the morphology of the martensite and the orientation of the last forming untempered regions in relation to the earlier formed auto-tempered martensite in both small and large austenite grains. A low-carbon martensitic steel plate was austenitized for 24 h and quenched to room temperature. The resulting microstructure was characterized using electron microscopy and electron back scattered diffraction (EBSD) imaging. It was found that all the untempered regions in the martensitic microstructure were oriented with the plane normals 100 close to the thickness, or normal, direction of the plates. Variant analysis revealed that the untempered regions and the auto-tempered regions are part of the same packet. | |
Kolli, Satish; Javaheri, Vahid; Kömi, Jukka; Porter, David On the Role of Grain Size and Carbon Content on the Sensitization and Desensitization Behavior of 301 Austenitic Stainless Steel Journal Article Metals, 9 (11), 2019, ISSN: 2075-4701. @article{met9111193, title = {On the Role of Grain Size and Carbon Content on the Sensitization and Desensitization Behavior of 301 Austenitic Stainless Steel}, author = {Satish Kolli and Vahid Javaheri and Jukka K\"{o}mi and David Porter}, url = {https://www.mdpi.com/2075-4701/9/11/1193}, doi = {10.3390/met9111193}, issn = {2075-4701}, year = {2019}, date = {2019-01-01}, journal = {Metals}, volume = {9}, number = {11}, abstract = {The effect of grain size in the range 72 to 190 μm and carbon content in the range 0.105–0.073 wt.% on the intergranular corrosion of the austenitic stainless steel 301 has been investigated. Grain boundary chromium depletion has been studied directly using energy dispersive X-ray spectroscopy combined with scanning transmission electron microscopy and indirectly using double loop electrochemical potentiokinetic reactivation tests. In addition, chromium depletion has been modelled using the CALPHAD Thermo-Calc software TC-DICTRA. It is shown that the degree of sensitization measured using the double loop electrochemical potentiokinetic reactivation tests can be successfully predicted with the aid of a depletion parameter based on the modelled chromium depletion profiles for heat treatment times covering both the sensitization and de-sensitization or self-healing. Additionally, along with intergranular M23C6 carbides, intragranular M23C6 and Cr2N nitrides that affect the available Cr for grain boundary carbide precipitation were also observed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of grain size in the range 72 to 190 μm and carbon content in the range 0.105–0.073 wt.% on the intergranular corrosion of the austenitic stainless steel 301 has been investigated. Grain boundary chromium depletion has been studied directly using energy dispersive X-ray spectroscopy combined with scanning transmission electron microscopy and indirectly using double loop electrochemical potentiokinetic reactivation tests. In addition, chromium depletion has been modelled using the CALPHAD Thermo-Calc software TC-DICTRA. It is shown that the degree of sensitization measured using the double loop electrochemical potentiokinetic reactivation tests can be successfully predicted with the aid of a depletion parameter based on the modelled chromium depletion profiles for heat treatment times covering both the sensitization and de-sensitization or self-healing. Additionally, along with intergranular M23C6 carbides, intragranular M23C6 and Cr2N nitrides that affect the available Cr for grain boundary carbide precipitation were also observed. | |
2018 |
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E.K. Ramasetti V.-V. Visuri, Sulasalmi P; Fabritius, T Lau, T C W; Kelso, R M (Ed.): Proceedings of the 21st Australasian Fluid Mechanics Conference, Australasian Fluid Mechanics Society Australasian Fluid Mechanics Society, Adelaide, SA 5005, AUSTRALIA, 2018, ISBN: 978-0-646-59784-3. @inproceedings{Ramasetti2018b, title = {Experimental and Numerical Investigation of Slag Thickness Effect on the Formation of Slag Eye in a Water Model of a Steel Making Ladle}, author = {E.K. Ramasetti, V.-V. Visuri, P. Sulasalmi and T. Fabritius}, editor = {T. C. W. Lau and R. M. Kelso }, url = {https://people.eng.unimelb.edu.au/imarusic/proceedings/21/Contribution_576_final.pdf}, isbn = {978-0-646-59784-3}, year = {2018}, date = {2018-12-13}, booktitle = {Proceedings of the 21st Australasian Fluid Mechanics Conference}, publisher = {Australasian Fluid Mechanics Society}, address = {Adelaide, SA 5005, AUSTRALIA}, organization = {Australasian Fluid Mechanics Society}, abstract = {In secondary steelmaking process, gas stirring is extensively used to homogenize the chemical composition of alloy elements and the removal of inclusions. During the process, gas is injected through a porous plug into the steel bath creating a buoyant bubble plume. The plume generates a recirculation flow pattern in the ladle, and the rising bubbles break the slag layer creating a slag eye at high gas flow rates. In the current work, the behaviour of the slag eye area for different slag layer thickness heights is been investigated through experimental measurements and CFD simulations. A 1/5- scale water model of 150-ton ladle was established for the experimental measurements and for studying the effect of slag thickness on the slag eye area. The physical modelling results show that the slag eye area changes from 227.6 to 27 cm2 when slag layer thickness height was increased from 0.75 to 7.5 cm for a gas flow rate of 3.5 NL/min. The mathematical model developed was based on the Eulerian Multiphase Volume of Fluid (VOF) approach and standard 𝑘−𝜀 turbulence model was used for solving the turbulent liquid flow. The simulation results of slag eye area showed a good agreement when compared to the experimental results measured. }, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } In secondary steelmaking process, gas stirring is extensively used to homogenize the chemical composition of alloy elements and the removal of inclusions. During the process, gas is injected through a porous plug into the steel bath creating a buoyant bubble plume. The plume generates a recirculation flow pattern in the ladle, and the rising bubbles break the slag layer creating a slag eye at high gas flow rates. In the current work, the behaviour of the slag eye area for different slag layer thickness heights is been investigated through experimental measurements and CFD simulations. A 1/5- scale water model of 150-ton ladle was established for the experimental measurements and for studying the effect of slag thickness on the slag eye area. The physical modelling results show that the slag eye area changes from 227.6 to 27 cm2 when slag layer thickness height was increased from 0.75 to 7.5 cm for a gas flow rate of 3.5 NL/min. The mathematical model developed was based on the Eulerian Multiphase Volume of Fluid (VOF) approach and standard 𝑘−𝜀 turbulence model was used for solving the turbulent liquid flow. The simulation results of slag eye area showed a good agreement when compared to the experimental results measured. | |
Mahyar Mohammadnejad Vahid Javaheri, Morteza Shamanian Shahram Rizaneh Jerzy Szpunar A Insight to the Microstructure Characterization of a HP Austenitic Heat Resistant Steel after Long-term Service Exposure Journal Article Acta Metallurgica Slovaca, 24 (4), pp. 296-305, 2018. @article{Mohammadnejad2018, title = {Insight to the Microstructure Characterization of a HP Austenitic Heat Resistant Steel after Long-term Service Exposure}, author = {Mahyar Mohammadnejad, Vahid Javaheri, Morteza Shamanian, Shahram Rizaneh, Jerzy A Szpunar}, url = {http://www.qip-journal.eu/index.php/ams/article/view/1160}, doi = {10.12776/ams.v24i4.1160}, year = {2018}, date = {2018-12-01}, journal = {Acta Metallurgica Slovaca}, volume = {24}, number = {4}, pages = {296-305}, abstract = {Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used in high temperature structural applications. Their composition include Nb as strong carbide former. Electron Backscatter Diffraction (EBSD) investigations revealed that, in the as-cast condition, alloys exhibit austenitic matrix with intergranular primary carbides such as MC, M23C6 and/or M7C3. During exposure at a high temperature, phase transformations occurred: chromium carbides of M7C3 type transform into the more stable M23C6 type, intergranular M23C6 carbides precipitate, and Lave phase due to increase of Niobium activity with temperature increase, as thermodynamic simulation confirmed. Therefore, combination of EBSD-EDS technique with thermodynamic calculation is one of the novel and most accurate method to investigation of phase transformation, as the precipitations are identified on the basis of their crystal structure, chemical composition and their thermodynamic features. }, keywords = {}, pubstate = {published}, tppubtype = {article} } Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used in high temperature structural applications. Their composition include Nb as strong carbide former. Electron Backscatter Diffraction (EBSD) investigations revealed that, in the as-cast condition, alloys exhibit austenitic matrix with intergranular primary carbides such as MC, M23C6 and/or M7C3. During exposure at a high temperature, phase transformations occurred: chromium carbides of M7C3 type transform into the more stable M23C6 type, intergranular M23C6 carbides precipitate, and Lave phase due to increase of Niobium activity with temperature increase, as thermodynamic simulation confirmed. Therefore, combination of EBSD-EDS technique with thermodynamic calculation is one of the novel and most accurate method to investigation of phase transformation, as the precipitations are identified on the basis of their crystal structure, chemical composition and their thermodynamic features. | |
Babu, Shashank Ramesh; Ivanov, Dmitry; Porter, David Influence of Microsegregation on the Onset of the Martensitic Transformation Journal Article ISIJ International, Advance online publication , 2018. @article{ShashankRameshBabu2018ISIJINT-2018-424, title = {Influence of Microsegregation on the Onset of the Martensitic Transformation}, author = {Shashank Ramesh Babu and Dmitry Ivanov and David Porter}, url = {https://www.jstage.jst.go.jp/article/isijinternational/advpub/0/advpub_ISIJINT-2018-424/_article}, doi = {10.2355/isijinternational.ISIJINT-2018-424}, year = {2018}, date = {2018-10-24}, journal = {ISIJ International}, volume = {Advance online publication}, abstract = {Due to the volume change accompanying the fcc to bcc or bct crystal structures in steels, it is a common practice to determine phase transformation temperatures using dilatometry. The martensite start temperature (Ms) is often of particular interest. Experimentally, it is found that the start of the martensite transformation is not indicated by a sharp change in the slope of the dilatation curve as is predicted by the Koistinen \textendash Marburger equation. Rather, there is a gradual change in the slope such that the martensite start temperature is ill-defined. The current work shows that this gradual change in slope can be related to chemical inhomogeneity in the steel caused by interdendritic microsegregation. It is shown that combining the Koistinen \textendash Marburger equation with measured concentration profiles allows experimental dilatation curves to be well predicted.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Due to the volume change accompanying the fcc to bcc or bct crystal structures in steels, it is a common practice to determine phase transformation temperatures using dilatometry. The martensite start temperature (Ms) is often of particular interest. Experimentally, it is found that the start of the martensite transformation is not indicated by a sharp change in the slope of the dilatation curve as is predicted by the Koistinen – Marburger equation. Rather, there is a gradual change in the slope such that the martensite start temperature is ill-defined. The current work shows that this gradual change in slope can be related to chemical inhomogeneity in the steel caused by interdendritic microsegregation. It is shown that combining the Koistinen – Marburger equation with measured concentration profiles allows experimental dilatation curves to be well predicted. | |
Ramasetti, Eshwar Kumar; Visuri, Ville-Valtteri; Sulasalmi, Petri; Fabritius, Timo A CFD and Experimental Investigation of Slag Eye in Gas Stirred Ladle Inproceedings Proceedings of the 5th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'18), June 7--9 , 2018, pp. 148-1–148–10, Niagara Falls, Canada, 2018. @inproceedings{ramasetticfd, title = {A CFD and Experimental Investigation of Slag Eye in Gas Stirred Ladle}, author = {Eshwar Kumar Ramasetti and Ville-Valtteri Visuri and Petri Sulasalmi and Timo Fabritius}, doi = {10.11159/ffhmt18.148}, year = {2018}, date = {2018-07-01}, booktitle = {Proceedings of the 5th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'18), June 7--9 , 2018}, pages = {148-1--148--10}, address = {Niagara Falls, Canada}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } | |
Javaheri, Vahid; Nyyssönen, Tuomo; Grande, Bjørnar; Porter, David Computational Design of a Novel Medium-Carbon, Low-Alloy Steel Microalloyed with Niobium Journal Article Journal of Materials Engineering and Performance, 2018, ISSN: 1544-1024. @article{Javaheri2018b, title = {Computational Design of a Novel Medium-Carbon, Low-Alloy Steel Microalloyed with Niobium}, author = {Vahid Javaheri and Tuomo Nyyss\"{o}nen and Bj\ornar Grande and David Porter}, doi = {10.1007/s11665-018-3376-9}, issn = {1544-1024}, year = {2018}, date = {2018-04-24}, journal = {Journal of Materials Engineering and Performance}, abstract = {The design of a new steel with specific properties is always challenging owing to the complex interactions of many variables. In this work, this challenge is dealt with by combining metallurgical principles with computational thermodynamics and kinetics to design a novel steel composition suitable for thermomechanical processing and induction heat treatment to achieve a hardness level in excess of 600 HV with the potential for good fracture toughness. CALPHAD-based packages for the thermodynamics and kinetics of phase transformations and diffusion, namely Thermo-Calc® and JMatPro®, have been combined with an interdendritic segregation tool (IDS) to optimize the contents of chromium, molybdenum and niobium in a proposed medium-carbon low-manganese steel composition. Important factors taken into account in the modeling and optimization were hardenability and as-quenched hardness, grain refinement and alloying cost. For further investigations and verification, the designed composition, i.e., in wt.% 0.40C, 0.20Si, 0.25Mn, 0.90Cr, 0.50Mo, was cast with two nominal levels of Nb: 0 and 0.012 wt.%. The results showed that an addition of Nb decreases the austenite grain size during casting and after slab reheating prior to hot rolling. Validation experiments showed that the predicted properties, i.e., hardness, hardenability and level of segregation, for the designed composition were realistic. It is also demonstrated that the applied procedure could be useful in reducing the number of experiments required for developing compositions for other new steels.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The design of a new steel with specific properties is always challenging owing to the complex interactions of many variables. In this work, this challenge is dealt with by combining metallurgical principles with computational thermodynamics and kinetics to design a novel steel composition suitable for thermomechanical processing and induction heat treatment to achieve a hardness level in excess of 600 HV with the potential for good fracture toughness. CALPHAD-based packages for the thermodynamics and kinetics of phase transformations and diffusion, namely Thermo-Calc® and JMatPro®, have been combined with an interdendritic segregation tool (IDS) to optimize the contents of chromium, molybdenum and niobium in a proposed medium-carbon low-manganese steel composition. Important factors taken into account in the modeling and optimization were hardenability and as-quenched hardness, grain refinement and alloying cost. For further investigations and verification, the designed composition, i.e., in wt.% 0.40C, 0.20Si, 0.25Mn, 0.90Cr, 0.50Mo, was cast with two nominal levels of Nb: 0 and 0.012 wt.%. The results showed that an addition of Nb decreases the austenite grain size during casting and after slab reheating prior to hot rolling. Validation experiments showed that the predicted properties, i.e., hardness, hardenability and level of segregation, for the designed composition were realistic. It is also demonstrated that the applied procedure could be useful in reducing the number of experiments required for developing compositions for other new steels. | |
Javaheri, Vahid; Nyo, Tun Tun; Porter, David On the Role of Nb on the Texture and Microstructure of a Novel As-Rolled Medium Carbon Wear Resistant Slurry Pipeline Steel Inproceedings Hwang, Jiann-Yang; Jiang, Tao; Kennedy, Mark William; Gregurek, Dean; Wang, Shijie; Zhao, Baojun; Yücel, Onuralp; Keskinkilic, Ender; Downey, Jerome P; Peng, Zhiwei; Padilla, Rafael (Ed.): 9th International Symposium on High-Temperature Metallurgical Processing. TMS 2018. The Minerals, Metals & Materials Series., pp. 365–379, Springer International Publishing, Cham, 2018, ISBN: 978-3-319-72138-5. @inproceedings{Javaheri2018, title = {On the Role of Nb on the Texture and Microstructure of a Novel As-Rolled Medium Carbon Wear Resistant Slurry Pipeline Steel}, author = {Vahid Javaheri and Tun Tun Nyo and David Porter}, editor = {Jiann-Yang Hwang and Tao Jiang and Mark William Kennedy and Dean Gregurek and Shijie Wang and Baojun Zhao and Onuralp Y\"{u}cel and Ender Keskinkilic and Jerome P Downey and Zhiwei Peng and Rafael Padilla}, doi = {10.1007/978-3-319-72138-5_37}, isbn = {978-3-319-72138-5}, year = {2018}, date = {2018-01-01}, booktitle = {9th International Symposium on High-Temperature Metallurgical Processing. TMS 2018. The Minerals, Metals & Materials Series.}, pages = {365--379}, publisher = {Springer International Publishing}, address = {Cham}, abstract = {A field emission scanning electron microscope equipped with EBSD has been employed to evaluate the role of 0.013 wt{%} Nb on the evolution of the microstructure and texture of a novel thermomechanically processed low-alloy, medium-carbon steel. Specimens were subjected to hot-rolling with a total reduction of 80{%}, four passes in the recrystallization regime and four passes below the non-recrystallization temperature. Immediately after rolling, the strips were quenched to 420 {textdegree}C and subsequently cooled slowly in a furnace to simulate strip coiling with transformation of austenite to bainite. The results showed that Nb microalloying results in a finer microstructure with a sharper texture when compared to an identical steel but without Nb. In addition, analysis of the retained austenite texture indicated that the main bcc texture components are the product transformed brass and copper components in the parent austenite.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } A field emission scanning electron microscope equipped with EBSD has been employed to evaluate the role of 0.013 wt{%} Nb on the evolution of the microstructure and texture of a novel thermomechanically processed low-alloy, medium-carbon steel. Specimens were subjected to hot-rolling with a total reduction of 80{%}, four passes in the recrystallization regime and four passes below the non-recrystallization temperature. Immediately after rolling, the strips were quenched to 420 {textdegree}C and subsequently cooled slowly in a furnace to simulate strip coiling with transformation of austenite to bainite. The results showed that Nb microalloying results in a finer microstructure with a sharper texture when compared to an identical steel but without Nb. In addition, analysis of the retained austenite texture indicated that the main bcc texture components are the product transformed brass and copper components in the parent austenite. | |
Javaheri, Vahid; Khodaie, Nasseh; Kaijalainen, Antti; Porter, David Effect of niobium and phase transformation temperature on the microstructure and texture of a novel 0.40% C thermomechanically processed steel Journal Article Materials Characterization, 142 , pp. 295 - 308, 2018, ISSN: 1044-5803. @article{JAVAHERI2018295, title = {Effect of niobium and phase transformation temperature on the microstructure and texture of a novel 0.40% C thermomechanically processed steel}, author = {Vahid Javaheri and Nasseh Khodaie and Antti Kaijalainen and David Porter}, url = {http://www.sciencedirect.com/science/article/pii/S1044580318307472}, doi = {https://doi.org/10.1016/j.matchar.2018.05.056}, issn = {1044-5803}, year = {2018}, date = {2018-01-01}, journal = {Materials Characterization}, volume = {142}, pages = {295 - 308}, abstract = {Field emission scanning electron microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) have been employed to investigate the effect of niobium and phase transformation temperature on the evolution of microstructure and texture in a novel thermomechanically processed, medium‑carbon, low-alloy steel intended for slurry pipeline applications. Thermomechanical processing consisted of hot-rolling in the austenitic region with deformation both above the recrystallization limit temperature and below the recrystallization stop temperature. Immediately after rolling, specimens were directly quenched in water to two different temperatures of 560 °C and 420 °C and subsequently furnace cooled from those temperatures to simulate the cooling of coiled strip on a hot strip mill. The microstructure of samples quenched to 560 °C mostly comprised of upper bainite, whereas the samples quenched to 420 °C mainly consisted of lath-type lower bainite. The transformation texture of all samples at the mid-thickness position consisted of α, γ and ε-fibers with high intensities close to the transformed copper, transformed brass and rotated cube components. The addition of 0.013 wt% Nb refined the microstructure and sharpened the texture. The texture of the small fraction of retained austenite present in the final microstructures indicated that the main bcc texture components result from the brass and copper components in the parent austenite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Field emission scanning electron microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) have been employed to investigate the effect of niobium and phase transformation temperature on the evolution of microstructure and texture in a novel thermomechanically processed, medium‑carbon, low-alloy steel intended for slurry pipeline applications. Thermomechanical processing consisted of hot-rolling in the austenitic region with deformation both above the recrystallization limit temperature and below the recrystallization stop temperature. Immediately after rolling, specimens were directly quenched in water to two different temperatures of 560 °C and 420 °C and subsequently furnace cooled from those temperatures to simulate the cooling of coiled strip on a hot strip mill. The microstructure of samples quenched to 560 °C mostly comprised of upper bainite, whereas the samples quenched to 420 °C mainly consisted of lath-type lower bainite. The transformation texture of all samples at the mid-thickness position consisted of α, γ and ε-fibers with high intensities close to the transformed copper, transformed brass and rotated cube components. The addition of 0.013 wt% Nb refined the microstructure and sharpened the texture. The texture of the small fraction of retained austenite present in the final microstructures indicated that the main bcc texture components result from the brass and copper components in the parent austenite. | |
Javaheri, Vahid; Porter, David; Kuokkala, Veli-Tapani Slurry erosion of steel – Review of tests, mechanisms and materials Journal Article Wear, 408–409 , pp. 248 - 273, 2018, ISSN: 0043-1648. @article{Javaheri2018248, title = {Slurry erosion of steel \textendash Review of tests, mechanisms and materials}, author = {Vahid Javaheri and David Porter and Veli-Tapani Kuokkala}, url = {https://www.sciencedirect.com/science/article/pii/S0043164817311262}, doi = {https://doi.org/10.1016/j.wear.2018.05.010}, issn = {0043-1648}, year = {2018}, date = {2018-01-01}, journal = {Wear}, volume = {408\textendash409}, pages = {248 - 273}, abstract = {Abstract Slurry erosion is a severe problem and a major concern for slurry handling equipment, as it leads to considerable expense caused by failures, downtime and material replacement costs. Slurry erosion is dependent on several parameters such as slurry properties, service conditions, and material properties. Hence, much high-quality research has been aimed at obtaining a fundamental understanding of this complex failure mode and developing new test methodologies and erosion resistant materials to minimize erosion rates. This is a review of the literature covering research into the effects of the main parameters influencing the slurry erosion of different types of steels, focusing on those which have been developed for pipeline applications. The types of bench-scale erosion test rigs, the mechanisms involved, and the behavior of different microstructures under slurry erosion conditions are discussed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract Slurry erosion is a severe problem and a major concern for slurry handling equipment, as it leads to considerable expense caused by failures, downtime and material replacement costs. Slurry erosion is dependent on several parameters such as slurry properties, service conditions, and material properties. Hence, much high-quality research has been aimed at obtaining a fundamental understanding of this complex failure mode and developing new test methodologies and erosion resistant materials to minimize erosion rates. This is a review of the literature covering research into the effects of the main parameters influencing the slurry erosion of different types of steels, focusing on those which have been developed for pipeline applications. The types of bench-scale erosion test rigs, the mechanisms involved, and the behavior of different microstructures under slurry erosion conditions are discussed. | |
Kaijalainen, A; Javaheri, V; Lindell, D; Porter, D A Development of crystallographic texture under plane and shear strain in ultrahigh-strength strip steels Journal Article IOP Conference Series: Materials Science and Engineering, 375 (1), pp. 012026, 2018. @article{1757-899X-375-1-012026, title = {Development of crystallographic texture under plane and shear strain in ultrahigh-strength strip steels}, author = {A Kaijalainen and V Javaheri and D Lindell and D A Porter}, url = {http://stacks.iop.org/1757-899X/375/i=1/a=012026}, year = {2018}, date = {2018-01-01}, journal = {IOP Conference Series: Materials Science and Engineering}, volume = {375}, number = {1}, pages = {012026}, abstract = {The effect of centerline and subsurface microstructures on the crystallographic texture of three 8 mm thick low-alloyed hot-rolled and direct-quenched ultrahigh-strength strip steels with yield strengths in the range 800 \textendash 1100 MPa has been investigated. Detailed microstructural features were studied using LCSM, FESEM, FESEM-EBSD. In addition textures and crystallographic features were analyzed using Matlab combined with MTEX software. Rolling to lower finish rolling temperatures increased austenite pancaking leading to the formation of ferritic/granular bainitic and the upper bainitic microstructures at the subsurface. In addition, increased austenite pancaking was found to increase the intensities of ∼554 α , ∼112 α and ∼112 α texture components at the centerline and ∼112 α and ∼110 α / α texture components in the surface layers, especially in upper bainitic microstructures. Parent austenite reconstruction shows that crystallographic texture at the centerline derived from 112 γ and 110 γ and the subsurface the shear texture components derived from the 112 γ and 111 γ components, as expected. The Matlab reconstruction code was found to work well for martensitic and upper bainitic morphologies even with the highly pancaked prior austenite structure. However, it was less precise for granular bainite and ferrite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of centerline and subsurface microstructures on the crystallographic texture of three 8 mm thick low-alloyed hot-rolled and direct-quenched ultrahigh-strength strip steels with yield strengths in the range 800 – 1100 MPa has been investigated. Detailed microstructural features were studied using LCSM, FESEM, FESEM-EBSD. In addition textures and crystallographic features were analyzed using Matlab combined with MTEX software. Rolling to lower finish rolling temperatures increased austenite pancaking leading to the formation of ferritic/granular bainitic and the upper bainitic microstructures at the subsurface. In addition, increased austenite pancaking was found to increase the intensities of ∼554 α , ∼112 α and ∼112 α texture components at the centerline and ∼112 α and ∼110 α / α texture components in the surface layers, especially in upper bainitic microstructures. Parent austenite reconstruction shows that crystallographic texture at the centerline derived from 112 γ and 110 γ and the subsurface the shear texture components derived from the 112 γ and 111 γ components, as expected. The Matlab reconstruction code was found to work well for martensitic and upper bainitic morphologies even with the highly pancaked prior austenite structure. However, it was less precise for granular bainite and ferrite. | |
Sehri, Masoud; Ghayour, Hamid; Amini, Kamran; Naseri, Masaab; Rastegari, Habib; Javaeri, Vahid Effects of cryogenic treatment on microstructure and wear resistance of Fe-0.35 C-6.3 Cr martensitic steel Journal Article Acta Metallurgica Slovaca, 24 (2), pp. 134–146, 2018. @article{sehri2018effects, title = {Effects of cryogenic treatment on microstructure and wear resistance of Fe-0.35 C-6.3 Cr martensitic steel}, author = {Masoud Sehri and Hamid Ghayour and Kamran Amini and Masaab Naseri and Habib Rastegari and Vahid Javaeri}, url = {http://www.qip-journal.eu/index.php/ams/article/view/1037}, doi = {10.12776/ams.v24i2.1037}, year = {2018}, date = {2018-01-01}, journal = {Acta Metallurgica Slovaca}, volume = {24}, number = {2}, pages = {134--146}, abstract = {The study is conducted to determine the effect of quenching and tempering processes on microstructural evolutions and abrasive properties of medium carbon-high chromium steel. For this purpose, Austenitizing was performed at the temperatures of 1000 °C for 15 min followed by oil quenching. To determine the optimum tempering temperature, tempering temperatures were selected in the temperature ranges of 350-600 °C. The samples cryogenically treated immediately after quenching in liquid nitrogen (-196 °C) for 24 hrs. Dry sand/rubber wheel test were used to evaluate the wear resistance properties. Microstructural observation, fractography and retain austeninte was evaluated by optical and scanning electron microscopy and X-ray diffraction analysis. The results show that the best wear resistance can be obtained at the tempering temperature of 500°C, due to the reduction of tendency to micro-cracking, decrease in internal stresses and improvement of impact energy. . Observation of the worn surfaces revealed that the wear mechanisms after tempering at 450°C are combination of abrasive, adhesive and fatigue wear. However, abrasive wear is the only active wear mechanism for specimen tempered at 500 °C. In addition, wear resistance of deep cryogenically treated sample was significantly increased (about 25%) by the removal of retained austenite and formation of uniform fine carbides distribution in the matrix.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The study is conducted to determine the effect of quenching and tempering processes on microstructural evolutions and abrasive properties of medium carbon-high chromium steel. For this purpose, Austenitizing was performed at the temperatures of 1000 °C for 15 min followed by oil quenching. To determine the optimum tempering temperature, tempering temperatures were selected in the temperature ranges of 350-600 °C. The samples cryogenically treated immediately after quenching in liquid nitrogen (-196 °C) for 24 hrs. Dry sand/rubber wheel test were used to evaluate the wear resistance properties. Microstructural observation, fractography and retain austeninte was evaluated by optical and scanning electron microscopy and X-ray diffraction analysis. The results show that the best wear resistance can be obtained at the tempering temperature of 500°C, due to the reduction of tendency to micro-cracking, decrease in internal stresses and improvement of impact energy. . Observation of the worn surfaces revealed that the wear mechanisms after tempering at 450°C are combination of abrasive, adhesive and fatigue wear. However, abrasive wear is the only active wear mechanism for specimen tempered at 500 °C. In addition, wear resistance of deep cryogenically treated sample was significantly increased (about 25%) by the removal of retained austenite and formation of uniform fine carbides distribution in the matrix. | |
2017 |
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Capone, Luigino; Ivanov, Dmitry; Petzold, Thomas; Hömberg, Dietmar Proceedings of Heat Treat 2017, 2017. @conference{capone2017b, title = {A novel integrated tool for parametric geometry generation and simulation for induction hardening of gears}, author = {Luigino Capone and Dmitry Ivanov and Thomas Petzold and Dietmar H\"{o}mberg}, url = {https://asm.confex.com/asm/ht2017/webprogram/Paper43582.html}, year = {2017}, date = {2017-10-25}, booktitle = {Proceedings of Heat Treat 2017}, abstract = {Application of 3D finite element method (FEM) simulation for induction hardening of gears is still a time-consuming and an expensive task. The significant cost of a simulation remains in the manual preparation of the 3D description of geometry. In the current work, we propose to complement the numeric simulations with automatic geometry generation based on a parametric representation of a gear and an induction coil. The parameters used to describe a gear are module, pitch diameter, pressure and helical angles. The circular coil is described by the height, external and internal diameters. FEM computations are implemented in PdeLib environment, solving magneto-quasi-static Maxwell׳s equations. A demonstration of the possibilities of such an approach via a parametric study is presented by varying the module of a gear while keeping a constant pitch diameter. A heuristic tuning of heating power-frequency-time is presented here and compared to the classical semi-analytical equations in use.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } Application of 3D finite element method (FEM) simulation for induction hardening of gears is still a time-consuming and an expensive task. The significant cost of a simulation remains in the manual preparation of the 3D description of geometry. In the current work, we propose to complement the numeric simulations with automatic geometry generation based on a parametric representation of a gear and an induction coil. The parameters used to describe a gear are module, pitch diameter, pressure and helical angles. The circular coil is described by the height, external and internal diameters. FEM computations are implemented in PdeLib environment, solving magneto-quasi-static Maxwell׳s equations. A demonstration of the possibilities of such an approach via a parametric study is presented by varying the module of a gear while keeping a constant pitch diameter. A heuristic tuning of heating power-frequency-time is presented here and compared to the classical semi-analytical equations in use. | |
Das, Prerana; Petzold, Thomas; Asperheim, John Inge; Grande, Bjørnar; Hömberg, Dietmar Proceedings of Heat Treat 2017, 2017. @conference{das2017, title = {Simulation Of Temperature Profile In Longitudinal Welded Tubes During High-Frequency Induction (HFI) Welding}, author = {Prerana Das and Thomas Petzold and John Inge Asperheim and Bj\ornar Grande and Dietmar H\"{o}mberg }, url = {https://asm.confex.com/asm/ht2017/webprogram/Paper43610.html}, year = {2017}, date = {2017-10-24}, booktitle = {Proceedings of Heat Treat 2017}, abstract = {The temperature profile of the Heat Affected Zone (HAZ) during induction welding is one of the most important factors to obtain a good weld quality of High-Frequency Induction (HFI) welded steel tubes. In this work, numerical computation of the 3D temperature profile in the steel tube has been done by coupling the electromagnetic model with the transient thermal model. The current and the magnetic fields in the tube, coil, and impeder have been evaluated. The resulting power from the induced current is used to evaluate the temperature in the joining edges of the tube. The continuous tube movement has been implemented by considering the transient thermal model of the tube. The simulations consider non-linear electromagnetic and thermal properties of the steel when it undergoes temperature rise to the welding temperature. The temperature profile from the resulting simulation gives information to control the subsequent process of joining the edges of the steel tube.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } The temperature profile of the Heat Affected Zone (HAZ) during induction welding is one of the most important factors to obtain a good weld quality of High-Frequency Induction (HFI) welded steel tubes. In this work, numerical computation of the 3D temperature profile in the steel tube has been done by coupling the electromagnetic model with the transient thermal model. The current and the magnetic fields in the tube, coil, and impeder have been evaluated. The resulting power from the induced current is used to evaluate the temperature in the joining edges of the tube. The continuous tube movement has been implemented by considering the transient thermal model of the tube. The simulations consider non-linear electromagnetic and thermal properties of the steel when it undergoes temperature rise to the welding temperature. The temperature profile from the resulting simulation gives information to control the subsequent process of joining the edges of the steel tube. | |
Kolli, Satish Kumar; Ohligschläger, Thomas; Porter, David A Continuous cooling sensitization and its evaluation in austenitic stainless steel EN 1.4310 Conference 9th European Stainless Steel Conference - Science & Market & 5th European Duplex Stainless Steel Conference & Exhibition, Associazione Italiana di Metallurgia, 2017, ISBN: 978-88-98990-12-2. @conference{kolli:2017, title = {Continuous cooling sensitization and its evaluation in austenitic stainless steel EN 1.4310}, author = {Satish Kumar Kolli and Thomas Ohligschl\"{a}ger and David A. Porter}, url = {http://urn.fi/urn:nbn:fi-fe201706197363}, isbn = {978-88-98990-12-2}, year = {2017}, date = {2017-06-19}, booktitle = {9th European Stainless Steel Conference - Science & Market & 5th European Duplex Stainless Steel Conference & Exhibition}, pages = {1-6}, publisher = {Associazione Italiana di Metallurgia}, abstract = {Sensitization in stainless steels is caused by chromium delpleted zones near grain boundaries which can lead to intergranular corrosion and intergranular stress corrosion cracking in service. A lot of work has been done in the past to understand sensitization behaviour under isothermal conditions. However, this study aims at studying the sensitization behaviour in continuous cooling, which is of more practical importance in steel production and in heat treatments such as welding. Conditions for sensitization were determined using experiments (Double-loop Electrochemical Potentiokinetic Reactivation tests (DL-EPR) and compared with DICTRA simulations. Using these conditions a continuous cooling sensitization (CCS) diagram is determined for EN 1.4310 (301) austentic stainless steel. DICTRA is a CALPHAD based simulation software used for diffusion related studies in multicomponent alloys. Solvus temperature for M23C6 is determined 959°C.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } Sensitization in stainless steels is caused by chromium delpleted zones near grain boundaries which can lead to intergranular corrosion and intergranular stress corrosion cracking in service. A lot of work has been done in the past to understand sensitization behaviour under isothermal conditions. However, this study aims at studying the sensitization behaviour in continuous cooling, which is of more practical importance in steel production and in heat treatments such as welding. Conditions for sensitization were determined using experiments (Double-loop Electrochemical Potentiokinetic Reactivation tests (DL-EPR) and compared with DICTRA simulations. Using these conditions a continuous cooling sensitization (CCS) diagram is determined for EN 1.4310 (301) austentic stainless steel. DICTRA is a CALPHAD based simulation software used for diffusion related studies in multicomponent alloys. Solvus temperature for M23C6 is determined 959°C. | |
Wilbrandt, Ulrich; Bartsch, Clemens; Ahmed, Naveed; Alia, Najib; Anker, Felix; Blank, Laura; Caiazzo, Alfonso; Ganesan, Sashikumaar; Giere, Swetlana; Matthies, Gunar; Meesala, Raviteja; Shamim, Abdus; Venkatesan, Jagannath; John, Volker ParMooN—A modernized program package based on mapped finite elements Journal Article Computers & Mathematics with Applications, 74 (1), pp. 74-88, 2017, ISSN: 0898-1221. @article{Wilbrandt2017, title = {ParMooN\textemdashA modernized program package based on mapped finite elements}, author = {Ulrich Wilbrandt and Clemens Bartsch and Naveed Ahmed and Najib Alia and Felix Anker and Laura Blank and Alfonso Caiazzo and Sashikumaar Ganesan and Swetlana Giere and Gunar Matthies and Raviteja Meesala and Abdus Shamim and Jagannath Venkatesan and Volker John}, url = {https://arxiv.org/abs/1705.08784}, doi = {10.1016/j.camwa.2016.12.020}, issn = {0898-1221}, year = {2017}, date = {2017-01-16}, journal = {Computers & Mathematics with Applications}, volume = {74}, number = {1}, pages = {74-88}, abstract = {Abstract ParMooN is a program package for the numerical solution of elliptic and parabolic partial differential equations. It inherits the distinct features of its predecessor MooNMD (John and Matthies, 2004): strict decoupling of geometry and finite element spaces, implementation of mapped finite elements as their definition can be found in textbooks, and a geometric multigrid preconditioner with the option to use different finite element spaces on different levels of the multigrid hierarchy. After having presented some thoughts about in-house research codes, this paper focuses on aspects of the parallelization for a distributed memory environment, which is the main novelty of ParMooN. Numerical studies, performed on compute servers, assess the efficiency of the parallelized geometric multigrid preconditioner in comparison with some parallel solvers that are available in the library PETSc. The results of these studies give a first indication whether the cumbersome implementation of the parallelized geometric multigrid method was worthwhile or not.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract ParMooN is a program package for the numerical solution of elliptic and parabolic partial differential equations. It inherits the distinct features of its predecessor MooNMD (John and Matthies, 2004): strict decoupling of geometry and finite element spaces, implementation of mapped finite elements as their definition can be found in textbooks, and a geometric multigrid preconditioner with the option to use different finite element spaces on different levels of the multigrid hierarchy. After having presented some thoughts about in-house research codes, this paper focuses on aspects of the parallelization for a distributed memory environment, which is the main novelty of ParMooN. Numerical studies, performed on compute servers, assess the efficiency of the parallelized geometric multigrid preconditioner in comparison with some parallel solvers that are available in the library PETSc. The results of these studies give a first indication whether the cumbersome implementation of the parallelized geometric multigrid method was worthwhile or not. | |
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Arenas, Manuel J; Hömberg, Dietmar; Lasarzik, Robert; Mikkonen, Pertti; Petzold, Thomas Modelling and simulation of flame cutting for steel plates with solid phases and melting Journal Article Journal of Mathematics in Industry, 10 (1), pp. 18, 0000, ISBN: 2190-5983. @article{manuel, title = {Modelling and simulation of flame cutting for steel plates with solid phases and melting}, author = {Manuel J Arenas and Dietmar H\"{o}mberg and Robert Lasarzik and Pertti Mikkonen and Thomas Petzold}, url = {https://doi.org/10.1186/s13362-020-00086-0}, doi = {10.1186/s13362-020-00086-0}, isbn = {2190-5983}, journal = {Journal of Mathematics in Industry}, volume = {10}, number = {1}, pages = {18}, keywords = {}, pubstate = {published}, tppubtype = {article} } | |
Publications
2021 |
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Optimal control of buoyancy-driven liquid steel stirring modeled with single-phase Navier--Stokes equations Journal Article Journal of Mathematics in Industry, 11 (1), pp. 10, 2021, ISBN: 2190-5983. | |
2020 |
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Modelling and simulation of flame cutting for steel plates with solid phases and melting Journal Article Journal of Mathematics in Industry, 10 (18), 2020. | |
2019 |
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Numerical study of multiphase flows in a ladle for different closure models Conference Proceedings of the 11th Pacific Symposium on Flow Visualization and Image Processing , http://jultika.oulu.fi/Record/nbnfi-fe2019082225151, 2019. | |
Comparison between experimental data and a cellular automata simulation of martensite formation during cooling Journal Article Journal of Physics: Conference Series, 1270 , pp. 012035, 2019. | |
Induction Hardening of a 0.40 % C Novel Microalloyed Steel: Effects of Heating Rate on the Prior Austenite Grain Size Inproceedings THERMEC 2018, pp. 64–70, Trans Tech Publications, 2019. | |
Insight into the induction hardening behavior of a new 0.40% C microalloyed steel: Effects of initial microstructure and thermal cycles Journal Article Materials Characterization, 149 , pp. 165 - 183, 2019, ISSN: 1044-5803. | |
Modeling of the Effect of the Gas Flow Rate on the Fluid Flow and Open-Eye Formation in a Water Model of a Steelmaking Ladle Journal Article steel research international, 90 (2), pp. 1800365, 2019. | |
Physical and CFD Modeling of the Effect of Top Layer Properties on the Formation of Open-Eye in Gas-Stirred Ladles With Single and Dual-Plugs Journal Article steel research international, 90 (8), pp. 1900088, 2019. | |
Numerical Modeling of Open-Eye Formation and Mixing Time in Argon Stirred Industrial Ladle Journal Article Metals, 9 (8), 2019, ISSN: 2075-4701. | |
Numerical Modelling of the Influence of Argon Flow Rate and Slag Layer Height on Open-Eye Formation in a 150 Ton Steelmaking Ladle Journal Article Metals, 9 (10), 2019, ISSN: 2075-4701. | |
Physically based modeling, characterization and design of an induction hardening process for a new slurry pipeline steel Journal Article Materials & Design, 182 , pp. 108047, 2019, ISSN: 0264-1275. | |
Quantitative Prediction of Sensitization in Austenitic Stainless Steel Accounting for Multicomponent Thermodynamic and Mass Balance Effects Journal Article ISIJ International, 59 (7), pp. 1330-1336, 2019. | |
Sensitization and Self-healing in Austenitic Stainless Steel: Quantitative Prediction Considering Carbide Nucleation and Growth Journal Article ISIJ International, advpub , 2019. | |
Study of Intergranular Corrosion in Austenitic Stainless Steels Using Electrochemical Impedance Spectroscopy Journal Article International Journal of Materials and Metallurgical Engineering, 13 (4), pp. 165 - 168, 2019, ISSN: eISSN: 1307-6892. | |
Revisiting the single-phase flow model for liquid steel ladle stirred by gas Journal Article 67 , pp. 549 - 556, 2019, ISSN: 0307-904X. | |
Vibrations of a laboratory-scale gas-stirred ladle with two eccentric nozzles and multiple sensors Journal Article Journal of Iron and Steel Research International, 26 (10), pp. 1031–1040, 2019, ISSN: 2210-3988. | |
The Effect of Hot-Mounting on the Microstructure of an As-Quenched Auto-Tempered Low-Carbon Martensitic Steel Journal Article Metals, 9 (5), 2019, ISSN: 2075-4701. | |
Observations on the Relationship between Crystal Orientation and the Level of Auto-Tempering in an As-Quenched Martensitic Steel Journal Article Metals, 9 (12), 2019, ISSN: 2075-4701. | |
On the Role of Grain Size and Carbon Content on the Sensitization and Desensitization Behavior of 301 Austenitic Stainless Steel Journal Article Metals, 9 (11), 2019, ISSN: 2075-4701. | |
2018 |
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Lau, T C W; Kelso, R M (Ed.): Proceedings of the 21st Australasian Fluid Mechanics Conference, Australasian Fluid Mechanics Society Australasian Fluid Mechanics Society, Adelaide, SA 5005, AUSTRALIA, 2018, ISBN: 978-0-646-59784-3. | |
Insight to the Microstructure Characterization of a HP Austenitic Heat Resistant Steel after Long-term Service Exposure Journal Article Acta Metallurgica Slovaca, 24 (4), pp. 296-305, 2018. | |
Influence of Microsegregation on the Onset of the Martensitic Transformation Journal Article ISIJ International, Advance online publication , 2018. | |
A CFD and Experimental Investigation of Slag Eye in Gas Stirred Ladle Inproceedings Proceedings of the 5th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'18), June 7--9 , 2018, pp. 148-1–148–10, Niagara Falls, Canada, 2018. | |
Computational Design of a Novel Medium-Carbon, Low-Alloy Steel Microalloyed with Niobium Journal Article Journal of Materials Engineering and Performance, 2018, ISSN: 1544-1024. | |
On the Role of Nb on the Texture and Microstructure of a Novel As-Rolled Medium Carbon Wear Resistant Slurry Pipeline Steel Inproceedings Hwang, Jiann-Yang; Jiang, Tao; Kennedy, Mark William; Gregurek, Dean; Wang, Shijie; Zhao, Baojun; Yücel, Onuralp; Keskinkilic, Ender; Downey, Jerome P; Peng, Zhiwei; Padilla, Rafael (Ed.): 9th International Symposium on High-Temperature Metallurgical Processing. TMS 2018. The Minerals, Metals & Materials Series., pp. 365–379, Springer International Publishing, Cham, 2018, ISBN: 978-3-319-72138-5. | |
Effect of niobium and phase transformation temperature on the microstructure and texture of a novel 0.40% C thermomechanically processed steel Journal Article Materials Characterization, 142 , pp. 295 - 308, 2018, ISSN: 1044-5803. | |
Slurry erosion of steel – Review of tests, mechanisms and materials Journal Article Wear, 408–409 , pp. 248 - 273, 2018, ISSN: 0043-1648. | |
Development of crystallographic texture under plane and shear strain in ultrahigh-strength strip steels Journal Article IOP Conference Series: Materials Science and Engineering, 375 (1), pp. 012026, 2018. | |
Effects of cryogenic treatment on microstructure and wear resistance of Fe-0.35 C-6.3 Cr martensitic steel Journal Article Acta Metallurgica Slovaca, 24 (2), pp. 134–146, 2018. | |
2017 |
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Proceedings of Heat Treat 2017, 2017. | |
Proceedings of Heat Treat 2017, 2017. | |
Continuous cooling sensitization and its evaluation in austenitic stainless steel EN 1.4310 Conference 9th European Stainless Steel Conference - Science & Market & 5th European Duplex Stainless Steel Conference & Exhibition, Associazione Italiana di Metallurgia, 2017, ISBN: 978-88-98990-12-2. | |
ParMooN—A modernized program package based on mapped finite elements Journal Article Computers & Mathematics with Applications, 74 (1), pp. 74-88, 2017, ISSN: 0898-1221. | |
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Modelling and simulation of flame cutting for steel plates with solid phases and melting Journal Article Journal of Mathematics in Industry, 10 (1), pp. 18, 0000, ISBN: 2190-5983. | |