Hot Deformability of Si-Steel Strips Containing Al

Authors: Mohamed Yousef, Magdy Samuel, Maha El-Meligy, Taher El-Bitar

Abstract:

The present work is dealing with 2% Si-steel alloy. The alloy contains 0.05% C as well as 0.85% Al. The alloy under investigation would be used for electrical transformation purposes. A heating (expansion) - cooling (contraction) dilation investigation was executed to detect the a, a+g, and g transformation temperatures at the inflection points of the dilation curve. On heating, primary a  was detected at a temperature range between room temperature and 687 ^oC. The domain of a+g was detected in the range between 687 ^oC and 746 ^oC. g phase exists in the closed g region at the range between 746 ^oC and 1043 ^oC. The domain of a phase appears again at a temperature range between 1043 and 1105 ^oC, and followed by secondary a at temperature higher than 1105 ^oC. A physical simulation of thermo-mechanical processing on the as-cast alloy was carried out. The simulation process took into consideration the hot flat rolling pilot plant parameters. The process was executed on the thermo-mechanical simulator (Gleeble 3500). The process was designed to include seven consecutive passes. The 1^st pass represents the roughing stage, while the remaining six passes represent finish rolling stage. The whole process was executed at the temperature range from 1100 ^oC to 900 ^oC. The amount of strain starts with 23.5% at the roughing pass and decreases continuously to reach 7.5 % at the last finishing pass. The flow curve of the alloy can be abstracted from the stress-strain curves representing simulated passes. It shows alloy hardening from a pass to the other up to pass no. 6, as a result of decreasing the deformation temperature and increasing of cumulative strain. After pass no. 6, the deformation process enhances the dynamic recrystallization phenomena to appear, where the z-parameter would be high.

Keywords: Si-steel, hot deformability, critical transformation temperature, physical simulation, thermo-mechanical processing, flow curve, dynamic softening.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1132409

References:

[1] P. Ghosh, R. R. Chromik, A. M. Knight and S. G. Wakade, "Effect of metallurgical factors on the bulk magnetic properties of non-oriented electrical steels," Journal of Magnetism and Magnetic Materials, vol. 356, pp. 42-51, 2014.
[2] H. T. Liu, H. Z. Lia, H. L. Lib, F. Gaoa, G. H. Liua, Z. H. Luo, F. Q. Zhangc, S. L. Chenc, G. M. Cao, S. L. Chenc, G. M. Caoa, Z. Y. Liua and G. D. Wanga, "Effects of rolling temperature on microstructure, texture, formability and magnetic properties in strip casting Fe-6.5 wt% Si non-oriented electrical steel," Journal of Magnetism and Magnetic Materials, vol. 391, pp. 65-74, 2015.
[3] I. Bogdanov, S. Kozub, P. Shcherbakov, L. Tkachenk, E. Fischer, F. Klos, G. Moritz and C. Muehle, "Study of Electrical Steel Magnetic Properties for Fast Cycling Magnets of SIS100 and SIS300 Rings," in The ninth European Particle Accelerator Conference, EPAC2004, Lucerne, Switzerland, 2004.
[4] J. Barrosa, T. Ros-Yannez, L. Vandenbossche, L. Dupre, J. Melkebeek and Y. Houbaert, "The effect of Si and Al concentration gradients on the mechanical and magnetic properties of electrical steel," Journal of Magnetism and Magnetic Materials, vol. 290–291, p. 1457–1460, 2005.
[5] G. Y. Chin and J. H. Wernick, "Soft Magnetic Metallic Materials," in Handbook of Magnetic Materials, UK, Elsevier, 2014, pp. Volume 23, Pages 1-426 (2015).
[6] T. Nakayama and N. Honjou, "Effect of aluminum and nitrogen on the magnetic properties of non-oriented semi-processed electrical steel sheet," Journal of Magnetism and Magnetic Materials, vol. 213, pp. 87-94, 2000.
[7] J. J. Sidora, K. Verbeken, E. Gomes, J. Schneider, P. R. Calvillo and L. A. Kestens, "Through process texture evolution and magnetic properties of high Si non-oriented electrical steels," Material Characterization, vol. 71, pp. 49-57, 2012.
[8] E. Gomes, J. Schneider, K. Verbeken, H. Hermann and Y. Houbaert, "Effect of hot and cold rolling on grain size and texture in Fe–Si strips with Si-content larger than 2 wt.%," Mater Sci Forum, Vols. 638-642, pp. 3561-6, 2010.
[9] J. Hunady, M. Cernik, E. J. Hilinski, M. Predmersky and A. Magurova, "Influence of Chemistry and Hot Rolling Conditions on High Permeability Non-Grain Oriented Silicon Steel.," Journal of Metals, Materials and Minerals, vol. 12, no. 2, pp. 17-23, 2005.
[10] K. Friedrich, B. Hammer, R. Kawalla and H. Pircher, "Non-textured Electrical Steel Sheet, Useful For Cores In Rotary Electrical Machines Such As Motors And Generators, Is Produced By Multi-pass Hot Rolling Mainly In The Two-phase Austenite-ferrite Region". German Patent DE 19930519, 2000.
[11] H. McQueen and N. D. Ryan, "Constitutive analysis in hot working," Materials Science & Engineering A, vol. 322, pp. 43-63, 2002.
[12] J. Kang and S. Torizuka, "Dynamic recrystallization by large strain deformation with a high strain rate in an ultralow carbon steel," Scripta Materialia, vol. 57, no. 11, pp. 1048-51, 2007.
[13] S. Medina and C. A. Hernandez, "General expression of the Zener-Hollomon parameter as a function of the chemical composition of low alloy and microalloyed steels," Acta Materialia, vol. 44, no. 1, pp. 137-148, 1996.
[14] T. El-Bitar, M. El-meligy and E. El-Shenawy, "Detection of dynamic softening during hot deformation of medium Si-steels by a thermo- mechanical simulator (Gleeble 3500)," International Journal of Mechanical and Production Engineering Research and Development, vol. 5, pp. 65-74, Dec,2015.
[15] T. El-Bitar, M. El-meligy and E. El-Shenawy, "Physical simulation for hot rolling policy of electrical Si-steels," International Journal of Mechanical and Production Engineering Research and Development, vol. 7, pp. 221-230., 2017.