The Work Softening by Deformation-Induced Disordering and Cold Rolling of 6.5 wt pct Si Steel Thin Sheets
- PDF / 3,258,905 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 4 Downloads / 191 Views
UCTION
6.5 wt pct Si steel, because of its excellent soft magnetic properties such as high electrical resistance, high permeability, and almost zero magnetostriction,[1,2] is the ideal core material for high frequency motors, generators, and transformers. However, high Si content can result in the formation of B2 (FeSi)- and DO3 (Fe3Si)-ordered phases, making it extremely hard and brittle at room temperature.[3,4] It is well accepted that rapid cooling from the disordered region (A2) may decrease the order degree and improve its room temperature ductility.[5–8] However, high thermal stress induced by rapid cooling can seriously deteriorate the shape and flatness of thin sheets.[9,10] It has been pointed out that the ordering degree of 6.5 wt pct Si steel can be reduced by warm compressions at 673 K and 823 K (400 C and 550 C).[11,12] But the relationship between ordering degrees and warm XIANGLONG WANG, HAOZE LI, and WEINA ZHANG, Ph.D. Students, and ZHENYU LIU and GUODONG WANG, Professors, are with State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, PR China. ZHONGHAN LUO and FENGQUAN ZHANG, Ministers, are with National Engineering Research Center for Silicon Steel, Wuhan Iron & Steel (Group) Corp, Wuhan 430083, PR China. Manuscript submitted November 11, 2015. Article published online June 29, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
deformation reductions has not been established. As compared to the deformation at intermediate temperatures, the deformation at relatively low temperatures can avoid the reordering phenomenon, and lead to better flatness, surface quality, and magnetic properties. Unfortunately, no work of warm rolling at relatively low temperatures has been carried out so far. The relationship between room temperature ductility and warm rolling reductions still remains unknown. Therefore, it is still not clear how to optimize the warm rolling process, let alone the subsequent cold rolling process. Twin-roll strip casting is a typical ‘‘near net shape forming’’ technology, which can produce as-cast strips with the thickness from one to several millimeters. Our previous work demonstrated that strip casting is a feasible way for the fabrication of 6.5 wt pct Si steel thin sheets,[13,14] because the substantially reduced rolling deformation can effectively avoid the hot rolled cracks. High cooling rate (103–104 K/s) during the strip casting can effectively suppress the formation of ordered phases to improve its room temperature ductility.[13] Also, the melt superheat can be optimized to refine the solidification structure, making the followed warm rolling more easily performed at relatively low temperatures.[15–18] In the present work, warm rolling at 373 K (100 C) was carried out to fabricate the thin sheets with cast strips of the 6.5 wt pct Si steel. The influence of rolling reductions on their room temperature ductilities was VOLUME 47A, SEPTEMBER 2016—4659
investigated, and the mechanisms of deformation-induced disordering (DID) were analyzed in detail. On
Data Loading...
