Microstructure refinement of structural Steel in China

TLDR: In this paper, the progress of on-going project has been briefly reported in Oct. 1998 Chinese government opened national program: Fundamental Research on New Generation of Iron and Steel Materials in China (N.G. Steels).

Abstract: In Oct. 1998 Chinese government opened national program: Fundamental Research on New Generation of Iron and Steel Materials in China (N.G. Steels). The progress of on-going project has been briefly reported in this paper. In order to get microstructure refinement in structural steels, the following 5 ways have been studied: For Ferrite+Pearlite microstructure in plain carbon steels and low-alloy steels, (1) Purified steel-making→Fully equiaxed continuous casting→Rough-mill with higher Zener-Hollman parameter (y-DRX refinement)→Finishing-mill rolling by Deformation Induce Ferrite Transformation (DIFT) technology. (2) For thin-slab continuous casting and rolling (CSP) process, ultra-fine sulfides (20-60 nm) and oxides (5∼20nm) controlling technology. (3) For Low Carbon Bainite (and Ultra Low Carbon Bainite) microstructure (LCB/ULCB) in microalloyed steels, combination of Deformation Induced Precipitation (DIP) and subsequent middle temperature phase transformation controlling. For quench-temperated martensite microstructure in alloy structural steels: (4) Ultra-fine y grains by innovated heat treatment and alloy design; (5) Carbide-free bainite/martensite microstructure with retained y films along lath/sub-lath boundaries.