	US 11,655,512 B2
	Rare-earth microalloyed steel and control method
Dianzhong Li, Liaoning (CN); Yikun Luan, Liaoning (CN); Pei Wang, Liaoning (CN); Xiaoqiang Hu, Liaoning (CN); Paixian Fu, Liaoning (CN); Hongwei Liu, Liaoning (CN); Lijun Xia, Liaoning (CN); Chaoyun Yang, Liaoning (CN); Hanghang Liu, Liaoning (CN); Hang Liu, Liaoning (CN); and Yiyi Li, Liaoning (CN)
Assigned to INSTITUTE OF METAL RESEARCH CHINESE ACADEMY OF SCIENCES, Shenyang (CN)
Appl. No. 17/641,732
Filed by INSTITUTE OF METAL RESEARCH CHINESE ACADEMY OF SCIENCES, Liaoning (CN)
PCT Filed Sep. 29, 2019, PCT No. PCT/CN2019/108857 § 371(c)(1), (2) Date Mar. 9, 2022, PCT Pub. No. WO2021/046937, PCT Pub. Date Mar. 18, 2021.
Claims priority of application No. 201910854347.5 (CN), filed on Sep. 10, 2019.
Prior Publication US 2022/0307097 A1, Sep. 29, 2022
Int. Cl. C21C 7/00 (2006.01); C21C 7/10 (2006.01); C22C 33/04 (2006.01); C22C 38/06 (2006.01); C22C 38/04 (2006.01); C22C 38/02 (2006.01); C22C 38/00 (2006.01)

CPC C21C 7/0006 (2013.01) [C21C 7/10 (2013.01); C22C 33/04 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01)]

20 Claims

1. A rare-earth microalloyed steel, wherein the steel has a microstructure comprising rare earth-rich nanoclusters with diameters of 1-50 nm, the rare earth-rich nanoclusters having the same crystal structure type as a matrix are nano-scale particle groups formed by an aggregation of several to hundreds of rare earth atoms, and the diameters of the rare earth-rich nanoclusters are directly proportional to a residual amount T_REof rare earth elements in the steel, but inversely proportional to a total oxygen content in the steel;

wherein the rare-earth microalloyed steel is prepared by a process comprising:

controlling a total oxygen content T_[O]mof molten steel to be within 50 ppm, T_[S]≤50 ppm, where T_[S]is a total sulphur content in the steel;

controlling a total oxygen content of a rare earth metal added in the molten steel to be less than 60 ppm;

controlling a temperature of the molten steel to exceed its liquidus line T_m+(20-100)° C. when adding the rare earth metal; and

controlling a deep vacuum cycle time after the addition of the rare earth metal to be more than 10 min and an Ar gas soft blowing time to be more than 15 min.