US 12,084,737 B2
Gradient-structured ultra-fine bainitic low-alloy rail steel and preparation method thereof
Zhinan Yang, Qinhuangdao (CN); Fucheng Zhang, Qinhuangdao (CN); Jianjun Wang, Qinhuangdao (CN); Hongguang Li, Qinhuangdao (CN); Zhuanqin Liang, Qinhuangdao (CN); Qingchao Wang, Qinhuangdao (CN); Changbo Liu, Qinhuangdao (CN); Dongyun Sun, Qinhuangdao (CN); Xinliang Gao, Qinhuangdao (CN); and Chen Chen, Qinhuangdao (CN)
Assigned to YANSHAN UNIVERSITY, Qinhuangdao (CN)
Filed by Yanshan University, Qinhuangdao (CN)
Filed on Sep. 20, 2023, as Appl. No. 18/471,144.
Claims priority of application No. 202211692832.5 (CN), filed on Dec. 28, 2022.
Prior Publication US 2024/0218478 A1, Jul. 4, 2024
Int. Cl. C21D 9/04 (2006.01); C21D 1/84 (2006.01); C21D 6/00 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01)
CPC C21D 9/04 (2013.01) [C21D 1/84 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/009 (2013.01)] 5 Claims
 
1. A preparation method of the gradient-structured ultra-bainitic rail steel, comprising following steps:
(1) carrying out a first thermal processing treatment on a rail steel to be treated, and making the rail steel to be treated obtain a dual-phase microstructure of ferrite-pearlite;
(2) carrying out a second thermal processing treatment on the rail steel to be treated with the dual-phase microstructure of ferrite-pearlite obtained in the step (1), enabling an bainite microstructure to be developed on a working surface side of the rail steel to be treated with the dual-phase microstructure of ferrite-pearlite, and the rail steel integrally forming a gradient structure transitioning from bainite to ferrite-pearlite; and
(3) carrying out a third thermal processing treatment on the rail steel to be treated with the gradient structure transitioning from bainite to ferrite-pearlite formed in step (2), so as to stabilize the gradient structure of the rail steel to be treated, then obtaining the gradient-structured bainitic rail steel;
wherein the step (2) specifically comprises following steps:
rapidly heating a working side surface of the rail steel to be treated with the dual-phase microstructure of ferrite-pearlite obtained in the step (1), followed by temperature holding, and cooling the rail steel to be treated to a fourth preset temperature at a third cooling speed, then performing second temperature holding or second slow cooling to develop the bainite microstructure in a region of rapid heating layer of the rail steel to be treated;
the third cooling speed is 0.6° C./s-20° C./s, the fourth preset temperature is Ms−20° C.-Ms+50° C., Ms is an onset temperature of martensitic transformation of the rail steel; and a speed of the second slow cooling is 0.005° C./s-0.2° C./s; and
a heating speed of the rapid heating is 5° C./s-200° C./s; a duration for the temperature holding is 1 s-10 min; the working side surface of the rail steel to be treated covers a depth of 0.5 mm-50 mm below a surface of the rail steel.