Roles of nanoscale precipitates and metastable austenite in determining strength and toughness of high-strength Nb-bearing steel  

作　　者：Qi-bin Ye Cheng Zhou Jun Hu Xiao-lan Gong Yong Tian Xiu-hua Gao Zhao-dong Wang 

机构地区：[1]State Key Laboratory of Rolling and Automation,Northeastern University,Shenyang,110819,Liaoning,China

出　　处：《Journal of Iron and Steel Research International》2022年第10期1646-1658,共13页

基　　金：The authors gratefully acknowledge financial support by the National Key R&D Program of China(Grant No.2017YFB0305300);the Joint Fund project of the Ministry of Education for Equipment Pre-research(6141A020222).

摘　　要：The effects of tempering temperature on the microstructure and mechanical properties of high-strength structural steel containing niobium were investigated to examine the roles of nanoscale precipitates and metastable austenite in determining the yield strength and toughness.After hot-rolling and quenching,three experimental steels were tempered at 590,630,and 670℃.During tempering,nanoscale Nb(C,N)precipitates were formed with the recovery of quenched martensite.The average diameters of Nb(C,N)precipitates increased from 5.4 to 8.2 nm as the tempering temperature was increased.Notably,reversed austenite with a volume fraction of 9%was formed at tempering temperatures up to 670℃.The yield strengths of steel containing tempered martensite tempered at 590 and 630℃ were 965 and 831 MPa,and the tensile strengths were 998 and 879 MPa,respectively.However,the steel comprising reversed austenite and tempered martensite tempered at 670℃ showed continuous yielding behavior,affording yield and tensile strengths of 610 and 889 MPa,respectively.The impact energy increased from 105 to 260 J at−60℃ with increasing tempering temperature.Reversed austenite improves low-temperature toughness by significantly increasing the crack propagation energy.

关 键 词：High-strength structural steel TEMPERING Nanoscale precipitate Metastable austenite Mechanical property 

分 类 号：TG142[一般工业技术—材料科学与工程]