A new step-cooling process for strength and toughness matching control of vanadium-containing railway wheels:effect of intragranular ferrite  

作　　者：YAO Sancheng LIU Xuehua ZHAO Hai JIANG Bo CHEN Gang XU Kang 

机构地区：[1]Technology Center,Ma’anshan Iron and Steel Co.,Ltd.,Ma’anshan 243003,China [2]Technology Center,Baowu Group Masteel Rail Transit Materials Technology Co.,Ltd.,Ma’anshan 243003,China

出　　处：《Baosteel Technical Research》2023年第3期40-48,共9页宝钢技术研究（英文版）

摘　　要：To improve the competitive relationship between strength and toughness,the effect of low undercooling in austenite(γ)on the microstructure and mechanical properties of commercial vanadium-containing wheel steels was studied using an optical microscope(OM),a scanning electron microscope(SEM),a transmission electron microscope(TEM),and mechanical property tests.The results show that when the wheel steel is slightly cooled to an appropriate temperature above A c3 point for a short time after it has been austenitized at an elevated temperature,the solid-solved vanadium is pre-precipitated in the form of V(C,N)second phase semicoherent with the matrix in the originalγgrain.This phase hardly participates in matrix strengthening.Due to the small mismatch between V(C,N)and ferrite(α),during the subsequent-cooling phase transformation stage,the pre-precipitated second phase becomes theαnucleation point,causing granular and ellipsoidal intragranular ferrite(IGF,with an average size of 4-6μm)to nucleate in the originalγ.The IGF production and strength loss increases with the increasing undercooling degree.Based on this,Masteel Co.,Ltd.has developed a new heat-treatment step-cooling process that can promote the formation of IGF,considerably improving the level and uniformity of fracture toughness on the premise that the strength and hardness of the wheel are almost unchanged.

关 键 词：vanadium microalloyed railway wheel strength and toughness match low undercooling in austenite intragranular ferrite second phase step-cooling process 

分 类 号：U270.33[机械工程—车辆工程] TG142.1[交通运输工程—载运工具运用工程]