冷却工艺对高性能桥梁钢微观组织和力学性能的影响  

Effect of cooling process on microstructure and mechanical properties of high performance bridge steel

作　　者：余宏伟 胡锋 董中波 吴开明 卜勇 王孝东 YU Hong-wei;HU Feng;DONG Zhong-bo;WU Kai-ming;BU Yong;WANG Xiao-dong(The State Key Laboratory of Refractories and Metallurgy,Wuhan University of Science and Technology,Wuhan 430080,China;Echeng Iron and Steel Co Ltd of Baowu Group,Ezhou 436002,China;R&D Center of Baosteel,Wuhan 430080,China)

机构地区：[1]武汉科技大学耐火材料与冶金省部共建国家重点实验室,湖北武汉430080 [2]宝武集团鄂城钢铁有限公司,湖北鄂州436002 [3]宝钢股份中央研究院,湖北武汉430080

出　　处：《材料热处理学报》2022年第10期79-90,共12页Transactions of Materials and Heat Treatment

基　　金：国家自然科学基金(U20A20279);高等学校学科创新引智计划资助项目(111计划)。

摘　　要：利用光学显微镜、扫描电镜(SEM)、透射电镜(TEM)、能谱仪(EDS)和拉伸及冲击试验等研究了冷却速率对高强度桥梁钢微观组织、第二相形貌及力学性能的影响。结果表明:随着冷却速率的增加(1~50℃/s),试验钢的组织由块状铁素体+珠光体向粒状贝氏体、板条贝氏体转变,但均有M/A岛弥散分布于铁素体基体或边界上。当冷却速率大于5℃/s时,随着冷却速率的增加,贝氏体铁素体晶粒细化,M/A岛数量减少、尺寸细化,并更加弥散分布。组织中大角度晶界占比随着冷却速率的增加呈现先减少、后增加的变化。当冷却速率为1℃/s时,在铁素体+珠光体组织中,大量块状铁素体具有大角度取向差;在形成贝氏体组织的10~50℃/s冷却速率范围内,冷却速率的增加促进了大角度晶界(取向差角度>15°)的形成。冷却速率的增加,阻碍了Nb、Ti的碳氮化物析出,晶内析出相的形貌由粒状或不规则块状转变为细小针状和球形状。冷却速率在1~30℃/s的范围内增加时,试验钢的屈服强度和抗拉强度上升,伸长率下降,冲击吸收能量先上升后下降。Effect of cooling rate on microstructure,second phase morphology and mechanical properties of high strength bridge steel was studied by means of optical microscope,scanning electron microscopy,transmission electron microscopy,energy dispersive spectroscopy analysis and tensile and impact test.The results show that with the increase of cooling rate(1-50℃/s),the microstructure of the experimental steel changes from massive ferrite+pearlite to granular bainite and lath bainite,and M/A islands are dispersed on the ferrite matrix or boundary.When the cooling rate is greater than 5℃/s,with the increase of cooling rate,the bainite ferrite grain is refined,and the number of M/A islands is reduced,its size is refined and more dispersed.With the increase of cooling rate,the proportion of large angle grain boundary decreases first and then increases.When the cooling rate is 1℃/s,a large number of massive ferrite has large angle orientation in ferrite+pearlite structure.In the cooling rate range of 10-50℃/s for the formation of bainite structure,the increase of cooling rate promotes the formation of large angle grain boundaries(orientation difference angle>15°).The increase of cooling rate hinders the precipitation of carbonitride of Nb and Ti,and the morphology of precipitated phase in the grains changes from granular or irregular block to fine needle and ball shape.When the cooling rate increases in the range of 1-30℃/s,the yield strength and tensile strength of the experimental steel increase,the elongation decreases,and the impact absorption energy first increases and then decreases.

关 键 词：高强度桥梁钢 冷却速率 微观组织 析出相 柔性轧制工艺 

分 类 号：TG142.3[一般工业技术—材料科学与工程]