回火温度对两相区退火海工钢组织和性能的影响  

Effect of Tempering Temperature on Microstructure and Properties of Intercritical Annealing Marine Steel

作　　者：张翔云 李激光[1] 严玲 何煦泽 郭菁[1] ZHANG Xiangyun;LI Jiguang;YAN Ling;HE Xuze;GUO Jing(School of Materials and Metallurgy,University of Science and Technology Liaoning,Anshan 114051,China;State Key Laboratory of Metal Materials for Marine Equipment and Applications,Anshan 114009,China)

机构地区：[1]辽宁科技大学材料与冶金学院,鞍山114051 [2]海洋装备用金属材料及其应用国家重点实验室,鞍山114009

出　　处：《材料研究学报》2020年第11期845-852,共8页Chinese Journal of Materials Research

基　　金：国家自然科学基金(U1860112);海洋装备用金属材料及其应用国家重点实验室和辽宁科技大学联合基金(SKLMEAUSTL-201701)。

摘　　要：对690 MPa级海工钢进行"淬火+两相区退火+回火"三步热处理,研究了回火温度对其组织和性能的影响、分析了力学性能变化与组织演变和残余奥氏体体积分数之间的关系。结果表明:回火后实验钢的显微组织为回火贝氏体/马氏体、临界铁素体和残余奥氏体的混合组织。随着回火温度的提高贝氏体/马氏体和临界铁素体逐渐分解成小尺寸晶粒,而残余奥氏体的体积分数逐渐增加;屈服强度由787 MPa降低到716 MPa,塑性和低温韧性明显增强,断后伸长率由20.30%增至29.24%,-40℃下的冲击功由77 J提升至150 J。残余奥氏体体积分数的增加引起裂纹扩展功增大,是低温韧性提高的主要原因。贝氏体/马氏体的分解和残余奥氏体的生成,引起组织细化、晶粒内低KAM值位错的比例逐渐提高和小角度晶界峰值的频率增大,使材料的塑性和韧性显著提高。The influence of tempering temperature on microstructure and mechanical properties of 690 MPa grade marine steel after quenching+intercritical annealing+tempering three-step heat treatment was investigated in terms of the microstructure evolution,the volume fraction of retained austenite and the change in mechanical properties.The results show that the microstructure of the steel after tempering is a mixture of tempered bainite/martensite,intercritical ferrite and retained austenite.With the increasing tempering temperature,bainite/martensite and intercritical ferrite gradually decomposed into small grains,while the volume fraction of retained austenite gradually increased.Yield strength decreased from 787 MPa to 716 MPa.Plasticity and low temperature toughness were significantly enhanced,elongation after fracture increased from 20.30%to 29.24%,and impact energy at-40℃increased from 77 J to 150 J.The increase of the volume fraction of retained austenite lead to the increase of crack propagation work,which was the main cause responsible to the improvement of low temperature toughness.The decomposition of bainite/martensite and the formation of retained austenite lead to grain refinement,the number of dislocations with low KAM values in the grains increased,and the frequency of low angle grain boundary peaks increased,which may be beneficial to the significant increment of plasticity and toughness of the steel.

关 键 词：金属材料 海工钢 两相区退火 残余奥氏体 低温韧性 

分 类 号：TG156.5[金属学及工艺—热处理]