预应变对高强钢DH780微观组织及力学性能的影响  

Effect of Pre-strain on Microstructure and Mechanical Properties of High Strength Steel DH780

作　　者：刘立现 LIU Lixian(Research Institute of Technology,Shougang Group Corporation,Beijing 100043,China)

机构地区：[1]首钢集团有限公司技术研究院,北京100043

出　　处：《热加工工艺》2022年第7期97-101,共5页Hot Working Technology

摘　　要：以冷轧退火的HC440/780DHD+Z(DH780)高强钢为研究对象,利用单轴拉伸试验机对不同大小预应变的试样进行拉伸变形,分别对预拉伸后钢的力学性能、显微组织、残余奥氏体含量进行了分析和评价。结果可知:DH780高强钢显微组织由铁素体+马氏体+少量的残余奥氏体组成,其中残余奥氏体的体积分数约4.2%。与DP780钢相比,由于残余奥氏体的TRIP效应,DH780钢具有较高的伸长率、加工硬化指数和杯突值,但是扩孔率较低。随着预应变的增加,处于亚稳态的残余奥氏体逐渐向马氏体转变,残余奥氏体含量逐渐降低直至趋于稳定,屈服强度和抗拉强度均相应增大,屈强比由0.564增大至0.959。同时加工硬化指数逐渐降低,断后伸长率变化不大。Taking the cold-rolled annealed high strength steel HC440/780DHD+Z as the research subject, the tensile deformation of the samples with different pre-strains was carried out by uniaxial tensile testing machine. The mechanical properties, microstructure and residual austenite content of the speec after pre-tension were analyzed and evaluated. The results show that the microstructure of DH780 steel is composed of ferrite, martensite and a small amount of residual austenite,of which the volume fraction of residual austenite is about 4.2%. Compared with those of DP780 steel, due to the TRIP effect of residual austenite,DH780 steel has higher elongation,work hardening index and cupping values, but the hole expansion rate is lower. With the increase of pre-strain, the metastable residual austenite gradually transforms to martensite, and the residual austenite content gradually decreases until it tends to be stable. The yield strength and tensile strength increase correspondingly, and the yield strength ratio increases from 0.564 to 0.959. At the same time, the work hardening index decreases gradually, and the elongation changes little.

关 键 词：预应变 残余奥氏体 相变强化 加工硬化 DH780钢 

分 类 号：TG386.32[金属学及工艺—金属压力加工]