等温热处理对700 MPa级冷轧TRIP钢组织和性能的影响

Effects of Isothermal Heat Treatment on Microstructure and Properties of 700MPa Cold Rolled TRIP Steel

利用金相显微镜、扫描电镜、X射线衍射仪和力学检测手段对不同等温热处理后700 MPa级冷轧TRIP钢的组织和力学性能进行了研究。结果表明:随着等温热处理温度和时间的增加,TRIP钢中贝氏体的含量增加,残余奥氏体的含量减少。随着等温温度的升高,TRIP钢的抗拉强度、屈服强度、伸长率都是先增高后降低;随着热处理时间的增加,TRIP钢的抗拉强度、屈服强度升高,而伸长率会降低。当TRIP钢在840℃退火5 min后,其最佳的等温热处理工艺为430℃保温10 min,试样的抗拉强度为740 MPa、屈服强度为510 MPa、伸长率为34%。

The microstructure and mechanical properties of 700 MPa cold-rolled TRIP steel treated under different isothermal treatments were studied by means of metallographic microscope,SEM,X-ray diffractometer and mechanical test.The results show that the content of bainite in TRIP steel increases,while the content of retained austenite decreases with the temperature and time of isothermal heat treatment increasing.With the isothermal temperature increasing,the tensile strength,yield strength and elongation of TRIP steel first increase and then decrease.The tensile strength and yield strength of TRIP steel increase,while the elongation decreases with the heat treatment time increasing.When TRIP steel is annealed at 840℃for 5 min,the optimum isothermal heat treatment process is 430℃for 10 min,the tensile strength is 740 MPa,yield strength is 510 MPa,elongation is 34%.