卷取温度对800MPa级高扩孔钢组织与性能的影响

Effect of coiling temperature on microstructure and properties of 800 MPa-level high hole expansion steel

利用光学显微镜、扫描电镜、拉伸试验机、冲孔扩孔试验机对不同卷取温度下800 MPa级热轧酸洗扩孔钢的组织、力学性能、扩孔性能进行分析。结果表明:卷取温度为450~600℃时,组织主要由铁素体+贝氏体组成,且随温度的升高,铁素体晶粒增大,贝氏体体积分数减少,材料的屈服强度和抗拉强度提升,伸长率变化不大,扩孔率明显减小。综合考虑,卷取温度为450~500℃时,抗拉强度在780 MPa以上,扩孔率达50%以上。

The microstructure,mechanical property and hole expansion property of 800 MPa-level hot-rolled acid-pickled hole expansion steel at different coiling temperatures were analyzed by optical microscope,scanning electron microscope,tensile tester and hole punching expansion tester.The results showed that the microstructure was mainly composed of ferrite+bainite when the coiling temperature was 450-600℃.With the increase of coiling temperature,the ferrite grains increased,while the volume fraction of bainite decreased gradually.The yield strength and tensile strength of the material were improved,the elongation had no significant change,and the hole expansion rate was reduced obviously.With overall consideration,when the coiling temperature was 450-500℃,the tensile strength was higher than 780 MPa,and the hole expansion rate was above 50%.