低碳超高强热轧双相钢的组织性能检测及研究

Test and Research on Microstructure and Properties of Low Carbon Ultra-High Strength Hot Rolled Dual Phase Steel

摘要: 基于合金减量化原则，应用热轧 + 超快冷 + 弛豫热处理一体化技术制备得到1000 MPa级热轧双相钢，并研究了弛豫时间对试验钢组织和性能的影响。结果表明：随着弛豫时间增加，试验钢中铁素体平均晶粒尺寸和体积分数均增加，屈服强度降低；屈强比降低，伸长率、n值和强塑积均先增加后减小。7 s弛豫的试验钢，铁素体体积分数为61.8%，铁素体晶粒尺寸为3.8 μm，组织中较多的长条马氏体和岛状马氏体提高了钢的可动位错密度和均匀变形能力，抗拉强度为1068 MPa，伸长率为17.0%，屈强比较低为0.48，n值最高为0.13，其综合力学性能最好。

Abstract: Based on the principle of alloy reduction, a 1000 MPa hot-rolled dual phase steel was prepared by hot rolling, ultra fast cooling and relaxation heat treatment, and the effect of relaxation time on microstructure and mechanical properties of the tested steel was studied. The results show that with the increase of relaxation time, the ferrite grain size and volume fraction increase, the yield strength decreases. The yield to strength ratio decreases, and the elongation, n value, and strength plastic product all increase first and then decrease. When the relaxation time is 7 s, the volume fraction of ferrite is 61.8%, and the grain size of ferrite is 3.8 μm. The presence of elongated martensite and island martensite in the microstructure increases the density of movable dislocations and uniform deformation ability of the steel. The tensile strength, elongation, yield ratio and n value of the tested steel are 1068 MPa, 17.0%, 0.48 and 0.13, respectively, which shows the best comprehensive property.