淬火后的逆相变退火温度对5%Mn冷轧中锰钢组织与性能的影响

对5%Mn冷轧中锰钢进行930 ℃×20 min淬火后再进行660、665、675、685 ℃保温30 min的逆相变退火处理,并用光学显微镜、扫描电镜、X射线衍射仪等研究退火温度对中锰钢组织和力学性能的影响。结果表明:5%Mn冷轧中锰钢经过高温淬火和逆相变退火后的组织为超细晶铁素体、板条马氏体和奥氏体。随着逆相变退火温度由660 ℃增加至685 ℃,奥氏体含量先增加后降低并在665 ℃逆相变退火后达到最大值,抗拉强度持续增加,屈服强度先升高后降低并在675 ℃退火时达到最大,伸长率先升高后降低并在665 ℃时达到最大值。综合来看,5%Mn中锰钢冷轧板经过930 ℃×20 min淬火和665 ℃×30 min逆相变退火后的综合力学性能最佳,此时奥氏体体积分数为24.24%,抗拉强度为980 MPa,伸长率为23.68%,强塑积达到了23.21GPa·%。

Effect of reverse phase transformation annealing temperature after quenching on microstructure and properties of 5%Mn cold rolled medium manganese steel

Effect of annealing temperature on microstructure and mechanical properties of a 5%Mn cold rolled medium manganese steel after quenching at 930 ℃ for 20 min and then reverse phase transformation annealing respectively at 660, 665, 675 and 685 ℃ for 30 min were studied by means of OM, SEM and XRD. The results show that after high temperature quenching and reverse phase transformation annealing, the microstructure of the 5%Mn cold rolled medium manganese steel is composed of ultra-fine-grained ferrite, lath martensite and austenite. As the reverse phase transformation annealing temperature increases from 660 ℃ to 685 ℃, the austenite content increases first then decreases and reaches the maximum value at 665 ℃, the tensile strength increases continuously, the yield strength increases first then decreases and reaches the maximum value at 675 ℃, and the elongation increases first then decreases and reaches the maximum value at 665 ℃. In conclusion, the comprehensive mechanical properties are the best for the 5%Mn cold rolled medium manganese steel after quenching at 930 ℃ for 20 min and then reverse phase transformation annealing at 665 ℃ for 30 min, at which the volume fraction of austenite is 24.24%, the tensile strength is 980 MPa, the elongation is 23.68%, and the product of strength and plasticity is 23.21 GPa·%.