退火工艺对低碳含镍DP钢组织及性能的影响

 设计了一种低碳含镍DP钢，采用Gleeble-3500测试了CCT曲线，用金相显微镜观察了微观组织。依据CCT曲线进行了退火工艺设计，采用五因素四水平正交试验方法，结合力学性能测试、SEM组织观察和彩色金相等分析手段，探讨分析了不同工艺参数对DP钢组织性能的影响。试验结果表明，试验材料的Ac1]为712 ℃，Ac3]为928 ℃；连续冷却过程中，出现贝氏体相变的临界冷速为5 ℃/s，马氏体相变的临界冷速为30 ℃/s；退火温度对屈强比和伸长率影响最大，而退火时间对n]值的影响最大，整体考虑3个性能指标，得出最合理的退火工艺为840 ℃退火210 s，缓慢冷却至740 ℃后快速淬火至350 ℃时效240 s。

Influence of annealing treatment on microstructure and mechanical properties of low-carbon Ni-containing DP steel

A low carbon and Ni-containing DP steel was studied. The CCT curve was analyzed by Gleeble3500 simulation tester，and then different annealing treatment was designed based on this curve. Based on the five factors and four levels of orthogonal test，combing mechanical test and SEM investigation，the influence of annealing treatment on microstructure and mechanical properties of DP steel was analyzed. The results indicate that theAc1]andAc3]are 712 and 928 ℃ respectively. During the continuous cooling process，the critical cooling rate of transformation of bainite and martensite are 5 and 30 ℃/s respectively. The biggest factors influencing ratio of yield strength and tensile strength is annealing temperature，and annealing time of n value. The heat treatment to gain best properties is to anneal at 840 ℃ for 210 s in the beginning，then cooled to 740 ℃ slowly，finally quenched to 350 ℃ and holding for 240 s.