304不锈钢板材冲压成形中应变诱发马氏体及其影响  

Strain-induced Martensite and Its Influence in Stamping of 304 Stainless Steel Sheet

作　　者：杨钒 梁君 杨瑞霞 YANG Fan;LIANG Jun;YANG Ruixia(School of Mechanical&Electrical Engineering,Mianyang Teachers'College,Mianyang 621000)

机构地区：[1]绵阳师范学院机电工程学院,绵阳621000

出　　处：《机械工程学报》2021年第8期175-183,共9页Journal of Mechanical Engineering

摘　　要：X射线衍射分析、磁针分析和力学性能及硬度测试等的结果表明,冷轧(固溶处理)状态的304奥氏体不锈钢板材在冷成(变)形过程中产生了应变诱发马氏体(Martensite,M),扩孔、杯突成形时可达35%M,单向拉伸变形不足10%M。另一方面,发现须在一定程度的应变量驱动下冷轧304钢的亚稳态奥氏体(Austenite,A)才能较明显地转变为马氏体,拉伸试验时此门槛值约为20%;对304钢板料扩孔成形的有限元分析表明,在应变约为10%时即可生成22%的马氏体;那些较高硬度地点,即应变诱发马氏体量较多的部位,也正是扩孔应变量最大的区域。分析认为,二向拉应力状态的扩孔、杯突成形更有利于具有体积膨胀效应的A→M转变,能在主要变形区域(凸台、杯突处)诱发多量的马氏体,产生的综合硬化效应可达Δ35 HRB。304钢薄板成形中所诱发的马氏体是甚低碳(wC<0.05%)的体心立方强韧结构(α′-马氏体),具有增加n值、促进变形传播和应变均匀化等作用,有利于不锈钢板料伸长类成形性能的提升以及获得高的扩孔值λ、杯突值IE,也有利于提高304不锈钢冲压制件的结构强度。The results of XRD diffraction analysis,magnetic needle analysis,mechanical properties and hardness tests show that the 304 austenitic stainless steel sheet in the cold-rolled(solution treated)condition produces strain-induced martensite(M)during cold forming(deformation)processes,which can reach 35%M for holes expansion and cup protrusion forming,but uni-directional tensile deformation being less than 10%M.On the other hand,it is found that the meta-stable austenite(A)of cold-rolled 304 steel must be driven by a certain degree of strain to be more obviously transformed into martensite.This threshold is about 20%εduring the tension test.The finite element analysis of 304 steel sheet expansion holes forming shows that 22%martensite can be formed at strain of about 10%,those locations with higher hardness,that is,areas with a lot of strain-induced martensite,are also the areas where the expansion holes strain is the largest.The analysis shows that the bi-directional tensile stress state of expansion holes and cupping forming is more conducive to the A→M transformation with volume expansion effect,which can induce a large amount of martensites in the main deformation area(boss,cupping)and the comprehensive hardening effect up toΔ35 HRB.The martensite induced in the forming of 304 steel sheet is a very low carbon(wC<0.05%)body-centered cubic tough structure(α′-martensite),which has the effects of increasing n value,promotes deformation propagation,strain homogenization and others,it is conducive to the improvement of the elongation-type forming properties of the stainless steel sheet,the attainment of a highλvalue of the expansion holes and the IE value of the cupping,and the promotion of structural strength of 304 stainless steel sheet stamping parts.

关 键 词：304奥氏体不锈钢 应变诱发马氏体 扩孔成形 杯突成形 拉伸变形 有限元 

分 类 号：TG142[一般工业技术—材料科学与工程]