临界退火中锰钢的组织性能和变形行为

Microstructure and properties as well as deformation behavior in an incritical annealing medium-Mn steel

为了研究临界退火中锰钢的微观组织演变规律以及组织对力学性能和变形行为的影响,对冷轧中锰钢(0.1C-7Mn-0.35Si)在570~650℃范围内进行了临界退火处理。研究结果表明,随着退火温度升高,双相"奥氏体+铁素体"组织逐步趋于等轴化且晶粒有粗化的趋势,并且在650℃时出现了马氏体组织;试验钢的抗拉强度随温度升高而增加,而伸长率和屈服强度均呈下降趋势,局部不均匀变形带随着退火温度升高逐步弱化,在620和650℃时完全消失;在相对较高的退火温度下,粗化的等轴奥氏体晶粒中形变诱导马氏体相变的增强和大尺寸的铁素体晶粒中动态回复的减弱,以及更高温度时马氏体的引入等,均改善了屈服阶段的加工硬化能力,从而有效减弱或抑制吕德斯带的扩展。

In order to investigate the evolution rule of microstructure of medium manganese steel and its influence on mechanical properties and deformation behavior in an intercritical annealing treatment,a cold-rolled medium manganese steel(0.1C-7Mn-0.35Si)was intercritically annealed from 570 to 650℃.The research results show that as the annealing temperature increases,the dual-phase structure containing of austenite plus ferrite structure gradually tends to be equiaxed and the grains become coarsened,and the martensite structure appears at 650 ℃.The tensile strength of the experimental steel increases with increasing temperature,while the elongation and yield strength all show a downward trend;the localized uneven deformation band was gradually weakened and was completely disappeared at 620 and 650 ℃.When annealed at a relatively high annealing temperature,the stimulative deformationinduced martensite transformation inside coarse equiaxed austenite grains and the reduced dynamic recovery in largesized ferrite grains,as well as the introduction of martensite at higher temperature etc.all enhance the work hardening capability at the yield stage,and hence recede or suppress the propagation of the Lüders band.