热处理工艺对高强中锰汽车用钢成形性能的影响

Effect of heat treatment process on formability of high strength medium manganese steel for automobile

针对第3代汽车用钢的研发,以中锰汽车用钢为研究对象,对试验钢采用两相区直接退火和ART退火,均获得了奥氏体、铁素体和马氏体组织。利用蔡司光学显微镜、SEM、XRD和万能试验机等检测手段研究了两种热处理工艺下试验钢板微观组织结构及力学性能。结果表明:当退火时间为10 min时,两种工艺的最佳退火温度均为630℃,此时ART退火的试验钢板屈服强度为750 MPa,抗拉强度为900 MPa,伸长率为30.5%,强塑积达到27.5 GPa·%,残余奥氏体体积分数为20.1%;两相区直接退火的试验钢板屈服强度为1000 MPa,抗拉强度为1100 MPa,伸长率为27.5%,强塑积达到30.3 GPa·%,残余奥氏体体积分数达到22.3%。此外,相较于ART退火,两相区直接退火后的试验钢板中{111}有利织构含量高,{100}不利织构含量低,进一步证明两相区直接退火工艺下试验钢具有更好的成形性能。

Aiming at the research and development of the third-generation automotive steel,the medium manganese automobile steel was taken as the research object.The two-phase zone direct annealing and ART annealing were used for the tested steel,and the microstructure of austenite,ferrite and martensite was obtained.The microstructure and mechanical properties of the tested steel plate under two heat treatment processes were studied by means of Zeiss optical microscope,SEM,XRD and universal testing machine.The results show that when the annealing time is 10 min,the optimum annealing temperature of the two processes is 630℃.At this time,the yield strength of the ART annealed tested plate is 750 MPa,the tensile strength is 900 MPa,the elongation is 30.5%,the product of strength and elongation reaches 27.5 GPa·%,and the volume fraction of retained austenite is 20.1%.The yield strength,tensile strength,elongation,product of strength and elongation and volume fraction of retained austenite of the tested plate directly annealed in two-phase zone are 1000 MPa,1100 MPa,27.5%,30.3 GPa·%and 22.3%,respectively.In addition,compared with ART annealing,the content of{111}favorable texture is higher and the content of{100}unfavorable texture is lower in the tested plate after direct annealing in the two-phase zone,which further proves that the tested steel has better formability under the direct annealing process in the two-phase zone.