加热工艺对1800 MPa级热成形钢冷弯性能的影响

Effect of heating process on cold bending ability of 1800 MPa grade hot stamped steel

利用冷弯试验机、光学显微镜、扫描电镜等研究手段,分析了热冲压成形工艺过程中的加热保温时间对1800 MPa级热成形钢微观组织和冷弯性能的影响。结果表明,随保温时间的增加,试验钢热冲压成形后的原始奥氏体晶粒长大,当保温时间为5 min时,原始奥氏体晶粒尺寸约为5μm,细小且均匀,当保温时间达到9 min时,出现异常粗大晶粒。冷弯角与原始奥氏体晶粒尺寸关系密切,冷弯角随着晶粒的长大而减小,在5 min时获得最大冷弯角54.5°。

Effect of holding time in pre-heating process for hot stamping on microstructure and cold bending property of a 1800 MPa grade hot stamped steel was analyzed by means of cold bending test machine,optical microscope and scanning electron microscope.The results show that with the increase of holding time,the prior austenite grains of the hot stamped steel grow up.When the holding time is 5 min,the prior austenite grains are fine and uniform with the average size of about 5μm.When the holding time reaches 9 min,abnormal coarse grains appear.The cold bending angle is closely related to the prior austenite grain size,i.e.,it decreases with grain growth.The maximum cold bending angle is 54.5°when the holding time is 5 min.