焊接热循环对07MnCrMoVR钢热影响区组织及韧性的影响

Effect of Thermal Cycle on Microstructure and Mechanical Properties of Heat Affected Zone of 07MnCrMoVR Steel

为深入分析07MnCrMoVR钢热影响区的脆化问题,采用热模拟技术和显微观察技术,对该钢热影响区的组织和性能进行了深入研究。研究结果表明:单次热循环时,粗晶区(CGHAZ)和临界区(ICHAZ)韧性恶化严重,晶粒长大及粒状贝氏体、M-A组元等非平衡组织的形成是粗晶区韧性恶化的主要原因。随着t8/5的增加,粗晶区冲击韧性随之降低,为防止热影响区脆化,t8/5应控制在30 s之内。粗晶区+临界区(IRCGHAZ)是多道焊二次热循环时热影响区韧性最差的区域,引起IRCGHAZ脆化的原因是大量沿晶界分布的块状M-A组元的形成。

For investigating the embrittlement problem of the heat affected zone,the mechanical properties and microstructure of 07MnCrMoVR heat affected zone was studied by thermal simulation technology and microstructure examination technology.The results indicate that coarsed grain zone（CGHAZ） and critical zone（ICHAZ） are the brittlement zones in heat affected zone during single thermal cycle testing,and the brittlement of coarse grain zone ascribes to the grain coarsening and the formation of granular bainite and M-A constituent.With the increase of t8/5,the impact toughness of coarse grain zone decrease,and the t8/5 should be controlled in 30 s in actual welding.IRCGHAZ is the weakest zone in the HAZ during the second thermal cycling,and the formation of lot of massive M-A constituents distributed along grain boundary is the main cause for the brittlement of intercritically reheated coarse grained HAZ（IRCGHAZ）.