分别在9．2,10．4,12．2,21．0 kJ?cm－1焊接热输入下对12MnNiCrMoV钢薄板进行对接焊,研究了焊接热输入对焊接接头粗晶热影响区显微组织、晶粒尺寸、硬度和冲击性能的影响；为了确定不同热输入下接头粗晶热影响区的焊接热循环曲线,对焊接过程的温度场进行了有限元模拟.结果表明：随着焊接热输入增大,粗晶热影响区的组织变化并不明显,均为粒状贝氏体和块状铁素体,但晶粒尺寸逐渐变大,－20℃冲击韧性和维氏硬度均逐渐降低；晶粒粗化是粗晶热影响区产生脆化与软化的最主要原因；通过有限元模拟可知,随着热输入增大,粗晶热影响区相同位置处的峰值温度逐渐升高,并且在高温停留的时间延长.
12MnNiCrMoV steel sheets were welded by butt welding at welding heat input of 9.2,10.4,12.2, 2 1 .0 kJ?cm-1 ,effects of welding heat input on microstructure,grains size,hardness and impact properties of coarse grain heat affected zone(CGHAZ)of welded joint were studied.In order to confirm welding thermal cycle curve of CGHAZ at different heat inputs,temperature field during welding was simulated.The results show that the microstructure of CGHAZ had not obvious changes with the increase of welding heat input,the microstructure consisted of granular bainite and massive ferrite,and the grains size gradually grew,meanwhile,the impact energy at -20 ℃and Vickers hardness gradually decreased.The main reason for CGHAZ embrittlement and softening is grains coarsening.It is known by finite element simulation,the peak temperature of CGHAZ at same position gradually increased,and staying time at high temperature extended with the increase of welding heat input.
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