低活化马氏体钢真空扩散焊接头力学性能

Mechanical properties of vacuum diffusion welded joints of low activation martensitic steel

在不同焊接工艺参数下对低活化马氏体钢进行真空扩散焊接试验,分别对焊缝区进行光学显微观察(OM)与扫描电镜观察(SEM)分析,并对焊件进行力学性能测试.结果表明,低活化马氏体钢的焊后组织主要为板条马氏体及少量的残余奥氏体,焊缝结合状况良好;在一定范围内提高焊接温度、延长保温时间可以提升接头抗拉强度,但过高的温度及保温时间会导致奥氏体晶粒粗化,损害接头的抗拉强度及冲击韧性.经过焊后热处理(正火+回火)的接头抗拉强度相对于热处理前有所降低,但组织稳定性及冲击韧性有一定改善.

The low-activated martensitic steel was subjected to vacuum diffusion welding test under different welding parameters.The microstructure of the weld zone was observed by optical microscope(OM)and scanning electron microscopy(SEM),and the mechanical properties of the welds were tested.The obtained microstructure of the low-activated martensitic steel welds is mainly composed of lath martensite and a small amount of retained austenite and exhibits preferable bonding effect.Increasing the welding temperature and prolonging the holding time in a certain range can improve the tensile strength of the joints.It also promotes the coarsening of austenite grain,which is detrimental to the tensile strength and impact toughness.The tensile strength of the joints after post weld heat treatment(normalizing+tempering)is lower than the as-welded one,but the microstructure stability and impact toughness of the welds are obviously improved.