In this paper,introduced the equipment and the principle parameters in Ultra-Narrow Gap MAG Welding process applied for 34Cr2Ni2Mo and 35CrMoV dissimilar steel welding,and then analyzed the microstructures and the mechanical performance via metallographic observation and a series of mechanical measurements of the welded joint.Observed that fine grain microstructures existed in weld bead and HAZ,and a little bigger grain microstructures appeared in a very narrow over-heated zone,the maximum hardness was within the allowable range.In 34Cr2Ni2Mo side HAZ,a few slag inclusion defects were found.The results of mechanical measurements show the mechanical performance of the welded non-defect founded joint which is much better than base metals.The use of ultra narrow gap MAG welding with low heat input welding technology is conducive to the formation of fine grains in the weld and heat affected zone,through the fine grain strengthening improve the tensile strength of the weld metal greatly,easy to obtain excellent welding joint toughness.%介绍34Cr2Ni2Mo与35CrMoV异种钢厚板对接焊的相关工艺.通过焊接接头的金相观察和力学性能试验,分析其组织分布和力学性能,发现焊缝区和正火区内的微观组织均为细晶形态,过热区晶粒略有长大但区域尺寸很窄,最高硬度在允许范围内.焊接接头的力学性能试验结果表明,在未出现缺陷的接头中,焊缝及热影响区的性能优于母材.应用超窄间隙MAG焊,较低的热输入焊接工艺有利于形成细晶粒的焊缝和热影响区组织,能够通过细晶强化大幅度提高熔敷金属的抗拉强度,获得强韧兼优的焊接接头.
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