V含量及回火工艺对高强钢TIG焊熔敷金属组织性能的影响

采用四种不同V含量焊丝对高强钢板进行钨极氩弧焊试验，焊后对熔敷金属进行640 ℃保温2 h的回火处理. 研究了V含量和回火处理对熔敷金属微观组织及力学性能的影响. 结果表明，焊态及焊后回火态条件下，随着V含量的增加，熔敷金属强度升高，延伸率和冲击功降低，经回火处理后，不含V熔敷金属内晶界处析出M₂C碳化物，而含V熔敷金属内析出弥散分布的VC析出相，焊后回火过程中位错回复引起基体软化的作用高于M₂C及VC的析出强化作用，导致回火后强度降低，断后伸长率冲击吸收能量升高. 细小VC具有阻碍位错运动的作用，导致回火后含V熔敷金属仍保留较高的位错密度. 实际应用中应根据熔敷金属性能要求合理选择V含量及焊后回火工艺.

Effect of V content and tempering treatment on microstructure and mechanical properties of the high strength steel TIG weld metal

Four kinds of welding wires with different V contents were used to weld the high strength steel plates by tungsten inert gas welding method. After welding, the weld metals of different welding wires were tempered at 640 ℃ for 2 h. The effects of V content and tempering treatment on microstructure and mechanical properties of weld metal were studied. The results show that for the as-welded and as-tempered weld metals, with the increase of V content, the strength increases and the elongation and impact energy decrease. Furthermore, after tempering treatment, M₂C carbide precipitated at the grain boundary of the V-free weld metal, while VC precipitated in V-bearing weld metals. During the post weld tempering process, the effect of dislocation recovery on matrix softening is stronger than precipitation strengthening of M₂C and VC. Therefore, under the combined effects of the two factors, the tempering treatment decreases the strength and improves the elongation and impact energy. The dispersed VC precipitates have the effect of hindering dislocation movement, which causes that the V-bearing weld metal retains high dislocation density after tempering. In practical application, V content and post weld tempering process should be selected reasonably according to the performance requirements of weld metal.