不同焊接条件下接头组织和断裂韧度的对比分析

Microstructure and fracture toughness of joint under different welding conditions

在球阀的焊接过程中采用振动埋弧焊和常规埋弧焊相结合的工艺。接头金相显示,附加振动后,焊接接头晶粒细化明显,熔合区和过热区变窄,魏氏组织减小。从断裂力学的角度分析机械振动对焊接接头韧度的影响,结果表明,焊缝的断裂韧度明显大于HAZ;振动焊接条件下的焊缝和HAZ的CTOD值明显高于常规焊接下焊缝和HAZ的CTOD值;且振动焊接使得焊接接头的各部分之间断裂韧度的差别明显缩小,断裂韧度更趋均匀化。经断口的扫描电镜可观察到振动焊接下焊缝的韧窝密度明显大于常规焊接下焊缝的韧窝密度。

The combination of vibratory submerged-arc welding (V-SAW) process and normal submerged-arc welding(SAW) process is used in ball valve welding. Metallographs show that a refined joint is produced under vibratory welding. The fusion area and the overheated zone are narrowed. And the dimension of widmanstaten structure is reduced. The effect of mechanical vibration on the toughness of the welded joint is analyzed from the point of view of fracture mechanics. The results indicate that the fracture toughness of the weld is obviously higher than that of HAZ(heat-affected zone). And the crack tip opening displacement value of the weld and HAZ under V-SAW condition is greater than that under normal SAW condition. And the difference in different regions of the welded joint is evidently reduced by applying vibratory SAW. Thereby, the fracture toughness is uniform. From fractography, it can be seen that the dimple density of the weld under V-SAW condition is greater than that under normal SAW condition.