基于电弧气泡调控的水下湿法焊接稳定性研究

Investigation on Underwater Wet Welding Process Stability Based on the Arc Bubble Control

为利用机械约束装置实现对水下湿法焊接过程中电弧气泡周期性上浮的可控调节,开展了机械约束装置辅助水下湿法焊接试验。采用高速摄像观察电弧气泡的动态行为,利用传感器采集施加机械约束装置时瞬时焊接电流、电弧电压值,通过光学显微镜分别观察焊缝截面尺寸和焊接接头微观组织,并与相同参数下常规水下湿法焊接进行对比。研究结果表明,机械约束装置能够实现对电弧气泡的可控调节,克服电弧气泡上浮破裂所带来的湿法焊接过程不稳定的问题。随着机械约束高度的降低,电流电压波动程度减弱,电弧稳定性明显提高。同时,机械约束装置的施加能够增大焊缝横截面尺寸,减小焊缝余高,并且减少焊缝和热影响区脆硬组织的含量。分析认为,机械约束装置通过增大电弧气泡尺寸,降低了熔池表面与动态水环境的直接热传导,进而延缓了水下湿法焊接接头的冷却速度,产生了优异的工艺效果。

In order to utilize the mechanical constraint to implement the control of floating arc bubble during underwater wet welding(UWW), the experimental system of the mechanical constraint assisted underwater wet welding(MC-UWW) is proposed and analysed under water. The dynamic behaviors of arc bubble under the mechanical constraint are observed by high-speed video camera and welding stability is characterized by real-time capturing welding electrical signal according to sensor module. Weld cross-section size and microstructure of the joints in MC-UWW are also detected by optical microscope. They are all compared to those in conventional UWW under identical welding parameters. The results show that the mechanical constraint realizes the control of arc bubble, and overcome the problem of arc instability caused by arc bubble burst. With the decreasing mechanical constraint height, the fluctuations of electrical signals reduce considerably and hence arc stability is improved. Furthermore, the applied mechanical constraint enlarges the size of weld cross-section, reduces the weld reinforcement, and restricts the formation of brittle microstructure in weld metal and heat affected zone. It is inferred that the exerted mechanical constraint enlarges the arc bubble size and reduces the heat loss between the weld pool surface and surrounding water, therefore decreasing the cooling speed of weld joint.