Nitrogen distribution in molten pool of gas pool coupled activating TIG welding with rapid cooling method

Rapid cooling method is used to cool the high temperature molten pool of gas pool coupled activating TIG welding of stainless steel. By controlling the onset cooling time, the distribution of nitrogen element in molten pool can be retained without affecting the weld appearance. AES is employed to study the nitrogen element distribution in different parts of the molten pool, respectively. The crosssection appearances and metallographic structures of the molten pool metals cool rapidly show that the effect of rapid cooling method is perfect if the molten pool is cooled at 0.6 s before arc being extinguished. The results of the AES analysis indicate that the nitrogen element distributes uniformly as the whole in the depth direction of the molten pool, while fluctuates sharply in local zone. The average nitrogen contents on the boundary zone in the front and tail parts of the molten pool are slightly higher than that in the central zone, while the average nitrogen content on the boundary zone in the middle part of the molten pool is slightly lower than that in the central zone. The overall average nitrogen content of the tail part is slightly higher than that of the front part, and the overall average nitrogen content of the middle part is between both of them.