Effects of welds distribution and high-low temperature humidity alternating aging on sealing performance of weld-bonded stainless steel structures

A sealant is introduced in the resistance spot welding (RSW) process to solve the poor sealing performance of stainless steel metro vehicles. The effects of welds distribution and high-low temperature humidity alternating aging on sealing performance are systematically studied by specially-designed pillow specimens and sealing tests apparatus. Study shows that the distributed RSW welds act as pinning points play a decisive role in sealant spreading and corresponding sealing performance. The sealing performance exhibits a maximal value when RSW spots centerline coincides with the gumming centerline and is inversely proportional to the weld pitch. Substrate deformation, sealant burning around the welds, and sealant thickness together contribute to the continuous invading of the high-pressure gas, and the initial failure prefers to happen adjacent to RSW welds. On the other hand, the sealing performance of the specimens has an inflection point at 240 h, which corresponds to the morphology evolution of the sealant, and should be attributed to the sealant state changes from non-drying state to set to touch state due to the degradation of the sealant. Hence, the sealant used in the current study is technically feasible to improve the sealing performance of metro stainless steel bodies.