The investigation of the ramping length of the stainless steel railway vehicle laser welding seam

Laser welding technology is widely applied in railway vehicles manufacturing, improving the appearance quality, improving the strength and reducing the weight. The outer surface of the stainless steel railway vehicle is not coated and it has high requirements on appearance quality, when the laser welding process is applied, the length of the ramping at the arc-starting position and the arc-closing position is required to ensure that there is no obvious deformation left on the outer surface. The laser welding process with different ramping length is investigated to clarify the influence of the ramping length on the deformation of the weld outer surface, to optimize the ramping length in the process. The comparison tests of different ramping lengths were carried out. The surface deformation, residual stress and tensile strength of different ramping length joints were compared, and the influence of the length of ramping on the deformation of the welding seam is analysed comprehensively. And with the increase of the length of ramping, the deformation of the welding seam decreases. There is no obvious influence on the weld arc position when we choose the ramping length from 3 - 5 mm, with the maximum deformation at the weld arc position about 100 mu m.