Comparison of processing window and porosity distribution in laser welding of 10 mm thick 30CrMnSiA ultrahigh strength between flat (1G) and horizontal (2G) positions

With the development of high brightness and high power laser, it is possible to weld thick sections using single pass autogenous laser welding. However, it often suffers from very narrow processing parameter windows when welding thick sections. Furthermore, porosity, back sagging, and undercut are the main defects for laser welding of thick section high strength steel plates. A comparison of flat welding position (1G) and horizontal welding position (2G) in laser welded 10 mm thick 30CrMnSiA high strength steel plates was investigated in this paper. The results show that the 1G position has a very narrow processing window, while the 2G position has a much wider processing window. The porosity in the 2G position laser welded joint distributed in the upper part of welds, while that in the 1G position laser welded joint was distributed along the weld center. Welded joints with acceptable porosity in the 2G position laser welding can be obtained for an X-shaped weld profile and wider weld bead. The peak longitudinal residual stresses of the 2G position laser welded 30CrMnSiA steel were located in the heat-affected zone (HAZ), and the lower residual stresses were presented in the weld center. The peak transverse residual stress was presented in the weld center with the lower stresses located in the two sides HAZ.