Development of a welding condition optimization program for narrow Gap SAW

Submerged arc welding (SAW) is widely used for butt welding of thick plates in large steel structures because of its high deposition rate and high weld quality. 1-pass per layer narrow gap welding with a narrow root width is an effective process that reduces welding time and deformation. However, compared with conventional grooves, it is at risk to occur lack of fusion due to narrow gap. And, the degradation of mechanical properties is a concern because the reheated region becomes thinner. In this study, a welding condition optimization program to control the weld shape for narrow gap SAW was developed. First, welds were conducted on plate under different welding conditions, and a weld shape model was established. Next, an optimization algorithm for deciding welding conditions that can achieve the target weld shape using the weld shape model was established. Then, welding conditions for achieving different layer thicknesses were calculated using the optimization method. The performance of the program was verified by multi-layer welding under the decided conditions.