Effect of Heat Source on the Formation of Welding Zone Structure between Carbon Steel and Stainless Steel Applied in Shipbuilding

Abstract

This work presents the influence of heat sources on forming the weld zone structures between carbon steel and stainless steel. The results show that the weld structure includes the melting, transition, and heat-affected zones. The microstructure on the stainless-steel side is in the form of δ-Ferrite with thin fibers and clusters of Widmantes Austenite formed due to the high cooling rate in this area. On the carbon steel side, the influence of the concentration gradient and cooling rate changes the crystallization pattern from A-A-FA. The structure obtained from the melting boundary is a completely Austenite to Austenite + δ-Ferrite zone with δ-Ferrite varying from cylindrical, dendritic, and axial crystal forms. The δ-Ferrite content is inversely proportional to the hardness. In the melting zone, the change in the ratio value between temperature gradient and crystallization rate is the cause of the change in δ-Ferrite in this region. The HAZ region has Widmanstet phases, Bainite, and Martensite, which are phases with high hardness and brittleness. This area is thus easily destroyed. The results on the microhardness of the weld in the transition zone on the carbon steel side show that the microhardness result is 390HV in the fusion boundary area, the hardness value in the weld metal area ranges from 160 to 173HV, and the primary metal hardness value of carbon steel is from 134 to 146HV.