Influence of the double layer technique on the HAZ microstructure during submerged arc welding of SAE 1020 steel

Abstract

The welding process is widely applied in industrial processes, but it causes undesirable changes in the microstructure and properties of the material, especially in steels, due to the high temperatures reached near the fusion zone. An alternative to mitigate this effect is the application of multipass welding, where each subsequent pass causes reheating of the welded joint, minimizing changes in microstructure and recovering material properties. However, the heat input from the new welding cycle can also generate harmful changes to the material. The present work aims to analyze the application of the double layer technique with different levels of heat input, seeking to evaluate the recovery of mechanical properties in the region of the heat affected zone (HAZ) in thick joints welded by the submerged arc process. Foram realizadas sequências com passe simples e passe duplo de solda variando o aporte térmico. O efeito desta variação foi avaliado através de microscopia óptica e teste de microdureza. It was observed that the double layer technique had a relevant effect on the recovery of steel properties. The HAZ after the first pass showed a refined microstructure, grains with acicular morphology and increased hardness. With the application of a second weld pass, gradually increasing the heat input, the reestablishment of the equiaxed microstructure and the hardness in the HAZ region was observed.