The impact of heating degree during arc welding on the structure formation in the heat affected zone of welded joints in carbon steels

Abstract

The study demonstrates that the degree of heating in the welding thermal cycle affects the process of metal structure formation in the heat affected zone (HAZ) of welded joints in carbon steels. During the heating phase, metal grains are formed, and their sizes are determined. Here, as the a-y transformation is completed, the level of austenite homogeneity, its resistance during cooling, and the inertia period of decomposition are determined, which influence the kinetics of structural transformations in the cooling phase. Thus, the formation of the metal structure in the HAZ begins during the heating phase, within the intercritical interval Ac1-Ac3. The cooling phase completes this process with the decomposition of austenite. The impact of heating rates on the structure formation process in the metal is considered. It is shown that with the increase in the heating rate of the welded joint, the positive effect on the kinetics of the supercooled austenite decomposition gradually increases, despite the negative impact of the increased cooling rate. Accordingly, it is shown that the heating phase of the welding thermal cycle has a dominant influence on the kinetics of metal structure formation in the HAZ of welded joints.