Aspects of Changing the Structure and Hardness of Metal of Heat-Affected Zone During Welding of Low-Carbon High-Strength Steels for Pipes with Increased Deformability

In this study, the influence of the parameters of welding thermal cycles on the structure formation and changes in the hardness of the metal of a heat-affected zone (HAZ) of welded joints from high-strength steels for pipes with increased deformation ability was examined. Findings reveal that the metal of the HAZ of welded joints made of pipe steels with increased deformability can be subjected to softening up to 20%-24% during the welding process. The structure and phase composition of the metal of the lowtemperature section of the thermal impact zone was determined, and the findings guarantee its equal strength with the base metal. A range of cooling speeds was established, which eliminate the metal softening in the HAZ of welded joints.