Weldability of thermomechanically treated steels having a high yield point

The article concerns the issue of weldability of S700MC steel, treated thermo-mechanically, with high yield point. The weakest area of welded joints of this steel is a high - temperature coarse heat affected zone (HAZ) in which due to the nucleation effect of the dissolved phases, strengthening the matrix and their subsequent uncontrolled separation precipitation in the form of finely disperse and rapid decrease impact strength is observed. Performed arc welding tests here have shown that in order to ensure high quality of welded joints, it is necessary to limit the welding linear heat input. During the welding process of S700MC steel, it is not recommended to use pre heating before the welding process and heat treatment after welding, and the number of repairs should be kept to a minimum, because it leads to a reduction of strength and plastic properties in the HAZ area, as a result of aging processes, dissolution of strengthening phases in the matrix and their subsequent uncontrolled precipitation during cooling.