Effect of pulsed treatment of the metal bath with an arc of variable power on the formation of structure, morphology and distribution of non-metallic inclusions in solidification of welded joints in low-alloy steel

In this article, the authors present the results of investigations into the special features of formation of the structure and non-metallic inclusions of weld metal in SWPA. Investigations were carried out on the metal of low-alloy joints produced by direct current (d.c.) welding with reverse polarity and by SWPA with two different heat inputs. Butt joints assembled with a gap of < =2 mm were welded with Sv-10G2 wire 4 mm in diameter under ANK-47 flux on a flux cushion made from the same flux. The parent metal was in the form of 16 mm thick sheets of 14KhGNDTs low-alloy steel with higher strength. It was found that the pulsed nature of arcing in submerged-arc welding greatly affects the conditions of formaiton of the weld metal microstructure. Variation of the thermal cycle in SWPA in comparison with d.c. welding suppresses in the process of formation of plate-shaped ferrite in the secondary structure of the weld metals, reduces the pearlite content, results in the formation of polygonal ferrite in a more disperse "block" form and increases the dispersion of the MaC-phase. On the basis of these results, SWPA can be recommended for welding sheet metal structures with a thickness of < =20 mm produced from low-alloy and carbon steels.