SUBMERGED WELDING PROCESS WITH PULSED ARC

There are considered features of the pulsed arc submerged welding process (PASW). It is shown that the burning arc pulsating nature makes it possible to exert an additional, in comparison with welding with a stationary arc, influence on the physical-chemical processes in the weld pool. Appropriate choice of PASW parameters makes it possible to change the distribution of flows in the weld pool and the welding thermal cycle characteristics. With a constant welding heat input, the welds made by PASW have a 20–25% greater penetration depth and, accordingly, a smaller width compared to welding with a stationary arc. It has been established that the heat supply pulsed nature makes it possible to approximately halve the duration of the HAZ metal exposure at temperatures above 1000 °C and reduce the metal cooling time by 30% in the 800...500 °C range. As a result, in welded joints made by PASW, the width of the HAZ decreases, and the austenite grain area in this area of the welded joint decreases by 2...3 times. The welding thermal cycle features with PASW compared with stationary arc welding cause the suppression of the lamellar ferrite formation process in the weld metal secondary structure, a decrease in the pearlite content, and the polygonal ferrite formation in a more dispersed "block" form. It can be assumed that the noted structures formation features are the changes cause in the weld metal service properties