Welding of High Strength Structural Steel for Shipbuilding Application Using Pulse-GMAW Process

摘要

DMR249B is a high strength (YS>560MPa) structural steel with high sub-zero impact toughness. In the present investigation, an attempt was made to obtain higher deposition rate at lower heat input using pulsed GMAW process without compromising on property. Pulsed Gas Metal Arc Welding (P-GMAW) process has a controlled method of metal transfer, in which the arc current is maintained at a high value which permits spray transfer at certain high current levels. Once the droplet is transferred, the current is reduced to a relatively low value to maintain the arc. Whenever arc current is periodically low, overall heat input to the metal is reduced. Periodic injection of high current pulses allows metal to be transferred in the spray mode. Bead-on-plate and bead-in-groove P-GMAW on 16 mm thick DMR249B steel were carried out using indigenously developed alloy wire of 1.2 mm diameter and 80% Ar+20%CO_2 as shielding gas. Bead morphological parameters like bead shape, amount of metal deposited, penetration, reinforcement, reinforcement area, bead width etc were determined as a function of welding parameters. Bead on plate welding experiments were carried out with different peak welding currents (I_p = 350, 300 and 250 A), background currents (I_B = 25, 50, 75% of I_P) and pulse frequency (F = 60, 100, and 140 Hz). Microstrutural studies and mechanical properties have also been evaluated.