High Deposition Pulse Current GMAW Can Change Current Scenario of Thick Wall Pipe Welding

The high deposition pulse current gas metal arc welding (P-GMAW) with multiple drop transfer per pulse has been used to weld thick wall austenitic stainless steel pipe. Welding of the pipe was also carried by the commonly used shielded metal arc welding (SMAW) and conventional gas metal arc welding (GMAW) processes and compared. Utility of the P-GMAW to facilitate narrow gap welding of the thick wall pipe by appropriate control of pulse parameters has been discussed in reference to produce superior quality weld. The superiority of weld quality has been justified through the microstructure, mechanical properties, residual stresses and fracture mechanics properties of weld joints. Basic characteristics of the P-GMAW process changing the scenario of thick wall pipe welding have been closely studied with respect to its arc characteristics and behaviour of metal transfer. A precise control of the process in order to achieve desired thermal, mechanical and microstructural effects in the narrow gap welding has been achieved by regulation of summarised influence of pulse parameters, mean current (I_m) and arc voltage. The summarised influence of pulse parameters is defined by a hypothetically defined dimensionless factor φ = [(I_b/I_p) f.t_b] where, the I_b, I_p, f and t_b are the base current, peak current, pulse frequency and pulse off (base) time respectively.