Prediction of dilution in GMA and UGMA stainless steel single layer cladding using response surface methodology

Abstract

This paper describes the use of a variant of GMAW process named as UGMAW (universal gas metal arc welding) process for single layer stainless steel cladding, which makes use of a specially designed torch to preheat the filler wire, using an auxiliary welding power source, before its emergence from the torch. The experimental work undertaken was that of single layer cladding of 12 mm thick low carbon steel with the austenitic stainless steel 316L solid filler wire of 1·14 mm diameter. Dependence of dilution was investigated using four factor five level central composite rotatable design to develop relationship for predicting dilution, which enables to quantify the direct and interactive effects of four numerical factors, namely, wire feed rate, open circuit voltage (OCV), welding speed, electrode stickout and one categorical factor, preheat current. External preheating of the filler wire in UGMAW process resulted in greater contribution of arc energy by resistive heating owing to which significant drop in the main welding current and hence low dilution values were observed. Numerical optimisation was carried out and the optimal solutions generated indicate that for same levels of dilution, higher deposition rates are achievable in UGMAW process, thus making it a good choice for low cost surfacing applications.