Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels

The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steel is studied over a wide range of the heat inputs (160–250 J mm− 1), which shows low porosity in weld bead ( < 2% of bead area) in low ( < 250 J mm− 1) and high (>350 J mm− 1) heat inputs and maximum at medium (250–350 J mm− 1) heat inputs. The high speed imaging of weld pool shows that the highest frequency of zinc vapour escapes at high heat...