Metallurgical investigation of welding wire rod grade during processing

Abstract

The research work provides an intensive analysis of premature failure of the wires during cold drawing operations. The steel wires are made of WR3M grade, which contains low carbon (0.06–0.08 wt%) with high ‘Mn’ (1.40–1.50 wt%) and ‘Si’ (0.80–1.00 wt%). It is a premium low carbon electrode grade, which can produce superior quality welds and trouble-free performance during different continuous welding process. This welding grade is manufactured from continuous cast billet of dimension 150 mm × 150 mm and then hot rolled through successive rolls to achieve desired dimension. Present work includes microstructural and different thermo-mechanical study to determine the origin of premature failures of wires. Investigation suggested that wire breakage took place due to the presence of light brown hard phase (martensite) which makes the material brittle and initiate chevron cracks during drawing operations. X-ray mapping doesn’t provide any segregation along or near the light brown hard phase. From different plant trials and thermo-mechanical study, it reveals that the light brown hard phase formed due to incomplete transformation of wire rods during retarded cooling process at hot rolling stage.