Breakage of electrode grade steel wires during manufacturing: A metallurgical investigation

Abstract

Wire rods of Electrode Quality (EQ) steel, in sizes ranging between 5.5 mm and 12 mm, are normally produced from continuously cast billets by hot rolling in wire rod mill. These wire rods are subsequently drawn into wires with reduced section in wire drawing plants.The most common grade for EQ steels is ER70S-6 grade which is made of low carbon steel (0.06–0.08 Wt%) with high ‘Mn’ (1.40–1.50 Wt%) and low ‘S' content (0.020 max Wt%). It is a premium mild steel wire formulated to high quality welds and trouble-free performance during applications involving heavy duty, high speed and spray transfer applications all the way to light duty, low speed and short-arc applications. Quality aspects of these drawn wires are of significance as any inherent abnormality in the material could lead to unwanted productivity losses or quality claims. In this present study, wire samples broken during manufacturing were collected from wire drawing plants for understanding their quality aspect and potential causes of breakage while drawing. Detailed microstructural investigation revealed that the root cause of breakage of the wires is related to the welding process deployed by the customer in joining the wire rods. The quality of weldment preparation needs to be paid attention because the two ends of the wires are not fused properly when subjected to welding.