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Divide shear assembly in a rebar rolling mill performs the function of cutting rebars into 72 m length. It uses two shear blades mounted on rotating arms, which rotate in directions opposite to each other and cut the rebars passing in between. These blades hit the rebars at a location from two opposite sides for cutting, and their cutting edges gradually become blunt after cutting of approximately 4000–5000 tons of rebars. Replacing the blunt blades results in interruption in operation leading to increased down time and resulting decreased productivity. A thorough metallurgical root cause analysis was carried out to improve the service life of shear blades. Damages on shear cutting blades were analyzed after trimming of 4000–5000T on thermo-mechanically treated rebars. Chemical analysis revealed that the material of the shear blade was AISI D2, which is a widely used material for cutting of rebars in cold conditions. AISI D2 is a high carbon grade with high Cr content. Microstructural examination revealed large fraction of coarse carbides in tempered martensitic matrix. However, excessive number of coarse carbides imparts brittleness which can limit its applications under severe conditions. The used blade exhibited chipping off materials at the cutting edge in brittle manner. The damaged blades and subsurface damage were examined using Profilometer, SEM, XRD and other metallography techniques. After detailed metallurgical investigation new material was developed to improve the (performance) of the cold shear blades. [ABSTRACT FROM AUTHOR]

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. Highlights • The presence of bainite in the defect location indicates breakage took place from the welding location. • The hardness variation also indicates effect of welding in broken wire samples. [ABSTRACT FROM AUTHOR]

• The work focused on breakage of wires during drawing. • It contains low carbon steel with high Mn and Si. • It is a premium electrode grade to produce high quality welds and trouble-free performance during welding process. • In the present work, microstructural and different thermo-mechanical study of failed wire and wire rod sample was conducted to determine the origin of failure. • Wire breakage took place due to presence of hard brown phase due to incomplete transformation during retarded cooling process at hot rolling operations. 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. [ABSTRACT FROM AUTHOR]