Failure Analysis of Thermo-Mechanically Treated (TMT) Bar During Bending Operation: A Metallurgical Investigation

Abstract

TMT bars means Thermo Mechanically Treated Bars made from medium carbon steel (Carbon 0.25 Max Wt. %) and are used in construction industry. Because of its corrosion and rust resistance features it is widely used in construction of buildings in humid areas as well as long lasting, high strength, quality construction. Quality aspects of these rebar's are of significance as any inherent abnormality in the material could lead to unwanted productivity losses or quality claims. In this present study, rebar samples failed during bending operation were collected from construction end for understanding their quality aspect and potential causes of failure while bending. Visual observations of rebar sample (U-bend) longitudinal surface defects were observed in both the tension and compression zone. On appearance, metal folded over the rebar surfaces at an angle. Detailed microstructural investigation revealed that scale entrapment in defects. The above observations indicated that the defect was of lap type and which was generated during hot rolling process.