Study of Inclusion Bands in Continuously Cast Steel Billets for Rolling Thermomechanically Treated Rebars

Abstract

The article presents the investigation results of inclusion bands generally formed toward the loose end/inner radius of continuously cast (CC) strands of thermomechanically treated (TMT) rebar grade cast through curved molds. The main analytical tool used for this purpose was an ultrasonic C-scan image analysis system to reveal this band, and the defects detected in this band using the preceding technique were further measured and analyzed in an optical microscope and a scanning electron microscope (SEM) using energy-dispersive system (EDS). The investigation results revealed the presence of macrolevel globular macroinclusions in the size range 50 to 711 lm. The main constituents of the globular inclusions were found to be SiO 2 and MnO. Impact test results revealed reduction in ductility in these bands when compared with the billet material without inclusion band toward the opposite face from the inner radius face. In Charpy testing, reduction in the impact energy in these bands was found to be 0.2 kg m. It is important to monitor the severity of macroinclusions present in these bands to avoid the cracking of TMT rebars during hot rolling.

Split Ends and Cracking Problem During Hot Rolling of Continuously Cast Steel Billets

“…Besides the rolling parameters discussed previously, other compositional variables in the rolled material such as Mn/S ratio [5], severity of nonmetallic inclusions [6], porosities, and so forth. are responsible for the ease of crack formation and propagation.…”