HIGH STRENGTH (YS : 640 MPA MIN.) THERMO MECHANICALLY TREATED (TMT) BAR AND A PROCESS FOR ITS PRODUCTION

摘要

The present invention relates to developing high strength (YS:640MPa Min.) Thermo Mechanically Treated (TMT) bar and a process for its production. The TMT bars of the invention is having yield strength above 640MPa, UTS/YS ratio of 1.15 Min., with super toughness (18% elongation Min.) properties of said TMT rebars through selective alloy design and optimizing process parameters. The alloy design comprising C-Mn chemistry wherein manganese content of steel is maintained in the range of 0.8-1.3 wt %, and no micro-alloying element is added so that cost of production remains competitive. The process parameters for the instantaneous quenching by accelerated cooling of the hot deformed rebars are adapted to provide thick martensitic structure at the periphery and the core containing predominantly acicular ferrite/bainite structure along with pearlite ensuring desired combination of strength and ductility properties, favoring wide scale application in RCC structures or as rock bolts for effective roof support in tunnel construction and the like.