Per: Emanuelle Garcia Reis (GERDAU OURO BRANCO), Antonio Augusto Gorni (GERDAU OURO BRANCO), Daniel Bojikian Matsubara (GERDAU OURO BRANCO), Edmar de Souza Silva (GERDAU OURO BRANCO), Gustavo de Sousa (GERDAU OURO BRANCO), Ian Robinson (GERDAU OURO BRANCO), José Herbert Dolabela da Silveira (GERDAU OURO BRANCO), Rafael Abreu Fraga (GERDAU OURO BRANCO), Rodney Pardo Alves (GERDAU OURO BRANCO), Thiago Xavier dos Santos (GERDAU OURO BRANCO)
Abstract:
The controlled rolling followed by accelerated cooling, known worldwide as TMCP, aims to increase mechanical properties without toughness deterioration. The process principle is to promote the plate cooling with water at fast speeds along the ranges of the transformation temperatures. The accelerated cooling process is only fully effective when controlled in an integrated manner, as it alone cannot ensure significant improvements in the final steels properties. The plate surface quality depends on some parameters that must be controlled before the plate initiates the accelerated cooling. Good flatness is essential to avoid irregular water accumulations during cooling. After the reheating process, the plate should have uniform temperature, uniform austenitic grain size and easily removable scale. The slab thermal and microstructural heterogeneities are inherited by the rolled plate and tend to increase further during the accelerated cooling. This results in flatness problems, high level of internal stresses and mechanical properties variation. The descaling strategy is an extremely important factor and must be determined with great caution. It is important that the scale thickness is uniform, to ensure a uniform cooling over the entire plate surface. Otherwise, there will be an uneven temperature distribution, which can cause serious problems of flatness, surface quality and mechanical properties.
