A Novel Low-cost Hot Rolled High Strength Steel for an Automatic Teller Machine

Abstract

A novel hot rolled steel LG600A with the tensile strength exceeding 700 MPa was developed for automatic teller machine application. The low-cost C-Mn steel was microalloyed with 0.08 mass% – 0.12 mass% Ti rather than noble alloying elements, such as Nb, V, Mo, and Cu, etc. The novel steel had a good surface quality and welding property. After the hot rolled steel coils were leveled, the steel plates, the length of which was even down to 1500 mm, had an excellent flatness. The effects of hot rolling parameters on mechanical performance, microstructure and recrystallization behavior were studied. The metallurgical concept for the steel production was also discussed. The result shows that decreasing the finish rolling temperature, increasing cooling rate in the first cooling stage and decreasing the cooling rate in the last cooling stage, together with coiling at a modestly high coiling temperature all resulted in the refined grains and TiC precipitates, thereby improving the strength and toughness of this new steel greatly.