Development of High Temperature Resistant Hot-dipped Aluminum Coated Steel Sheet

A study has made of the high temperature properties of a newly developed Al-9%Si coated extra-low carbon-0.2Ti-0.6Si-1.0Mn steel sheet. Heating at high temperatures resulted in formation of diffusion layer of Al such as a cementation coatings by calorizing at the surface of the steel, because Ti in the substrate stabilizes interstitial elements which can inhibit Al to diffuse in α-Fe. Therefore the weight gain by oxidation of the steel was only about ten times that of SUS410L stainless steel sheet at 700°C and 800°C in air. It was found that the alloying behavior between coatings and substrate was caused by diffusion of Al from coatings to substrate, and diffusion depth of Al was represented as a function of temperature and time. Since the strength of the steel at high temperature up to 800°C is nearly equal to that of SUS410L, it is expected to apply the steel to automotive exhaust systems and the like in place of SUS410L.