ATI 409HP (UNS S40900) ferritic stainless steel was introduced by ATI Allegheny Ludlum to provide improved oxidation and corrosion resistance for automotive exhaust systems in comparison to carbon steel. The alloy was designated "MF-1", indicating its end use: automotive mufflers. The good fabricability of this alloy, combined with its basic corrosion resistance and economy have significantly broadened the utility of ATI 409HP stainless steel. ATI 409HP consists of four grades: UNS S40900, S40910, S40920, and S40930. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, machining, and joining. Filing Code: SS-1135. Producer or source: Allegheny Technologies Inc..