Patent ID: 6827797
Filing Date: 2004-12-07
Classification: C21D,C22C

Abstract:
A process for manufacturing a high-strength, corrosion-resistant tough alloy carbon steel, said process comprising:(a) forming an alloy composition comprising iron and at least one alloying element comprising a maximum of about 0.35% by weight of carbon in proportions selected to provide said alloy composition with a martensite transition range having a martensite start temperature of at least about 300Â° C.; (b) heating said alloy composition to a temperature sufficiently high to cause austenitization thereof, under conditions causing said alloy composition to assume a homogeneous austenite phase with all alloying elements in solution; (c) cooling said homogeneous austenite phase sufficiently to transform a portion of said austenite phase to ferrite crystals, thereby forming a two-phase microstructure comprising ferrite crystals fused with austenite crystals; and (d) cooling said two-phase microstructure through said martensite transition range under conditions causing conversion of said austenite crystals to a microstructure containing laths of martensite alternating with films of retained austenite.