Fe-Cr-Mn microduplex ferritic-martensitic stainless steels

An alloy development program has been undertaken with the aim of identifying an Fe-Cr-Mn stainless steel with ferritic-martensitic microduplex phase balance of sufficient stability to produce moderate strength and ductility, good impact resistance and acceptable as-welded properties. A microduplex, low C and N, Ti stabilized composition of Fe-11.5 pct Cr-3 pct Mn has been found to provide a yield strength of ⋍550 MPa, a tensile strength of ≃650 MPa, tensile elongation of 20 pct, a CVN impact transition temperature of-115°C (at 0.33 cm gage) and good weldability as determined by bend, impact, and intergranular corrosion testing. The alloy possesses general corrosion resistance roughly comparable to T405 and T430 ferritic stainless steels. The impact resistance achieved with the mixture of ferrite and martensite is inconsistent with previous concepts of second phase toughening in microduplex alloys, with the mixture apparently being significantly tougher than either of its components in bulk form. J.R. WOOD formerly with Allegheny Ludlum Steel Corporation, Brackenridge, PA