Abstract: The present invention relates to a ferritic-martensitic Mn-Cr-Ni-N-steel in which the austenite phase is transformed into martensite at cold deformation so that the steel obtains high strength with maintained good ductility. The distinguishing feature is an alloy analysis comprising max 0.1% C, 0.1-1.5% Si, max 5.0% Mn, 17-22% Cr, 2.0-5.0% Ni, max 2.0% Mo, max 0.2% N, balance Fe and normal amounts of impurities whereby the ferrite content is 5-45% and austenite stability, S.sub.m, expressed as S.sub.m =462 (% C+% N)+9.2% Si+8.1% Mn+13.7% Cr+34% Ni shall fulfill the condition 475<S.sub.m <600.

Abstract: The present invention presents a ferritic-austenitic Cr-Ni-N-Steel alloy with a stable austenite phase, high corrosion resistance and good weldability, said steel alloy consisting essentially of the following elements by weight; max 0.06% C, 21-24.5% Cr, 2-5.5% Ni, 0.05-0.3% N, max 1.5% & Si, max 4.0% Mn, 0.01-1.0% Mo, 0.01-1.0% Cu, the remainder being iron and normal impurities, the contents of said elements being balanced so that the ferrite content, .alpha., amounts to 35-65%. The analysis of the steel is so optimized that it becomes especially useful for those environments where the steel is exposed to temperatures above 60.degree. C. and chloride amounts up to 1000 ppm while the alloy being stable towards deformation form austenite into martensite at a total deformation oft 10-30% in room temperature.