Also has information such steel into Martensitic precipitation - hardening stainless and maraging stainless steel, solid solution State, the former in Martensitic matrix containing a small amount of ferrite ( about 10 ) and a small amount of residual austenite, the latter martensite matrix, only a small amount of residual austenite, the latter relatively high toughness. Precipitation - hardening of semi - austenitic stainless steel is after the solution heat-treatment, cooled to room temperature, austenite organization exists, and contains 5-20 ferrite organization, but the body is not very stable austenitic, through a series of hot - cold treatment or mechanical deformation processing, austenite into martensite, then through time and strengthening.