Volume 3, Issue 5 (May 2006)
Development of a Supermartensitic Stainless Steel Microalloyed with Niobium
The new class of supermartensitic stainless steels (SMSS) exhibits higher mechanical strength, corrosion resistance, and weldability properties when compared with conventional martensitic stainless steels. This paper presents the results of detailed investigations on 12,50Cr-5,36Ni-2,10Mo-0,20Nb steels that were obtained in a conventional furnace under vacuum and subsequently hot rolled and heat treated similar to the procedure used in production of conventional stainless steels. The microstructural characterization was carried out by optical microscopy (OM), scanning electron microscopy (SEM), and hot stage microscopy. Phase transformations and the effects from heat treatment were examined using a dilatometer. The microstructure, after quenching and tempering, is typical of a martensite matrix with carbonitride of Nb (C,N) small precipitates (40 nm) and mechanical properties of 26RC hardness, 910 MPa tensile strength, 860 MPa yield strength, 20,8% elongation and 199J Charpy impact.