High-strength stainless steel for use as a material of fuel injection nozzle or needle for internal combustion engine, fuel injection nozzle fabricated from the stainless steel, and method for fabricating the fuel injection nozzle

摘要

The stainless steel according to the invention is a tempered martensitic stainless steel which has a hardness of at least HRC 58 after quenching and thermal tempering treatment. The limiting forging ratio of this tempered martensitic stainless steel is at least 75%. The hardness of the tempered martensitic stainless steel is at most HB 157. Preferably, the number of the carbides having dimensions of 0.2 mu m or less represents at most 50% of the total carbides, the limiting forging ratio of the tempered martensitic stainless steel being at least 75% or its hardness being at most HB 157. Preferably the stainless steel has a chemical composition which, in terms of weight, comprises 0.4-0.6% of C, at most 0.5% of Si, at most 0.5% of Mn, 8.0-13.0% of Cr, 0.1-2.0% of W and/or Mo, calculated as (W/2 + Mo), 0.05-1.0% of Nb and/or V, calculated as (Nb/2 + V), 0.2-2.0% of Co, the remainder being Fe and chance impurities.