Hitachi Metals, Ltd.

Nippondenso Co., Ltd.

Masakazu Ito

Toshio Okuno

Katsuaki Fukushima

Keizo Takeuchi

Toshiaki Terada

A high-strength stainless steel for use as a material of a fuel injection nozzle or a fuel injection needle of an internal combustion engine. The stainless steel is an as annealed martensitic stainless steel which exhibits a hardness not less than HRC 58 after quenching and tempering heat-treatment. The limit swaging ratio of said as annealed martensitic stainless steel is not less than 75%. The hardness of said as annealed martensitic stainless steel is not higher than HB 157. Preferably, the number of carbides having sizes of 0.2 .mu.m or less occupies not more than 50% of the total carbides, and wherein the limit swaging ratio of said as annealed martensitic stainless steel is not less than 75% or the hardness of said as annealed martensitic stainless steel is not higher than HB 157. Preferably, the stainless steel has a chemical composition containing, by weight: 0.4 to 0.6% of C; not more than 0.5% of Si; not more than 0.5% of Mn; 8.0 to 13.0% of Cr; 0.1 to 2.0% of one or both of W and Mo in terms of W/2+Mo; one or both of 0.05 to 1.0% of one or both of Nb and V in terms of Nb/2+V, and 0.2 to 2.0% of Co; and the balance substantially Fe and incidental impurities.

High-strength stainless steel for use as material of fuel injection

The present invention provides a material which is superior in all of peel resistance, corrosion resistance and abrasion resistance against alcoholic fuels. The material comprises an Fe-Cr-C based steel or Fe-Cr-C-Cu based steel. For applications wherein members formed from the material are subjected to impacts, the Cr content is within the range of at least 8.0% and less than 16.0%, the relation between the C content and the Cr content satisfies % Cr+25.times.% C.ltoreq.32 based on weight, and the ratio of the area of a primary carbide to the total sectional area of the material is 1.5% or less. For non-impact applications Cr content is more than 12.0% and less than 16.0%, % C and % Cr satisfy % Cr+25.times.% C&gt;32, and the ratio of the area of a primary carbide to the total sectional area of the material is 8.0% or less. This material is especially superior in peel resistance against alcoholic fuels. The Fe-Cr-C based steel may optionally contain Cu, Si, Mn, W, Mo, V, Co, and Ni.

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Yasugi, Japan

Masakazu Ito