Denso Corporation

Fuji Oozx Inc.

Tohoku Steel Co., Ltd.

Yoshitaka Nishizawa

Masami Tanaka

Saburo Sugiura

Akihiro Hamada

Shinichi Umino

Shu Miyashita

The high carbon stainless steel containing more than 0.5 mass % carbon and more than 8 mass % chromium, or the tool steel containing more than 0.5 mass % carbon and more than 0.5 mass % at least one of carbide producing metal elements including chromium, molybdenum, tungsten, vanadium, niobium and titanium is processed by cold-warm working such as forging at a temperature of less than 800 &deg; C. to make more than 10% plastic deformation to an extent that cracks and voids are formed in the crystallized first stage carbide and, further, processed by a Hot Isostatic Pressing treatment so that the cracks and voids may be cured.

Cold-warm working and heat treatment method of high carbon-high alloy group steel

A steel for exhaust valves comprises C: 0.50-0.65 wt %, Si: 0.1-0.3 wt %, Mn: 5.0-8.0 wt %, Cr: 22.0-24.0 wt %, Ni: 5.0-7.0 wt %, Cu: 0.4-1.0 wt %, Mo: 0.4-2.0 wt %, W: 0.4-2.0 wt %, Nb: 0.4-2.0 wt %, Ti: 0.1-0.3 wt %, N: 0.35-0.50 wt %, sol. Al: 0.005-0.03 wt %, B: 0.001-0.01 wt %, provided that (Cu+Ni): 5.8-7.6 wt %, and the balance being Fe and inevitable impurities and has excellent high-temperature strength, corrosion resistance at room and higher temperatures and oxidation resistance.

Steels for exhaust valves having improved fatigue strength at high

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Sendai, Japan

Yoshitaka Nishizawa