Daido Tokushuko Kabushiki Kaisha

Daido Seiko Kabushiki Kaisha

Hisao Kamiya

Susumu Isobe

Takayoshi Shimizu

Noriyoshi Shibata

Toshiyuki Watanabe

A high strength stainless steel having a tensile strength of not less than 230 kgf/mm.sup.2 is disclosed, which comprises 0.01-0.015 st % of C and/or N, 1.0-4.0 wt % of Cu, 9.5-10.9 wt % of Ni, 12.0-17.0 wt % of Cr, 0.5-2.5 wt % of Al and/or Ti, 0.003-0.011 wt % of B, 0.02-0.2 wt % of Be and the balance of Fe, and has a temperature (Md.sub.30) of transforming 50% of austenite into martensite under a true strain of 0.3 within a range of from room temperature to -196.degree. C.

High strength stainless steel

A steel which is suitable for the material of a mold used for plastic molding and which has an improved resistance to corrosion under exposure to a halogen gas generated in injection molding of a thermoplastic synthetic resin blended with a halogen-containing flame-retarding agent is obtained by shaping a steel which consists essentially of up to 0.05% carbon, up to 1.0% silicon, up to 2.0% manganese, 5.0-8.0% nickel, 11.0-15.0% chromium, 1.0-4.0% molybdenum, 0.5-4.0% copper, 0.5-2.0% cobalt and the balance iron into a mold, and then subjecting the mold to age-hardening treatment at a temperature in the range of 400.degree.-450.degree. C. to obtain a hardness of H.sub.R C 30 or higher. The steel may further contain a small, predetermined amount of at least one machinability-improving component such as lead, tellurium, calcium and bismuth and/or a small, predetermined amount of at least one toughness or hardness-improving component such as tungsten, boron, titanium, vanadium, niobium and tantalum.

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Kariya, Japan

Hisao Kamiya