Nippon Yakin Kogyo Co., Ltd.

Asahi Seiko Company Ltd.

Toshihiko Taniuchi

Masaomi Tsuda

Yoshito Fujiwara

Hiroshi Abe

Rikio Nemoto

Stainless steels for coins and method of producing coins of stainless

A continuously cast slab of Fe-Ni series alloy comprising 30-50 wt % of Ni or further 0.001-0.03 wt % of B and the balance of Fe is controlled to an eqiaxial crystal ratio of 20% or 30% in accordance with the existence or nonexistence of B content in the continuous casting and, if necessary, subjected to an electromagnetic stirring treatment or the like for controlling the eqiaxial crystal ratio and then heated at a temperature of not lower than 950.degree. C., 1000.degree. C. and 1100.degree. C. to economically produce Fe-Ni series alloys having improved effect for restraining streaks during etching.

Method of producing Fe-Ni series alloys having improved effect for

An ingot of Fe-Ni series alloy comprising 30-80 wt % of NI or further 0.001-0.03 wt % and B and the balance of Fe is upset at a forging ratio of at least 1/1.2U, hot forged at a total sectional reduction ratio of at least 30% to form a slab, from which fine crystal grains are formed at final heat treating stage, whereby Fe-Ni series alloys for electronic and electromagnetic materials are economically produced without generating streaks at the etching.

Particularly important properties required for exterior protective members for sheathing heaters are resistance to oxidation, anti-stress corrosion properties and weldability. An austenitic stainless steel for the exterior protective members has been developed from the findings that, firstly, the resistance to oxidation can be remarkably improved by increasing the Cr content together with a combined addition of Al and rare earth metals. Secondly, a small amount of Co addition is effective to enhance alloy ability to withstand stress corrosion cracking in the environment to which sheathing heaters are subjected, and that the weldability of such members can be made superior by maintaining the content of Si and Ti within a specified region.

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Kanagawa, Japan

Toshihiko Taniuchi