Nippon Steel Corporation

Michihisa Ito

Akihiro Miyasaka

Yasushi Nakamura

Hiroyuki Ogawa

Tetsuo Ishitsuka

Hiroyuki Katayama

Hiroyuki Kajioka

Takamasa Ohno

Mizuo Sakakibara

Makoto Inatomi

Kozo Denpo

Kazuumi Harashima

An alloy exhibiting corrosion resistance in a combustion environment where V, Na, S and Cl are present comprises, in weight percent, not more than 0.05% C, 0.02-0.5% Si, 0.02-0.5% Mn, 15-35% Cr, 0.5-4% Mo, 10-40% Co, 5-15% Fe, 0.5-5% W, 0.0003-0.005% Ca and the remainder of Ni at a content of not less than 4% and unavoidable impurities, provided that Cr (%)+0.5Ni (%)+3Mo (%).gtoreq.30 (%) and Ni (%)+0.5Co (%).gtoreq.Cr (%)+Mo (%)+W (%). A composite steel tube exhibiting corrosion resistance in a combustion environment where V, Na, S and Cl are present comprises an inner tube constituted of Cr-containing boiler tube and an outer tube constituted of the alloy.

Alloy and composite steel tube with corrosion resistance in combustion

A carbon-unsaturated molten metal or molten alloy containing elements more oxidizable than iron such as chromium and silicon is dephosphorized by addition of a flux composition comprising calcium carbide and a halide of alkali earth metal such as calcium fluoride in a non-oxidizing atmosphere, and thereafter the slag as a by-product is stabilized against formation of undesirable gases. This method when employed in refining ferrochromium or crude stainless steel makes feasible dephosphorization, and it is particularly suited for economical production of low phosphorus stainless steel.

Method of dephosphorization of metal or alloy

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Kanagawa-ken, Japan

Michihisa Ito