Hitachi Metals, Ltd.

Hitachi, Ltd.

Ryoji Takahashi

Tetsuo Nakazawa

Junji Sakai

Fumio Obata

Syogo Morimoto

Seiji Okazaki

Takashi Kawai

Takatoshi Tanigawa

Michio Makino

Yoshimi Kubo

In a mold to be hardened by a CO.sub.2 gas, a mold binder material comprising a combination of polymers containing carboxyl groups, at least one of multi-valent metal oxides and multi-valent metal hydroxides, and resins of polyvinyl alcohol group, and at least one of sodium salt of gluconic acid and polyhydric alcohols or a mold binder material comprising a combination of polymers having carboxyl groups, at least one of multi-valent metal oxides and multi-valent metal hydroxides, and at least one of sodium salt of gluconic acid and polyhydric alcohols is provided. By use of the present binder material, the following various effects can be obtained: (1) easy preparation of mold sand, (2) easy removal of the binder material by water washing even if bodies or clothes are fouled by the binder material, (3) a longer working time of mold sands, (4) a higher mold strength, (5) an improved working atmosphere at shaping of the mold, (6) an improved production efficiency of molds, (7) the desired mold strength being obtained with a smaller amount of CO.sub.2 gas used, etc.

Mold binder material

A cast iron melting process comprising the steps of charging recarburizer in the lower portion of an electric arc furnace, charging iron scraps, and charging oxidizing slag-forming agents and/or sponge irons, and/or blowing oxygen therein to make oxidizing slag, whereby a recarburizing reaction of an iron melt with the recarburizer is carried out in parallel with an oxidizing reaction of an iron melt with an oxidizing slag, thereby minimizing the loss of C and Si, while improving a recarburizing yield, with the resulting improvements in economy.

Cast iron melting process

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Yukuhashi, Japan

Ryoji Takahashi