PURPOSE: To provide a pipe of gating system made of metal which prevents the erosion and carburization phenomenon of the charging flow of molten metal by coating Al on the inside surface of a metallic pipe in contact with the molten metal, and heat-treating the same thereby providing it with an Fe-Al alloy layer wherein the concn. and thickness of Al are specified and an Al2O3 film.
CONSTITUTION: Al is coated at least on the side (inside surface side) of a metallic pipe made of carbon steel, alloy steel, stainless steel or the like in contact with molten metal. The Al coated layer is heat-treated to form an Fe-Al alloy layer wherein the concn. of the Al in the outermost part is 15W35wt% and the thickness is 0.1W1.0mm and an Al2O3 film on the surface. The Al2O3 film prevents the intrusion of oxygen atoms and metallic atoms, and further it prohibits the intrusion of carbon atoms; therefore, the film can be prevented from the carburization phenomenon by the carbon in the molten metal. The metallurgical binding between the Al2O3 film and the alloy and between the alloy and the metallic base is secure and there is no possibility of failure owing to thermal impact in the stage of casting. Such pipe of gating system is suited for a casting mold, etc.
EDA TETSUYA
NISHI ATSUSHI
SHICHIRI SHIGEMI
SINTOKOGIO LTD
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