PURPOSE: To fine cating crystal grains and improve low temperature characteristics by contg. a specific small amt. of N and coating mill scale powder as a mold coating material on the inside surface of a mold at the casting in a low temp. service Ni-Cx type cast stainless steel.
CONSTITUTION: In producing a stainless steel contg. <0.08C, <2.0% Si, <2.0% Mn, <0.04% P, <0.04% S, 18-21% Cr, 8W11% Ni, and 0.12W0.16% N, and producing cast steel products to be used in low temp. environment such as in LNG plants, a mold coating material contg. mill scale powder is beforehand coated on the inside surface of a sand mold for casting in contact with molten metal. The casting crystal grains of cast steel products are fined by the heat depriving effect of the mill scale at the casting, the stability of an austenite phase at low temp. is improved considerably, superior work-induced martensite resistance is imparted and the mechanical properties at low temp. are improved.
TAJIMA TSUTOMU
YAMAZAKI KATSUO
OOTA YOSHIMITSU
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