PURPOSE: To reduce adhesion of base metal to a molten metal tank by keeping stable blowing with high pressure gas from a buffer tank upon starting the blowing and during the blowing when powder is blown into the molten metal, and closing passages of the buffer tank and a blowing tank upon final end of the blowing to restrict the amount of gas blowing through the molten metal.

CONSTITUTION: Powder 13 is put into a blowing tank 1, and there are opened a gas supply valve 5, an automated valve 6, and an automated shutoff valve 7 to pressurized the inside of a blowing tank 1. Then, a feeder 2 and a powder fluid supply valve 8 are opened, and the powder is ejected with gas pressure on a uniform pressure line 11 and is blown into the molten cast after passage through a blowing line 12. The blowing tank 1 that is connected with a buffer tank 3 is restricted in pressure variations therein, and hence stable blowing is kept. Although upon final end of the blowing only gas in the blowing tank 1 is blown through the molten cast, the amount of gas and gas pressure are small, and hence is reduced in the amount not adhesion of base metal to a wall and a cover of a molten metal tank caused by splash of the melt. Further, since the blowing tank is filled with the powder so that the capacity of the tank is reduced.