Abstract: The object is to introduce a bottom-blown gas into a molten metal refining furnace so as to minimize the rate of blowing gas flow and increase the control range of the rate of blowing gas flow. There are included a refractory (1) having a plurality of holes (2) having an inner diameter of from 0.5 to 3.0 mm.phi. formed through said refractory and extending its working surface to its back, a metal cover (3) enclosing at least a part of the sides of the refractory (1) and a pressure box (4) formed in the bottom of the refractory (1) so as to communicate with the holes (2) and define a gas reservoir space. The molten metal is prevented from entering the holes (2) when the blowing gas pressure and the rate of blowing gas flow are decreased.

Abstract: A gas blowing nozzle is produced by molding a non-porous substance into a molding frame under pressure and at the same time positioning a plurality of gas passageways forming members at predetermined spaces and distances from each other. The passageway holes have cross sectional shapes as desired, so that the gas blowing may be accurately controlled to perform refining of molten metal.