Abstract: In an electric furnace for producing ordinary steels, alloy and others by arc heat of electrodes incorporated with gas blowing from a furnace bottom into dissolving and refining, plugs having fine pipe holes as gas blowing means are positioned in space each other in the furnace bottom for blowing the gas from beginning of refining to tapping in amount of 1 to 40 N/min per one pipe hole, 20 to 800 N/min per one plug, and at pressure of less than 10 kg/cm.sup.2.g, so that the heats upheaves swell in height of less than 1000 mm, preferably 50<.DELTA.h<500 mm. The gas is blown in a melting period to splash up the molten metal toward solid raw scraps. Further, a part of the molten steel produced by a previous charge is stayed in the furnace bottom, and the gas is blown from a charging period of scraps, and the melting time is shortened.

Abstract: A plug comprises a refractory body having a plurality of gas passgeways through which gas is blown into a refining apparatus. Each gas passageway may be defined by at least two metal tubes which are longitudinally spaced apart from each other. Alternatively, each gas passageway may be at least partly defined by an electrically insulating tube. The plug may alternatively have a plurality of gas passageways each having a bare refractory wall, while the body is reinforced with nonconductive mineral fibers, or metal wires which do not continuously extend throughout the plug. The plug may further be provided with a plurality of elongated holes extending in parallel to the gas passgeways from the inner surface of the body facing the interior of the refining apparatus to an intermediate portion thereof.

Abstract: A method for automatic pouring of molten metal from a ladle into a tundish through the use of a rotary nozzle, wherein the pouring operation between a ladle and a tundish in continuous casting of metal is effected by a rotary nozzle, and a plurality of pouring nozzles having different diameters are mounted on the rotary nozzle, whereby the pouring nozzles are used alternately by 100% fully opening and closing the same. The plurality of pouring nozzles with different diameters include at least a pouring nozzle whose pouring rate for wide open pouring is greater than that required to maintain the level of the molten metal in the tundish at a predetermined reference level and another pouring nozzle whose pouring rate for wide open pouring is less than that required to maintain the predetermined reference level.

Abstract: There is disclosed a molten metal level monitoring and controlling apparatus for continuous casting machines which employs an eddy-current type distance measuring device for measuring the level of the molten metal in the mold of a continuous casting machine. The eddy-current type distance measuring device generates a molten metal level signal by detecting in a noncontact manner the distance between its detecting mechanism fixedly mounted in place just above the surface of the molten metal and the molten metal level.