Abstract: In this invention, the smelting reduction operation can be carried out in a high efficiency by charging a carbonaceous material in such an amount that total surface area is not less than 60 m.sup.2 per 1 ton of slag weight. Carbon substance finely particulating through thermal crumbling under a high-temperature atmosphere inside the vessel is used as the carbonaceous material, whereby it is possible to stably conduct the smelting reduction while controlling the scattering of the carbonaceous material, and also the erosion, particularly locally erosion of refractory in the smelting reduction furnace, which was a serious problem in the conventional technique, can considerably be decreased to largely prolong the service life of refractory.

Abstract: A method of removing non-metallic inclusions from a molten metal by allowing the molten metal to pass through at least first and second vessels which are intermediate between a ladle and a mold. The molten metal is made to stay in the vessel for a period not shorter than 40 seconds while a horizontal rotation is imparted to the molten metal in the first vessel. The molten metal is then transferred from the first vessel to the second vessel. The molten metal in the second vessel is then heated. This method is suitably carried out by an apparatus comprising a first vessel having a discharge opening at its bottom and surrounded by a rotational magnetic field generating device for centrifugation of the molten metal in the first vessel, and a second vessel for receiving the molten metal discharged from the first vessel and provided with a heating device for heating the molten metal received therein.

Abstract: A method of stabilizing a steel making slag composed mainly of dicalcium silicate is disclosed, which comprises adding a boron-containing mineral obtained by adjusting an amount of crystal water to 4-12% by weight, whereby the powdering of the slag is prevented in the cooling.

Abstract: Disclosed herein is a flow change-over valve for the blowing of fluids into a molten metal vessel, which includes a housing provided with at least three inlet ports for different fluids and an outlet port, a valve body with a main passage communicating selectively between one of the inlet ports and the outlet port and rotatably supported in the housing to perform the changing-over of inlet passages. Among these inlet ports, an inlet port for purging fluid is opened in the housing, and a shroud-like gap surrounding the valve body is formed between the inner periphery of the housing and the outer periphery of the valve body in such a manner that it communicates with the inlet port for the purging fluid disposed in the housing and is always to be communicated with an opening of an inlet port of the main passage during the changing-over through the rotation of the valve body.

Abstract: A process for producing a steel in at least two converters using a great or substantial amount of an iron-bearing cold material. The iron-bearing cold material and a carbonaceous material are supplied into one of the converters under the presence of a molten iron or a preliminarily treated molten iron and are melted therein under oxygen-blowing to obtain a preliminarily treated molten iron containing a high content of carbon, and the preliminarily treated molten iron is refined in the other converter under oxygen-blowing to obtain a molten steel having the given composition.

Abstract: Injection-desulfurization of a molten iron is carried out in a low cost by using powdery CaCO.sub.3 obtained by pulverizing limestone as a desulfurizing agent. This injection-desulfurization also can be attained by using a powdery mixture in which a main ingredient is said powdery calcium carbonate and not more than 30% by weight of powdery quicklime is added thereto, a powdery mixture in which a main ingredient is said powdery calcium carbonate and 5.about.20% by weight of a carbonaceous material and 2.about.15% by weight of at least one of halides of alkali and alkaline earth metals are added thereto, or a powdery mixture in which a main ingredient is said calcium carbonate and 5.about.20% by weight of a carbonaceous material, 2.about.15% by weight of at least one of halides of alkali and alkaline earth metals and not more than 30% by weight of powdery quicklime are added thereto, as the desulfurizing agent.

Abstract: In order to enhance the CO concentration contained in exhaust gas generated during the refining of metal and to recover the CO as an energy source, granular limestone is blown into molten iron containing at least 0.3% of carbon through a tuyere together with a refining gas, and CO.sub.2 generated by the decomposition of the limestone is reacted with carbon contained in the molten iron to form CO, and the resulting CO is recovered.

Abstract: A method of dephosphorizing molten pig iron, wherein molten pig iron is charged into a refining vessel provided at its bottom with tuyeres for blowing gas and, if necessary, at its top with a gas injecting member, and a powdery refining agent together with the blowing gas is blown into molten pig iron through the tuyeres, while a flux for the refining agent is charged into the refining vessel to perform desiliconization and subsequent dephosphorization of molten pig iron, is disclosed. This method comprises(a) charging a coolant together with molten pig iron into the refining vessel to control a temperature of molten pig iron during the blowing to a range of 1,250.degree.-1,450.degree. C.;(b) blowing the powdery refining agent into molten pig iron so as to adjust a value of slag basicity after the treatment to not less than 2.5; and(c) blowing the blowing gas at a rate of not less than 0.5 Nm.sup.3 /min.t so that a net oxygen quantity is 8-15 Nm.sup.3 per ton of molten pig iron.

Abstract: A desulfurizing agent for injection mainly consisting of lime powders having a particle diameter which allows at least 50 wt. % of the lime powders to pass through a screen mesh of 100 .mu.m and containing 0.015 to 1.0 wt. % of silicone oil surfactant, 10 to 40 wt. % of carbonate or hydroxide of alkaline earth metal, and 2 to 20 wt. % of carbon. The desulfurizing agent further contains 2 to 10 wt. % of at least one fluoride selected from the group consisting of fluoride of alkaline metal, fluoride of alkaline earth metal, cryolite, and sodium silicofluoride.