Abstract: During continuous casting of metals, a non-moving, vibrating magnetic field is applied to a molten metal in a casting mold to impose only vibration on the molten metal. This continuous casting method can produce a cast slab much less susceptible to flux entrainment, capture of bubbles and non-metal inclusions near the surface of the molten metal, and surface segregation. The magnetic field is preferably produced by arranging electromagnets in an opposing relation on both sides of the mold to lie side by side in the direction of longitudinal width of the mold, and supplying a single-phase AC current to each coil. The single-phase AC current preferably has frequency of 0.10 to 60 Hz. A static magnetic field can be applied intermittently in the direction of thickness of a cast slab. This technique can produce a cast slab substantially free from the flux entrainment and the surface segregation. Preferably, the static magnetic field is intermittently applied under setting of an on-time t1=0.

Abstract: At least three electromagnets are disposed along the longitudinal direction of a mold. While the electromagnets generate a vibrating magnetic field, peak positions of the vibrating magnetic field is shifted in the longitudinal direction of the mold.

Abstract: At least three electromagnets are disposed along the longitudinal direction of a mold. While the electromagnets generate a vibrating magnetic field, peak positions of the vibrating magnetic field is shifted in the longitudinal direction of the mold.

Abstract: The composition of inclusions and the S concentration in steel are controlled in a manner such that, among the CaO-containing oxide inclusions present in a Ca-containing steel, an equilibrium S soluble amount (% S inc.) of at least 80% of the oxide inclusion particles having a particle diameter of 2 ?m or more are about 0.03 wt % or less, thereby inhibiting rust formation due to the inclusions, thus solving a problem which has long been of concern in Ca-containing steels.

Abstract: During continuous casting of metals, a non-moving, vibrating magnetic field is applied to a molten metal in a casting mold to impose only vibration on the molten metal. This continuous casting method can produce a cast slab much less susceptible to flux entrainment, capture of bubbles and non-metal inclusions near the surface of the molten metal, and surface segregation. The magnetic field is preferably produced by arranging electromagnets in an opposing relation on both sides of the mold to lie side by side in the direction of longitudinal width of the mold, and supplying a single-phase AC current to each coil. The single-phase AC current preferably has frequency of 0.10 to 60 Hz. A static magnetic field can be applied intermittently in the direction of thickness of a cast slab. This technique can produce a cast slab substantially free from the flux entrainment and the surface segregation. Preferably, the static magnetic field is intermittently applied under setting of an on-time t1 0.

Abstract: A method of producing a high nitrogen, ultra low carbon steel suitable to rolling material for use in cold rolled steel sheets having excellent age hardening property by an age hardening treatment after forming by working, with no defects in slabs or steel sheets, reliably, at a reduced cost and with a high productivity is proposed. The method for producing a rolling material for use in ultra low carbon steel sheets at: C≦0.0050 mass % comprises; applying primary decarburization refining to molten iron from a blast furnace, then controlling the composition in the molten steel after primary decarburization refining to a range satisfying the following relation: [mass % N]−0.15[mass % C]≧0.0060,  subsequently conducting secondary decarburization refining to a ultra low carbon concentration region while suppressing denitridation using a vacuum degassing facility, then conducting deoxidation by Al and, further, controlling the composition.

Abstract: During continuous casting of metals, a non-moving, vibrating magnetic field is applied to a molten metal in a casting mold to impose only vibration on the molten metal. This continuous casting method can produce a cast slab much less susceptible to flux entrainment, capture of bubbles and non-metal inclusions near the surface of the molten metal, and surface segregation. The magnetic field is preferably produced by arranging electromagnets in an opposing relation on both sides of the mold to lie side by side in the direction of longitudinal width of the mold, and supplying a single-phase AC current to each coil. The single-phase AC current preferably has frequency of 0.10 to 60 Hz. A static magnetic field can be applied intermittently in the direction of thickness of a cast slab. This technique can produce a cast slab substantially free from the flux entrainment and the surface segregation. Preferably, the static magnetic field is intermittently applied under setting of an on-time t1=0.

Abstract: Molten steel is poured using an immersion nozzle and a direct current magnetic field zone is applied to a cast slab over the entire width in the thickness direction thereof at a predetermined distance below the molten metal level in a continuously-casting mold. The immersion nozzle is provided with ejection holes located in at least upper and lower stages, at least one lower ejection hole is disposed such that these satisfy the following formula (1). The supply rate of molten steel from the upper ejection holes is set smaller than the rate consumed by solidification in an upper pool, and a particular solute element is added to the molten steel in the upper pool. 0<h<(½)·w·tan &thgr;  (1) where, &thgr;: downward angle of lower ejection hole(s) (°); w: length of mold in width direction (m); and h: distance from center of lower ejection hole to center of height of magnetic pole (m).

Abstract: A method of producing a high nitrogen, ultra low carbon steel suitable to rolling material for use in cold rolled steel sheets having excellent age hardening property by an age hardening treatment after forming by working, with no defects in slabs or steel sheets, reliably, at a reduced cost and with a high productivity is proposed.

Abstract: When molten steel is poured using an immersion nozzle in a state in which a direct current magnetic field zone is applied to a cast slab over the entire width in the thickness direction thereof at a position a predetermined distance below the molten metal level in a continuously-casting mold, the immersion nozzle is provided with ejection holes located in at least upper and lower two stages, at least one lower ejection hole is disposed such that these satisfies the following formula (1), the supply rate of the molten steel from upper ejection holes is set smaller than the rate consumed by solidification in an upper pool, and a particular solute element is added to the molten steel in the upper pool.

Abstract: Desulfurization is carried out by blowing CaO into molten iron, and a gas mixture of an inert gas and a hydrocarbon gas is used as a carrier. The ratio of the hydrocarbon gas to the desulfurizing agent is maintained in the range of from about 2.0 to about 50 Nl/kg. This desulfurizing method improves the desulfurization efficiency of the desulfurizing agent, increases the productivity of the desulfurizing process, and reduces the amount of slag generated in the desulfurizing process. Alternatively, a desulfurizing flux is blown into the molten iron together with a carrier gas comprising a gas mixture of an inert gas and a hydrocarbon gas or an inert gas alone at the start of desulfurization. The hydrocarbon gas in the carrier gas is increased, is added, or the unit gas is replaced by the hydrocarbon gas at adequate timing, whereby the desulfurization efficiency is improved.

Abstract: A process for desulfurizing a molten iron alloy in which a desulfurizing agent is applied to the molten iron alloy under agitation. Concurrently, a gas containing a hydrocarbon gas is blown onto the bath surface of the molten iron alloy, or a substance generating a hydrocarbon gas is added to the bath surface.

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 charging an iron scrap melting cupola with iron scrap and coke enables the iron scrap to be melted with high energy efficiency. The charging pipe feed is set at a level "h" which meets the condition of h .ltoreq. (r-r') tan .theta., and iron scrap of a quantity Ws meeting the condition of Ws .ltoreq. 1/3.multidot..pi.r.sup.3 .multidot.tan .theta..multidot..rho..sub.s is charged through the charging pipe, followed by charging of coke, wherein h represents the height of the charging feed above the material in the cupola (meters), r represents the inside radius of the cupola (meters), r' represents the inside radius of the charging pipe (meters), .theta. represents the angle of repose of the iron scrap (degrees), Ws represents the quantity of iron scrap per cycle (kg/ch), and .rho..sub.s represents the bulk specific gravity of the iron scrap (kg/m.sup.3).

Abstract: In a process of withdrawing castings while vertically oscillating a mold formed with long side walls and short side walls, the long side walls are moved apart from the castings by operating a hydraulic cylinder in the time zones for which the castings are applied with a large frictional force. On the contrary, the separated long side walls are made to move together to the casting in the other time zones for which the casting is not applied with the large frictional force. By repeating the separation and approaching of the long side walls, it is possible to obtain castings which are reduced in the depths of oscillation marks and suppressed in segregations at oscillation mark trough portions.

Abstract: One or more streams of molten metal poured into a continuous casting mold are acted on magnetically by static magnetic fields, covering substantially the entire width of the casting mold, thereby reducing the speed of the molten metal streams from the immersion nozzle, unifying the flow profile of the molten metal in the mold, preventing trapping and accumulating of mold powders and inclusions into the cast products. Magnetic poles are provided which are at least as wide as or wider than the minimum width of the cast products and the iron core is arranged on the same face of the casting mold with mutually opposite polarities in the drawing direction. Even if casting conditions change from time to time, defects in final products made of the cast metal are substantially reduced.

Abstract: Steel is continuously cast while adding a mold powder using a vertical continuous casting mold having two pairs of mold surfaces which form a casting cavity, wherein the surface temperature of the mold is kept at 700.degree. C. or more by forming the mold surfaces of a Ni-Cr alloy, and a mold powder having a solidifying point lower than the surface temperature is used so that the mold powder is maintained in a liquid-phase state.

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 removing non-metallic inclusions from a molten metal comprises the step of simultaneously applying both a horizontal rotation of the molten metal and heating of the molten metal by induction heating. After the simultaneous application of rotational force and heat, the induction heating may be stopped while the horizontal flow of the molten metal is maintained, so as to promote the separation of the particles of the inclusions. The method is carried out by using an apparatus which has a vessel which contains the molten metal, a rotary magnetic field generating device surrounding the vessel, and an induction heating device also surrounding the vessel. Each of the rotary magnetic field generating device and the induction heating device may be divided into a plurality of circumferential segments and arranged such that the segments of both devices are alternately disposed around the vessel.

Abstract: A process for producing an extremely low carbon steel in a top- and bottom-blown converter. The process is characterized in top-blowing a mixed gas of oxygen gas and an inert gas onto a molten steel in the top- and bottom-blown converter. The mixed gas is blown through a top-blowing lance at the final decarburization stage, while a gas (selected from a group consisting of an inert gas, oxygen gas and a mixture of oxygen and an inert gas) is bottom-blown into the molten steel in the converter.