A spring steel according to the present embodiment has a chemical composition consisting of, in mass %, C: 0.4 to 0.7%, Si: 1.1 to 3.0%, Mn: 0.3 to 1.5%, P: 0.03% or less, S: 0.05% or less, Al: 0.01 to 0.05%, rare earth metal: 0.0001 to 0.002%, N: 0.015%, O or less: 0.0030% or less, Ti: 0.02 to 0.1%, with the balance being Fe and impurities. In the spring steel, the number of oxide inclusions having an equivalent circular diameter of equal to or greater than 5 m is equal to or less than 0.2/mm.sup.2, the oxide inclusions each being one of an Al-based oxide, a complex oxide containing REM, O and Al, and a complex oxysulfide containing REM, O, S, and Al. Further, a maximum value among equivalent circular diameters of the oxide inclusions is equal to or less than 40 m.

A spring steel according to the present embodiment has a chemical composition consisting of, in mass %, C: 0.4 to 0.7%, Si: 1.1 to 3.0%, Mn: 0.3 to 1.5%, P: 0.03% or less, S: 0.05% or less, Al: 0.01 to 0.05%, rare earth metal: 0.0001 to 0.002%, N: 0.015%, O or less: 0.0030% or less, Ti: 0.02 to 0.1%, with the balance being Fe and impurities. In the spring steel, the number of oxide inclusions having an equivalent circular diameter of equal to or greater than 5 m is equal to or less than 0.2/mm.sup.2, the oxide inclusions each being one of an Al-based oxide, a complex oxide containing REM, O and Al, and a complex oxysulfide containing REM, O, S, and Al. Further, a maximum value among equivalent circular diameters of the oxide inclusions is equal to or less than 40 m.

Provided is a device for preparing a large-sized high-quality aluminium alloy ingot, which is mainly composed of a uniform cooler, a hot top, an oil-gas lubrication mold, an induction coil and a dummy ingot, wherein the hot top is arranged above the oil-gas lubrication mold, the induction coil is arranged outside the oil-gas lubrication mold, the uniform cooler is arranged inside the oil-gas lubrication mold, and the dummy ingot is arranged below the oil-gas lubrication mold. Further provided is a method for preparing a large-sized high-quality aluminium alloy ingot. The device combines a partitioned gas supply mold with the uniform cooler and an electromagnetic stirrer, and the effective coupling of the three achieves forced and uniform solidification forming of a melt under gas pressure contact conditions, such that a stable and continuous gas film is formed between the melt and the mold. The ingot has a smooth surface, and a fine and uniform internal structure.

Provided is a device for preparing a large-sized high-quality aluminium alloy ingot, which is mainly composed of a uniform cooler, a hot top, an oil-gas lubrication mold, an induction coil and a dummy ingot, wherein the hot top is arranged above the oil-gas lubrication mold, the induction coil is arranged outside the oil-gas lubrication mold, the uniform cooler is arranged inside the oil-gas lubrication mold, and the dummy ingot is arranged below the oil-gas lubrication mold. Further provided is a method for preparing a large-sized high-quality aluminium alloy ingot. The device combines a partitioned gas supply mold with the uniform cooler and an electromagnetic stirrer, and the effective coupling of the three achieves forced and uniform solidification forming of a melt under gas pressure contact conditions, such that a stable and continuous gas film is formed between the melt and the mold. The ingot has a smooth surface, and a fine and uniform internal structure.

Production plant of metal rods, casting machine, casting process and control method of at least three electromagnetic stirrer devices, wherein one provides at least one phase of switching between two operating configurations of the electromagnetic stirrer devices of which a first operating configuration with the generation of a rotating electromagnetic field inducing in the metallic material in the molten state a rotational motion and a second operating configuration with the generation of a linear electromagnetic field inducing in the metallic material in the molten state a linear motion.

Production plant of metal rods, casting machine, casting process and control method of at least three electromagnetic stirrer devices, wherein one provides at least one phase of switching between two operating configurations of the electromagnetic stirrer devices of which a first operating configuration with the generation of a rotating electromagnetic field inducing in the metallic material in the molten state a rotational motion and a second operating configuration with the generation of a linear electromagnetic field inducing in the metallic material in the molten state a linear motion.

There is provided a molding device for continuous casting equipped with an agitator that reduces the amount of generated heat, is easy to carry out maintenance, is inexpensive, and is easy to use in practice. The molding device for continuous casting equipped with an agitator of the invention receives liquid-phase melt of a conductive material, and a solid-phase cast product is taken out from the molding device through the cooling of the melt. The molding device includes a casting mold and an agitator provided so as to correspond to the casting mold. The casting mold includes a casting space that includes an inlet and an outlet at a central portion of a substantially cylindrical side wall, and a magnetic field generation device receiving chamber that is formed in the side wall and is positioned outside the casting space. The casting mold receives the liquid-phase melt from the inlet into the casting space and discharges the solid-phase cast product from the outlet through the cooling in the casting space. The agitator includes a magnetic field generation device having an electrode unit that includes first and second electrodes supplying current to at least the liquid-phase melt present in the casting space, and a permanent magnet that applies a magnetic field to the liquid-phase melt. The magnetic field generation device is received in the magnetic field generation device receiving chamber of the casting mold, generates magnetic lines of force toward a center in a lateral direction, makes the magnetic lines of force pass through a part of the side wall of the casting mold and reach the casting space, and applies lateral magnetic lines of force, which cross the current, to the melt.

There is provided a molding device for continuous casting equipped with an agitator that reduces the amount of generated heat, is easy to carry out maintenance, is inexpensive, and is easy to use in practice. The molding device for continuous casting equipped with an agitator of the invention receives liquid-phase melt of a conductive material, and a solid-phase cast product is taken out from the molding device through the cooling of the melt. The molding device includes a casting mold and an agitator provided so as to correspond to the casting mold. The casting mold includes a casting space that includes an inlet and an outlet at a central portion of a substantially cylindrical side wall, and a magnetic field generation device receiving chamber that is formed in the side wall and is positioned outside the casting space. The casting mold receives the liquid-phase melt from the inlet into the casting space and discharges the solid-phase cast product from the outlet through the cooling in the casting space. The agitator includes a magnetic field generation device having an electrode unit that includes first and second electrodes supplying current to at least the liquid-phase melt present in the casting space, and a permanent magnet that applies a magnetic field to the liquid-phase melt. The magnetic field generation device is received in the magnetic field generation device receiving chamber of the casting mold, generates magnetic lines of force toward a center in a lateral direction, makes the magnetic lines of force pass through a part of the side wall of the casting mold and reach the casting space, and applies lateral magnetic lines of force, which cross the current, to the melt.

A method for manufacturing carbon fiber reinforced aluminum composites is provided. Particularly, the method uses a stir casting process during a melting and casting process and reduces a contact angle of carbon against aluminum by inputting carbon fibers while supplying a current to liquid aluminum to induce the carbon fibers to be spontaneously and uniformly distributed in the liquid aluminum and inhibits a formation of an aluminum carbide (Al.sub.4C.sub.3) phase on an interface between the aluminum and the carbon fiber, thereby manufacturing carbon fiber reinforced aluminum composites having excellent electrical, thermal and mechanical characteristics.

A method for manufacturing carbon fiber reinforced aluminum composites is provided. Particularly, the method uses a stir casting process during a melting and casting process and reduces a contact angle of carbon against aluminum by inputting carbon fibers while supplying a current to liquid aluminum to induce the carbon fibers to be spontaneously and uniformly distributed in the liquid aluminum and inhibits a formation of an aluminum carbide (Al.sub.4C.sub.3) phase on an interface between the aluminum and the carbon fiber, thereby manufacturing carbon fiber reinforced aluminum composites having excellent electrical, thermal and mechanical characteristics.