Disclosed is a continuous rapid solidification apparatus, which has a cooling roll configured to cool a molten metal supplied to an outer circumference surface thereof; a crucible configured to supply the cooling roll with the molten metal; a molten metal supply configured to melt a raw material metal and supply the crucible with the molten metal; a first chamber configured to form a sealed space where the molten metal supplied from the crucible is cooled by the cooling roll; and a second chamber configured to be formed of a space separated from the first chamber and to form a sealed space where the molten metal is supplied to the crucible by the molten metal supply.

Disclosed is a continuous rapid solidification apparatus, which has a cooling roll configured to cool a molten metal supplied to an outer circumference surface thereof; a crucible configured to supply the cooling roll with the molten metal; a molten metal supply configured to melt a raw material metal and supply the crucible with the molten metal; a first chamber configured to form a sealed space where the molten metal supplied from the crucible is cooled by the cooling roll; and a second chamber configured to be formed of a space separated from the first chamber and to form a sealed space where the molten metal is supplied to the crucible by the molten metal supply.

Provided is casting equipment and a casting method using same. A casting method includes: preparing a tundish; injecting molten steel to the tundish; installing a vacuum forming member on an upper portion of the tundish to form vacuum in at least a partial area of an upper portion of a melting surface of molten steel accommodated in the tundish; forming a rotational flow by blowing a gas into the molten steel; and forming vacuum in at least a partial area of the upper portion of the melting surface of the molten steel. More particularly, the present disclosure may effectively remove inclusions in the molten steel and restrict reoxidation of the molten steel.

Provided is casting equipment and a casting method using same. A casting method includes: preparing a tundish; injecting molten steel to the tundish; installing a vacuum forming member on an upper portion of the tundish to form vacuum in at least a partial area of an upper portion of a melting surface of molten steel accommodated in the tundish; forming a rotational flow by blowing a gas into the molten steel; and forming vacuum in at least a partial area of the upper portion of the melting surface of the molten steel. More particularly, the present disclosure may effectively remove inclusions in the molten steel and restrict reoxidation of the molten steel.

A spring steel includes a predetermined chemical composition and a composite inclusion having a maximum diameter of 2 m or more that TiN is adhered to an inclusion containing REM, O and Al, in which the number of the composite inclusion is 0.004 pieces/mm.sup.2 to 10 pieces/mm.sup.2, the maximum diameter of the composite inclusion is 40 m or less, the sum of the number density of an alumina cluster having the maximum diameter of 10 m or more, MnS having the maximum diameter of 10 m or more and TiN having the maximum diameter of 1 m to 10 pieces/mm.sup.2.

A spring steel includes a predetermined chemical composition and a composite inclusion having a maximum diameter of 2 m or more that TiN is adhered to an inclusion containing REM, O and Al, in which the number of the composite inclusion is 0.004 pieces/mm.sup.2 to 10 pieces/mm.sup.2, the maximum diameter of the composite inclusion is 40 m or less, the sum of the number density of an alumina cluster having the maximum diameter of 10 m or more, MnS having the maximum diameter of 10 m or more and TiN having the maximum diameter of 1 m to 10 pieces/mm.sup.2.

A system and method for continuous casting. The system includes a melt chamber, a withdrawal chamber, and a secondary chamber therebetween. The melt chamber can maintain a melting pressure and the withdrawal chamber can attain atmospheric pressure. The secondary chamber can include regions that can be adjusted to different pressures. During continuous casting operations, the first region adjacent to the melt chamber can be adjusted to a pressure that is at least slightly greater than the melting pressure; the pressure in subsequent regions can be sequentially decreased and then sequentially increased. The pressure in the final region can be at least slightly greater than atmospheric pressure. The differential pressures can form a dynamic airlock between the melt chamber and the withdrawal chamber, which can prevent infiltration of the melt chamber by non-inert gas in the atmosphere, and thus can prevent contamination of reactive materials in the melt chamber.

A system and method for continuous casting. The system includes a melt chamber, a withdrawal chamber, and a secondary chamber therebetween. The melt chamber can maintain a melting pressure and the withdrawal chamber can attain atmospheric pressure. The secondary chamber can include regions that can be adjusted to different pressures. During continuous casting operations, the first region adjacent to the melt chamber can be adjusted to a pressure that is at least slightly greater than the melting pressure; the pressure in subsequent regions can be sequentially decreased and then sequentially increased. The pressure in the final region can be at least slightly greater than atmospheric pressure. The differential pressures can form a dynamic airlock between the melt chamber and the withdrawal chamber, which can prevent infiltration of the melt chamber by non-inert gas in the atmosphere, and thus can prevent contamination of reactive materials in the melt chamber.

A method is disclosed for the operationally reliable production of a cold-rolled flat steel product of ?0.5 mm in thickness for deep-drawing and ironing applications. In the method, a steel melt which (in wt %) comprises up to 0.008% C, up to 0.005% Al, up to 0.043% Si, 0.15-0.5% Mn, up to 0.02% P, up to 0.03% S, up to 0.020% N and in each case optionally up to 0.03% Ti and up to 0.03% Nb and, as a remainder, iron and unavoidable impurities, is, with the omission of a Ca treatment, subjected to a secondary metallurgical treatment which, in addition to a vacuum treatment, comprises a ladle furnace treatment and during which the steel melt to be treated is kept under a slag, the Mn and Fe contents of which are, in sum total, <15 wt %. From the steel melt, a thin slab or a cast strip are produced, which are subsequently hot-rolled to form a hot strip with a thickness of <2.5 mm and wound to form a coil. Subsequently, the hot strips are cold-rolled to form a flat steel product of up to 0.5 mm in thickness.

Provided are a high-strength steel sheet having a specified chemical composition, in which a Mn-segregation degree in a region within 100 m from a surface thereof in a thickness direction is 1.5 or less, in a plane parallel to the surface of the steel sheet in a region within 100 m from the surface of the steel sheet in the thickness direction, the number of oxide-based inclusion grains having a grain long diameter of 5 m or more is 1000 or less/100 mm.sup.2, a proportion of the number of oxide-based inclusion grains having a chemical composition containing alumina of 50 mass % or more, silica of 20 mass % or less, and calcia of 40 mass % or less to the total number of oxide-based inclusions having a grain long diameter of 5 m or more is 80% or more, a specified metallographic structure, and a TS of 980 MPa or more, a high-strength galvanized steel sheet, and a manufacturing method thereof.