In a continuous casting method for casting aluminum-deoxidized molten stainless steel 1 by using a continuous casting apparatus 100 in which a long nozzle 3 extending into a tundish 101 is provided at a ladle 2, the molten stainless steel 1 is poured into the tundish 101 through the long nozzle 3, while the spout 3a of the long nozzle 3 is being immersed in the molten stainless steel 1 that has been poured, and the molten stainless steel 1 in the tundish 101 is poured into a casting mold 105. A TD powder 5 is sprayed so that the powder covers the surface of the molten stainless steel 1 in the tundish 101, and nitrogen gas is supplied around the molten stainless steel 1. A calcium-containing material is added to the molten stainless steel 1 in a state other than a state of retention in the tundish 101.

The present invention provides a method for casting a slab with good cast surface quality. The method includes pouring molten metal 8 into a mold 2 from one of the paired shorter sides of the mold 2 while allowing superheat T [ C.], which is a temperature difference obtained by subtracting the melting point Tm [ C.] of the raw material from the temperature Tin [ C.] of the molten material on the surface of the molten metal in the mold and at the pouring point of the molten metal, to satisfy the following Formula (1) and Formula (2):

0.0014T.sup.2 +0.0144T+699.45>800 Formula (1)

0.0008T.sup.2 +0.2472T+853.02<1250 Formula (2)

Provided are a method for analyzing nitrogen in a metal sample, an apparatus for analyzing nitrogen in a metal sample, a method for adjusting nitrogen concentration in molten steel, and a method for manufacturing steel. The method includes: a melting process in which a metal sample containing a nitrogen component is melted in an argon gas atmosphere by performing impulse heating to gasify the nitrogen component; and an analyzing process in which nitrogen content in the metal sample is determined by analyzing nitrogen gas generated in the melting process and the argon gas by using a gas discharge optical emission method. By analyzing the nitrogen concentration of a sample taken from molten steel by using the analysis method described above, and by determining treatment conditions for adjusting nitrogen concentration on the basis of the nitrogen analysis value derived by the analysis, nitrogen concentration in molten steel is adjusted.

Provided are a method for analyzing nitrogen in a metal sample, an apparatus for analyzing nitrogen in a metal sample, a method for adjusting nitrogen concentration in molten steel, and a method for manufacturing steel. The method includes: a melting process in which a metal sample containing a nitrogen component is melted in an argon gas atmosphere by performing impulse heating to gasify the nitrogen component; and an analyzing process in which nitrogen content in the metal sample is determined by analyzing nitrogen gas generated in the melting process and the argon gas by using a gas discharge optical emission method. By analyzing the nitrogen concentration of a sample taken from molten steel by using the analysis method described above, and by determining treatment conditions for adjusting nitrogen concentration on the basis of the nitrogen analysis value derived by the analysis, nitrogen concentration in molten steel is adjusted.

Provided is a device for titanium continuous casting (1) capable, even when continuously casting large diameter titanium ingots or titanium alloy ingots, of suppressing component segregation thereof. The device for titanium continuous casting (1) comprises: a mold (3) having an upper section having a circular upper opening (3a) for pouring in molten metal (6), and a bottom section having a lower opening for continuously drawing ingots (11); and a plurality of plasma torches (4, 5) to heat the molten metal in the mold (3) from the upper opening (3a) side. The plurality of plasma torches (4, 5) are disposed so that the amount of heat input to the molten metal (6) present in the outer circumference enclosing the center of the upper opening (3a) is greater than the amount of heat input to the molten metal (6) present in the center of the upper opening (3a).

Provided is a device for titanium continuous casting (1) capable, even when continuously casting large diameter titanium ingots or titanium alloy ingots, of suppressing component segregation thereof. The device for titanium continuous casting (1) comprises: a mold (3) having an upper section having a circular upper opening (3a) for pouring in molten metal (6), and a bottom section having a lower opening for continuously drawing ingots (11); and a plurality of plasma torches (4, 5) to heat the molten metal in the mold (3) from the upper opening (3a) side. The plurality of plasma torches (4, 5) are disposed so that the amount of heat input to the molten metal (6) present in the outer circumference enclosing the center of the upper opening (3a) is greater than the amount of heat input to the molten metal (6) present in the center of the upper opening (3a).

Provided is a steel sheet having a predetermined chemical composition and structure wherein (Fe, Mn).sub.2B precipitates having a circle equivalent diameter of 50 to 300 nm are present in a number density of 1/500 m.sup.2 or more in a surface layer region down to a depth of 100 m from the surface in the sheet thickness direction. Further, provided is a method for producing a steel sheet comprising continuously casting a molten steel having a predetermined chemical composition to form a steel slab, wherein the continuously casting includes introducing more than 10 ppm and less than 100 ppm of oxygen into the surface layer of the steel slab, hot rolling including finish rolling the steel slab, wherein a completion temperature of the finish rolling is 650 to 950 C., coiling the obtained hot rolled steel sheet at a coiling temperature of 400 to 700 C., and cold rolling the hot rolled steel sheet, then annealing it.

Provided is a steel sheet having a predetermined chemical composition and structure wherein (Fe, Mn).sub.2B precipitates having a circle equivalent diameter of 50 to 300 nm are present in a number density of 1/500 m.sup.2 or more in a surface layer region down to a depth of 100 m from the surface in the sheet thickness direction. Further, provided is a method for producing a steel sheet comprising continuously casting a molten steel having a predetermined chemical composition to form a steel slab, wherein the continuously casting includes introducing more than 10 ppm and less than 100 ppm of oxygen into the surface layer of the steel slab, hot rolling including finish rolling the steel slab, wherein a completion temperature of the finish rolling is 650 to 950 C., coiling the obtained hot rolled steel sheet at a coiling temperature of 400 to 700 C., and cold rolling the hot rolled steel sheet, then annealing it.

A method and apparatus used to achieve alignment during mold assembly and accommodate thermal expansion comprising employing a compressible region and a modified interface dimension.

When a ribbon is cast by heating raw materials to prepare a molten R-T-B-based alloy and supplying the molten alloy to a chill roll to solidify the molten alloy, the temperature of the molten alloy is adjusted in accordance with at least one of the arithmetic mean roughness Ra and the mean spacing of profile irregularities Sm of the surface of the chill roll, thereby controlling the spacing between adjacent R-rich phases in a crystal structure of resulting alloy flakes to a desired value. This makes it possible to inhibit variations in the crystal structure of the resulting alloy flakes that may occur due to wear of the chill roll. In adjusting the temperature of the molten alloy in accordance with at least one of the arithmetic mean roughness Ra and the mean spacing of profile irregularities Sm, it is preferred that the molten alloy temperature be adjusted using the equation: t=7(|Ra||Sm|).sup.0.5/ where t is an amount of adjustment of the molten alloy temperature ( C.); Ra is an amount of change (m) in the arithmetic mean roughness Ra; Sm is an amount of change (m) in the mean spacing of profile irregularities Sm; and is a correlation coefficient.