Abstract: In the continuous steel casting method of the present invention, a gap between strand support rolls with a strand in a rectangular shape interposed therebetween is increased toward a downstream side in a casting direction to thereby bulge the strand having an unsolidified layer thereinside such that the thickness between long-side surfaces of the strand increases within the range of 0.1% or more and 10% or less of the thickness of the strand inside a mold. A portion of the strand in which the solid phase fraction in a central portion of the strand is within the range of 0.2 or more and less than 0.9 satisfies a prescribed total rolling reduction and a prescribed reduction gradient, and a portion of the strand in which the solid phase fraction is within the range of 0.9 or more satisfies a prescribed total rolling reduction and a prescribed reduction gradient.

Abstract: In the continuous steel casting method of the present invention, a gap between strand support rolls with a strand in a rectangular shape interposed therebetween is increased toward a downstream side in a casting direction to thereby bulge the strand having an unsolidified layer thereinside such that the thickness between long-side surfaces of the strand increases within the range of 0.1% or more and 10% or less of the thickness of the strand inside a mold. A portion of the strand in which the solid phase fraction in a central portion of the strand is within the range of 0.2 or more and less than 0.9 satisfies a prescribed total rolling reduction and a prescribed reduction gradient, and a portion of the strand in which the solid phase fraction is within the range of 0.9 or more satisfies a prescribed total rolling reduction and a prescribed reduction gradient.

Abstract: A steel plate for line pipes containing, in terms of % by weight, C: 0.02 to 0.06%, Si: 0.5% or less, Mn: 0.8 to 1.6%, P: 0.008% or less, S: 0.0008% or less, Al: 0.08% or less, Nb: 0.005 to 0.035%, Ti: 0.005 to 0.025%, and Ca: 0.0005 to 0.0035%, and optionally contains one or more of Cu: 0.5% or less, Ni: 1% or less, Cr: 0.5% or less, Mo: 0.5% or less and V: 0.1% or less, and has a CP value of 0.95 or less represented by CP=4.46C(%)+2.37Mn(%)/6+{1.18Cr(%)+1.95Mo(%)+1.74V(%)}/5+{1.74Cu(%)+1.7Ni(%)}/15+22.36P(%), and a Ceq value of 0.30 or more represented by Ceq=C(%)+Mn(%)/6+{Cr(%)+Mo(%)+V(%)}/5 +{Cu(%)+Ni(%)}/15.

Abstract: A steel plate for line pipes containing, in terms of % by weight, C: 0.02 to 0.06%, Si: 0.5% or less, Mn: 0.8 to 1.6%, P: 0.008% or less, S: 0.0008% or less, Al: 0.08% or less, Nb: 0.005 to 0.035%, Ti: 0.005 to 0.025%, and Ca: 0.0005 to 0.0035%, and optionally contains one or more of Cu: 0.5% or less, Ni: 1% or less, Cr: 0.5% or less, Mo: 0.5% or less and V: 0.1% or less, and has a CP value of 0.95 or less represented by CP=4.46C(%)+2.37Mn(%)/6+{1.18Cr(%)+1.95Mo(%)+1.74V(%)}/5+{1.74Cu(%)+1.7Ni(%)}/15+22.36P(%), and a Ceq value of 0.30 or more represented by Ceq=C(%)+Mn(%)/6+{Cr(%)+Mo(%)+V(%)}/5+{Cu(%)+Ni(%)}/15.

Abstract: An immersion nozzle for continuous casting of steel supplies molten steel into a mold. At least a part of the immersion nozzle is formed of a refractory having a desulfurizing ability. A method for continuous casting of steel employs the immersion nozzle to supply molten steel into a mold using the immersion nozzle for continuous casting.

Abstract: An alloyed hot-dip galvanized steel sheet has a composition containing about 0.05 to about 0.25 wt % of C, about 0.5 wt % or less of Si, about 1 to about 3 wt % of Mn, about 0.1 wt % or less of P, about 0.01 wt % or less of S, about 0.1 to about 2 wt % of Al, and less than about 0.005 wt % of N, and satisfying the relations, Si+Al?0.6 wt %, (0.0006×Al) wt %?N?(0.0058?0.0026×Al) wt %, and Al?(1.25×C0.5?0.57×Si+0.625×Mn) wt %, the balance including Fe and inevitable impurities. The alloyed hot-dip galvanized steel sheet can be obtained without passing through a complicated process, has excellent surface appearance and anti-secondary work embrittlement and high strength, and is thus suitable for application to an automobile steel sheet.

Abstract: A galvannealed steel sheet contains, by % by mass, about 0.05 to about 0.25% of C, about 2.0% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfies the relations, Si +Al >0.6% and Cr +V +Mo =0.1 to 2%, the balance being Fe and inevitable impurities.

Abstract: A manufacturing method for a continuously cast product of steel includes the steps of detecting a position of a crater end of the product by a method for measuring a solidification state of continuously cast product using a sensor arranged so as to be in non-contact with the product, and controlling at least one condition selected from the conditions of the casting speed and the quantity of secondary cooling water based on the detected position of crater end.

Abstract: A manufacturing method for a continuously cast product of steel includes the steps of detecting a position of a crater end of the product by a method for measuring a solidification state of the continuously cast product using a sensor arranged so as to be in non-contact with the product, and controlling at least one condition selected from the conditions of the casting speed and the quantity of secondary cooling water based on the detected position of crater end.

Abstract: An immersion nozzle for continuous casting of steel supplies molten steel into a mold. At least a part of the immersion nozzle is formed of a refractory having a desulfurizing ability. A method for continuous casting of steel employs the immersion nozzle to supply molten steel into a mold using the immersion nozzle for continuous casting.

Abstract: A manufacturing method for a continuously cast product of steel includes the steps of detecting a position of crater end of product by a method for measuring a solidification state of continuously cast product using a sensor arranged so as to be in non-contact with the product, and controlling at least one condition selected from the conditions of the casting speed and the quantity of secondary cooling water based on the detected position of crater end. The method for measuring a solidification state of continuously cast product includes the steps of cooling the product until a surface layer portion thereof is ? transformed, transmitting transverse waves of electromagnetic ultrasonic waves to the cooled product, receiving the signal after the transmitting signal propagates in the product, and judging the solidification state of the product based on the received signal.

Abstract: A manufacturing method for a continuously cast product of steel includes the steps of detecting a position of crater end of product by a method for measuring a solidification state of continuously cast product using a sensor arranged so as to be in non-contact with the product, and controlling at least one condition selected from the conditions of the casting speed and the quantity of secondary cooling water based on the detected position of crater end. The method for measuring a solidification state of continuously cast product includes the steps of cooling the product until a surface layer portion thereof is ? transformed, transmitting transverse waves of electromagnetic ultrasonic waves to the cooled product, receiving the signal after the transmitting signal propagates in the product, and judging the solidification state of the product based on the received signal.

Abstract: The present invention provides a manufacturing method for a continuously cast product of steel comprising the steps of: detecting a position of crater end of product by a method for measuring a solidification state of continuously cast product using a sensor arranged so as to be in non-contact with the product; and controlling at least one condition selected from the conditions of the casting speed and the quantity of secondary cooling water based on the detected position of crater end, the method for measuring a solidification state of continuously cast product comprising the steps of: cooling the product until a surface layer portion thereof is &agr; transformed; transmitting transverse waves of electromagnetic ultrasonic waves to the cooled product; receiving the signal after the transmitting signal propagates in the product; and judging the solidification state of the product based on the received signal.