A device to cool a steel material having undergone hot rolling mills, the device including: a conveying mechanism which conveys the steel material while accelerating the steel material; a water cooling mechanism which cools the steel material while the conveying mechanism conveys the steel material; and a control unit which controls the conveying mechanism and the water cooling mechanism to cause the cooling of the steel material to satisfy Formula (1) below, wherein a water cooling time decrease rate in Formula (1) below is decided based on a length of a water cooling zone where the water cooling mechanism is provided and a time t.sub.c(0) required to cool a leading end portion of the steel material down to a target temperature,

t.sub.c(x)=t.sub.c(0).Math.xFormula (1),

where x: a conveyance-direction position in the steel material relative to the leading end portion of the steel material serving as a reference point, and t.sub.c(x): a time required to cool a portion at the position x of the steel material down to the target temperature.

Regarding each rolling mill, a rolling torque Gi before biting into a downstream stand is stored, the peripheral velocity of a most downstream stand Rn is controlled to be Gn1=Gn1* after biting into Rn, and a rolling torque Gn** of Rn after tension is stabilized is stored. After that, the peripheral velocity of a rolling mill Ri is controlled to be Gi=Gi* toward an upstream side, and the peripheral velocity of a rolling mill Rk at a downstream side of the rolling mill Ri is controlled to keep Gk=Gk** (k=i+1 to n) so that a rolling torque of a most upstream rolling mill R1 becomes equal to a stored G1*. Stabilization of material passage and improvement in accuracy of a product dimension are enabled by controlling tension between stands with high accuracy by using a simple control system without using table values or the like by each rolling condition even under a condition where a distance between stands is short.

Regarding each rolling mill, a rolling torque Gi before biting into a downstream stand is stored, the peripheral velocity of a most downstream stand Rn is controlled to be Gn1=Gn1* after biting into Rn, and a rolling torque Gn** of Rn after tension is stabilized is stored. After that, the peripheral velocity of a rolling mill Ri is controlled to be Gi=Gi* toward an upstream side, and the peripheral velocity of a rolling mill Rk at a downstream side of the rolling mill Ri is controlled to keep Gk=Gk** (k=i+1 to n) so that a rolling torque of a most upstream rolling mill R1 becomes equal to a stored G1*. Stabilization of material passage and improvement in accuracy of a product dimension are enabled by controlling tension between stands with high accuracy by using a simple control system without using table values or the like by each rolling condition even under a condition where a distance between stands is short.

A large-size H-shaped steel product is efficiently and stably produced by performing flat shaping and rolling of a large-size raw blank while improving a generation efficiency of flanges without bringing about problems such as elongation in a web height direction and deformation of a flange corresponding part. A rough rolling step includes an edging rolling step of rolling and shaping a material to be rolled into a predetermined almost dog-bone shape, and a flat rolling step of performing rolling of a web part by rotating the material to be rolled after completion of the edging rolling step by 90 or 270, upper and lower caliber rolls of at least one caliber of calibers configured to perform the flat rolling step include recessed parts configured to form a raised part at a middle of a web part of the material to be rolled, the recessed parts being provided at roll barrel length middle parts of the upper and lower caliber rolls, a width of the raised part formed in the flat rolling step is set to 25% or more and 50% or less of a web part inner size of the material to be rolled, and a thickness of the web part rolled in the flat rolling step is set to a predetermined thickness thicker than a web part thickness when the intermediate rolling step is started.

A large-size H-shaped steel product is efficiently and stably produced by performing flat shaping and rolling of a large-size raw blank while improving a generation efficiency of flanges without bringing about problems such as elongation in a web height direction and deformation of a flange corresponding part. A rough rolling step includes an edging rolling step of rolling and shaping a material to be rolled into a predetermined almost dog-bone shape, and a flat rolling step of performing rolling of a web part by rotating the material to be rolled after completion of the edging rolling step by 90 or 270, upper and lower caliber rolls of at least one caliber of calibers configured to perform the flat rolling step include recessed parts configured to form a raised part at a middle of a web part of the material to be rolled, the recessed parts being provided at roll barrel length middle parts of the upper and lower caliber rolls, a width of the raised part formed in the flat rolling step is set to 25% or more and 50% or less of a web part inner size of the material to be rolled, and a thickness of the web part rolled in the flat rolling step is set to a predetermined thickness thicker than a web part thickness when the intermediate rolling step is started.

[Object] To suppress occurrence of shape defects in a material to be rolled and enable efficient and stable production of an H-shaped steel product with a flange width larger than a conventional flange width by creating deep splits on end surfaces of a material (e.g., slab) using projections with acute-angle tip shapes, and sequentially bending formed flange portions. [Solution] Provided is a method for producing H-shaped steel, the method including: a rough rolling step; an intermediate rolling step; and a finish rolling step. In a rolling mill that performs the rough rolling step, a plurality of calibers to shape a material to be rolled are engraved, the number of the plurality of calibers being four or more. Shaping of one or a plurality of passes is performed on the material to be rolled in the plurality of calibers. In a first caliber and a second caliber among the plurality of calibers, projections to create splits vertically with respect to a width direction of the material to be rolled are formed. In a second caliber and subsequent calibers among the plurality of calibers, reduction is performed in a state where end surfaces of the material to be rolled are in contact with caliber peripheral surfaces in shaping of at least one pass. In a third caliber and subsequent calibers among the plurality of calibers, a step of sequentially bending divided parts formed by the splits is performed.

[Object] To suppress occurrence of shape defects in a material to be rolled and enable efficient and stable production of an H-shaped steel product with a flange width larger than a conventional flange width by creating deep splits on end surfaces of a material (e.g., slab) using projections with acute-angle tip shapes, and sequentially bending formed flange portions. [Solution] Provided is a method for producing H-shaped steel, the method including: a rough rolling step; an intermediate rolling step; and a finish rolling step. In a rolling mill that performs the rough rolling step, a plurality of calibers to shape a material to be rolled are engraved, the number of the plurality of calibers being four or more. Shaping of one or a plurality of passes is performed on the material to be rolled in the plurality of calibers. In a first caliber and a second caliber among the plurality of calibers, projections to create splits vertically with respect to a width direction of the material to be rolled are formed. In a second caliber and subsequent calibers among the plurality of calibers, reduction is performed in a state where end surfaces of the material to be rolled are in contact with caliber peripheral surfaces in shaping of at least one pass. In a third caliber and subsequent calibers among the plurality of calibers, a step of sequentially bending divided parts formed by the splits is performed.

[Object] To produce an H-shaped steel product with a flange width larger than a conventional flange width by, in a rough rolling step using calibers in producing H-shaped steel, creating deep splits on end surfaces of a material (e.g., slab) using projections with acute-angle tip shapes, and sequentially bending flange portions formed by the splits. [Solution] Provided is a method for producing H-shaped steel using a slab as a material. In a rolling mill that performs a rough rolling step, a plurality of calibers to shape a material to be rolled, and a web thinning caliber to thin a web of the material to be rolled that has been shaped in the plurality of calibers are engraved, the number of the plurality of calibers being three or more. Shaping of a plurality of passes is performed on the material to be rolled in part or all of the plurality of calibers. In a first caliber and a second caliber among the plurality of calibers, projections to create splits vertically with respect to a width direction of the material to be rolled are formed. In a third caliber and subsequent calibers among the plurality of calibers, a step of sequentially bending divided parts formed by the splits is performed. The projections formed in the first caliber and the second caliber have a tip angle of 40 or less.

[Object] To produce an H-shaped steel product with a flange width larger than a conventional flange width by, in a rough rolling step using calibers in producing H-shaped steel, creating deep splits on end surfaces of a material (e.g., slab) using projections with acute-angle tip shapes, and sequentially bending flange portions formed by the splits. [Solution] Provided is a method for producing H-shaped steel using a slab as a material. In a rolling mill that performs a rough rolling step, a plurality of calibers to shape a material to be rolled, and a web thinning caliber to thin a web of the material to be rolled that has been shaped in the plurality of calibers are engraved, the number of the plurality of calibers being three or more. Shaping of a plurality of passes is performed on the material to be rolled in part or all of the plurality of calibers. In a first caliber and a second caliber among the plurality of calibers, projections to create splits vertically with respect to a width direction of the material to be rolled are formed. In a third caliber and subsequent calibers among the plurality of calibers, a step of sequentially bending divided parts formed by the splits is performed. The projections formed in the first caliber and the second caliber have a tip angle of 40 or less.

The present invention relates to a method for producing H-shaped steel using a slab or the like having a rectangular cross-section as a material, for example. Provided is a method for producing H-shaped steel, the method including: a rough rolling step; an intermediate rolling step; and a finish rolling step. A slab material whose ratio of slab width to slab thickness is equal to or more than 6.0 and equal to or less than 7.7 is used as a material to be rolled. In a rolling mill a plurality of calibers having projections may be provided to shape the material to be rolled. The projections may have a height of 100 mm or more, and the tip of the projections may have an angle of equal to or more than 25 and equal to or less than 40.