Abstract: A device and a method for cooling a hot strip capable of uniformly cooling the hot-rolled steel strip from the leading end to the trailing end thereof during cooling of the steel strip using cooling water are provided. A cooling device 10 includes a plurality of tubular nozzles 15 inclined so as to eject rod-like flows of cooling water to a steel strip 12 at an ejecting angle ? in a traveling direction of the steel strip 12 and a pinch roller 11 disposed downstream of the tubular nozzles, the steel strip 12 to be nipped between the pinch roller 11 and a table roller 8.

Abstract: A method for cooling a hot strip conveyed on a run-out table after finishing, including ejecting rod-like flows of cooling water from nozzles to the upper surface of the steel strip such that the flows are inclined toward a traveling direction of the steel strip, and draining the cooling water using draining means disposed downstream of the nozzles.

Abstract: A hot-strip cooling device for cooling a hot strip that has been subjected to finish rolling while being conveyed over a run-out table. The device includes a plurality of cooling nozzles that are disposed above a steel strip and eject rod-like flows of coolant at an ejection angle tilted toward the upstream side in a steel-strip traveling direction; and purging means that is disposed on the upstream side with respect to the cooling nozzles and purges the coolant that has been ejected from the cooling nozzles and resides on the steel strip.

Abstract: A hot-strip cooling device and a cooling method are provided wherein uniform cooling of a hot-rolled steel strip using coolant is possible from the leading end to the trailing end of the steel strip. A cooling device (10) includes a plurality of round nozzles (15) disposed obliquely in such a manner as to eject rod-like flows of coolant at an ejection angle ? toward the upstream side in a direction in which a steel strip (12) travels, and a pinch roll (11) disposed on the upstream side with respect to the round nozzles (15) and configured to pinch the steel strip (12) in combination with a roller table (8).

Abstract: A hot rolled steel sheet cooling apparatus includes a gradual cooling header 2 including a rod-like cooling water nozzle 3 for gradual cooling and a rapid cooling header 4 including a rod-like cooling water nozzle 5 for rapid cooling such that the headers constitute a cooling unit 9. The cooling unit 9 includes an elevating unit 7 capable of moving upward and downward in unison with the cooling unit. In cooling the upper surface of a hot rolled steel sheet (hot rolled steel strip or steel plate), uniform and stable cooling is achieved while both of high cooling rate and low cooling rate are ensured.

Abstract: A method for manufacturing a high strength hot rolled steel sheet includes heating a slab to a temperature in the range of 1150 to 1300° C.; hot rolling the slab with a finishing rolling temperature being in the range of 800 to 1000° C.; cooling the steel sheet at a mean cooling rate of 30° C./s or higher to a cooling termination temperature in the range of 525 to 625° C.; suspending cooling for a time period in the range of 3 to 10 seconds; cooling the steel sheet in such a manner that cooling of the steel sheet is nucleate boiling; and coiling the steel sheet at a temperature in the range of 400 to 550° C.

Abstract: The method for cooling a hot strip which is obtained after a hot rolling process to the temperature range of 500° or less. Cooling water is brought into contact with the hot strip. The method includes a first cooling step and a subsequent second cooling step. Cooling is stopped at a strip temperature that is higher than a transition boiling initiation temperature in the first cooling step, and the cooling is conducted using the cooling water having a water flow rate that causes nucleate boiling in the subsequent second cooling step. Entering the temperature range of transition boiling can be completely prevented to avoid thermal instability in cooling resulting from the transition boiling, and the temperature variation of the strip after cooling is controlled to be small while the cooling end temperature can be precisely controlled.

Abstract: An ultra soft high carbon hot-rolled steel sheet has excellent workability. The steel sheet is a high carbon hot-rolled steel sheet containing 0.2 to 0.7% C, and has a structure in which mean grain size of ferrite is 20 ?m or larger, the volume percentage of ferrite grains having 10 ?m or smaller size is 20% or less, mean diameter of carbide is in a range from 0.10 ?m to smaller than 2.0 ?m, the percentage of carbide grains having 5 or more of aspect ratio is 15% or less, and the contact ratio of carbide is 20% or less.

Abstract: The present invention provides an ultra soft high carbon hot-rolled steel sheet. The ultra soft high carbon hot-rolled steel sheet contains 0.2% to 0.7% of C, 0.01% to 1.0% of Si, 0.1% to 1.0% of Mn, 0.03% or less of P, 0.035% or less of S, 0.08% or less of Al, 0.01% or less of N, and the balance being Fe and incidental impurities and further contains 0.0010% to 0.0050% of B and 0.05% to 0.30% of Cr in some cases. In the texture of the steel sheet, an average ferrite grain diameter is 20 ?m or more, a volume ratio of ferrite grains having a grain diameter of 10 ?m or more is 80% or more, and an average carbide grain diameter is in the range of 0.10 to less than 2.0 ?m. In addition, the steel sheet is manufactured by the steps, after rough rolling, performing finish rolling at a reduction ratio of 10% or more and at a finish temperature of (Ar3?20° C.) or more in a final pass, then performing first cooling within 2 seconds after the finish rolling to a cooling stop temperature of 600° C.

Abstract: An ultra soft high carbon hot-rolled steel sheet has excellent workability. The steel sheet is a high carbon hot-rolled steel sheet containing 0.2 to 0.7% C, and has a structure in which mean grain size of ferrite is 20 ?m or larger, the volume percentage of ferrite grains having 10 ?m or smaller size is 20% or less, mean diameter of carbide is in a range from 0.10 ?m to smaller than 2.0 ?m, the percentage of carbide grains having 5 or more of aspect ratio is 15% or less, and the contact ratio of carbide is 20% or less.

Abstract: A method for cooling a hot strip with less facilities and processing costs in which the temperature variation of a strip after cooling is controlled to be small and a cooling end temperature can be precisely controlled particularly when the hot strip is cooled to the temperature range of 500° C. or less is provided. The method for cooling a hot strip, which is obtained after a hot rolling process, by bringing cooling water into contact with the hot strip, includes a first cooling step and a subsequent second cooling step. In this method, cooling is stopped at a strip temperature that is higher than a transition boiling initiation temperature in the first cooling step, and the cooling is conducted using the cooling water having a water flow rate that causes nucleate boiling in the subsequent second cooling step.

Abstract: A cooling device and a cooling method for a hot strip allow uniform and stable cooling of the strip at a high cooling rate when supplying the coolant to the upper surface of the hot strip. The cooling device includes an upper header unit 21 for supplying a rod-like flow to the upper surface of the strip 10. The upper header unit 21 is formed of the first upper header group including plural first upper headers 21a arranged in a conveying direction and a second upper header group including plural second upper headers 21b arranged in the conveying direction. The cooling device is provided with an ON-OFF mechanism 30 to allow each of the upper headers 21a and 21b of the first and the second upper header groups to independently execute the ON-OFF control (start/end injection control) of an injection (feeding) of the rod-like flow.

Abstract: There are provided a cooling device and a cooling method for a hot-rolled strip in which the strip can be uniformly cooled from a leading edge to a trailing edge with coolant by properly realizing a great cooling ability and a stable cooling zone. Specifically, the following three methods are adopted. (1) Round nozzles 14 for ejecting inclined rodlike flows of coolant to a downstream side in the traveling direction of a strip 12 and round nozzles 14 for ejecting inclined rodlike flows of coolant to an upstream side in the traveling direction are arranged on an upper side of the strip 12 so as to oppose each other. (2) Round nozzles 14 for ejecting inclined rodlike flows of coolant from the upstream side of a roller table 9 toward just above the roller table 9 and round nozzles 14 for ejecting inclined rodlike flows of coolant from the downstream side of the roller table 9 toward just above the roller table 9 are arranged on the upper side of the strip 12 so as to each other.

Abstract: A device and a method for cooling a hot strip capable of uniformly cooling the hot-rolled steel strip from the leading end to the trailing end thereof during cooling of the steel strip using cooling water are provided. A cooling device 10 includes a plurality of tubular nozzles 15 inclined so as to eject rod-like flows of cooling water to a steel strip 12 at an ejecting angle ? in a traveling direction of the steel strip 12 and a pinch roller 11 disposed downstream of the tubular nozzles, the steel strip 12 to be nipped between the pinch roller 11 and a table roller 8.

Abstract: The present invention provides an ultra soft high carbon hot-rolled steel sheet. The ultra soft high carbon hot-rolled steel sheet contains 0.2% to 0.7% of C, 0.01% to 1.0% of Si, 0.1% to 1.0% of Mn, 0.03% or less of P, 0.035% or less of S, 0.08% or less of Al, 0.01% or less of N, and the balance being Fe and incidental impurities and further contains 0.0010% to 0.0050% of B and 0.05% to 0.30% of Cr in some cases. In the texture of the steel sheet, an average ferrite grain diameter is 20 ?m or more, a volume ratio of ferrite grains having a grain diameter of 10 ?m or more is 80% or more, and an average carbide grain diameter is in the range of 0.10 to less than 2.0 ?m. In addition, the steel sheet is manufactured by the steps, after rough rolling, performing finish rolling at a reduction ratio of 10% or more and at a finish temperature of (Ar3?20° C.) or more in a final pass, then performing first cooling within 2 seconds after the finish rolling to a cooling stop temperature of 600° C.

Abstract: A hot-strip cooling device and a cooling method are provided wherein uniform cooling of a hot-rolled steel strip using coolant is possible from the leading end to the trailing end of the steel strip. A cooling device (10) includes a plurality of round nozzles (15) disposed obliquely in such a manner as to eject rod-like flows of coolant at an ejection angle ? toward the upstream side in a direction in which a steel strip (12) travels, and a pinch roll (11) disposed on the upstream side with respect to the round nozzles (15) and configured to pinch the steel strip (12) in combination with a roller table (8).