Provided is an endless rolling apparatus and method, which have improved cooling conditions for producing advanced high strength steel. The endless rolling apparatus includes: a continuous casting machine for casting a slab; and a cooling bed having at least one piece of water-cooling equipment and at least one rolling mill continuously connected to the continuous casting machine, wherein, in the cooling bed, an initial position (S) at which the water-cooling equipment is provided so as to manufacture advanced high strength steel through at least one water-cooling is defined by mathematical formula 1. Here, H is the thickness (mm) of a slab, V is the casting speed (m/sec) of the slab, h is the product thickness (mm), and t is the target arrival time (sec) until entry into the cooling bed.

Provided is an endless rolling apparatus and method, which have improved cooling conditions for producing advanced high strength steel. The endless rolling apparatus includes: a continuous casting machine for casting a slab; and a cooling bed having at least one piece of water-cooling equipment and at least one rolling mill continuously connected to the continuous casting machine, wherein, in the cooling bed, an initial position (S) at which the water-cooling equipment is provided so as to manufacture advanced high strength steel through at least one water-cooling is defined by mathematical formula 1. Here, H is the thickness (mm) of a slab, V is the casting speed (m/sec) of the slab, h is the product thickness (mm), and t is the target arrival time (sec) until entry into the cooling bed.

A hot-rolled steel sheet is cooled by jetting cooling water from spray nozzles to a steel sheet conveyance region in a width direction of the steel sheet conveyance region. The steel sheet conveyance region is a region that the hot-rolled steel sheet occupies on conveyor rolls, a pair of spray nozzles is arranged on both lateral sides in the width direction of the steel sheet conveyance region, and a plurality of spray nozzle pairs are aligned in a conveyance direction of the hot-rolled steel sheet. In regard to a collision region of cooling water jetted from the spray nozzle at the steel sheet conveyance region, a far end in a jet direction is positioned at an end of the steel sheet conveyance region, and a near end is positioned on an inner side of the steel sheet conveyance region. In the spray nozzle pair, the near ends of two collision regions coincide in the width direction to form a meeting.

A cooling section for flat rolling stock (1) has a working region (2), through which the flat rolling stock (1) is guided. The working region (2) can be supplied with a liquid coolant (4) by means of a number of spray beams (3i). The liquid coolant (4) is fed from a reservoir (7) for the liquid coolant (4) to the spray beams (3i) by means of a pump (5) and a supply system (6). Valves (9i) are arranged upstream of the spray beams (3i) in the supply system (6). Opening positions (si) of the valves (9i) are set by a control unit (10) of the cooling section according to a respective sub-flow (fi) that is to be applied to the flat rolling stock (1) by means of each spray beam (3i). Also, the delivery rate (M) of the pump (5) and/or a line pressure (p) generated by the pump (5) in the supply system (6) are set by the control unit (10) according to the total flow (F) that is to be applied to the flat rolling stock (1) by means of all the spray beams (3i).

A method for improving the flatness of a rolled sheet or strip includes the application of differential cooling. A cooling agent can be selectively applied along the width of the strip. More cooling can be applied to the edges of the strip, where tension is greatest, to increase tension at the edges. The strip can be allowed to lengthen at these edges, which can improve flatness. In some embodiments, a closed loop flatness control system is used to measure the flatness of a strip and automatically adjust the differential cooling based on the measurement.

A method for producing ultra-thin hot-rolled strip steel, the method comprising the following process steps: A. a smelting process: feeding scrap steel into an induction electric furnace (1) for smelting so that the scrap steel melts into molten steel; B. a refining process: using a ladle refining furnace (2) and a ladle vacuum degassing furnace (3) to refine the molten steel; C. a continuous casting process: casting the refined molten steel into a cast strip blank that has a thickness of 1.6-2.5 mm by means of a dual-roller thin strip continuous casting system (4); D. a hot rolling process: directly feeding the cast strip blank that was cast in the continuous casting process to a single-stand hot rolling mill (9) for rolling to produce hot-rolled strip steel, the thickness of the hot-rolled strip steel being 0.8-1.5 mm; E. a cooling coiling process: performing atomizing cooling on the hot-rolled strip steel, and coiling after the strip steel temperature is controlled to be 400-750 C. The present method achieves an extremely compact, environmentally-friendly and economical ultra-thin hot-rolled strip steel production process flow, and achieves the environmentally-friendly and economical continuous production of metal plates and strips.

A temperature calculation method includes: dividing a cross section perpendicular to a longitudinal direction of a steel plate to be hot-rolled into a plurality of rectangular elements; and calculating a temperature of each of the rectangular elements using a finite difference method. A first region 31 that includes an edge part of the cross section is divided such that a plurality of the rectangular elements are lined up in a plate-thickness direction and such that a plurality of the rectangular elements are lined up in a plate-width direction. A second region 32 that includes a center of the cross section and is wider than the first region 31 is divided such that a plurality of the rectangular elements are lined up in the plate-thickness direction but the second region 32 is not divided in the plate-width direction.

A temperature calculation method includes: dividing a cross section perpendicular to a longitudinal direction of a steel plate to be hot-rolled into a plurality of rectangular elements; and calculating a temperature of each of the rectangular elements using a finite difference method. A first region 31 that includes an edge part of the cross section is divided such that a plurality of the rectangular elements are lined up in a plate-thickness direction and such that a plurality of the rectangular elements are lined up in a plate-width direction. A second region 32 that includes a center of the cross section and is wider than the first region 31 is divided such that a plurality of the rectangular elements are lined up in the plate-thickness direction but the second region 32 is not divided in the plate-width direction.

Systems and methods for improving the flatness of a rolled sheet or strip by the application of differential cooling. A cooling agent can be selectively applied along the width of the strip. More cooling can be applied to the edges of the strip, where tension is greatest, to increase tension at the edges. The strip can be allowed to lengthen at these edges, which can improve flatness. In some embodiments, a closed loop flatness control system is used to measure the flatness of a strip and automatically adjust the differential cooling based on the measurement.

The present invention relates to controlled cooling in manufacture of steel plate, and in particular, to an on-line cooling system for controlled rolling with an inter-pass cooling process, which comprises a rolling mill and on-line cooling equipment. The cooling equipment is accessorily arranged on the exit of the rolling mill, so that the rolling mill and the cooling equipment are combined. One rolling mill and one set of on-line cooling equipment are considered a cooling group, and several such groups are connected in series, so the steel plate can be cooled in any rolling pass. In this invention, both the cooling system and the water supply system are arranged on the main frame, and the rolling process and the cooling process are synchronized by using inter-pass cooling. Consequently, satisfied rolling effect in the condition of a temperature gradient along the thickness direction, grain refinement at the surface and drastic strength improvement without sacrificing toughness are achieved. Besides, better quality of the plate center region is obtained, double bulging is avoided and the yield of steel plate is improved due to the higher deformation permeability.