Apparatus and method for cooling rolls used for rolling in a high-turbulence environment

Abstract

The present invention relates to at least a pair of working rolls, at least a pair of backup rolls, at least one water pillow cooling device capable of emitting a plurality of cooling jets under pressure to at least one of the working rolls, a removable plate, which is disposed between the water pillow cooling device and the working roll, is concave, and the gap between the removable plate and the working roll is constant or increases when moving in the direction of the backup roll, and is curved with a curvature such that the gap is 5 to 200 mm, and a removable plate having holes formed therein so that the cooling jets can pass through the removable plate, and relates to a rolling stand for metal products.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for cooling a work roll. According to this apparatus, cooling conditions can be easily satisfied for any work roll diameter.

[0002] During hot rolling of metal products, a coolant is sprayed onto the work roll to limit flatness defects caused by thermal expansion and prevent excessive roll deterioration and strip defects. Thermal-mechanical fatigue occurs due to thermo-mechanical deformation, which reduces the life of the work roll and degrades the surface quality of the rolled strip.

Background Art

[0003] As shown in FIG. 1, European Patent No. 2114584 discloses a rolling stand 1 for metal products, which includes a pair of work rolls (2, 2'), a pair of backup rolls (3, 3'), and a pair of water pillow cooling devices (4, 4') each having a plurality of nozzles capable of spraying a cooling jet (5) under pressure onto at least one of the work rolls. The cooling device has a concave cylindrical shape facing the work roll provided with the nozzles. The nozzles are arranged at a short distance of 5 to 200 mm from the work roll.

[0004] In use, such a system is capable of creating a liquid cushion having a highly turbulent state between the nozzles and the work roll, thus improving the cooling of the work roll.

[0005] In order to accurately discharge water and regenerate the coolant in contact with the work roll, the gap between the work roll and the nozzles must increase in the direction of the backup roll, i.e., in the direction away from the product being rolled.

[0006] Working rolls tend to deteriorate during use. For example, their wrinkles may increase, and their curvature and diameter may deviate from the desired values. All these changes result in marks and defects on the surface of the metal rolled products as well as flatness defects. This is the reason why working rolls are regularly disassembled and ground in order to obtain the desired properties and shape.

[0007] Unfortunately, grinding leads to a reduction in the working roll diameter, thus affecting the geometric gap, reducing the cooling performance and the pass line.

[0008] Although the cooling device of European Patent No. 2114584 improves the cooling capacity compared to the sprayed coolant, it cannot maintain the optimal water cushion in a turbulent state, for example, in the optimal gap. The gap is the space between the working rolls (2, 2') and the cooling device (4, 4'). When the working rolls are new, there is a gap of 5 - 200 mm as shown in Figure 2A. However, as shown in Figure 2B, after grinding when the working roll diameter shrinks, especially at the upper part of the cooling device, the gap exceeds 200 mm.

[0009] As a result, the same cooling heads are used in rolling stands with different working roll diameters, and the gap conditions are not optimal. Note that the gap between the cooling box and the working roll should not exceed 200 mm and should increase in the direction of the backup roll.

[0010] There is a need to find a way to increase the flexibility of the cooling heads and enable a turbulent water cushion for various working roll diameters, especially with respect to changes in the working roll diameter.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] An object of the present invention is to solve the above problems.

Means for Solving the Problems

[0013] This object is achieved by providing the device according to claim 1. This device can also have any of the features of claims 2 to 8. This object is achieved by the method according to claims 9 to 11.

[0014] Other features and advantages of the present invention will become apparent from the following detailed description of the present invention.

[0015] To explain the present invention, various embodiments of non-limiting examples will be described with particular reference to the following figures.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0017] In the following specification, the expressions "downstream" and "upstream" should be understood with respect to the path of the metal strip.

[0018] As shown in FIG. 3, the present invention includes a pair of working rolls (12, 12'), and a pair of backup rolls (13, 13'), and At least one water pillow cooling device (14, 14') capable of ejecting a plurality of cooling jets under pressure onto at least one of the working rolls, A removable plate (15, 15'), Disposed between the water pillow cooling device (14, 14') and the working roll (12, 12'), Concave, having a curvature such that the gap between the removable plate and the working roll is constant or increases when the gap moves in the direction of the backup roll, and the gap is 5 to 200 mm, A removable plate (15, 15') having holes formed therein so that the cooling jets can pass through the removable plate, relates to a rolling stand 11 for metal products comprising.

[0019] The water pillow cooling device is in a box connected to a coolant container and a pump (not shown) via a supply pipe. This box is watertight itself except for its front face, is positioned at a short distance from the working roll, and nozzles or slits are arranged or machined. The box is concave and cylindrical at the level of its front part and forms a curved surface. The coolant can be, for example, water or an emulsion of water and oil, stabilized or not stabilized with a surfactant.

[0020] Preferably, the cooling device comprises side plates. These side plates facilitate the formation of a turbulent coolant cushion by reducing the flow of coolant flowing out through the sides. Similar side plates are disclosed in European Patent No. 2114584.

[0021] The cooling device can comprise a scraper nozzle as described in International Publication No. WO 2008 / 149195. A mechanical scraper is a device that contacts the roll and mechanically interrupts the flow of the cooling fluid. This scraper closes the passage for the cooling fluid coming from the roll cooling device and avoids contact of the fluid, which can be harmful to the product, with the metal product.

[0022] The purpose of the removable plate is to enable the formation of a coolant cushion in a turbulent state between the removable plate and the working roll. Depending on the diameter of the working roll, a removable plate that satisfies the gap width and gap increase in the backup roll direction can be used.

[0023] For example, after a polishing operation in which the diameter of the working roll is reduced, the removable plate can be replaced with a removable plate having a smaller curvature. However, the curvature of the removable plate must be greater than that of the working roll so that it has a constant or increasing gap when moving in the direction of the backup roll, i.e., when moving away from the product being rolled, and so that a gap of 5 to 200 mm can be provided between the removable plate and the upper working roll.

[0024] The removable plate is preferably attached to a water pillow cooling device. Preferably, the removable plate is attached to the cooling head via any means such as screws or nuts and bolts. Even more preferably, the removable plate is attached to the front surface of the cooling head.

[0025] The removable plate is not an element of the water pillow cooling device. The removable plate is not part of the watertight box and is different from the front surface of the box.

[0026] In the prior art cooling system, as disclosed in European Patent No. 2114584, the water pillow cooling device is optimal only for a narrow range of working roll diameters. In contrast, the object of the present invention is to enable the formation of a coolant cushion having an optimal turbulent state for a wide range of working roll diameters by using an appropriate removable plate.

[0027] Preferably, the at least one water pillow cooling device (14, 14') comprises a plurality of cooling nozzles capable of spraying cooling jets. Preferably, the cooling nozzles have an orientation perpendicular to the working roll surface for nozzles far from the roll bite and a tangential orientation for nozzles close to the roll bite.

[0028] Preferably, the cooling nozzles can have various cross-sectional shapes and / or sizes. Preferably, they are arranged in parallel rows so as to create a checkerboard pattern, and each row is laterally shifted from the adjacent row. The nozzles can also be replaced by lateral slits that extend parallel to the ground along all or part of the cooling device to generate a flat jet.

[0029] Preferably, the outlet of the nozzle is arranged along a curved surface whose curvature is greater than the radius of the working roll.

[0030] Preferably, the curvature of the removable plate (15, 15') is smaller than the curvature of the curved surface.

[0031] Preferably, the removable plate comprises a metal layer and a protective layer for preventing corrosion. Even more preferably, the metal layer is made of stainless steel or aluminum. Even more preferably, the protective layer for preventing corrosion contains silicon and / or polypropylene and / or polytetrafluoroethylene. Preferably, the metal layer is a stainless steel layer and the protective layer is a silicon layer. The protective layer for preventing corrosion faces the working roll, and the metal layer faces the cooling device.

[0032] Preferably, the water pillow cooling device is 100 - 700 m 3 .h per square meter of the working roll surface -1The coolant can be sprayed at a pressure of 0.5 to 6 bar. These features facilitate the formation of a turbulent coolant cushion along the upper roll width, thus improving the cooling of the upper working roll. Even more preferably, the water pillow cooling device sprays 300 to 700 m 3 .h -1 of coolant at a pressure of 2 to 6 bar.

[0033] The present invention also relates to a cooling method for cooling a working roll in the aforementioned equipment, which includes the step of spraying coolant by the cooling device towards the working roll to create a highly turbulent coolant pillow within the gap between the surface of the working roll and the removable plate.

[0034] Preferably, the coolant is essentially water.

[0035] Preferably, the coolant is sprayed at a rate of 100 to 600 m per square meter of the working roll surface 3 .h -1 and a pressure of 0.5 to 6 bar. Even more preferably, the coolant is sprayed at a rate of 300 to 600 m per square meter of the working roll surface 3 .h -1 and a pressure of 2 to 6 bar.

Claims

1. A pair of working rolls (12, 12'), A pair of backup rolls (13, 13'), At least one water pillow cooling device (14, 14') capable of spraying a plurality of cooling jets under pressure onto at least one of the working rolls, A removable plate (15, 15'), Disposed between the water pillow cooling device and the working roll, Being concave, the gap between the removable plate and the working roll being constant or increasing when moving in the direction of the backup roll, having a curvature such that the gap is 5 to 200 mm, A removable plate (15, 15') having holes formed therein so that the cooling jets can pass through the removable plate, a rolling stand (11) for metal products comprising the same.

2. The rolling stand according to claim 1, wherein the at least one water pillow cooling device (14, 14') comprises a plurality of nozzles capable of spraying cooling jets.

3. The rolling stand according to claim 2, wherein the outlet of the nozzle is arranged along a curved surface having a curvature greater than the radius of the working roll.

4. The rolling stand according to claim 3, wherein the curvature of the removable plate (15, 15') is smaller than the curvature of the curved surface.

5. The rolling stand according to any one of claims 1 to 4, wherein the removable plate comprises a metal layer and a protective layer for preventing corrosion.

6. The rolling stand according to claim 5, wherein the metal layer is a stainless steel layer and the protective layer is a silicon layer.

7. The water pillow cooling device sprays 100 to 700 m per square meter of the working roll surface ３ .h －１The rolling stand according to any one of claims 1 to 6, wherein the coolant can be sprayed at a pressure of 0.5 to 6 bar.

8. The water pillow cooling device sprays 300 to 700 m ３ .h －１ of coolant at a pressure of 2 to 6 bar, the rolling stand according to claim 7.

9. Creating a highly turbulent coolant pillow in the gap between the working roll surface and the removable plate, and spraying coolant by the cooling device towards the working roll, the cooling method for cooling a working roll in the facility according to any one of claims 1 to 8.

10. The coolant is sprayed at a rate of 100 to 600 m per square meter of the working roll surface ３ .h －１ and a pressure of 0.5 to 6 bar, the cooling method according to claim 9.

11. The coolant is sprayed at a rate of 300 to 600 m per square meter of the working roll surface ３ .h －１ and a pressure of 2 to 6 bar, the cooling method according to claim 10.

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