Device and method for cooling rolls for rolling in a high turburization environment

Abstract

The invention relates to a rolling stand for metal products, comprising:-at least one pair of working rolls; -at least one pair of support rollers; -at least one water pillow cooling device capable of projecting a plurality of cooling jets under pressure on at least one of the working rolls; -a removable plate placed between the cooling device and the working roll,-the removable plate is concave and bent with a curvature such that, upon movement in the direction of the support roll, the gap between the removable plate and the upper working roll is constant or increased and such that the gap is between 5 mm and 200 mm,-the removable plate is placed between the cooling device and the working roll,-the removable plate is concave and bent with a curvature such that, upon movement in the direction of the support roll, the gap between the removable plate and the upper working roll is between 5 mm and 200 mm. And the removable plate is perforated such that the cooling jet can pass through the removable plate.

Description

Technical Field

[0001] The present invention relates to a device and a method for cooling a working roll. The device allows to easily obtain satisfactory cooling conditions for any working roll diameter. Background Art

[0002] During hot rolling of metal products, coolant is sprayed on the work rolls to limit thermal expansion that causes flatness defects and prevent excessive roll degradation and strip defects. Due to thermomechanical deformation, thermomechanical fatigue is generated, which reduces the life of the work rolls and reduces the surface quality of the rolled strip.

[0003] like Figure 1 As shown in the figure, patent EP 2 114 584 Bl discloses a rolling stand 1 for metal products, which rolling stand 1 comprises a pair of working rolls (2, 2'), a pair of support rolls (3, 3') and a pair of water pillow cooling devices (4, 4'), the water pillow cooling devices (4, 4') comprising a plurality of nozzles capable of spraying cooling jets (5) under pressure on at least one of the working rolls. The cooling device has a cylindrical concave shape facing the working rolls, which comprises the nozzles. The nozzles are located at a short distance between 5 mm and 200 mm from the working rolls.

[0004] When in use, such a system allows to create a liquid cushion with a highly turbulent state between the nozzles and the work rolls and thus improves the cooling effect on the work rolls.

[0005] In order to accurately drain the water and renew the coolant in contact with the working rolls, the gap between the working rolls and the nozzles should be larger in the direction of the backup rolls, ie away from the rolled product.

[0006] Work rolls are susceptible to deterioration during use. For example, their roughness may increase, their curvature and diameter may deviate from the target values. All these changes can lead to marks and defects on the surface of the metal rolled product as well as flatness defects. This is why the work rolls are regularly disassembled and ground to obtain the desired properties and shape.

[0007] Unfortunately, grinding leads to a reduction in the work roll diameter and thus affects the geometric gap, which reduces cooling performance and the rolling line.

[0008] The cooling device of EP 2 114 584, although it increases the cooling capacity compared to sprayed coolant, cannot maintain an optimal water cushion, for example an optimal gap, under turbulent conditions. The gap is the space between the working roll (2, 2') and the cooling device (4, 4'). When the working roll is new, such as Figure 2 As shown in Figure A, the gap is 5 mm to 200 mm. However, after grinding causes the working roll diameter to decrease, as shown in Figure Figure 2 As illustrated in B, the gap is larger than 200 mm, especially at the upper part of the cooling device the gap is larger than 200 mm.

[0009] Therefore, using the same cooling head on rolling stands with different working roll diameters, the gap conditions are not optimal. It should be reminded 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 head, especially in the case of varying work roll diameters, thereby allowing a water cushion in a turbulent state for a variety of work roll diameters. Summary of the invention

[0011] The object of the present invention is to solve the above mentioned problems. This object is achieved by providing a device according to claim 1. The device may also include any of the features described in claims 2 to 8. This object is achieved by a method according to claims 9 to 11.

[0012] Other features and advantages of the present invention will become apparent from the following detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to illustrate the present invention, various embodiments of the present invention will be described with particular reference to the following drawings, which are non-limiting examples:

[0014] Figure 1 An embodiment of a rolling stand using a cooling device known from the prior art is presented.

[0015] Figure 2 Presented in Figure 1 The gap changes caused by the change in the working roll diameter in the implementation method.

[0016] Figure 3 The embodiments of the present invention are illustrated. DETAILED DESCRIPTION

[0017] In the following description, the expressions "downstream" and "upstream" are to be understood relative to the path of the metal strip.

[0018] like Figure 3 As shown in the figure, the present invention relates to a rolling stand 11 for metal products, which rolling stand comprises:

[0019] - a pair of working rolls (12, 12'),

[0020] - a pair of support rollers (13, 13'),

[0021] at least one water pillow cooling device (14, 14') capable of projecting a plurality of cooling jets under pressure onto at least one of the working rolls,

[0022] - removable plates (15, 15'),

[0023] - the removable plate (15, 15') is placed between the water pillow cooling device (14, 14') and the working roll (12, 12'),

[0024] - the removable plate (15, 15') is concave and has a curvature such that, when moving in the direction of the support rolls, the gap between the removable plate and the working rolls is constant or increases and such that the gap is from 5 mm to 200 mm, and

[0025] - The removable plate (15, 15') is perforated so that the cooling jet can pass through the removable plate.

[0026] The water pillow cooling device comprises a box connected to a coolant container and a pump (not shown) by a feed pipe. The box itself is watertight, except for its front face, which is located at a short distance from the working rolls and in which nozzles or slits have been located or machined. The box is cylindrically concave at the level of its front face, forming a curved surface. For example, the coolant can be water, or an emulsion of water and oil stabilized or destabilized with surfactants.

[0027] Preferably, the cooling device comprises side plates. These side plates facilitate the formation of a turbulent coolant pad by reducing the flow of coolant out of the sides. Similar side plates are disclosed in EP 2 114 584.

[0028] The cooling device may include a scraper nozzle as disclosed in WO2008149195. A mechanical scraper is a device that contacts the roller and mechanically blocks the flow of cooling fluid. The scraper closes the passage of the cooling fluid from the roller cooling device, preventing the fluid from contacting the metal product, which may be harmful to the product.

[0029] The purpose of the removable plate is to allow a coolant cushion in turbulent state to form between the removable plate and the working roll. Depending on the working roll diameter, a removable plate can be used that meets the gap width and increases in the direction of the backup roll.

[0030] For example, after a grinding operation in which the diameter of the work roll has been reduced, the removable plate can be replaced by a removable plate having a smaller curvature. However, the curvature of the removable plate should be greater than that of the work roll in order to have a constant gap or an increasing gap when moving in the direction of the support roll, i.e., moving away from the rolled product, and also to allow a gap of 5 mm to 200 mm between the removable plate and the upper work roll.

[0031] The removable plate is preferably attached to the 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 face of the cooling head.

[0032] 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 distinct from the front surface of the box.

[0033] In prior art cooling systems, such as disclosed in EP 2 114 584, water pillow cooling arrangements are optimized only for a narrow range of work roll diameters. In contrast, the object of the present invention is to allow the formation of a coolant cushion with optimized turbulence conditions for a wider range of work roll diameters by using appropriate removable plates.

[0034] Preferably, the at least one water pillow cooling device (14, 14') comprises a plurality of cooling nozzles capable of spraying cooling jets. Preferably, for nozzles away from the roll bite, the cooling nozzles are oriented perpendicular to the working roll surface, and for nozzles close to the roll bite, the cooling nozzles are oriented tangentially to the working roll surface.

[0035] Preferably, the cooling nozzles may have various cross-sectional shapes and / or sizes. Preferably, they are arranged in parallel rows, each row being laterally offset from the adjacent row to form a five-point arrangement. The nozzles may also be replaced by transverse slits extending parallel to the ground along all or part of the cooling device to produce a flat jet.

[0036] Preferably, the outlet of the nozzle is arranged along a curved surface, the curvature of the curved surface being greater than the radius of the working roll.

[0037] Preferably, the curvature of said removable plate (15, 15') is smaller than the curvature of said curved surface.

[0038] Preferably, the removable plate comprises a metal layer and an anti-corrosion protective layer. Even more preferably, the metal layer is made of stainless steel or aluminum. Even more preferably, the anti-corrosion protective layer comprises 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 anti-corrosion protective layer faces the working rolls and the metal layer faces the cooling device.

[0039] Preferably, the water pillow cooling device is capable of spraying 100m2 of water per square meter of the working roll surface at a pressure of 0.5 bar to 6 bar. 3 .h -1 Up to 700m 3 .h -1 These features facilitate the formation of a turbulent coolant cushion along the width of the upper roll and thus improve the cooling effect on the upper work roll. Even more preferably, the water pillow cooling device is capable of spraying 300m per square meter of work roll surface at a pressure of 2 to 6 bars. 3 .h -1 Up to 700m 3 .h -1 of coolant.

[0040] The present invention also relates to a cooling method for cooling a working roll in an apparatus as described above, the method comprising the step of spraying coolant onto the working roll by means of the cooling device to produce a coolant pillow in a highly turbulent state in the gap between the working roll surface and the removable plate.

[0041] Preferably, the coolant is substantially water.

[0042] Preferably, the coolant is applied at a pressure of 0.5 bar to 6 bar at a rate of 100 m2 per square meter of the working roll surface. 3 .h -1 Up to 600m 3 .h -1 Even more preferably, the coolant is sprayed at a rate of 300 m2 per square meter of the working roll surface at a pressure of 2 to 6 bar. 3 .h -1 Up to 600m 3 .h -1 Spray at a rate of .

Claims

1. A rolling stand (11) for metal products, comprising: - a pair of working rolls (12, 12'), - a pair of support rollers (13, 13'), at least one water pillow cooling device (14, 14') capable of projecting a plurality of cooling jets under pressure onto at least one of the working rolls, - removable plates (15, 15'), - the removable plate is placed between the water pillow cooling device and the working roll, - the removable plate is concave and has a curvature such that, when moving in the direction of the support rolls, the gap between the removable plate and the working rolls is constant or increases and such that the gap is between 5 mm and 200 mm, and - The removable plate is perforated so that the cooling jet can pass through the removable plate.

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, and the curvature of the curved surface is 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 to prevent 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 rolling stand according to any one of claims 1 to 6, wherein: The water pillow cooling device can spray 100m per square meter of the working roll surface at a pressure of 0.5 bar to 6 bar. 3 .h -1 Up to 700m 3 .h -1 of coolant.

8. The rolling stand according to claim 7, wherein: The water pillow cooling device can spray 300m per square meter of the working roll surface at a pressure of 2 bar to 6 bar. 3 .h -1 Up to 700m 3 .h -1 of coolant.

9. A cooling method for cooling a working roll in an apparatus according to any one of claims 1 to 8, the cooling method comprising the step of spraying coolant to the working roll by means of the cooling device to produce a coolant pillow in a highly turbulent state in the gap between the working roll surface and the removable plate.

10. The cooling method according to claim 9, wherein: The coolant is applied at a pressure of 0.5 bar to 6 bar at a rate of 100 m2 per square meter of the working roll surface. 3 .h -1 Up to 600m 3 .h -1 Spray at a rate of .

11. The cooling method according to claim 10, wherein: The coolant is cooled at a pressure of 2 to 6 bar at a rate of 300 m2 per square meter of the working roll surface. 3 .h -1 Up to 600m 3 .h -1 Spray at a rate of .

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