RU2840526C2 - Device and method for cooling rolls used for rolling in highly turbulent environment - Google Patents

Abstract

FIELD: performed operations; cooling.

SUBSTANCE: invention relates to rolling mill rolls cooling. Rolling mill comprises a pair of working rolls, a pair of support rolls, device for water cushion cooling, which is capable of spraying multiple cooling jets under pressure to at least one of the above working rolls, and detachable panel located between the above water cushion cooling device and the above working roll. Said panel is concave and has such a curvature that the gap between said detachable panel and said working roll is constant or increases with movement in the direction of the support roll. Said clearance makes 5-200 mm. Panel has holes so that the specified cooling jets can pass through it.

EFFECT: higher operational flexibility of cooling head, which allows obtaining water cushion in turbulent state during cooling of working rolls of various diameters.

8 cl, 3 dwg

Description

The present invention relates to a device and method for cooling work rolls. The said device makes it easy to provide proper cooling conditions for work rolls of any diameter.

During hot rolling of metal products, a cooling agent is sprayed onto the working rolls to limit thermal expansion, which causes flatness defects, and to prevent deterioration of the roll characteristics and the occurrence of strip defects. Thermomechanical deformation results in thermomechanical fatigue, which reduces the service life of the working rolls and degrades the surface quality of the rolled strip.

Patent EP 2 114 584 B1, as shown in Fig. 1, describes a stand 1 of a rolling mill for producing metal products, comprising a pair of working rolls (2, 2'), a pair of support rolls (3, 3') and a pair of water cushion cooling devices (4, 4'), comprising a plurality of nozzles capable of spraying cooling jets (5) under pressure onto at least one of said working rolls. The cooling device has a concave cylindrical shape facing the working roll, where said nozzles are contained. The nozzles are located at a close distance of 5-200 mm from the working rolls.

During operation, the system ensures the creation of a liquid cushion between the nozzles and the working roll, which has a highly turbulent state and, thus, improves the cooling of the working roll.

To properly remove water and replace the coolant in contact with the work roll, the gap between the work roll and the nozzles must increase in the direction of the support roll, i.e. away from the product to be rolled.

Working rolls are prone to destruction during operation. For example, the roughness of the rolls may increase, and their curvature and diameter may deviate from the specified parameters. All of these changes lead to the formation of imprints and defects on the surface of the rolled metal product and flatness defects. That is why working rolls are periodically dismantled and subjected to grinding to obtain the required characteristics and shape.

However, grinding reduces the diameter of the work rolls and thus affects the geometric clearance, reducing the cooling efficiency and having a negative impact on the rolling line.

The cooling device described in EP 2 114 584, despite the increase in cooling capacity compared to a spray coolant, is not able to maintain an optimal water cushion in a turbulent state, for example, to ensure an optimal gap. Said gap is the distance between the working roll (2, 2') and the cooling device (4, 4'). When the working roll is new, as shown in Fig. 2A, the gap is 5-200 mm. However, after grinding, which leads to a reduction in the diameter of the working roll, the gap becomes larger than 200 mm, especially in the upper section of the cooling device, as shown in Fig. 2B.

Accordingly, the same cooling head is used in rolling stands containing working rolls with different diameters, and the gap condition becomes suboptimal. It should be recalled that the gap between the cooling tank and the working roll should not exceed 200 mm and should not increase in the direction of the support roll.

There is a need to propose a method for increasing the operational flexibility of a cooling head, in particular, with respect to changing the diameters of the working rolls, which will make it possible to obtain a water cushion in a turbulent state for different diameters of the working rolls.

The objective of the present invention is to solve the above-mentioned problems. The said objective is solved by means of the equipment according to claim 1 of the invention formula. The said equipment also has the characteristics according to claims 2–8. The said objective is solved by means of the method according to claims 9–11.

Other characteristics and advantages of the present invention will become apparent from the following detailed description of the invention.

To explain the invention, a description of a non-limiting example embodiment is given below with reference to the following drawings:

Fig. 1 – an embodiment of a rolling stand in which a cooling device known from the existing level of technology is used;

Fig. 2 – changes in the gap in the embodiments from Fig. 1 as a result of changing the diameter of the working rolls;

Fig. 3 – embodiment of the present invention.

In the description below, the expressions "downstream" and "upstream" should be considered relative to the direction of movement of the metal strip.

As shown in Fig. 3, the present invention relates to a stand 11 of a rolling mill for the production of metal products, comprising:

- a pair of working rolls (12, 12’),

- a pair of support rollers (13, 13’),

- at least one water cushion cooling device (14, 14’) capable of releasing a plurality of cooling jets under pressure onto at least one of said working rolls,

- removable panel (15, 15’)

- placed between the said water cushion cooling device (14, 14’) and the said working roll (12, 12’),

- said panel is concave and has such a curvature that the gap between said removable panel and said working roller is constant or increases when moving in the direction of the support roller, and said gap is 5–200 mm, and

- said panel has openings so that said cooling jets can pass through said removable panel.

The water cushion cooling device consists of a tank connected by means of a supply pipe to a reservoir for cooling liquid and a pump (not shown). Said tank is essentially watertight except for the front surface located at a close distance from the working roll, in which nozzles are installed or slots are made by mechanical processing. On the front side, the tank has a concave cylindrical shape, forming a curved surface. Said cooling liquid can be, for example, water or an emulsion consisting of water and oil, stabilized by surfactants.

Preferably, said cooling device comprises side panels. Said side panels facilitate the formation of a turbulent cushion by reducing the flow of coolant from the outlets by means of the sides. Similar side panels are described in EP 2 114 584.

The cooling device may comprise scraper nozzles as described in WO2008149195. The mechanical scraper is a device that is in contact with the roll and mechanically blocks the flow of the cooling fluid. The said scraper closes the passage for the cooling fluid coming from the roll cooling device, excluding the fluid from coming into contact with the metal product, which could adversely affect the said product.

The removable panel serves to ensure the formation of a cooling agent cushion between the removable panel and the working roll in a turbulent state. Depending on the diameter of the working roll, the removable panel compensates for the width of the gap, and the increase in the gap can be used in the direction of the support roll.

For example, after a grinding operation during which the diameter of the working roll is reduced, the removable panel can be replaced by a removable panel having a smaller curvature. However, the curvature of the removable panel must be greater than the curvature of the working roll, so that the gap is constant or increases when moving in the direction of the support roll, i.e. when moving away from the product being rolled, and also so that the gap between said removable panel and said upper working roll is 5-200 mm.

The removable panel is preferably attached to the water cushion cooling device. Preferably, the removable panel is attached to the cooling head by means such as screws or nuts and bolts. Even more preferably, the removable panel is attached to the front side of the cooling head.

The removable panel is not a part of the water cushion cooling device. The removable panel is not part of the said water-resistant tank and is different from the front surface of the said tank.

In the cooling system of the existing state of the art described in EP 2 114 584, the water cushion cooling device is an optimal solution for a narrow range of working roll diameters. In contrast, the subject matter of the present invention makes it possible to form a cooling agent cushion having an optimal turbulent state for a wide range of working roll diameters using a corresponding removable panel.

Preferably, said at least one water cushion cooling device (14, 14') comprises a plurality of cooling nozzles capable of spraying a cooling jet. Preferably, the cooling nozzles have an orientation perpendicular to the surface of the working roll for nozzles located at a distance from the roll opening, and a tangential orientation for nozzles located closer to the roll opening.

Preferably, the cooling nozzles may have a variety of cross-sectional shapes and/or sizes. Preferably, they are arranged in parallel rows, each row being offset laterally from the adjacent rows to ensure a staggered arrangement. The nozzles may also be replaced by transverse slots extending over the entire cooling device or part thereof parallel to the floor to form flat jets.

Preferably, the outlets of said nozzles are located along a curved surface, the curvature of which is greater than the radius of said working roll.

Preferably, the curvature of said removable panel (15, 15’) is less than the curvature of said curved surface.

Preferably, said removable panel comprises a metal layer and a protective layer preventing corrosion. Even more preferably, said metal layer is made of stainless steel or aluminum. Even more preferably, said protective layer preventing corrosion comprises silicone and/or polypropylene and/or polytetrafluoroethylene. Preferably, said metal layer is a layer of stainless steel, and said protective layer is a layer of silicone. The protective layer preventing corrosion faces the working roll, while the metal layer faces the cooling device.

Preferably, said water cushion cooling device is capable of spraying 100-700 ^m3 /h of coolant per square meter of the working roll surface under a pressure of 0.5-6 bar. Such characteristics simplify the formation of a turbulent coolant cushion across the width of the upper roll and, thus, contribute to improving the cooling of the upper working roll. Even more preferably, said water cushion cooling device is capable of spraying 300-700 ^m3 /h of coolant per square meter of the working roll surface under a pressure of 2-6 bar.

The invention also relates to a method for cooling a working roll in the above-described installation, which includes the step of spraying a coolant using said cooling device onto said working roll, creating a cushion of coolant in a highly turbulent state in the gap between the surface of said working roll and said removable panel.

Preferably, said cooling agent is essentially water.

Preferably, said cooling agent is sprayed at a flow rate of 100-600 ^m3 /h per square meter of the surface of the working roll under a pressure of 0.5-6 bar. Even more preferably, said cooling agent is sprayed at a flow rate of 300-600 ^m3 /h per square meter of the surface of the working roll under a pressure of 2-6 bar.

Claims (14)

1. A rolling mill (11) for the production of metal products, containing a pair of working rolls (12, 12’), a pair of support rollers (13, 13’), at least one water cushion cooling device (14, 14') comprising a plurality of nozzles that spray a plurality of cooling jets under pressure onto at least one of said working rolls, wherein the outlets of said nozzles are arranged along a curved surface, the curvature of which is greater than the radius of said working roll, a removable panel (15, 15’) located between said water cushion cooling device (14, 14’) and said working roll, wherein said panel is concave and has such a curvature that the gap between said removable panel and said working roller is constant or increases when moving in the direction of the support roller, and said gap is 5-200 mm, wherein the curvature of said removable panel (15, 15’) is less than the curvature of said curved surface, wherein said panel has openings so that said cooling jets can pass through said removable panel. 2. A rolling mill according to claim 1, wherein said removable panel comprises a metal layer and a protective layer that prevents corrosion. 3. The rolling mill according to claim 2, wherein said metal layer is a layer of stainless steel and said protective layer is a layer of silicone. 4. A rolling mill according to any one of paragraphs 1-3, in which said water cushion cooling device is capable of spraying 100-700 ^m3 /h of cooling liquid per square meter of the surface of the working roll under a pressure of 0.5-6 bar. 5. A rolling mill according to item 4, wherein said water cushion cooling device is capable of spraying 300-700 ^m3 /h of cooling liquid per square meter of the surface of the working roll under a pressure of 2-6 bar. 6. A method for cooling a working roll in a rolling stand according to any one of paragraphs 1-5, including the step of spraying a cooling liquid using said cooling device onto said working roll, ensuring the creation of a cushion of cooling liquid in a highly turbulent state in the gap between the surface of said working roll and said removable panel. 7. The method according to item 6, wherein said cooling liquid is sprayed at a flow rate of 100-600 ^m3 /h of cooling liquid per square meter of the surface of the working roll under a pressure of 0.5-6 bar. 8. The method according to item 7, wherein said cooling liquid is sprayed at a flow rate of 300-600 ^m3 /h of cooling liquid per square meter of the surface of the working roll under a pressure of 2-6 bar.