Coolant applicator

Abstract

 A coolant applicator is described in which a flexible, apertured plate (36) is hydraulically loaded so the flexible plate is brought close to the surface to be cooled; coolant is supplied to pass through and form a hydrostatic bearing layer between the plate and the surface, and the plate being deformed to the shape of the surface by the hydraulic loading. In one embodiment a hydraulically loaded coolant applying pad comprises a piston-cylinder assembly (14, 16) is connected to a supply of coolant under pressure, while the piston (16) is hollow to allow passage of the coolant, and a flexible plate (36) movably mounted on the piston, has apertures in fluid connection with the cylinder (14) via the piston (16), and is arranged so that, in use, coolant passing through the apertures in the plate (36) forms a hydrostatic bearing layer between the plate (36) and the surface.

Description

[0001] This invention is concerned with means for applying coolant fluid and is particularly concerned with applying a coolant liquid during the rolling of metals.

[0002] In metal rolling, it is customary to apply a coolant liquid to the work rolls and/or back-up rolls to control the temperature of those rolls and thus the thermal crown of the rolls in order to maintain the correct shape or profile of the strip material being rolled. The coolant is conventionally applied by spraying from nozzles either in the form of jets or water curtains. In either case a great amount of coolant, either water or kerosene, is used.

[0003] It has been found that the volume of coolant which is jetted on to the surface of the rolls does not necessarily relate to the amount of heat extracted from the rolls and this is due to the fact that only that coolant which is in close contact with the roll is effective in extracting heat from the roll. It is found in fact that a thin layer of water passed at high velocity over part of the roll effects much higher heat transfer than the hitherto normal spray system.

[0004] It is an object-of the invention to provide means for applying coolant to a surface in a thin layer and in a manner that will adapt readily to the contour of the surface being cooled.

[0005] According to one aspect the invention provides a coolant applicator comprising a flexible, apertured plate which is hydraulically loaded so that a surface of the plate becomes close to the surface to be cooled; the apertures allowing passage of coolant and the coolant forming a hydrostatic bearing layer between the said surface of the plate and the surface to be cooled.

[0006] In another aspect the invention provides a hydraulically loaded pad for applying coolant to a surface, comprising a piston-cylinder assembly for connection to a supply of coolant under pressure, the piston being apertured to allow passage of the coolant, characterised by a flexible plate which is movable with the piston, has apertures in fluid connection with the cylinder via the piston, and is arranged so that, in use, coolant passing through the apertures in the plate forms a hydrostatic bearing layer between the plate and the surface.

[0007] When the device is used for applying coolant to the rolls of a rolling mill, a series of pads may be located across the width of the roll surface and each one, or a group, of the pads may be so controlled to effect cooling of the roll in zones as required.

[0008] Preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

Figure 1 is a view, partly in section, of a coolant applicator according to the invention,

Figure 2 is a view in the direction of the arrow II on Figure 1,

Figure 3 is an underneath view of one of the pads, .

Figure 4 is a scrap view of parts of Figure 1 to a larger scale, and

Figure 5 is a diagrammatic view of continuous casting machine incorporating coolant applicators according to the invention.

[0009] Referring to Figures 1 to 4 of the drawings, a rolling mill roll 2 is provided with a series of coolant applying devices 4. Each device comprises a hydraulic cylinder 6 formed in a beam 8 and a capping piece 10. The cylinder is provided with an inlet port 12 through which coolant is fed under pressure. A hollow piston 14 is slideable within a bore 16, leading from the cylinder 6 and a spring 18 surrounds the piston between the bottom of the cylinder 6 and a circlip 20 fast on the piston. The lower end of the piston is formed as a ball-end 22 and mounted thereon by means of a spherical seating 24 is a support member 26. The support member is formed with a central bore 28 and passageways 30 lead from the bore 28 to bores 32. The bore 28 is in communication with the cylinder 6 through the hollow piston 14, as seen clearly in Figure 1. Within each bore 28, 32 is a hollow piston 34 to which is secured a thin flexible plate 36 and a passageway 38 in the piston 34 connects with a cavity 40 in the plate 36. The plate 36 extends across the entire width of the roll and as seen clearly in Figures 2 and 3 is connected to each of the pistons 34.

[0010] In use, the coolant system is pressurised urging the pistons 14 towards the mill roll 2 until the flexible plate 36 is close to the roll. At the same time coolant fluid passes into the bores 28, 32 through passages 38 into cavities 40 and passes between the plate 36 and the surface of the roll 2. The piston 34 and the cavities 40 are so dimensioned that the gap between the plate 36 and roll 2 is between 0.2 and 0.5 millimetres. All the coolant is forced to flow through this gap at high velocity thus providing highly efficient cooling.

[0011] Each coolant applying device 4 is separately fed with coolant via an independent valve, and so the roll temperature can be controlled in zones across its width to vary the roll camber in e.g. a shape control system. Supply of coolant to each device is then controlled by signals issuing from a suitable shapemeter located downstream of the mill stand.

[0012] Preferably there is always sufficient pressure of coolant within the cylinders 6 to overcome the retraction spring 18 and maintain the plate 36 close to the roll.

[0013] To accommodate various roll diameters, as rolls are reground, the flexible plate 36 readily conforms in shape to match the surface of the roll, the change in shape being effected by the advance of the pistons 34 until the plate closely approaches the roll surface.

[0014] The system as described above has been found to give much higher heat transfer coefficients than the customary spray nozzle arrangements, and better control of the coolant zones, making the arrangement far more suitable for shape control systems.

[0015] Although the invention has been described with respect to a device for applying coolant to the rolls of a rolling mill the same principle can also be used, with little modification, to apply coolant to a moving strip as it issues into or from a mill during a rolling operation.

[0016] In the embodiment shown in Figure 5 a coolant applicator as broadly described above is employed in a machine for continuously casting metal in elongate form, in order to cool the rolls of the machine and/or the cast metal.

[0017] The casting machine 50 comprises a pair of rolls 52, a nozzle 54, tundish 56 and feed channel 58. Molten metal 60, e.g. alumi-nium, passes upwards from the nozzle and contacts the surface of the rolls 54 which chill the metal and promote initiation of freezing. In the figure, the metal is shown as being in a "mushy" state, i.e. a mixture of liquid and solid, and then frozen into a solid state at'64 before the full nip of the rolls is encountered. The resulting cast strip S then passes over a guide roll (not shown) to a coiler (not shown), or directly to a rolling mill.

[0018] To chill the rolls and strip S, hydrostatic coolant applying devices 104 are provided on either side of the cast strip and each comprises a beam 108 having formed therein cylinders 106, 106A, each being fed with coolant under pressure through ports 112, 112A respectively. Hollow pistons 114, 114A are slideable within bores 116, l16A and springs 118, 118A surround the pistons between the closed ends of the cylinders 106, 106A and circlips 120, 120A fast on the pistons. The outermost ends of the pistons are formed as ball-ends 122, 122A and carry support members 126, 126A formed with passageways, bores and thin flexible plates 136, 136A identical with those described above, except that the support members 126A and their plates 136A are flat to conform to the shape of the strip, rather than arcuate as is the case of the members and plates 126 and 136.

[0019] The beams 108 and the plates 136, 136A extend across the entire width of the rolls 52 and the strip S, and the plates are connected to the pistons 114, 114A in the same way as described above. The operation of the coolant applying device is the same as that described above, the dimensions being so chosen that the hydraulic loading on the pistons 114, 114A is countered by the pressure of the liquid acting between the rolls or strip and the plates 136, 136a so that the gaps between the plates and the rolls and strip are maintained constant.

[0020] By using this deyice for cooling casting rolls, it is found that the need for expensive internally cooled casting rolls is eliminated and cheaper solid rolls may be utilized. The passage of coolant at high velocity between the plates and the roll provides highly efficient cooling and effectively chills the rolls sufficiently to freeze the molten aluminium in the roll gap.

[0021] It is found that a facility for roll bending, as practiced in rolling mill technology, can be more effectively applied with the solid casting rolls than with hollow, internally cooled rolls, and thus rapid and accurate correction of any non-parallel roll gap is possible.

[0022] By the use of this coolant system, the roll gap can be varied by the application of coolant from selected devices 104 across the width. Roll contour control in this way can be effected in response to signals from sensors which detect either the roll contour itself or the contour of the cast strip.

[0023] It is also found that by varying the relative amounts of coolant applied to the rolls and the emerging strip, it is possible to control the shape and position of the so-called "solidification front", i.e. the region 62 where the molten metal becomes first "mushy" i.e. a combination of liquid plus solid, and then solid, can be closely controlled. This close control of the solidification makes possible the casting of alloys which could not previously be cast using twin-roll casters.

Claims

1. A coolant applicator comprising a flexible, apertured plate (36; 136; 136A) which is hydraulically loaded so that a surface of the plate becomes close to the surface to be cooled; the apertures allowing passage of coolant and the coolant forming a hydrostatic bearing layer between the said surface of the plate and the surface to be cooled.

2. A hydraulically loaded pad for applying coolant to a surface, comprising a piston-cylinder assembly (6, 14; 116, 114; 116A, 114A;) for connection to a supply of coolant under pressure, the piston (14; 114; 114A) being apertured to allow passage of the coolant, characterised by a flexible plate (36; 136; 136A) which is movable with the piston (14; 114; 114A), has apertures (40) in fluid connection with the cylinder (6; 116; 116A) via the piston (14; 114; 114A), and is arranged so that, in use, coolant passing through the apertures (40) in the plate forms a hydrostatic bearing layer between the plate and the surface.

3. A pad as claimed in claim 2 wherein the piston_' has a body portion (22; 122; 122A) pivotally connected to a plate supporting portion (26; 126; 126A), the body portion (22; 122; 122A) cooperating with the cylinder (6; 116; 116A) and the flexible plate (36; 136; 136A) being mounted on the support portion (26; 126; 126A) and having fluid connection with the cylinder through the support and body piston portions.

4. A pad as claimed in claim 2 or 3 wherein the flexible plate (36; 136; 136A) is movably mounted on the piston.

5. A pad as claimed in claim 3 wherein the piston (14; 114; 114A) has bores which receive apertured pistons (34) fixed to the flexible plate (36; 136; 136A) so that the flexible plate (36) is hydraulically loaded to be adjacent the surface to be cooled.

6. A pad as claimed in any preceding claim wherein the piston (14; 114; 114A) is biased to move the flexible plate (36; 136; 136A) away from the suface to be cooled when coolant is not being supplied.

7. A pad as claimed in any one of claims 2 to 6 wherein there are a plurality of piston-cylinder assemblies each movably connected with the plate.

8. A continuous casting machine for continuously casting metal in elongate form wherein there is a coolant applicator as claimed in any preceding claim for cooling the rolls of the machine and/or the cast metal.

Drawing