THERMAL CROWN CONTROLLED ROLLS

Abstract: Rolling mill work and back-up rolls comprising an arbor (35) with a sleeve (36) shrunk thereon have circum­ ferential grooves (37, 38, 39) formed in the external surface of the arbor (35), through which heating or cooling liquid is supplied from external sources so as to expand or contract the sleeve (36) and change the roll crown and contour. The fins (53), or material between grooves, may have higher heat conductivity than the material of the arbor (35) and sleeve (36), and are proportioned to transmit roll­ ing forces without reducing roll stiffness. A liquid supply system provides liquids of different temperatures to selected sections of the grooves along the roll work­ ing surface; and strip of different widths but of uniform gauge across the strip is rolled by suitably adjusting the temperatures of the hot and cold liquids so supplied.

Description: This invention relates to adjustable crown rolling mill rolls. It is more particularly concerned with rolls in which their crowns are adjusted by the addition or extraction of heat to or from the rolls. All industries that roll flat products such as paper, plastic, steel or other metal sheets must contour the roll surface in order to obtain an acceptable flatness or profile of the product. The most common approach has been the grinding of a crown onto the rolls which compensates for the composite roll deflections under load. This method, unfortunately, is effective only for a fixed loading and a unique product size. It is well known that in the rolling of metals between rolls which themselves are hardened metal, usually steel, heat affects the crown of the rolls. In hot rolling most of the heat imparted to the rolls is derived from their contact with the hot metal but even in cold rolling the working of the metal generates heat, some of which is transferred to the rolls. As the roll heats its crown increases. The change in the crown is measured in hundredths of a millimeter but in the rolling of strip of a few hundredths of a millimeter thickness changes in crown alter not only the gauge of the strip but its flatness or shape. Radial heat flow in a steel roll is of course quite slow. A 1500 millimeter diameter back-up roll which has reached a steady state temperature of 120 degrees C will require more than an hour for an 0.08 millimeter radial crown change and a 750 millimeter diameter work roll would require about half an hour for the same change. It is well known to spray a liquid coolant on a roll to control its crown but the thermal inertia of conventional rolls severely limits the usefulness of that expedient. In addition to gauge and shape the strip producer is also concerned with the effect known as "edge drop", or feathering, which is another aspect of roll crowning. A strip mill operator is required to roll on the same mill strip of various widths as the customer orders. A perfectly flat strip from edge-to-edge could only be obtained, prior to my invention to be described hereinafter, when the strip is the same width as the mill. When narrower strip had to be rolled the paired roll ends extending beyond the strip on each side were forced together producing a tapered edge on the strip extending inwardly from perhaps 25 millimeters to as much as 100 millimeters in some cases. That edge had to be trimmed off in a later operation, so reducing the yield from the mill. One method of dealing with that problem is suggested in Feldmann, et al. U.S. Patent 4, 479,374 of October 30, 1984. A roll stand is there disclosed which has lathe-type tools adjusted to trim down the ends of the work roll projecting beyond the strip. With such a mill rolling must be scheduled so that all wide strip orders are rolled before narrow strip orders are rolled. DE-A-2408769 discloses a backing roll for guiding the hot steel strand emerging from a continuous casting mould. The roll comprises a core provided with a helical cooling channel located on the surface of the core and further comprises a thin cylindrical shell fitted over the core. DE-A-2707907 discloses a roll for guiding the hot strand emerging from a continuous casting mould and which comprises a cylindrical shell shrunk onto a central core which is provided with helical ribs. Cooling liquid is supplied to the passages defined between the ribs at a position mid-way along the roll and passes along these passages to either end of the roll. Again there is no disclosure of any means for controlling any "crown" of the roll, nor would such control be relevant in the strand guiding application. DE-B-1003946 discloses a roll having cooling means in the form of helically formed grooves on a roll arbor surrounded by a cylindrical roll sleeve, the assembled roll being in the nature of a callendar roll for processing rubber or plastics. The radial height of the ribs defined between the grooves on the arbor is substantially less than the width of said ribs, making rapid expansion or contraction of the sleeve by the ribs impracticable. In DE-B-1003946, the roll temperature is intended to be controlled within a narrow band of 160 to 180° C. According to the invention there is provided a strip rolling mill having an adjustable crown rolling roll comprising a substantially inflexible metal arbor with a shrunk fit metal sleeve thereon, said arbor having a plurality of parallel circumferential grooves in the surface thereof, said grooves being connected together and spaced from each other along said arbor so as to divide said arbor surface encompassed therebetween into fins having ends contacting said sleeve, said fins having a radial dimension substantially greater than the axial dimension and the distance between juxtaposed fins being smaller than their radial extension to effectuate greater heat transfer between the fins and said heat transfer fluid than between said roll sleeve and said heat transfer fluid for pushing said roll sleeve outwardly when said fins are thermally expanded radially outwardly upon heating by said heat transfer fluid and for contracting said roll sleeve radially inward when said fins are thermally contracted upon cooling by said heat transfer fluid, said circumferential grooves forming a central section or heat exchange zone, disposed centrally with respect to the longitudinal ends of the roll, and off-centre sections disposed adjacent the ends of the roll on either side of said central section, the mill including conduits for introducing a heating or cooling heat transfer fluid into said zones and for removing said fluid from said zones, the mill including a hot heat exchange liquid source external to said roll, a cold heat exchange liquid source external to said roll and valve means connecting said hot heat exchange liquid source and said cold heat exchange liquid source with said conduits, whereby, in a first position of said valve means, the valve means can conduct hot heat exchange liquid to said central section and cold heat exchange liquid to and from said off-centre sections and in a second position of said valve means said valve means can conduct hot heat exchange liquid to and from said off-centre sections and can conduct cold heat exchange liquid to and from said central section. Figure 1 illustrates the prior art rolling of a crowned workpiece in a strip mill with flat rolls. Figure 2 illustrates the prior art rolling of a flat workpiece in a strip mill with flat rolls. Figure 3 illustrates the prior art rolling of a flat workpiece in a strip mill with crowned rolls. Figure 4 is a sectional view of a four-high mill with rolls of my invention. Figure 5 is a detail of a roll of my invention. Figure 6A is a schematic section of a roll of my invention showing the directions of the three components of heat flow therein. Figure 6B is a schematic section of a prior art roll showing the directions of the two components of heat flow therein. Figure 7 is a detail of a second embodiment of a roll of my invention. Figure 8 is a detail of a third embodiment of a roll of my invention. Figure 9 is a cross-section of Figure 8 taken on the plane IX-IX. Figure 10 is a schematic of heat exchange liquid supply apparatus for rolls of my invention in forward flow condition and the direction of liquid flow therein. Figure 11 is a profile of a roll of my invention controlled by the apparatus of Figure 10 showing in exaggerated form the resulting convex roll crown. Figure 12 is a schematic of heat exchange liquid supply apparatus for rolls of my invention in reverse flow condition and the direction of liquid flow therein. Figure 13 is a profile of a roll of my invention supplied by the apparatus of Figure 12 showing in exaggerated form the resulting concave roll crown. Three conditions of strip mill operation known in the prior art are shown in exaggerated form in Figures 1, 2 and 3. One or another of those conditions occurs when metal strip is rolled on a mill wider than the strip itself. In Figure 1 a workpiece 11 having a positive crown from prior processing is passed between flat work rolls 12, usually supported by back-up rolls 13. The workpiece deforms work rolls 12 in their center portion 14 and the deformed work rolls 12 correspondingly deform back-up rolls 13 in their center portion 15. That roll deformation is greatest at the mid-point between roll ends, as is shown, and decreases toward each end of the roll. The edges 16 of the resulting strip are squeezed down to a thickness less than the desired gauge, the "edge drop" before noted, and those edges must be trimmed as was also before mentioned. In Figure 2 workpiece 17 entering work rolls 12 is flat. It deforms flat work rolls 12 in their center portion 18 and the deformed work rolls deform back-up rolls 13 in their center portions 19 but those deformations are relatively flat over most of their extent. The edges 20 of the resulting strip are however, as before, squeezed down to a thickness less than the desired gauge and must also be trimmed. Figure 3 shows an effect on an initially flat workpiece 21, of deliberately crowning work rolls 12 and back-up rolls 13, the crown being more or less coextensive with the workpiece width. Under load the deformed regions 22 of work rolls and back-up rolls are relatively flat in profile over most of the workpiece 21 but in regions 23 and 24 where the crown merges into the roll ends there is an edge rise, or negative edge drop 25. By careful contouring of the work rolls and the back-up rolls the strip edges may be maintained at the gauge of the strip center but only for a unique width of strip. My invention is diagrammatically represented in Figure 4 which illustrates a roll stack of work rolls 30 and back-up rolls 31, only one of which back-up rolls is shown in full. The rolls of both types preferably comprise an arbor 35 with a sleeve 36 shrunk on it, as will be described in detail hereinafter. Work rolls 30 have arbors 35 comprising a plurality of circumferential heat exchange element groups 32 set therein of which only two are shown, preferably evenly disposed on each side of a central element group 33. The individual heat exchange unit groups 32 and heat exchange unit 33 are each supplied with heating and cooling fluid generated externally of the rolls through bores such as 41 and 45 extending to the ends of the roll and cross-bores to be described hereinafter. At the roll end the bore are connected to an external supply of heat exchange liquid through a rotating joint 26. Back-up rolls 31 are similarly constructed. Where a number of individual heat exchange units 32 are placed together side-by-side it is sometimes desirable to have individual entry and exit cross-bores 27 and 28 for each unit 32, which cross-bores connect to a rotating joint 29 in the interior of the arbor. The non-rotating element of that joint and feed and drain lines thereto, not shown, then extend through the end of the arbor, thus simplifying the heat exchange liquid supply system in the roll. By varying the heating or cooling medium supplied to the respective heat exchange elements the crown or contour of the roll shell 36 can be adjusted for strip of any width. For example if relatively narrow strip is to be rolled the three outside heat exchange units 32 at each end of the roll would be unheated or perhaps cooled; the two units 32 of each side of the central unit 33 could be warmed and the central unit 33 could be heated to obtain maximum crown in that region. It is essential to my invention that heat transfer to and away from the roll sleeve be rapid. One embodiment of roll satisfactory in that respect is shown in section in Figure 5. The roll comprises an arbor 35 and a cylindrical sleeve 36 shrunk thereon. Sleeve 36 is conventional. Arbor 35 is formed with a pair of spiral circumferential grooves 37 and 38 of opposite hand joining in groove 39 at the center of the roll. That groove is connected by cross-bore 40 to longitudinal bore 41 which extends through one end of the arbor to external supply means, not shown, for a heat exchange medium. The outside end of groove 37 is connected by a cross-bore 43 to a longitudinal bore 45 which extends through arbor 35 and the outside end of groove 38 is likewise connected to bore 45 through cross-bore 44. The arrangement above-described provides for two control sections 37 and 38. To increase the roll crown a heating medium is supplied to both sections through bores 40 and 41 and drawn off through bores 43, 44 and 45. To decrease crown a cooling medium would be substituted for the heating medium or the heating medium could be supplied through bores 43, 44 and 45 and drawn off through bores 40 and 41. The arrangement is greatly improved by connecting the center groove 47 of section 37 by a cross-bore 49 to a longitudinal bore 51 and the center groove 48 of section 38 by a cross bore 50 to longitudinal bore 51, thus providing four control sections. The central sections of course need not be of the same size and it may not always be desirable to operate them so as to obtain a symmetrical crown. The circumferential roll section forming fins 53 between grooves 47 and 48 shown in Figure 5 must be strong enough to withstand rolling pressure but should not be any thicker than necessary so that heat transfer from the medium in the grooves to the sleeve should be rapid. In Figure 6A hot heat transfer medium is shown as being introduced through axial bore 41 and cross bore 40 into center groove 39 of Figure 5 so as to transfer heat to fins 53 adjoining groove 39. The fins and groove can be spiral, as shown in Figure 5, or independently circumferential, as shown in Figure 6A. Independent circumferential grooves must of course be connected together if they are not separately connected to the input and output conduits or by axial or cross bores, and can conveniently be so connected by holes 54 or channels 57 in alternate fins. In Figure 6A each fin 53 in arbor 35 of a roll of my invention has a radial dimension about five times its axial dimension. The primary or principal transfer of heat from the hot fluid in conduit 41 is through the fins 53 as shown on Figure 6A by small arrows. There is a large area of contact between hot fluid and fins on both sides of grooves 37. From the heating fluid there is a secondary transfer of heat directly to sleeve 36 also shown by arrows at the outside edges of grooves 37 which are relatively narrow. Finally, there is a tertiary transfer of heat from the fluid to arbor 35 at the bottom of grooves 37. The primary transfer of heat shown in Figure 6A is much greater than the secondary and tertiary transfers and it is also greater nearer the cross bore 40 than it is remote from that bore. Figure 6B illustrates the two components of heat transfer in prior art thermal crown controlled rolls such as are used in calendars and other apparatus where the material rolled must be heated. The arbor 112 is formed with a spiral groove 111 on its circumference and sleeve 113 is fitted over it. The arbor 112 is bored on its centerline to form an axial duct 114 and inside it is placed a coaxial smaller diameter duct 115 which has openings 118 into duct 114 at intervals along its length. Duct 114 is connected by riser 116 with one end of spiral groove 111 and by riser 117 with the other end of that groove. A component of heat transfer from groove 111 to sleeve 113 shown by arrows is marked "secondary" because it corresponds to some extent with the secondary component of Figure 6A. Another component of heat transfer from duct 114 to arbor 112 marked "tertiary" corresponds to the tertiary component of Figure 6A. There is no significant component of Figure 6B corresponding to the heat transfer marked "primary" in Figure 6A. The diameter of the fins will of course depend on the size of the roll, its function, and the nature of the control desired. For continuous rolling mills it is important to have gauge (thickness along the strip) and profile (thickness across the strip) corrected within seconds or fractions thereof. Hydraulic cylinders effect quick correction of gauge. Various methods are used for profile correction, the fastest being hydraulic roll bending and the slowest, prior to my invention described herein, by supplying heat to or withdrawing it from the roll body. The time required for heat transfer through a body increases approximately with the square of the distance it must travel and for conventional rolling mill rolls would take much too long for on-line crown changes. I have found that in steel rolling mill rolls as herein described the ratio of fin length, the radial distance from the root of the fin to its surface, to its width, measured axially, is desirably in the range from about 4 to about 10 for on-line crown correction. For continuous rolling mill applications, it is of utmost importance to have gauge and profile changes corrected within seconds or fractions thereof. Hydraulic cylinders make quick corrections for gauge changes. For strip profile correction various methods are used the fastest being hydraulic roll bending and the slowest by inserting or extracting heat in and out of the roll body. The most customary heat exchange is by spraying the roll body externally and, internally, but it is too slow for on-line use. In the roll of my invention, as shown in Figure 6A, a sleeve 36 is shrunk upon the upright fins 53 cut into the roll arbor 35. The slenderness ratio L/T of those fins is kept as large as possible without affecting the mechanical stiffness of the roll to a larger extent. Minimum value of L/T is about 4 and maximum is about 10, in backup rolls. Buckling of these fins under the heavy shrinking and rolling forces is prevented by tying them together with rods or the like as in Figures 8 and 9. For achieving a convex crown, hot fluid is channeled to the center of the mill roll expanding the center fins at ends 53′ a certain ΔL. While going up and down through grooves 37 between the fins 53, the fluid temperature will drop a pre-calculated amount, expanding each of the following fins a smaller amount with the last one having only a small δL. By varying the fluid volume and temperature, the amount of roll crown can be pre-established and changed quickly by measuring the results on the strip in closed loop operation. For a concave roll crown, the flow is reversed. The total expansion of the roll is comprised of three sub-expansions: 1. The primary fin expansion which is largest because of the ratio of fin length to fin wall thickness. This lateral heat exchange is the principal control feature, pushing out the sleeve with temperature increase and letting the sleeve collapse, due to the shrink and rolling forces, with temperature decrease. 2. Secondary (through radial heat exchange between heating fluid and sleeve) expansion of the sleeve. There is no need to wait for this much slower and smaller action on the roll crown. 3. Tertiary expansion through radial heat exchange between heating fluid and arbor is still slower and can be practically ignored. The amount of thermal expansion (ΔL) of the fins 53 in the radial direction i.e., toward the roll sleeve 36 according to known thermal expansion formulas, is directly proportional to the length of the fins, the increase in temperature (ΔT) of the fins and coefficient of thermal expansion of the fin material. The fin geometry of my invention maximizes the length as well as the surface area in contact with the heat transfer medium. These features then maximize the length and ΔT factors in the known thermal expansion equation. As the fins 53 are rapidly heated by the hot fluid flowing through the grooves 37, the fins rapidly expand radially outwardly whereby the ends 53′ of the fins push the roll sleeve 36 outwardly to a position shown in phantom lines 36′ in Figure 6A. A new roll crown profile is, thus, established. In a reverse mode or cooling mode, the opposite action occurs and the roll sleeve 36 rapidly contracts following the radially contracting cooled fins due to the shrink fit between the sleeve and arbor and also due to the rolling forces applied. My internal roll structure provides: a) the largest surface for efficient heat exchange while maintaining mechanical strength, b) the quickest maximum shape changes per time unit, c) the best fluid pumping efficiency created by extending fluid travel through the fins, permitting a maximum temperature gradient, d) still faster reaction can be obtained by making fins of high conductive material, such as bronze or aluminum alloys as will appear. Rolls of the prior art, Figure 6B, do not have primary, lateral heat exchange across large areas of thin material. Only secondary and tertiary radial exchanges, over very long time units, are available. L/T approaches R/W <1 where R is roll radius and W is roll width, with no practical effect on roll expansion. It follows that the treating fluid should be introduced into the grooves between the fins at the center of the roll and withdrawn at the roll end. Improved heat transfer to and from the fins can be obtained by utilizing a metal having heat conductivity higher than steel for the fins. In figure 7 a steel arbor 35 is formed with a circumferential cavity 63 in its surface below sleeve 36. In that cavity are fixed groups 64 of annular fins 65 as in Figure 8, of a higher thermal conductivity than steel. Bronze with a thermal conductivity about four times that of steel is commercially available for such purposes. Each fin 65 is spaced from adjacent fins along the axis of the roll as is shown in Figure 8, but only by an amount adequate to permit circulation of a heat exchange fluid between them. The fins in each group 64 are held together by longitudinal ties 66 which pass through holes in the fins. In the bottom surface 67 of cavity 63 a channel 68 is formed extending longitudinally beneath one or more of the fins of group 64 in cavity 63 and connecting with the spaces between identical fins 65 in those groups. A cross-bore 70 opening from channel 68 connects with longitudinal bore 71 which extends through an end of arbor 35. "O" rings 72 of rubber or like material are fitted between arbor 35 and each end of group 64 so as to seal off each group 64 from adjoining groups. In order to assemble fin groups 64 in cavity 63 they are split in halves on a plane through a diameter as is shown in Figure 9, and the halves sealed by gasket 73. The planes of splitting of the various groups 64 are angularly offset from each other as is shown in the dash lines in Figure 9. The split fin groups 64 are held in place on arbor 35 during assembly by wires 74 pulled around tie bolts 66. Apparatus for supplying heat exchange fluid to my roll is shown diagrammatically in two conditions in Figures 10 and 12 and the resulting roll crowns are shown in exaggerated form in Figures 11 and 13 respectively. The roll itself is not shown in Figures 10 and 12; merely a representation of the spiral grooves 37 and 38 of Figure 5 which constitute roll heat exchange zones, and their connecting bores 41, 50 and 51. A hot water or other heat exchange liquid system 76 including a reservoir, pump, heater and valving has a hot water delivery pipe 78 connecting it with a proportioning valve 80 which delivers hot water to line 82, and also to line 88 which returns the hot water to system 76, in proportion determined as will be described hereinafter. A cold water or other heat exchange liquid system 77 including a reservoir, pump, cooling and valving has a delivery pipe 79 connecting it with a proportioning valve 81 which delivers cold water to line 83, and also to line 85 which returns cold water to system 77, in proportion likewise to be described. Hot water system outlet 78 also connects with pipe 88 which delivers water to three-way valve 90. One outlet of valve 90 recirculates hot water through pipe 92 to system 76. The other outlet of valve 90 connects with pipe 96, which in turn connects through bore 45 in the roll and cross-bores 44 and 43 with the outside ends of spiral grooves 38 and 37. Cold water system outlet 79 also connects with pipe 89 which delivers cold water to three-way valve 91. One outlet of valve 91 recirculates cold water through pipe 93 to system 77. The other outlet of valve 91 connects with pipe 97 which connects in turn through bore 45 in the roll and cross-bores 43 and 44 with the outside ends of spiral grooves 37 and 38. The junction 39 of spiral grooves 43 and 44 connects through cross-bore 40 and bore 41 with one port of four-ways valve 94. The center grooves of heat exchange zones 37 and 38 respectively connect through cross-bores 49 and 50 to longitudinal bore 51 which is connected with a second port of four-way valve 94. The third port connects with lines 82 and 83 previously mentioned, and the fourth port through a line 95 and lines 86 and 87 connects with hot water system 76 and cold water system 77 respectively. A temperature sensor 97 is affixed to line 51 and a temperature sensor 98 is affixed to line 41. Temperature sensors 97 and 98 convert the temperature of the water they sense into electrical signals. Sensor 97 is connected by lead 100 to a microprocessor 104 and to sensor 98 and through leads 102 and 103 to proportioning valves 80 and 81 respectively. Microprocessor 104 is connected by lead 101 to temperature sensor 98. A feedback signal 105 from a shape sensor in a roll or other device downstream, not shown, is applied to leads 99 and 101. Manual inputs 106 to microprocessor 104 allow it to be preset to a desired crown. My apparatus described hereinabove will control the temperature along the roll so as to maintain the roll crown at the desired profile. Figure 11 illustrates the roll crown so obtained. Figure 10 illustrates my control apparatus in the forward flow condition, that is, in which hot water is supplied to the adjoining channels of the heat exchange zones 37 and 38 and cold water to the outside ends of each zone. The direction of flow shown by the arrows is controlled by three-way valves 90 and 91 and four-way valve 94. Hot water from lines 78 and 82 passes through four-way valve 94 into line 41 and to the junction of heat exchange zones 37 and 38 in the roll. Cold water from line 89 passes through line 97 and bore 45 to cross-bores 43 and 44 and the outside ends of heat exchange zones 37 and 38. Water at intermediate temperature leaving those zones through cross bores 49 and 50 and pipe 51 passes through four-way valve 94 which directs it through pipe 95 to pipes 86 and 87. Whether the return water goes to the hot water system 76 or the cold water system 77 is governed by proportioning valves 80 and 81 which are adjusted so that when one acts to increase the flow of water circulating back to its system, such as hot water through valve 80 and pipe 84 to hot water system 76, the other acts to decrease the flow of cold water circulating through valve 81 and pipe 85 to the cold water system 77. Under those conditions the bulk of the water returning through pipe 95 goes through pipe 87 to cold water system 77. The proportioning valves 80 and 81 are automatically controlled in accordance with the temperatures of the water entering the heat exchange zones 37 and 38 and the temperature of the water leaving those zones. The first-mentioned temperature is measured by the temperature sensor 98 and the second by temperature sensor 97. Suitable proportioning valves and temperature sensors are commercially available. The signals from temperature sensors 97 and 98 together with a signal 105 from a roll shape sensor positioned downstream in the mill in question, preferably in a measuring roll, are supplied to microprocessor 104 which sends control signals to proportioning valves 80 and 81. Manual controls 106 in the microprocessor are set to a predetermined crown. Figure 12 illustrates the same circuit as Figure 10 but in its reverse flow condition. The two proportioning valves 80 and 81 and four-way valve 94 are turned to their second or reverse positions as shown. The arrows on the figures show the flow direction in the reverse flow condition. The ends of the mill roll are heated and its center is cooled, bringing about the roll profile of Figure 13. While hot and cold water comprise the most convenient hot and cold heat exchange fluids, my invention can be practiced with other liquids or with gases. Superheated water, or steam, for example, could be used for the hot heat exchange medium. In the following claims the term "center section" includes a single center section of circumferential grooves and sections which adjoin each other on opposite sides of a central plane normal to the roll axis. In the foregoing specification I have described presently preferred embodiments of my invention; however, it will be understood that my invention can be otherwise embodied within the scope of the following claims.

Claims: A strip rolling mill having an adjustable crown rolling roll (30) comprising a substantially inflexible metal arbor (35) with a shrunk fit metal sleeve thereon, said arbor having a plurality of parallel circumferential grooves (47, 48) in the surface thereof, said grooves being connected together and spaced from each other along said arbor so as to divide said arbor surface encompassed therebetween into fins (53) having ends contacting said sleeve, said fins (53) having a radial dimension substantially greater than the axial dimension and the distance between juxtaposed fins (53) being smaller than their radial extension to effectuate greater heat transfer between the fins (53) and said heat transfer fluid than between said roll sleeve (36) and said heat transfer fluid for pushing said roll sleeve (36) outwardly when said fins (53) are thermally expanded radially outwardly upon heating by said heat transfer fluid and for contracting said roll sleeve (36) radially inward when said fins (53) are thermally contracted upon cooling by said heat transfer fluid, said circumferential grooves (47, 48) forming a central section or heat exchange zone, disposed centrally with respect to the longitudinal ends of the roll, and off-centre sections disposed adjacent the ends of the roll on either side of said central section, the mill including conduits (41, 45, 49, 50, 51) for introducing a heating or cooling heat transfer fluid into said zones and for removing said fluid from said zones, the mill including a hot heat exchange liquid source (76) external to said roll (30), a cold heat exchange liquid source (77) external to said roll (30) and valve means (94) connecting said hot heat exchange liquid source (76) and said cold heat exchange liquid source (77) with said conduits, whereby, in a first position of said valve means (94), the valve means can conduct hot heat exchange liquid to said central section and cold heat exchange liquid to and from said off-centre sections and in a second position of said valve means (94) said valve means can conduct hot heat exchange liquid to and from said off-centre sections and can conduct cold heat exchange liquid to and from said central section. The strip rolling mill of claim 1 in which in said adjustable crown rolling roll, the radial dimension of the fins (53) is at least four times the axial dimension of the fins. The strip rolling mill of claim 2 in which the radial dimension of the fins (53) of said adjustable crown roll is not more than about 10 times the axial dimension of the fins. The strip rolling mill of claim 1 in which said fins (53) of said adjustable crown roll are formed of material having a higher heat conductivity than the material of the arbor (35). The strip rolling mill of claim 1 in which said parallel circumferential grooves (47, 48) in said arbor (35) are connected by passages (54) through adjoining fins (57). A strip rolling mill according to claim 1 wherein said conduits include a first conduit (41) in said arbor (35) connecting with the mid-point of said central section, a second conduit (45) in said arbor (35) connecting with the ends, remote from said central section, of said off-centre sections, and a third conduit (49, 50) in said arbor connecting with the junctions between said central section and said off-centre sections. A strip rolling mill according to claim 6 wherein said hot heat exchange liquid source (76) has an inlet for liquid to be heated, means for heating liquid supplied via the last-mentioned inlet, and an outlet (78) for liquid heated by the last-mentioned means, said cold heat exchange liquid source (77) has an inlet for liquid to be cooled, means for cooling liquid supplied via the last-mentioned inlet and an outlet (79) for liquid cooled by the last-mentioned means, the rolling mill including a first three-way valve (90) with an outlet port (92) connected with said inlet of the hot heat exchange liquid source, an inlet port (88) connected with said outlet (78) of the hot heat exchange liquid source and a further port (96) connected with said second conduit (45) in said arbor (35), and the rolling mill further including a second three-way valve (91) with an outlet port (93) connected with said inlet of the cold heat exchange liquid source (72), an inlet port (89) connected with said outlet (79) of the cold heat exchange liquid source (72) and a further port (92) connected with said second conduit (45) in said arbor (35). A strip rolling mill according to claim 7 including a first proportioning valve (80) having an inlet port connected with said outlet (78) of said hot heat exchange liquid source (76), and a first outlet port (84) connected with said inlet of said hot heat exchange liquid source (76), a second proportioning valve (81) having an inlet port connected with said outlet (79) of said cold heat exchange liquid source (77) and a first outlet port (93) connected with said inlet of said cold heat exchange liquid source (77), said first and second proportioning valve (80, 81) each having a further outlet port connected with said valve means (94) whereby adjustment of said proportioning valves adjusts the volumes of said hot heat exchange liquid and said cold heat exchange liquid supplied to said conduits in said arbor. A strip rolling mill according to claim 8 including first temperature measuring means (98) positioned externally to said roll adapted to measure the temperature of heat exchange liquid at the centre of said working surface, second temperature measuring means (47) positioned external to said roll adapted to measure the temperature of heat exchange liquid at said positions intermediate said centre and said ends of said working surface and means for adjusting said proportioning valves in accordance with the differences between said temperatures.

Inventors: EIBE, WERNER W.
Applicants: ITALIMPIANTI OF AMERICA, INC.
Application year: 1988
Main classification: B21B27
IPC codes: B21B27