Abstract:
Apparatus for continuously forming a continuous strip of aluminum sheet material using a belt caster for forming a continuous strip of aluminum sheet material and a roll caster for immediately reducing the thickness of the continuous strip of aluminum sheet material wherein the continuous loop belt means used in the belt caster are driven by the rolls of said roll caster.

Description:
FIELD OF THE INVENTION 
     This invention relates to apparatus for the continuous strip casting of aluminum sheet material and, more particularly, to a belt-type caster apparatus which may be used independently to convert molten aluminum material into a continuous strip of aluminum sheet material and in combination with a roll-type caster apparatus to reduce the thickness of the formed continuous strip of aluminum sheet material. 
     BACKGROUND OF THE INVENTION 
     There are several types of prior art apparatus for continuous strip casting of aluminum sheet material. A first type is a roll caster such as that disclosed in U.S. Pat. No. 2,790,216 to J. L. Hunter which comprises flowing molten aluminum into the nip between chill rollers which function to solidify the molten aluminum and form it into a continuous strip. A second type is known as a block caster such as that disclosed in U.S. Pat. No. 4,238,248 to Gyongyos comprising continuously casting an aluminum melt into strip form and hot rolling the continuous strip at a casting speed in a temperature range of between 300 degrees C. and the non-equilibrium solidus temperature of the melt with a total reduction in thickness in excess of 70% and coiling the hot strip and allowing it to cool. A third type is a belt caster such as that disclosed in U.S. Pat. No. 3,933,193 to Baker et al. which comprises feeding a continuous supply of molten aluminum material between moving upper and lower continuous belts and cooling the material while between the moving upper and lower belts to form a continuous strip of aluminum sheet material. Other variations of belt-type casters are disclosed in U.S. Pat. No. 3,036,348 to Hazelett et al. and U.S. Pat. No. 4,190,103 to Silvilotti et al. 
     Each of the foregoing apparatus and processes have certain advantages and disadvantages. For example, a roll-type caster operates at low speed whereas block and belt casters can accommodate high alloy and harder metals. 
     SUMMARY OF THE INVENTION 
     This invention provides a belt-type caster for forming a continuous strip of aluminum sheet material and a roll-type caster for immediately reducing the thickness of the continuous strip of aluminum sheet material wherein the continuous loop belt means used in the belt-type caster are driven by the rollers in the conventional Hunter horizontal cast roll-type caster. 
     In the preferred embodiment of the invention, the belt-type caster comprises an upper and a lower roll means, an upper and a lower guide arcuate guide means, an upper and a lower continuous loop belt means journalled around associated rolls and arcuate guide means and having opposed spaced apart straight sections each extending between the roll means and the arcuate guide means, dam means are provided to cooperate with the straight sections of the continuous loop belt means to form a rectangular cavity between the straight portions of the upper and lower continuous loop belt means. Means are provided for moving the upper and lower continuous loop belt means. The dam means comprise a plurality of short length individual dam means connected to a sprocket chain with means being provided to connect each individual dam means with one of the continuous loop belt means so that the dam means provide an outwardly directed force to each side of one of the continuous loop belt means to remove any buckling therein. A supply of molten aluminum material is fed between the upper and lower continuous loop belt means adjacent to the upper and lower arcuate guide means for movement with the upper and lower continuous loop belt means and the dam means through the straight portions. Cooling means associated with the straight portions of the upper and lower continuous loop belt means functions to cool the molten aluminum material to form a continuous strip of aluminum sheet material. In a preferred arrangement, the upper and lower rolls around which the upper and lower continuous loop belt means are journalled also form a roll-type caster so that the continuous strip of aluminum sheet material form by the belt-type caster moves with the upper and lower continuous loop belt means between the nip between the upper and lower rolls so that the thickness of the continuous strip of aluminum sheet material is reduced. 
     The cooling system in the preferred embodiment comprises a plurality of rows of high pressure and high velocity cooling water spray means each of which extends across the width of each belt and which rows are spaced apart in the direction of movement of the belt means. Low pressure plenum means are located between adjacent rows of the high pressure and high velocity cooling water spray means. Each row of the high pressure and high velocity cooling water spray means is mounted for linear movement toward and away from an associated belt means. A low pressure plenum removes the heated water with means being provided to control the rate of heated water removed out of the low pressure plenum means to create a vacuum on the associated one of the continuous loop belt means. This allows for maximum heat extraction and helps the continuous loop belt means to conform to the profile of the rows of high pressure and high velocity cooling water sprays defining a mold cavity and to reduce water leakage. Also, hydrostatic means provide bearing surfaces on the arcuate guide means and which hydrostatic means may include steam to preheat the upper and lower continuous loop belt means. In addition to the foregoing, the preferred embodiment has means associated with the upper and lower continuous loop belt means and the dam means to compensate for the shrinkage of the molten aluminum material as it cools, during passage through the straight portions. 
     It is an object of this invention to provide a belt-type caster with moving upper and lower continuous loop belt means cooperating with moving side dam means to form a rectangular cavity in combination with cooling means for the upper and lower continuous loop belt means adjacent to the rectangular cavity so as to convert a continuous supply of molten aluminum material fed between the upper and lower continuous loop belt means into a continuous strip of aluminum sheet material during passage through the rectangular cavity. 
     It is another object of this invention to provide a combination of a belt-type caster and a roll-type caster wherein the continuous loop belt means of the belt-type casters are driven by the rollers of the roll-type caster so that the continuous strip of aluminum sheet material formed by the belt-type caster is immediately fed into the nip between the rollers of the roll-type caster to be reduced in thickness. 
     Other objects and advantages of the invention will be apparent from the following more particular description of the preferred embodiments as illustrated in the accompanying drawings in which like reference characters refer to the same part throughout the various views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, side elevational view of the apparatus of the present invention showing a portion of a conventional roll-type horizontal caster apparatus in combination with a belt-type caster apparatus; 
     FIG. 2 is a partial, cross-sectional view taken along line 2--2 in FIG. 1; 
     FIG. 3 is a partial top plan, view with parts in section of the dam means; 
     FIG. 4 is an enlarged, partial cross-sectional view illustrating the arcuate guide means and the cooling means; and 
     FIG. 5 is an enlarged partial view of alignment means for guide means shown in FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, as shown in FIG. 1, the invention comprises a pair of continuous loop steel belt means 20, 22 having front end portions 24, 26 mounted on and driven by a pair of roll means 28, 30 of a conventional roll-type caster. Rear end belt portions 32, 34 are supported by semi-circular guide means 36, 38. Outer intermediate belt portions 40, 42 extend inwardly and rearwardly between roll means 28, 30 and guide shoe means 36, 38. Inner intermediate elongated straight portions 44, 46 extend forwardly between guide means 36, 38 and roll means 28, 30 in spaced, generally parallel relationship to define an elongated cavity 48 of rectangular, cross-sectional configuration therebetween. As explained below, the cavity 48 will have a slight taper with the smallest portion adjacent to the rolls 28 and 30. 
     Dam means 50, 52 are located on opposite sides of the cavity 48 for confining the molten material therebetween. The dam means comprises a plurality of individual short length dam members 54, 55, 56, 58, etc., FIG. 1 mounted on a continuous loop chain means 60 for movement about sprocket means 62, 64 to provide an innermost intermediate length portion 66, FIG. 3, extending approximately between the vertical axes of rotation of sprocket means 62, 64, along which adjacent ones of the individual dam members 68, 70, 72, FIG. 3 are held in abutting side-by-side relationship to form a continuous side surface dam means 74 extending along a forming area 76, FIG. 1. The individual dam members 68, 70, 72 are in contact with the upper and lower straight belt portions 44 and 46 during movement through the distance defined by the forming area portion 76 of the elongated cavity 48. Lower belt means 22 is driven by drive roll means 30 in a fixed path. Upper roll means 28 is driven by the lower roll means 30 so as to drive the upper belt means 20. The central axis 80 of the upper roll means 28 provides a pivot axis whereby the upper belt means 20 and associated apparatus including guide means 36 may be upwardly and downwardly pivotally displaced relative to the lower belt means 22 between a lowermost operating position shown by solid lines in FIG. 1 and an uppermost non-operating position shown by dotted lines in FIG. 1. Guide and support means 82 in the form of an arcuate track and roller means are provided in concentric relationship to pivot 80. Guide means 36, 38 are mounted on slidably movable support structure means 84 connected to pivotally mounted cylinder means 88, 90 for causing movement of the guide means between a non-tension and a tension position whereby the tension in the belt means may be varied. 
     Cooling means 92, 94 are associated with the inner surfaces 93, 95, FIG. 2, of each of the belt means in the forming area 76. Each of the cooling means comprises a high pressure plenum means 96 having a coolant inlet chamber 97 for receiving cooling water at relatively high pressures (e.g. 20 to 40 psi), a plurality of individual rectangular-shape conduit (channel) means such as 98, 100, 102, etc., FIGS. 2 and 4, for enabling flow of water from high pressure plenum means 96 to the inner surface of the belt means and across the belt surface with return of heated water through return conduit (channel) means 104, 106, 108, etc. to low pressure water plenum means 110, having a coolant outlet chamber 118, FIG. 2, and then to exhaust conduit means 112, 114, 116, etc. 
     The cooling means is divided into the high pressure plenum 96 and the low pressure plenum 110 by a rectangular-shape plate 120 having a plurality of transverse slots 122 formed therein. As illustrated in the drawings, the high pressure plenum and the low pressure plenum extend across the width of the belt and for substantially the complete length of the forming area 76. The individual conduit means 98, 100 and 102 are mounted in the slots 122 for linear sliding movement toward and away from an associated continuous loop belt means 20 and 22. Sealing gaskets 124 are seated in grooves 126 to form a seal between the individual conduit means 98, 100 and 102 and the plate 120. Each of the individual conduit means 98, 100 and 102 comprises a generally rectangularly shaped member 127 having longitudinally spaced parallel side walls 128 and transversely spaced parallel opposite end walls 130 with an open end 132 of a central rectangular passage 133 in fluid communication with the chamber 97 of high pressure plenum 96. A bar 134, extends across passage 133 and is secured in a fluid tight relationship to the inner surfaces of the side walls 128 and end walls 130. The bar 134 is provided with a plurality of transversely spaced nozzle-type apertures 136 and the bar is spaced a predetermined distance from the other open end 137 of the side walls 128 and end walls 130 and located adjacent to an associated continuous loop belt means 20 or 22. An edge flange 138 secured to each side of the upper end of the side walls 128 and end walls 130 limits the linear movement of the member 127 toward the continuous loop belt means 20 or 22. A plurality of laterally spaced cross openings 140 are provided in the side walls 128 adjacent to the edge surfaces 142 thereof to provide for passageways through which water flowing through the apertures 136, as described below, may escape into return channel means 104, 106, 108 and return plenum chambers 118. 
     The low pressure plenum means 110 comprises a pair of opposed side walls 144 extending along the side edge portions of the belt means and end walls 146 secured to the surface 148 of the support plate 120. A plate 150 is secured to the side walls 144 and end walls 146 so that an outer surface 152 thereof is adjacent to the side edge portions of an associated continuous loop belt means 20 or 22. The plate 150 each side of the belt means is provided with a plurality of slots 153 having a chamferred bottom surface 155 for slidably receiving and supporting the bottom side surfaces 157 of the sidewalls 128 and the end walls 130. This holds the members 127 in position. The plate 150 is provided with a plurality of openings 154 FIGS. 2 and 4, beneath and between inlet channel means 127 so that a portion of the cooling water flowing out of the orifices 136 onto the associated continuous loop belt means 20 or 22 will absorb heat from the molten material and pass laterally outwardly through the side edge openings 154 into the low pressure plenum 110. A plurality of exhaust conduits, such as 112, 114 and 116 are connected to the side wall 144 and are connected at their ends (not shown) to suitable pump means so as to draw the water from the low pressure plenum means 110. In this way, the heated water is induced to flow through channels 104, 106, 108 and the openings 154 into the low pressure plenum means 110. The pump means function at a rate sufficient to create a vacuum so that the continuous loop belt means 20 and 22 are urged toward the adjacent side surfaces of the slab of metallic material 155, FIG. 2, by edges 142 of the members 127 because of the pressure differential between the relatively high pressure inlet coolant acting against members 127 and the relatively low pressure outlet coolant while the coolant is rapidly removed without significant leakage because of the low pressure condition. As illustrated in FIG. 2, the upper and lower plates 150 are provided with sealing gaskets 156 which function to keep the coolant water confined between the chambers 118 and the associated continuous loop belt means 20 or 22. 
     The dam means is illustrated more specifically in FIGS. 2 and 3 wherein each of the individual dam members 68, 70, 72 comprise an upper L-shaped member 158 and a lower L-shaped member 160. Adjacent to the edges 162 and 164, the L-shaped members 158 and 160 are provided with a pair of spaced apart openings 166 and 168 which receive rods 170 associated with the links 172 of the continuous loop chain means 60. This mounting of the L-shaped members 158 and 160 functions to keep the individual dam members 68, 70, 72 in side-by-side abutting relationship as they move through the forming area 76. An upper rotatable cam follower 174 and a lower rotatable cam follower are mounted on the opposite ends of each rod 170 for a purpose to be described below. 
     A support block 176 is located between the upper L-shaped member 158 and the lower L-shaped member 160 and is located to provided supporting surfaces 177 for the edge portions of the continuous loop belt means 20 and 22 engaging the side surfaces of members 158, 160 to ensure sealing engagement of the continuous loop belt means and the sealing gaskets 156. Each support block 176 is provided with a generally cylindrical opening 178 in which is located a pin 180 which is mounted for reciprocal movement in the cylindrical opening 178 and is normally urged outwardly by spring means 182. A shoulder 184 on each pin 180 retains the pin 180 in the cylindrical opening 178. The upper continuous loop belt means 20 is provided with a plurality of openings 186 adjacent the opposite side edges 187 thereof. Although only one side of the apparatus is illustrated in FIGS. 2 and 3, it is understood that the opposite side of the continuous loop belt means 20 is provided with similar structures and functions as described in relation to FIGS. 2 and 3. The openings 186 are spaced at locations so that as the continuous loop belt means moves around the arcuate guide 32, the pins 180 move through the openings 186 and remain therein during passage of the continuous loop belt means through the forming area 76. 
     A cooperating pair of upper cam blocks 188 and 190 are mounted on the side wall 144 of the upper chamber 118 and a cooperating pair of lower cam blocks 192 and 194 are mounted on the side wall 144 of the upper and lower chamber 118. The upper cam blocks 188 and 190 are slidably adjustable relative to each other so as to move the bearing surface 196, FIG. 3, of the cam block 190 toward or away from the side wall 144 of the upper chamber 118. Similarly, the lower cam blocks 192 and 194 are slidably adjustable relative to each other so as to move the bearing surface 198 of the cam block 194 toward or away from the side wall 144 of the lower chamber 118. As illustrated in FIG. 3, the leading and trailing portions 195, 197 of the bearing surface 196 are inclined. Although not shown, the bearing surface 198 is similarly structured. The cam blocks 188 and 190 and 192 and 194 function to apply outwardly directed forces to the edges of upper continuous loop belt means 20 as as to insure that there are no buckles in the upper continuous loop belt means 20 as it is moved into contact and travels along with the molten material. This is to ensure intimate flat surface belt contact with the molten material. Thus, after the pins 180 have moved through the openings 186, the cam followers 174 contact the inclined lead end portions 195 of the bearing surfaces 196 and 198. The upper cam blocks 188 and 190 and the lower cam blocks 192 and 194 have been adjusted to space the bearing surfaces 196 and 198 a distance from the associated side wall 144 so that, when the cam followers 174 are in contact with the bearing surfaces 196 and 198, sufficient force is being applied to the upper continuous loop belt means 20 so as to stretch the continuous loop belt means 20 so that there are no buckles therein. A wheel 200 FIGS. 1 &amp; 3, with a horizontal axis of rotation is rotatably mounted at a location spaced a short distance from the end of the cam block 188. The outer surface 202 of the wheel 200 is located so as to contact each pin 180 and move it downwardly so as to disengage each pin 180 from its associated opening 186. 
     The lip portion 204, FIG. 2, on the flexible cantilevered end portion of the upper L-shaped member 158 is nested within the lip portion 206 on the flexible cantilevered end portion of the lower L-shaped member 160 so that the outer surface of each lip portion 206 is in contact with the side edge surface of the molten material. The lip portions 204 and 206 are dimensioned so as to permit limited relative movement of the upper L-shaped member 158 and the lower L-shaped member 160 toward each other. This structure cooperates with the upper and lower continuous loop belt means 20 and 22, as described below, to accommodate for the shrinkage of the molten material as it is cooled during passage through the forming area 76. 
     As described above, the upper and lower continuous loop belt means 20 and 22 are driven by conventional drive means associated with the upper and lower rolls 28 and 30 and the rear end portions 32 and 24 are supported by semi-circular guide means 36 and 38. The upper guide means 36 is illustrated in FIG. 4 and comprises a hollow member 208 having concentric outer and inner walls 210 and 212 closed by appropriate end walls 214. The outer wall 210 is provided with a plurality of openings 216 which are spaced apart across the width of the hollow member 208 and along the length thereof in the direction of movement of the continuous loop belt means 20. The openings 216 are associated with tapered recesses 218 in the outer surface of the outer wall 210. Sealing means (not shown) are provided along each outer edge of the outer wall 210 so as to provide a seal between the continuous loop belt means 20 and the outer wall 210. Steam is fed into the hollow member 208 and moves through the openings 216 and recesses 218 to provide a low friction hydrostatic bearing surface for the continuous loop belt means 20 and to raise the temperature of the continuous loop belt means 20 prior to its contact with the molten material as described below. While only the upper continuous loop belt means 20 and the associated structures have been discussed, it is understood that similar structures are associated throughout relative to the lower continuous loop belt means 22. 
     In FIG. 1, there is illustrated a belt welding fixture 220 comprising two adjacent members 222 and 224 each of which have means for holding an end of the continuous loop belt means 20 in a fixed location so that the ends of the continuous loop belt means 20 are positioned relative to each other so that they may be welded together. After the weld has been completed, the same fixture is used to finish grind the weld. The members 222 and 224 are supported by beams 226 and 228 which are secured to a slidable support means 230 which are operatively connected to a piston 232 by clevis means 234. The piston 232 moves in and out of a hydraulic cylinder 88 which is secured to a fixed support 236. The guide means 36 is connected to the slidable support means 230 so that movement of the piston 232 out of the hydraulic cylinder 88 moves the guide means 36 to apply tension to the upper continuous loop belt means 20. As illustrated in FIG. 5, a plurality of adjusting screws 238 on a bracket 239 are used to adjust the alignment of the guide means 36 with the continuous loop belt means 20. As stated above, similar structures are associated with the lower continuous belt means 22. 
     The operation will be described generally with the apparatus in assembled relationship and the various moving parts in operational relationship. That is, the continuous loop belt means 20 and 22 have been welded together and aligned, the rolls 28 and 30 are rotating to drive the continuous loop belt means 20 and 22, water is being supplied to the high pressure plenum 96 and being withdrawn through the low pressure plenum 110 and the bearing surfaces 196 and 198 have been located to place the proper tension across the width of the upper continuous loop belt means 20. Steam is being fed into the hollow member 208 to form a hydrostatic bearing surface for the continuous loop belt means 20 and to heat such belt means 20 prior to its movement into contact with the molten material. 
     Molten material 25, such as aluminum, is fed into the forming area between the upper and lower continuous loop belt means 20 and 22 as they reach adjacent portions of the upper and lower arcuate guide means 36, 38 in a conventional manner. Then, upper and lower opposite surfaces of the continuous loop belt means 20 and 22 move into engagement with the upper and lower surfaces of the individual dam members 68, 70 and 72. The spring-urged piston 180 projecting from each individual dam member enters into an associated opening 186 in the upper continuous loop belt means 20 so that the dam means moves with and is driven by the upper continuous loop belt means 20. The dam members are moved outwardly by cam followers 174 in engagement with the bearing surfaces 196 and 198 so that the proper tension is placed across the width of the upper continuous loop belt means to remove any buckles therefrom. The pressure of the cooling water in the high pressure plenum is controlled so that the pressure on the bars 134 is in an amount to exert the desired pressure on the continuous loop belt means 20 and 25 so as to control the thickness of the molten aluminum located in the cavity formed by the upper and lower continuous belt means 20 and 22 and the dam members 68, 70, 72 and 74. Also, the rate at which the heated water withdrawn from the low pressure plenum 110 by the pump means is controlled so as to create a slight vacuum to assist in creating a sufficient pressure differential to hold the continuous loop belt means 20 and 22 in a desired continuous surface contacting relationship with the upper and lower slab surfaces by force exerted through the members 127 and so that the cooling water passing through the apertures 136 moves into contact with the adjacent surfaces of the continuous loop belt means 20 and 22 at relatively high velocity and is removed in a most efficient manner to effect cooling of the molten aluminum material. The pressure on the water in the high pressure plenum 96 is sufficient to move the water through the apertures 136 by a venturi effect at a relatively high velocity. It is understood that metals other than aluminum may be processed with the apparatus of this invention. 
     During passage of the molten material through the elongated forming area 76, the surfaces of the molten aluminum material are continually cooled by cooling water discharged under high pressure jet conditions across the entire inner surfaces of the continuous loop belt means. As the molten material cools there is some shrinkage so that the thickness of the material gradually decreases. The controlled pressures of the high pressure plenum 96 and the low pressure plenum 110 function to move the upper continuous belt means 20 and the lower continuous belt means 22 relative to each other to accommodate this shrinkage and keep the upper and lower continuous loop belt means 20 and 22 in contact with the associated surfaces of the aluminum. Since the weight of the slab material is usually sufficient to keep the lower surface of the material in full contact with the upper surface of the lower belt means, the apparatus may be constructed and arranged to only force the upper belt means downwardly toward the lower belt means to provide the aforedescribed relative movement between the belt means. Also, as described above, the L-shaped members 158 and 160 are also permitted to move toward each other to accommodate this shrinkage. As the individual dam means reach the end of the forming area 76, the wheel 200 contacts and depresses the piston 180 so that the upper continuous loop belt means 20 is disengaged from the individual dam members. The formed continuous strip of aluminum sheet material leaves the forming area 76 of the belt means caster and moves with the continuous loop belt 20 and 22 toward the rolls 28 and 30. If necessary, lubricating wick means 240 and 242 are provided to lubricate the upper and lower of surfaces of the continuous strip of aluminum just prior to entering the nip area between roll means 28, 30 whereat the thickness of the hot continuous strip of aluminum sheet material is reduced by a suitable amount by a hot rolling pressure and then discharged for further processing in a conventional manner. The temperature of any lubricating means must be such that the temperature of the strip is not cooled below the rolling temperature. 
     In the preferred embodiment of the invention, the continuous strip of aluminum leaving the forming area 76 has a width of about 60 inches and a thickness of about 0.280 inches. To obtain this, molten aluminum material is deposited between the upper and lower continuous loop belt means 20 and 22 at the rate of about 300 to 500 lbs./min. and at a temperature of about 1100 to 1200 degrees F. The width between opposed individual dam members at the beginning of the forming area is about 63 inches and the distance between the upper and lower continuous loop belt means 20 and 22 at the beginning of the forming area 76 is about 0.410 inches. The continuous loop belt means 20 and 22 move at a rate of about 12 ft./min. The pressure of the cooling water in the high pressure plenum is about 20 psi and the velocity of the water as it exits the apertures 136 is about 0.08 cu.ft/min./aperture. The pump means extracts heated water from the low pressure plenum at a rate to have a pressure of about 1 to 5 psi below atmospheric on the associated continuous loop belt means 20 and 22 to facilitate rapid removal of water without significant leakage along the edges of the belt means. The continuous strip of aluminum is fed into the nip between the rolls 28 and 30 and exits therefrom at a thickness of about 0.280 inches and at the rate of about 17.5 ft/min. At these flow rates the mold cavity can be around 9 inches long. The strip should be above 900 degrees F. at the entry to the rolls. 
     The illustrative embodiment of the invention may be variously modified for adaption to various apparatus and conditions of operation to achieve various results. Some of the features of this invention are alternative and may be selectively utilized only as necessary or desirable for under particular circumstances and conditions. Thus, it is intended that the appended claims be construed to include various alternative and modified constructions and arrangements except insofar as limited by the prior art.