Title of Invention	A METHOD DIRECT SHILL CASTING A MULTI-LAYERED METAL INGOT AND A MULTI-LAYERED METAL PRODUCT
Abstract	A method of casting a multi-layered metal ingot comprising the steps of delivering a metallic divider (14) member into a direct chill mold (4), pouring a first molten metal into the mold on one side of the divider member, and pouring a second molten metal into the mold on the other side of the divider member, and allowing the first molten metal and the second molten metal solidify to form a metal ingot (10) which includes the divider metal layer disposed there between.

Title of Invention

A METHOD DIRECT SHILL CASTING A MULTI-LAYERED METAL INGOT AND A MULTI-LAYERED METAL PRODUCT

Abstract

A method of casting a multi-layered metal ingot comprising the steps of delivering a metallic divider (14) member into a direct chill mold (4), pouring a first molten metal into the mold on one side of the divider member, and pouring a second molten metal into the mold on the other side of the divider member, and allowing the first molten metal and the second molten metal solidify to form a metal ingot (10) which includes the divider metal layer disposed there between.

Full Text	A Method Of Direct Chill Casting A Multi-Layered Metal Ingot And A Multi-Layered Metal Product The present invention relates to the simultaneous casting of multiple alloys, in particular, direct chill casting of multiple aluminum alloys using a metallic member between the alloys to form a multi-component cast product and/or the use of a metallic member as an external layer on a cast ingot. In the production of aluminum alloy ingots by a conventional direct chill (DC) casting process, molten aluminum is poured into an opened end mold. The lower end of the mold is initially closed by a platform referred to as bottom block and the molten metal pools within the mold. The bottom block is progressively lowered in step with the pouring of the molten metal. The wall of the DC mold is continuously cooled so that a solid skin of metal forms in contact with the mold wall at the level of the surface of the pool of molten metal in the mold. An example of the method of DC casting is described in U.S. Patent No. 4,071,072, incorporated herein by reference. In this conventional operation, a single molten aluminum alloy is direct cast into an ingot. Such aluminum ingots are often times incorporated with other alloys to form a composite product. For example, brazing sheet for the header of a heat exchanger or for reinforcement structures may be produced from an Aluminum Association (AA) 3000 series aluminum alloy with a clad layer of an AA 4000 series alloy. Evaporator sheet product or plate type heat exchangers typically include a 3000 series alloy clad on both sides with a 4000 series alloy. Likewise, radiators often are formed from a 3000 series alloy with a 4000 series cladding and water-side liner of an AA 1000, 5000, 6000, or 7000 series alloy. The clad layer is conventionally roll bonded in plate form onto an ingot of the core alloy (e.g., a 3000 series alloy). Roll bonding requires multiple rolling passes, scalping, reheating, and sealing steps to produce the clad alloy in sheet form. Each of those processes adds to the cost of the final clad product. In addition, the thickness of cladding produced via roll bonding is generally limited to a maximum of only about 35% of the total sheet thickness. Roll bonding can also be extremely difficult if the mechanical properties of the alloys being roll bonded are too dissimilar at the rolling temperatures. For example, when one alloy deforms very easily while the other alloy does not, the alloys do not seal properly or the target cladding ratio is off. More recently, attempts have been made at casting composite metal products. One such process is described in DE 4420697 in which one alloy of a billet is DC cast on one side of a fixed barrier and another alloy is DC cast on the opposite side of the barrier. The process is controlled such that the two molten metals come in contact with one another while in the molten state to provide a controlled mixing of the two melts. In this manner, the composition of the composite billet in the direction perpendicular to the contact surface of the two metal components changes continuously. The concentration of the individual alloy elements changes continuously from the values of one alloy to the values in the other. The fixed barrier maintains the two components apart from each other within the mold, and the barrier is positioned off center so that one component is narrower than the other. The alloy closest to the mold (the narrower component) cools and solidifies earlier in the process than the other alloy, i.e., at a great height from the bottom block. The bottom block is withdrawn at a speed whereby the levels of the melts within the mold remain approximately even. Although one alloy solidifies before the other alloy, there is a small region between the melts in which the melts are able to flow into one another and mix briefly to promote adhesion between the two alloys. While this method provides some adhesion between the two components of the cast product, the mixing of the components which occurs during the casting can be detrimental to the finished product. The location and shape of the fixed barrier are also critical to avoid intermixing of the molten alloys. The properties of the alloys simultaneously cast in this manner may be affected by the mixing of the alloying components. This method also requires careful control of molten metal flow to avoid mixing due to hydraulic pressure differences as well as careful control of the solidification rate of the alloy forming the narrower component to ensure only brief mixing of the alloys in the region immediately below the barrier. Another method of DC casting a composite ingot is disclosed in U.S. Patent No. 4,567,936 in which an outer layer is simultaneously cast within an inner component. According to this method, the outer layer solidifies prior to contact within the molten inner alloy. This avoids mixing between the components of the inner component and the outer layer. A drawback to this method is that the outer layer must solidify completely before the inner alloy can be cast within* the outer layer. The thickness of the outer layer also is limited because the heat of the inner component must exit through the outer layer to the exterior surfaces of the cast product. Hence, the configuration of the final multi-component product also is limited. Accordingly, a need remains for a method of simultaneously casting a multi-alloy metal product with a minimum of mixing between the alloys of the product and which can produce cast metal products in a variety of configurations. This need is met by the method of the present invention of casting a multi-layered metal ingot including the steps of delivering a metallic divider member into a direct chill mold, pouring a first molten metal into the mold on one side of the divider member and pouring a second molten metal into the mold on the other side of the divider member, and allowing the first molten metal and the second molten metal to solidify to form a metal ingot which includes the divider metal layer disposed between the two cast layers. The multi-layered metal ingot removed from the mold contains at least two cast layers including the first and second metals separated by a layer of the divider member. Alternatively, the divider member may be positioned against a wall of the mold and a single molten metal is poured into the mold to produce one cast layer bound to the divider member thereby forming an outer shell or cladding on the ingot. The divider member may be a sheet having a thickness of up to about 0.25 inch or a plate having a thickness of up to about 6 inches. The position of the divider member may be shifted within the mold to produce varying thicknesses of the cast metals. More than one divider member may be placed in the mold with molten metals poured on opposite sides of each divider member to produce a metal product having at least three cast layers separated by the divider members. The fundamental principles guiding the attainment of a strongly bonded interface between the divider member and the molten metal are identical regardless of where the divider member is located within the ingot. The divider member may also be tubular in shape. One metal is poured into the tubular divider member while another metal is poured between the tubular divider member and the mold. The molten metals may each be an alloy of AA series 1000,2000,3000, 4000,5000,6000,7000, or 8000. The divider member may be a solid metal that will survive exposure to the molten aluminum during the casting operation. For the purpose of maintaining a "clean" scrap loop, the divider member preferably is aluminum or an aluminum alloy or a clad aluminum product that has a solidus temperature greater than the liquidus temperatures of the alloys cast on either side thereof. It is preferred that the solidus temperature of the divider member be at least 610°C. A particularly suitable metal for the divider member is an AA 1000 series alloy. Alternatively, the divider member may be in the form of a screen alloys of iron, titanium, magnesium, copper, or nickel. A complete understanding of the invention will be obtained from the following description when taken in connection with the accompanying drawing figures wherein like reference characters identify like parts throughout. Fig. 1 is a partially sectioned schematic of an apparatus for simultaneously producing a composite metal product having two cast layers according to the present invention; Fig. 2 is a cross-section of the metal product produced in the apparatus shown in Fig. 1; Fig. 3 is a partially sectioned schematic of an apparatus for producing a composite metal product having one cast layer according to another embodiment of the present invention; Fig. 4 is a cross-section of the metal product produced in the apparatus shown in Fig. 3; Fig. 5 is a partially sectioned schematic of a device for simultaneously producing a composite metal product having three cast layers according to the present invention; Fig. 6 is a cross section of the metal product produced using the device shown in Fig. 5; Fig. 7 is a cross-section of the metal product produced in the device shown in Fig. 1 with additional layers roll bonded thereto; Fig. 8 is a cross-section of the metal product produced in the device shown in Fig. 5 with a layer roll bonded thereto; Fig. 9 is a cross-section of the metal product produced according to the present invention wherein the thickness of the layers of the composite product is not constant across the width of the product; Fig. 10 is a cross-section of the metal product of Fig. 9 following a rolling step; Fig. 11 is a partially sectioned schematic of another device for simultaneously casting multiple alloys to produce a billet using a tubular divider member; Fig. 12 is a cross-section of the device shown in Fig. 11 taken along lines 12-12; Fig. 13 is a cross-section of the billet produced in the device shown in Fig. 11; Fig. 14 is a photograph of a cross-section of an ingot produced according to the present invention; Fig. 15 is a photomicrograph of a portion of the ingot shown in Fig. 14; Fig. 16 is a photomicrograph of a portion of the ingot shown in Fig. 14 after hot rolling; Fig. 17 is a photomicrograph of the portion of the ingot shown in Fig. 16 after cold rolling; Fig. 18 is a photograph of a cross-section of another ingot produced according to the present invention; Fig. 19 is a photograph of a cross-section of yet another ingot produced according to the present invention; and Fig. 20 is a photomicrograph an interface between the layers of another ingot produced according to the present invention. For purposes of the description hereinafter, the terms "upper", "lower", "right", "left", "vertical", "horizontal", "top", "bottom" and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting. The present invention is directed to a method of casting a multi-layered metal ingot and the product produced thereby. The method of the present invention uses an apparatus 2 schematically shown in Fig. 1 which incorporates a conventional direct chill mold 4. The direct chill mold 4 defines a water chamber 6 and a slit 8 through which water is emitted directly onto the surface of an ingot 10 emerging from the mold 4. The cast ingot 10 solidifies on a bottom block 12. A metallic divider member 14 is suspended into the mold 4 and seats on the bottom block 12. The metallic divider member 14 provides a barrier between a first molten metal 16 which is fed into the mold 4 via a first trough 18 and a second molten metal 20 fed into the mold 4 via a second trough 22. The bottom block 12 is withdrawn in the direction of arrow A while coolant (water) is applied to the surfaces of the ingot 10. Suitable speeds for the bottom block 12 are about I to about 6 inches per minute, preferably about 2 to about 3 inches per minute. When citing such ranges herein, the range includes all intermediate values. The divider member 14 remains in contact with the bottom block 12 and accordingly travels downwardly at the speed that the bottom block 12 travels. A crane (not shown) equipped with movable grips (e.g., wheels) may be used to suspend the divider member 14 over the apparatus 2 and deliver the divider member 14 into the mold 4. Other mechanisms may be used to suspend and deliver the divider member 14 into the mold 4. Each of the first and second molten metals 16 and 20 solidify as generally shown in Fig. 1. The portion 24 of the metal 16 closest to the mold 4 solidifies very quickly, e.g. in less than about 10 seconds. Solidification of the metal 20 likewise occurs at a region 26 adjacent the mold 4. Semi-solid zones 28 and 30 form below the level of the respective first solidification regions 24 and 26. The metals 16 and 20 also begin to solidify adjacent the divider member 14 at respective locations 32 and 34. The locations 24,26,32 and 34 may be at the same height as each other or at different heights from the bottom block 12. In many cases, the melting point of the metal of the divider member 14 is less than the temperature of the incoming molten metals 16 and 20. Nevertheless, the divider member 14 does not completely melt and serves to prevent mixing of the metals 16 and 20 by acting as a heat sink and as an interface between the metals 16 and 20. Some heat from the molten metals 16 and 20 transfers into the divider member 14 and subsequently is transferred out of the portion 36 of the divider member 14 that extends up and out of the mold 4. Similarly, some of the heat transferred to the divider member 14 is also subsequently transferred out of the divider member to the solidifying ingot 10 below the molten metals 16 and 20. The divider member 14 may experience minimal melting (erosion), but this minimal amount does not affect the metallurgical properties of each of the metals 16 and 20 cast on opposing sides of a divider member 14. Upon complete solidification, the metals 16 and 20 form respective solid components 38 and 40 separated by the divider member 14. The minimal melting of the divider member 14 provides for some mixing of the components of the divider member 14 with the components of the metal 16 on one side and with the components of the metal 20 on the other side. The minimally mixed metals solidify and thereby adhere the components 38 and 40 to the divider member 14. Superior adhesion between the divider member 14 and components 38 and 40 is achieved when the temperature of the divider member 14 reaches at least the higher of the liquidus temperature of component 38 and the liquidus temperature of component 40. It is believed that when the divider member 14 initially contacts the molten metals 16 and 20, some solidification of the metals rapidly occurs on the surfaces of the divider member 14. This temporary solidification is not shown in Fig. 1. Inherent oxides on the surfaces of the divider member 14 generally remain and become entrapped between the divider member 14 and the solidified metal. When the molten metal temperatures are sufficiently high, the divider member 14 locally reaches a temperature greater than the liguidus temperature of the metals 16 and 20 and the initially solidified metal remelts as the divider member 14 travels in the direction of the arrow A. The divider member 14 is then directly exposed to the molten metals 16 and 20 and the oxide destabilizes with some minimal melting of the divider member 14. As the divider member 14 continues downwardly, the local temperatures of the molten metals 16 and 20 decrease to their liquidus temperatures and solidification begins. The local temperatures continue to drop until the solidus temperatures are reached and the alloys fully solidify resulting in strong bonds between the components 38 and 40 and the respective sides of the divider member 14. Alternatively or in addition thereto, flux may be applied to one or both sides of the divider member 14. The flux may be applied to the divider member 14 directly (e.g. by coating the surfaces of the divider member 14 with flux) or flux may be applied to the upper surfaces of the molten metals 16 and 20 that pool in the mold 4. Immediately prior to contact between the divider member 14 and the molten metals 16 and 20, the flux melts and chemically reduces oxides on the divider member 14 which could otherwise interfere in the adhesion of the molten metals 16 and 20 to the divider member 14. Suitable flux includes potassium aluminum fluoride based fluxes (e.g. Nocolok®) along with but not limited to fluxes based on cesium-potassium aluminum fluoride based fluxes and cesium fluoroaluminate based fluxes. The flux may be any material capable of removing the oxide layer by chemical reaction prior to contact of the molten metals 16 and 20 with the divider member 14. When flux is used, lower molten metal temperatures should be used during casting to reduce the risk of melting the divider member 14 yet achieve strong adhesion of the components 38 and 40 to the divider member 14. A cross section of the ingot 10 produced in the apparatus 2 is shown in Fig. 2. The ingot 10 is depicted as having a rectangular configuration with the divider member 14 positioned centrally between the layers of components 38 and 40. However, the divider member 14 may be positioned off-center and may be as close as about 0.S inch from side surfaces 42 and 44 of the ingot 10. The divider member 14 has a width between edges 46 and 48 thereof which is slightly smaller than the width of the ingot 10 between edges 49a and 49b. Edges 46 and 48 preferably are positioned about 0.1 to about 3 inches from the mold 4 and are shown not to scale in Figs. 2 and 6-8. The cooling rates are highest near the surface of the ingot 10, and the molten metals 16 and 20 rapidly solidify at the surface of the ingot. The rapid solidification of molten metals 16 and 20 around the edges 46 and 48 minimizes opportunities for mixing of the molten metals 16 and 20. Nevertheless, some minimal mixing may enhance adhesion of the solid components 38 and 40 together. In any event, the edges 49a and 49b of the ingot 10 are typically trimmed off during rolling to eliminate edge cracking so these areas of intermixing around the edges 46 and 48 of the divider member 14 generally are discarded. The thickness of the divider member 14 may range between about 0.07 inch to about 0.25 inch (referred to as a sheet) or over about 0.25 inch to about 6 inches thick (occasionally referred to as a shlate when up to one inch thick and generally referred to as a plate when up to 6 inches thick). The thickness of the divider member 14 preferably is about 0.5 to about 6% of the thickness of the ingot 10, more preferably about 1 to about 3% of the thickness of the ingot 10. A thinner divider member 14 may be used when the risk of melting of the divider member 14 is low and/or the desired metallurgical or structural properties of the ingot 10 dictate that the layer 14 has a minimal thickness. Conversely, a thicker divider member 14 may provide a more significant barrier to mixing of the molten metals 16 and 20 and may serve as one layer in a multi-layered ingot. If the divider member 14 transfers heat too rapidly out of the solidifying metals 16 and 20, the resultant components 38 and 40 may be prone to cracking. Hence, when the divider member 14 is over about 0.25 inch thick., it may be desirable to preheat the divider member 14 to within about 400°C of the temperature of the molten metals 16 and 20 thereby reducing the rate of heat transfer through the divider member 14. Generally, the divider member 14 has a melting point of at least 610° C. The divider member 14 may be an aluminum alloy and preferably contains at least about 97% aluminum and has a high solidus temperature such as an AA 1000 series alloy. Other suitable materials for the divider member 14 are composite products containing layers of aluminum alloys, stainless steel, nickel alloys, titanium alloys, magnesium alloys and combinations thereof that are clad, plated or coated thereto. The chemistry of the divider member 14 may be selected to improve the corrosion resistance of the final product being cast. For example, the addition of Zn to the divider member 14 makes the divider member 14 more electrochemically negative than at least one of the components 38 and 40. This results in galvanic protection, whereby the Zn enriched areas (the divider member 14 and the portion of components 38 and 40 into which Zn has diffused) sacrificially protect the more cathodic alloys of components 38 and 40. The divider member 14 may define a plurality of small holes to allow some wetting between the molten metals 16 and 20 without significant intermixing. Alternatively, the divider member 14 may be a screen produced from iron, titanium, molybdenum or alloys thereof. Suitable screens are 14x18 mesh about 0.01 inch thick or 32x32 mesh about 0.006 inch thick. The molten metals 16 and 20 each may be the same or different and each is preferably an aluminum alloy and may be an alloy of the AA series 1000, 2000, 3000,4000, 5000,6000, 7000, or 8000. Other suitable metals may include magnesium alloys. For products in which one of the molten metals requires a specialized alloy, the other molten metal may have a high scrap alloy content. The low value scrap metal may be simultaneously cast with a thinner layer of the specialized alloy to produce high value products with a specialized surface such as reflector sheet, anodized products, architectural products and the like. The temperature of the first molten metal 16 may be about equal to the temperature of the second molten metal 20, or the temperatures of the first and second molten metals 16 and 20 may differ by up to about 150°C. Selection and control of the temperatures of the molten metals 16 and 20 during casting is critical, particularly when flux is not used. When no flux is used to remove the oxide on the divider member 14, the selection of molten metal temperatures should be such that the temperature of the divider member 14 rises above the liquidus temperature of the molten metals 16 and 20. When a flux is used or when the material of the divider member 14 is selected such that the oxide is disrupted prior to contacting the molten metals 16 and 20 or when the presence of an oxide on the surfaces of the divider member 14 is not detrimental to achieving a strong bond, lower molten metal temperatures may be used and the divider member 14 does not necessarily need to reach the liquidus temperatures of the molten metals 16 and 20. In fact, it is desirable that the divider member 14 does not reach the liquidus temperature(s) because the divider member 14 remains protected from the molten metals 16 and 20 by the metal that initially solidifies onto the divider member 14. In any case, the molten metal temperatures cannot be so high as to cause complete melting of the divider member 14. Some melting of the divider member 14 is acceptable, but complete melting of the divider member 14, even locally (i.e. a "bum through"), is undesired. The temperatures for this process depend on the chemistries of the molten metals 16 and 20 and of the divider member 14. Referring to Figs. 3 and 4, the present invention may also be used to produce a composite ingot having a single cast layer with a layer of divider metal;. In system 2', the divider member 14 may be delivered into the mold 4 at a location adjacent to the wall of the mold 4 and the molten metal 16 is delivered into the mold 4 via the trough 18. The metal 16 begins to solidify in semi-solid zone 28 and ultimately solidifies as component 38 bound to the divider member 14 in manner similar to the solidification of metal 16 described above to yield an ingot 10'. This embodiment of the invention allows for production of an ingot 10 having a solid layer 14 bound to a cast layer 38 which avoids the prior art roll bonding processes. Flux may be applied to the surface of the divider member 14 which contacts the molten metal 16 in the system 2' or to the surface of pool of molten metal 16 as described above. The divider member 14 and component 38 of the ingot 10' may be selected from the same materials listed above for ingot 10. The method of the present invention may also be used to cast more than two molten metals. For example, in the apparatus 50 shown in Fig. 5, two divider members 14 and 52 may be delivered into the direct chill mold 4 while molten metals 16,20, and 53 are delivered into the mold via respective troughs 18,22, and 54. Casting of an ingot 60 from three separate molten metals 16,20, and 53 is performed in a manner similar to that described above. The molten metal 16 solidifies first at locations 24 (adjacent the mold 4) and 32 (adjacent the divider member 14), while molten metal 20 solidifies first at locations 34 (adjacent the divider member 14) and location 55 (adjacent the divider member 52). Molten metal 53 first solidifies at location 56 (adjacent the divider member 52) and location 57 (adjacent the mold 4). The solidifying metals 16, 20, and 53 form respective semi-solid zones 28,30 and 58. The locations 24, 32,34, 55,56, and 57 may be at the same height as each other or at different heights from the bottom block 12. The resultant product includes three cast layers 38,40, and 62 separated from each other by divider members 14 and 52 as shown in Fig. 6. The divider members 14 and 52 are positioned within the mold in the embodiment of Fig. 5 similar to divider member 14 of Fig. 1. The distance between the divider members 14 and 52 is selected based on the desired thicknesses of the components 38,40, and 62 in the ingot 60 and the size of the mold 4. The embodiment shown in Figs. 5 and 6 relates to simultaneous casting of three alloys with divider layers interspersed between, thereby creating a five-layer product. This is not meant to be limiting. More than three alloys may be simultaneous cast according to the present invention in rectangular configurations or in other configurations by using other shapes for the mold (e.g. square or oval) and non-planar divider members. Additional layers of metal may be bonded to the cast multi-layered ingots 10 and 60 resulting in the products 70 and 80 shown in Figs. 7 and 8. Product 70 includes the ingot 10 and a pair of metal layers 72 roll bonded to the ingot 10. Product 80 includes the ingot 60 with a metal layer 82 roll bonded thereto. Products 70 and 80 each may have one or two respective layers 72 or 82. When two layers 72 are included as shown in Fig. 7, the metal of those layers may be the same or different from each other. The layers 72 and 82 may also be multi-component products produced according to the present invention or produced by conventional roll bonding practices. One of the advantages of the present invention is borne out when a multi-layered metal ingot produced according to the present invention is subsequently rolled, for example, into a plate or sheet product. In conventional roll bonded ingots, the thickness of a clad layer at the ends of the ingot often times becomes unacceptably thin during the rolling process. The edges of the resulting coil made from the composite ingot must be trimmed and scrapped so that the clad layer is uniformly thick across the width of the coil. Edge trimming of about 4 inches (for about 3-5% cladding) to about 8 inches (for about 10-15% cladding) is typical for conventional roll bonded brazing sheet. Such scrap losses can be minimized in the present invention by producing an ingot 90 as shown in Fig. 9 which has an arcuately shaped divider member 92 with metals 94 and 96 cast on opposing sides thereof. The cast metal 96 (corresponding to a conventional clad layer) is thickest at the edges of the ingot 90. Upon rolling the ingot 90 to a plate 90', the divider member 92' flattens and the cast metals 94' and 96' are substantially uniformly thick as shown in Fig. 10. The divider member 92 may be tapered or bent into other configurations to locally achieve differing thickness of the metals cast on opposing sides thereof. The present invention may also be used to produce cylindrical products (e.g., a billet) of multiple alloys. The embodiment of the invention shown in Figs. 11 and 12 includes an apparatus 100 having a cylindrical mold 104 defining a water chamber 106 and a slit 108 through which water is emitted directly onto the surface of an ingot 110 emerging from the mold 104. The cast ingot 110 seats on a circular bottom block 112 traveling in the direction of arrow B. A tubular divider member 114 is fed into the mold 104 and acts as a barrier between molten metal 116 fed from trough 118 on the outside of the tubular divider member 114 and molten metal 120 fed from another trough (not shown) on the inside of the tubular divider member 114. Delivery of the divider member 114 and movement of the bottom block 112 are controlled as described above regarding the apparatus 2. The tubular divider member 114 may define a longitudinal slot 122 to ease access of the molten metal 120 into the divider member 114 during casting. Particularly during startup, the molten metal 120 may be delivered into the tubular divider member 114 via the slot 122 near the bottom block 112 instead of pouring the molten metal 120 into the tubular divider member 114 which can result in turbulence of the molten metal 120. The slot 122 is sufficiently narrow (e.g. about 1 to about 20 inches wide, depending on the size of the billet being cast) and may extend down into the molten pools of metals 116 and 120 to prevent excessive mixing between the molten metals 116 and 120 in the vicinity of the slot 122. Molten metal 116 first solidifies adjacent the mold 104 at region 124 and molten metal 120 first solidifies adjacent the tubular divider member 114 at region 126. An annular semi-solid zone 128 forms below the level of the first solidification region 124, and a cylindrical semi-solid zone 130 forms below the level of the region 126. Upon complete solidification, the metals 116 and 120 form respective solid components 138 and 140 separate by the tubular divider member 114. A cross-section of the billet 110 produced in the apparatus 100 is shown in Fig. 13. The present invention provides significant improvements over conventional clad products. The cladding ratio of roll bonded products is generally a maximum of 35%, i.e. the interface between roll bonded layers can generally be no greater than about 35% of the distance from either face of the ingot. In the present invention, the only limitation on the location of cast layers is that a cast layer is at least about 1 inch thick to allow for distribution of molten metal across the width of the ingot. The alloys which may be bonded together using the present invention are much more numerous than those which may be reliably and/or economically roll bonded together. Product quality is improved in the elimination of roll bonding blisters. The productivity of a hot mill used to initially breakdown or roll an ingot produced according to the present invention is also significantly increased as the many sealing passes may be eliminated. Although the invention has been described generally above, the following particular examples give additional illustrations of the products and process steps typical of the present invention. EXAMPLES 1-3 In each of Examples 1-3, a sheet of AA 1350 (20 inches wide, 0.375 inch thick, and 24 inches long) was positioned in the center of 12 inch x 22 inch mold spanning the width with a gap of about 1 inch between the edge of the sheet and the mold walls. In each Example, a melt A of the alloy listed in Table 1 was poured into the mold on one side of the sheet and a melt B of the alloy B listed in Table 1 was poured into the mold on the other side of the sheet. In Example 3, flux was applied to the side of the sheet which contacted melt A. The metals were cast on opposing sides of the sheet while the bottom block with sheet seated thereon was lowered at a rate of 2.75 inches per minute. A 12 inch x 22 inch x about 42 inch ingot having sheet of AA 1350 bonded between a layer of alloy A and a layer of alloy B was produced. A block was sectioned from the ingot of Example 1 and was rolled (hot and cold) without any delaminating along the interface between the AA 1350 sheet and the cast layers of AA 3003 and 7051. A photograph of a horizontal cut through the ingot appears in Fig. 14. A close-up photomicrograph of the interface between the layers of AA alloy 3003 and modified AA alloy 7051 showing minimal erosion of the sheet appears in Fig. 15. A portion of the ingot was hot rolled to 0.250 inch (shown in Fig. 16) and subsequently cold rolled to 0.005 inch (shown in Fig. 17). A photograph of a horizontal cut through the ingot produced in Example 2 appears in Fig. 18. A photograph of a horizontal cut through the ingot produced in Example 3 appears in Fig. 19. Example 3 was repeated without flux and a photomicrograph of the AA3003/AA1350/AA4343 interface is shown under polarized light in Fig. 20 after etching in barkers etch to illustrate the microstructural details of the interface. WE CLAIM : 1. A method of direct chill casting a multi-layered metal ingot comprising the steps of: (a) delivering a metallic divider member into a direct chill mold; (b) pouring a first molten aluminum-based metal into the cirect chill mold on one side of the divider member; (c) pouring a second molten metal into the direct chill mold on the other side of the divider member; (d) allowing the first molten metal and the second molten metal to solidify to form a multi-layer metal ingot comprising a divider metal layer disposed between a layer of the first metal and a layer of the second metal; and (e) withdrawing the multi-layered metal ingot from the mold, wherein the thickness of the divider metal layer is about 0.5% to about 6% of the thickness of the multi-layered metal ingot. 2. The method as claimed in claim 1, wherein the divider member comprises a sheet having a thickness of about 0.07 to about 0.25 inch. 3. The method as claimed in claim 1, wherein the divider member comprises a plate having a thickness of over about 0.25 to about 6 inches thick. 4. The method as claimed in claim 1, wherein the divider member defines a plurality of holes therethrough. 6. The method as claimed in claim 1, wherein the divider member comprises a screen. 7. The method as claimed in claim 5, wherein the screen comprises iron, titanium, molybdenum or alloys thereof. 8. The method as claimed in claim 1, wherein the divider member is tubular and one of the first and second molten metals is poured into the tubular divider member and the other molten metal is poured between the tubular divider member and the mold. 8. The method as claimed in claim 7. wherein the tubular divider member defines a longitudinal slot. 9. The method as claimed in claim 1, wherein the first metal and the second metal each comprise an aluminum alloy. 10. The method as claimed in claim 9, wherein the first metal and the second metal are different compositions. 11. The method as claimed in claim 9, wherein the first metal and the second metal are each an alloy of an Aluminum Association series selected from the group consisting of 1000,2000. 3000,4000, 5000,6000. 7000 and 8000. 12. The method as claimed in claim 11, wherein the divider member has a melting point of at least 610°C. 13. The method as claimed in claim 11, wherein the divider member comprises an Aluminum Association 1000 series alloy. 14. The method as claimed in claim 11, wherein the divider member comprises a composite of a plurality of layers of materials selected from the group consisting of aluminum alloy, steel, titanium alloy, copper alloy, magnesium alloy and nickel alloy. 15. The method as claimed in claim 1. wherein step (a) comprises delivering another metallic divider member into the mold and step (b) comprises pouring a third molten metal on one side of the other divider member to produce an ingot comprising a pair of layers of divider metal interspersed between layers of the first, second, and third metals. 16. The method as claimed in claim 15, wherein the first metal, the second metal, and the third metal are each an alloy of an Aluminum Association series selected from the group consisting of 1000,2000, 3000,4000, 5000,6000, 7000 and 8000. 17. The method as claimed in claim 1, wherein the ingot is withdrawn from the mold at a rate of about 1 to about 6 inches per minute. 18. The method as claimed in claim 1. wherein the ingot is withdrawn from the mold at a rate of about 2 to about 3 inches per minute. 19. The method as claimed in claim 1, wherein a distance from a surface of the divider metal layer to a closest edge of the ingot is at least about 0.5 inch. 20. The method as claimed in claim 1, wherein the divider member is planar and step (a) comprises positioning opposing edges of the divider member about 0.1 inch to about 3 inches from the mold. 21. The method as claimed in claim 1, wherein the temperature of the first molten metal is about equal to the temperature of the second molten metal. 22. The method as claimed in claim 1, wherein the temperature of the first molten metal differs from the temperature of the second molten metal by 150°C or less. 23. The method as claimed in claim 1, wherein the solidus temperature of the metal of the divider member is greater than the liquidus temperature of each of the first metal and the second metal. 24. The method as claimed in claim 1, wherein at least one side of the divider member is coated with a flux. 25. The method as claimed in claim 1, wherein the first molten metal and the second molten form pools of molten metal in the mold and comprising applying flux to the surfaces of the pools of molten metal. 26. A multi-layered metal product comprising: a layer of a divider metal; and a first metal layer direct chill cast onto one side of said divider metal layer, wherein the thickness of the layer of divider metal is about 0.5 to about 6% of the thickness of the thickness of the metal product. 27. The metal product as claimed in claim 26, comprising a second metal layer direct chill cast onto the other side of said divider metal layer. 28. The metal product as claimed in claim 26. wherein said divider metal comprises an alloy containing at least about 97% aluminum. 29. The metal product as claimed in claim 27, wherein said first metal layer and said second metal layer each are an alloy of an Aluminum Association series selected from the group consisting of 1000.2000, 3000,4000, 5000,6000, 7000 and 8000. 30. The metal product as claimed in claim 26. wherein the thickness of said layer of divider metal is about 1 to about 3% of the thickness of said metal product. 31. The metal product as claimed in claim 26, wherein said metal product is an ingot or a billet. 32. The metal product as claimed in claim 31, wherein said layer of a divider metal is about 0.07 to about 0.25 inch thick. 33. The metal product as claimed in claim 31, wherein said layer of a divider metal is over about 0.25 to about 6 inches thick. 34. The metal product as claimed in claim 27. wherein said metal product is a plate, a sheet or foil. 35. The metal product as claimed in claim 34, comprising an outer metal layer roll bonded to one of said first metal layer and said second metal layer. 36. The metal product as claimed in claim 34, comprising a pair of outer metal layers, each said outer metal layers being roll bonded to one of said first metal layer and said second metal layer. 37. The metal product as claimed in claim 35, wherein said outer metal layer comprises a pair of metal layers direct chill cast onto opposing sides of a divider metal layer. 38. The metal product as claimed in claim 27, comprising at least one other layer of divider metal and at least one other metal layer direct chill cast onto one side of said other layer of divider metal and one of the first or second metals is direct chill cast onto the other side of the other layer of divider metal. 39. The metal product as claimed in claim 27, wherein the melting point of the divider metal is at least about 5°C greater than the melting points of each of the first metal and the second metal. 40. A multi-layered metal ingot comprising: a layer of a divider metal; a first metal layer bonded to one side of said divider metal layer; and a second metal layer bonded to another side of said divider metal layer, wherein the thickness of said layer of divider metal comprises no more than about 3% of the thickness of said ingot. 41. The ingot as claimed in claim 40, wherein said first metal layer and said second metal layer are each direct chill cast onto said divider metal layer. 42. The ingot as claimed in claim 40. wherein said divider metal comprises an alloy containing at least about 97% aluminum. 43. The ingot as claimed in claim 40, wherein said first metal layer and said second metal layer each are an alloy of an Aluminum Association series selected from the group consisting of 1000,2000, 3000,4000, 5000.6000, 7000 and 8000. 44. The ingot as claimed in claim 40, wherein said layer of a divider metal is about 0.07 to about 0.25 inch thick. 45. The ingot as claimed in claim 40, wherein said layer of a divider metal is over about 0.25 to about 6 inches thick. 46. The ingot as claimed in claim 40, comprising an outer metal layer roll bonded to one of said first metal layer and said second metal layer. 47. The ingot as claimed in claim 46, wherein said outer metal layer comprises a pair of metal layers direct chill cast onto opposing sides of a divider metal layer. 48. The ingot as claimed in claim 40, comprising a pair of outer metal layers, each said outer metal layers being roll bonded to one of said first metal layer and said second metal layer. 49. The ingot as claimed in claim 40, comprising at least one other layer of divider metal and at least one other metal direct chill cast onto one side of said other layer of divider metal with one of the first or second metals direct chill cast onto the other side of the other layer of divider metal. 50. The ingot as claimed in claim 49, wherein said first metal, said second metal, and said at least one other metal are each an alloy of an Aluminum Association series selected from the group consisting of 1000.2000. 3000,4000, 5000,6000. 7000 and 8000. 51. The method as claimed in claim 1, wherein inherent oxides of the divider layer are located within the multi-layered metal product, and wherein these inherent oxides are at least proximal a surface of the divider layer. 52. The multi-layered metal product as claimed in claim 26, wherein inherent oxides of the layer of divider metal are located within the multi-layered metal product, and wherein these inherent oxides are at least proximal a surface of the divider metal layer. 53. The multi-layered metal product as claimed in claim 40, wherein inherent oxides of the layer of divider metal are located within the multi-layered metal product, and wherein these inherent oxides are at least proximal a surface of the divider metal layer. A method of casting a multi-layered metal ingot comprising the steps of delivering a metallic divider (14) member into a direct chill mold (4), pouring a first molten metal into the mold on one side of the divider member, and pouring a second molten metal into the mold on the other side of the divider member, and allowing the first molten metal and the second molten metal solidify to form a metal ingot (10) which includes the divider metal layer disposed there between.

Full Text

A Method Of Direct Chill Casting A Multi-Layered Metal Ingot
And A Multi-Layered Metal Product
The present invention relates to the simultaneous casting of multiple
alloys, in particular, direct chill casting of multiple aluminum alloys using a metallic
member between the alloys to form a multi-component cast product and/or the use of a
metallic member as an external layer on a cast ingot.
In the production of aluminum alloy ingots by a conventional direct
chill (DC) casting process, molten aluminum is poured into an opened end mold. The
lower end of the mold is initially closed by a platform referred to as bottom block and
the molten metal pools within the mold. The bottom block is progressively lowered in
step with the pouring of the molten metal. The wall of the DC mold is continuously
cooled so that a solid skin of metal forms in contact with the mold wall at the level of
the surface of the pool of molten metal in the mold. An example of the method of DC
casting is described in U.S. Patent No. 4,071,072, incorporated herein by reference. In
this conventional operation, a single molten aluminum alloy is direct cast into an ingot.
Such aluminum ingots are often times incorporated with other alloys to
form a composite product. For example, brazing sheet for the header of a heat
exchanger or for reinforcement structures may be produced from an Aluminum
Association (AA) 3000 series aluminum alloy with a clad layer of an AA 4000 series
alloy. Evaporator sheet product or plate type heat exchangers typically include a 3000
series alloy clad on both sides with a 4000 series alloy. Likewise, radiators often are
formed from a 3000 series alloy with a 4000 series cladding and water-side liner of an
AA 1000, 5000, 6000, or 7000 series alloy. The clad layer is conventionally roll
bonded in plate form onto an ingot of the core alloy (e.g., a 3000 series alloy). Roll
bonding requires multiple rolling passes, scalping, reheating, and sealing steps to
produce the clad alloy in sheet form. Each of those processes adds to the cost of the
final clad product. In addition, the thickness of cladding produced via roll bonding is
generally limited to a maximum of only about 35% of the total sheet thickness. Roll
bonding can also be extremely difficult if the mechanical properties of the alloys being
roll bonded are too dissimilar at the rolling temperatures. For example, when one alloy
deforms very easily while the other alloy does not, the alloys do not seal properly or
the target cladding ratio is off.
More recently, attempts have been made at casting composite metal
products. One such process is described in DE 4420697 in which one alloy of a billet
is DC cast on one side of a fixed barrier and another alloy is DC cast on the opposite
side of the barrier. The process is controlled such that the two molten metals come in
contact with one another while in the molten state to provide a controlled mixing of the
two melts. In this manner, the composition of the composite billet in the direction
perpendicular to the contact surface of the two metal components changes
continuously. The concentration of the individual alloy elements changes continuously
from the values of one alloy to the values in the other. The fixed barrier maintains the
two components apart from each other within the mold, and the barrier is positioned
off center so that one component is narrower than the other. The alloy closest to the
mold (the narrower component) cools and solidifies earlier in the process than the
other alloy, i.e., at a great height from the bottom block. The bottom block is
withdrawn at a speed whereby the levels of the melts within the mold remain
approximately even. Although one alloy solidifies before the other alloy, there is a
small region between the melts in which the melts are able to flow into one another
and mix briefly to promote adhesion between the two alloys. While this method
provides some adhesion between the two components of the cast product, the mixing
of the components which occurs during the casting can be detrimental to the finished
product. The location and shape of the fixed barrier are also critical to avoid
intermixing of the molten alloys. The properties of the alloys simultaneously cast in
this manner may be affected by the mixing of the alloying components. This method
also requires careful control of molten metal flow to avoid mixing due to hydraulic
pressure differences as well as careful control of the solidification rate of the alloy
forming the narrower component to ensure only brief mixing of the alloys in the region
immediately below the barrier.
Another method of DC casting a composite ingot is disclosed in U.S.
Patent No. 4,567,936 in which an outer layer is simultaneously cast within an inner
component. According to this method, the outer layer solidifies prior to contact within
the molten inner alloy. This avoids mixing between the components of the inner
component and the outer layer. A drawback to this method is that the outer layer must
solidify completely before the inner alloy can be cast within* the outer layer. The
thickness of the outer layer also is limited because the heat of the inner component
must exit through the outer layer to the exterior surfaces of the cast product. Hence,
the configuration of the final multi-component product also is limited.
Accordingly, a need remains for a method of simultaneously casting a
multi-alloy metal product with a minimum of mixing between the alloys of the product
and which can produce cast metal products in a variety of configurations.
This need is met by the method of the present invention of casting a
multi-layered metal ingot including the steps of delivering a metallic divider
member into a direct chill mold, pouring a first molten metal into the mold on one side
of the divider member and pouring a second molten metal into the mold on the other
side of the divider member, and allowing the first molten metal and the second molten
metal to solidify to form a metal ingot which includes the divider metal layer disposed
between the two cast layers. The multi-layered metal ingot removed from the mold
contains at least two cast layers including the first and second metals separated by a
layer of the divider member. Alternatively, the divider member may be positioned
against a wall of the mold and a single molten metal is poured into the mold to produce
one cast layer bound to the divider member thereby forming an outer shell or cladding
on the ingot. The divider member may be a sheet having a thickness of up to about
0.25 inch or a plate having a thickness of up to about 6 inches. The position of the
divider member may be shifted within the mold to produce varying thicknesses of the
cast metals. More than one divider member may be placed in the mold with molten
metals poured on opposite sides of each divider member to produce a metal product
having at least three cast layers separated by the divider members. The fundamental
principles guiding the attainment of a strongly bonded interface between the divider
member and the molten metal are identical regardless of where the divider member is
located within the ingot. The divider member may also be tubular in shape. One metal
is poured into the tubular divider member while another metal is poured between the
tubular divider member and the mold.
The molten metals may each be an alloy of AA series 1000,2000,3000,
4000,5000,6000,7000, or 8000. The divider member may be a solid metal that will
survive exposure to the molten aluminum during the casting operation. For the
purpose of maintaining a "clean" scrap loop, the divider member preferably is
aluminum or an aluminum alloy or a clad aluminum product that has a solidus
temperature greater than the liquidus temperatures of the alloys cast on either side
thereof. It is preferred that the solidus temperature of the divider member be at least
610°C. A particularly suitable metal for the divider member is an AA 1000 series
alloy. Alternatively, the divider member may be in the form of a screen alloys of iron,
titanium, magnesium, copper, or nickel.
A complete understanding of the invention will be obtained from the
following description when taken in connection with the accompanying drawing
figures wherein like reference characters identify like parts throughout.
Fig. 1 is a partially sectioned schematic of an apparatus for
simultaneously producing a composite metal product having two cast layers according
to the present invention;
Fig. 2 is a cross-section of the metal product produced in the apparatus
shown in Fig. 1;
Fig. 3 is a partially sectioned schematic of an apparatus for producing a
composite metal product having one cast layer according to another embodiment of the
present invention;
Fig. 4 is a cross-section of the metal product produced in the apparatus
shown in Fig. 3;
Fig. 5 is a partially sectioned schematic of a device for simultaneously
producing a composite metal product having three cast layers according to the present
invention;
Fig. 6 is a cross section of the metal product produced using the device
shown in Fig. 5;
Fig. 7 is a cross-section of the metal product produced in the device
shown in Fig. 1 with additional layers roll bonded thereto;
Fig. 8 is a cross-section of the metal product produced in the device
shown in Fig. 5 with a layer roll bonded thereto;
Fig. 9 is a cross-section of the metal product produced according to the
present invention wherein the thickness of the layers of the composite product is not
constant across the width of the product;
Fig. 10 is a cross-section of the metal product of Fig. 9 following a
rolling step;
Fig. 11 is a partially sectioned schematic of another device for
simultaneously casting multiple alloys to produce a billet using a tubular divider
member;
Fig. 12 is a cross-section of the device shown in Fig. 11 taken along
lines 12-12;
Fig. 13 is a cross-section of the billet produced in the device shown in
Fig. 11;
Fig. 14 is a photograph of a cross-section of an ingot produced
according to the present invention;
Fig. 15 is a photomicrograph of a portion of the ingot shown in Fig. 14;
Fig. 16 is a photomicrograph of a portion of the ingot shown in Fig. 14
after hot rolling;
Fig. 17 is a photomicrograph of the portion of the ingot shown in Fig.
16 after cold rolling;
Fig. 18 is a photograph of a cross-section of another ingot produced
according to the present invention;
Fig. 19 is a photograph of a cross-section of yet another ingot produced
according to the present invention; and
Fig. 20 is a photomicrograph an interface between the layers of another
ingot produced according to the present invention.
For purposes of the description hereinafter, the terms "upper", "lower",
"right", "left", "vertical", "horizontal", "top", "bottom" and derivatives thereof shall
relate to the invention as it is oriented in the drawing figures. However, it is to be
understood that the invention may assume various alternative variations and step
sequences, except where expressly specified to the contrary. It is also to be understood
that the specific devices and processes illustrated in the attached drawings, and
described in the following specification, are simply exemplary embodiments of the
invention. Hence, specific dimensions and other physical characteristics related to the
embodiments disclosed herein are not to be considered as limiting.
The present invention is directed to a method of casting a multi-layered
metal ingot and the product produced thereby. The method of the present invention
uses an apparatus 2 schematically shown in Fig. 1 which incorporates a conventional
direct chill mold 4. The direct chill mold 4 defines a water chamber 6 and a slit 8
through which water is emitted directly onto the surface of an ingot 10 emerging from
the mold 4. The cast ingot 10 solidifies on a bottom block 12.
A metallic divider member 14 is suspended into the mold 4 and seats on
the bottom block 12. The metallic divider member 14 provides a barrier between a
first molten metal 16 which is fed into the mold 4 via a first trough 18 and a second
molten metal 20 fed into the mold 4 via a second trough 22. The bottom block 12 is
withdrawn in the direction of arrow A while coolant (water) is applied to the surfaces
of the ingot 10. Suitable speeds for the bottom block 12 are about I to about 6 inches
per minute, preferably about 2 to about 3 inches per minute. When citing such ranges
herein, the range includes all intermediate values. The divider member 14 remains in
contact with the bottom block 12 and accordingly travels downwardly at the speed that
the bottom block 12 travels. A crane (not shown) equipped with movable grips (e.g.,
wheels) may be used to suspend the divider member 14 over the apparatus 2 and
deliver the divider member 14 into the mold 4. Other mechanisms may be used to
suspend and deliver the divider member 14 into the mold 4.
Each of the first and second molten metals 16 and 20 solidify as
generally shown in Fig. 1. The portion 24 of the metal 16 closest to the mold 4
solidifies very quickly, e.g. in less than about 10 seconds. Solidification of the metal
20 likewise occurs at a region 26 adjacent the mold 4. Semi-solid zones 28 and 30
form below the level of the respective first solidification regions 24 and 26. The metals
16 and 20 also begin to solidify adjacent the divider member 14 at respective locations
32 and 34. The locations 24,26,32 and 34 may be at the same height as each other or
at different heights from the bottom block 12. In many cases, the melting point of the
metal of the divider member 14 is less than the temperature of the incoming molten
metals 16 and 20. Nevertheless, the divider member 14 does not completely melt and
serves to prevent mixing of the metals 16 and 20 by acting as a heat sink and as an
interface between the metals 16 and 20. Some heat from the molten metals 16 and 20
transfers into the divider member 14 and subsequently is transferred out of the portion
36 of the divider member 14 that extends up and out of the mold 4. Similarly, some of
the heat transferred to the divider member 14 is also subsequently transferred out of
the divider member to the solidifying ingot 10 below the molten metals 16 and 20.
The divider member 14 may experience minimal melting (erosion), but this minimal
amount does not affect the metallurgical properties of each of the metals 16 and 20
cast on opposing sides of a divider member 14. Upon complete solidification, the
metals 16 and 20 form respective solid components 38 and 40 separated by the divider
member 14.
The minimal melting of the divider member 14 provides for some
mixing of the components of the divider member 14 with the components of the metal
16 on one side and with the components of the metal 20 on the other side. The
minimally mixed metals solidify and thereby adhere the components 38 and 40 to the
divider member 14. Superior adhesion between the divider member 14 and
components 38 and 40 is achieved when the temperature of the divider member 14
reaches at least the higher of the liquidus temperature of component 38 and the
liquidus temperature of component 40. It is believed that when the divider member 14
initially contacts the molten metals 16 and 20, some solidification of the metals rapidly
occurs on the surfaces of the divider member 14. This temporary solidification is not
shown in Fig. 1. Inherent oxides on the surfaces of the divider member 14 generally
remain and become entrapped between the divider member 14 and the solidified metal.
When the molten metal temperatures are sufficiently high, the divider member 14
locally reaches a temperature greater than the liguidus temperature of the metals 16
and 20 and the initially solidified metal remelts as the divider member 14 travels in the
direction of the arrow A. The divider member 14 is then directly exposed to the
molten metals 16 and 20 and the oxide destabilizes with some minimal melting of the
divider member 14. As the divider member 14 continues downwardly, the local
temperatures of the molten metals 16 and 20 decrease to their liquidus temperatures
and solidification begins. The local temperatures continue to drop until the solidus
temperatures are reached and the alloys fully solidify resulting in strong bonds between
the components 38 and 40 and the respective sides of the divider member 14.
Alternatively or in addition thereto, flux may be applied to one or both
sides of the divider member 14. The flux may be applied to the divider member 14
directly (e.g. by coating the surfaces of the divider member 14 with flux) or flux may
be applied to the upper surfaces of the molten metals 16 and 20 that pool in the mold 4.
Immediately prior to contact between the divider member 14 and the molten metals 16
and 20, the flux melts and chemically reduces oxides on the divider member 14 which
could otherwise interfere in the adhesion of the molten metals 16 and 20 to the divider
member 14. Suitable flux includes potassium aluminum fluoride based fluxes (e.g.
Nocolok®) along with but not limited to fluxes based on cesium-potassium aluminum
fluoride based fluxes and cesium fluoroaluminate based fluxes. The flux may be any
material capable of removing the oxide layer by chemical reaction prior to contact of
the molten metals 16 and 20 with the divider member 14. When flux is used, lower
molten metal temperatures should be used during casting to reduce the risk of melting
the divider member 14 yet achieve strong adhesion of the components 38 and 40 to the
divider member 14.
A cross section of the ingot 10 produced in the apparatus 2 is shown in
Fig. 2. The ingot 10 is depicted as having a rectangular configuration with the divider
member 14 positioned centrally between the layers of components 38 and 40.
However, the divider member 14 may be positioned off-center and may be as close as
about 0.S inch from side surfaces 42 and 44 of the ingot 10. The divider member 14
has a width between edges 46 and 48 thereof which is slightly smaller than the width
of the ingot 10 between edges 49a and 49b. Edges 46 and 48 preferably are positioned
about 0.1 to about 3 inches from the mold 4 and are shown not to scale in Figs. 2 and
6-8. The cooling rates are highest near the surface of the ingot 10, and the molten
metals 16 and 20 rapidly solidify at the surface of the ingot. The rapid solidification of
molten metals 16 and 20 around the edges 46 and 48 minimizes opportunities for
mixing of the molten metals 16 and 20. Nevertheless, some minimal mixing may
enhance adhesion of the solid components 38 and 40 together. In any event, the edges
49a and 49b of the ingot 10 are typically trimmed off during rolling to eliminate edge
cracking so these areas of intermixing around the edges 46 and 48 of the divider
member 14 generally are discarded.
The thickness of the divider member 14 may range between about 0.07
inch to about 0.25 inch (referred to as a sheet) or over about 0.25 inch to about 6
inches thick (occasionally referred to as a shlate when up to one inch thick and
generally referred to as a plate when up to 6 inches thick). The thickness of the divider
member 14 preferably is about 0.5 to about 6% of the thickness of the ingot 10, more
preferably about 1 to about 3% of the thickness of the ingot 10. A thinner divider
member 14 may be used when the risk of melting of the divider member 14 is low
and/or the desired metallurgical or structural properties of the ingot 10 dictate that the
layer 14 has a minimal thickness. Conversely, a thicker divider member 14 may
provide a more significant barrier to mixing of the molten metals 16 and 20 and may
serve as one layer in a multi-layered ingot.
If the divider member 14 transfers heat too rapidly out of the solidifying
metals 16 and 20, the resultant components 38 and 40 may be prone to cracking.
Hence, when the divider member 14 is over about 0.25 inch thick., it may be desirable
to preheat the divider member 14 to within about 400°C of the temperature of the
molten metals 16 and 20 thereby reducing the rate of heat transfer through the divider
member 14.
Generally, the divider member 14 has a melting point of at least
610° C. The divider member 14 may be an aluminum alloy and preferably contains at
least about 97% aluminum and has a high solidus temperature such as an AA 1000
series alloy. Other suitable materials for the divider member 14 are composite
products containing layers of aluminum alloys, stainless steel, nickel alloys, titanium
alloys, magnesium alloys and combinations thereof that are clad, plated or coated
thereto. The chemistry of the divider member 14 may be selected to improve the
corrosion resistance of the final product being cast. For example, the addition of Zn to
the divider member 14 makes the divider member 14 more electrochemically negative
than at least one of the components 38 and 40. This results in galvanic protection,
whereby the Zn enriched areas (the divider member 14 and the portion of components
38 and 40 into which Zn has diffused) sacrificially protect the more cathodic alloys of
components 38 and 40. The divider member 14 may define a plurality of small holes
to allow some wetting between the molten metals 16 and 20 without significant
intermixing. Alternatively, the divider member 14 may be a screen produced from
iron, titanium, molybdenum or alloys thereof. Suitable screens are 14x18 mesh about
0.01 inch thick or 32x32 mesh about 0.006 inch thick.
The molten metals 16 and 20 each may be the same or different and
each is preferably an aluminum alloy and may be an alloy of the AA series 1000, 2000,
3000,4000, 5000,6000, 7000, or 8000. Other suitable metals may include magnesium
alloys. For products in which one of the molten metals requires a specialized alloy, the
other molten metal may have a high scrap alloy content. The low value scrap metal
may be simultaneously cast with a thinner layer of the specialized alloy to produce
high value products with a specialized surface such as reflector sheet, anodized
products, architectural products and the like.
The temperature of the first molten metal 16 may be about equal to the
temperature of the second molten metal 20, or the temperatures of the first and second
molten metals 16 and 20 may differ by up to about 150°C. Selection and control of the
temperatures of the molten metals 16 and 20 during casting is critical, particularly
when flux is not used. When no flux is used to remove the oxide on the divider
member 14, the selection of molten metal temperatures should be such that the
temperature of the divider member 14 rises above the liquidus temperature of the
molten metals 16 and 20.
When a flux is used or when the material of the divider member 14 is
selected such that the oxide is disrupted prior to contacting the molten metals 16 and
20 or when the presence of an oxide on the surfaces of the divider member 14 is not
detrimental to achieving a strong bond, lower molten metal temperatures may be used
and the divider member 14 does not necessarily need to reach the liquidus
temperatures of the molten metals 16 and 20. In fact, it is desirable that the divider
member 14 does not reach the liquidus temperature(s) because the divider member 14
remains protected from the molten metals 16 and 20 by the metal that initially
solidifies onto the divider member 14. In any case, the molten metal temperatures
cannot be so high as to cause complete melting of the divider member 14. Some
melting of the divider member 14 is acceptable, but complete melting of the divider
member 14, even locally (i.e. a "bum through"), is undesired. The temperatures for
this process depend on the chemistries of the molten metals 16 and 20 and of the
divider member 14.
Referring to Figs. 3 and 4, the present invention may also be used to
produce a composite ingot having a single cast layer with a layer of divider metal;. In
system 2', the divider member 14 may be delivered into the mold 4 at a location
adjacent to the wall of the mold 4 and the molten metal 16 is delivered into the mold 4
via the trough 18. The metal 16 begins to solidify in semi-solid zone 28 and ultimately
solidifies as component 38 bound to the divider member 14 in manner similar to the
solidification of metal 16 described above to yield an ingot 10'. This embodiment of
the invention allows for production of an ingot 10 having a solid layer 14 bound to a
cast layer 38 which avoids the prior art roll bonding processes. Flux may be applied to
the surface of the divider member 14 which contacts the molten metal 16 in the system
2' or to the surface of pool of molten metal 16 as described above. The divider
member 14 and component 38 of the ingot 10' may be selected from the same
materials listed above for ingot 10.
The method of the present invention may also be used to cast more than
two molten metals. For example, in the apparatus 50 shown in Fig. 5, two divider
members 14 and 52 may be delivered into the direct chill mold 4 while molten metals
16,20, and 53 are delivered into the mold via respective troughs 18,22, and 54.
Casting of an ingot 60 from three separate molten metals 16,20, and 53 is performed
in a manner similar to that described above. The molten metal 16 solidifies first at
locations 24 (adjacent the mold 4) and 32 (adjacent the divider member 14), while
molten metal 20 solidifies first at locations 34 (adjacent the divider member 14) and
location 55 (adjacent the divider member 52). Molten metal 53 first solidifies at
location 56 (adjacent the divider member 52) and location 57 (adjacent the mold 4).
The solidifying metals 16, 20, and 53 form respective semi-solid zones 28,30 and 58.
The locations 24, 32,34, 55,56, and 57 may be at the same height as each other or at
different heights from the bottom block 12. The resultant product includes three cast
layers 38,40, and 62 separated from each other by divider members 14 and 52 as
shown in Fig. 6. The divider members 14 and 52 are positioned within the mold in the
embodiment of Fig. 5 similar to divider
member 14 of Fig. 1. The distance between the divider members 14 and 52 is selected
based on the desired thicknesses of the components 38,40, and 62 in the ingot 60 and
the size of the mold 4. The embodiment shown in Figs. 5 and 6 relates to
simultaneous casting of three alloys with divider layers interspersed between, thereby
creating a five-layer product. This is not meant to be limiting. More than three alloys
may be simultaneous cast according to the present invention in rectangular
configurations or in other configurations by using other shapes for the mold (e.g.
square or oval) and non-planar divider members.
Additional layers of metal may be bonded to the cast multi-layered
ingots 10 and 60 resulting in the products 70 and 80 shown in Figs. 7 and 8. Product
70 includes the ingot 10 and a pair of metal layers 72 roll bonded to the ingot 10.
Product 80 includes the ingot 60 with a metal layer 82 roll bonded thereto. Products
70 and 80 each may have one or two respective layers 72 or 82. When two layers 72
are included as shown in Fig. 7, the metal of those layers may be the same or different
from each other. The layers 72 and 82 may also be multi-component products
produced according to the present invention or produced by conventional roll bonding
practices.
One of the advantages of the present invention is borne out when a
multi-layered metal ingot produced according to the present invention is subsequently
rolled, for example, into a plate or sheet product. In conventional roll bonded ingots,
the thickness of a clad layer at the ends of the ingot often times becomes unacceptably
thin during the rolling process. The edges of the resulting coil made from the
composite ingot must be trimmed and scrapped so that the clad layer is uniformly thick
across the width of the coil. Edge trimming of about 4 inches (for about 3-5%
cladding) to about 8 inches (for about 10-15% cladding) is typical for conventional roll
bonded brazing sheet. Such scrap losses can be minimized in the present invention by
producing an ingot 90 as shown in Fig. 9 which has an arcuately shaped divider
member 92 with metals 94 and 96 cast on opposing sides thereof. The cast metal 96
(corresponding to a conventional clad layer) is thickest at the edges of the ingot 90.
Upon rolling the ingot 90 to a plate 90', the divider member 92' flattens and the cast
metals 94' and 96' are substantially uniformly thick as shown in Fig. 10. The divider
member 92 may be tapered or bent into other configurations to locally achieve
differing thickness of the metals cast on opposing sides thereof.
The present invention may also be used to produce cylindrical products
(e.g., a billet) of multiple alloys. The embodiment of the invention shown in Figs. 11
and 12 includes an apparatus 100 having a cylindrical mold 104 defining a water
chamber 106 and a slit 108 through which water is emitted directly onto the surface of
an ingot 110 emerging from the mold 104. The cast ingot 110 seats on a circular
bottom block 112 traveling in the direction of arrow B. A tubular divider member 114
is fed into the mold 104 and acts as a barrier between molten metal 116 fed from
trough 118 on the outside of the tubular divider member 114 and molten metal 120 fed
from another trough (not shown) on the inside of the tubular divider member 114.
Delivery of the divider member 114 and movement of the bottom block 112 are
controlled as described above regarding the apparatus 2. The tubular divider member
114 may define a longitudinal slot 122 to ease access of the molten metal 120 into the
divider member 114 during casting. Particularly during startup, the molten metal 120
may be delivered into the tubular divider member 114 via the slot 122 near the bottom
block 112 instead of pouring the molten metal 120 into the tubular divider member
114 which can result in turbulence of the molten metal 120. The slot 122 is
sufficiently narrow (e.g. about 1 to about 20 inches wide, depending on the size of the
billet being cast) and may extend down into the molten pools of metals 116 and 120 to
prevent excessive mixing between the molten metals 116 and 120 in the vicinity of the
slot 122. Molten metal 116 first solidifies adjacent the mold 104 at region 124 and
molten metal 120 first solidifies adjacent the tubular divider member 114 at region
126. An annular semi-solid zone 128 forms below the level of the first solidification
region 124, and a cylindrical semi-solid zone 130 forms below the level of the region
126. Upon complete solidification, the metals 116 and 120 form respective solid
components 138 and 140 separate by the tubular divider member 114. A cross-section
of the billet 110 produced in the apparatus 100 is shown in Fig. 13.
The present invention provides significant improvements over
conventional clad products. The cladding ratio of roll bonded products is generally a
maximum of 35%, i.e. the interface between roll bonded layers can generally be no
greater than about 35% of the distance from either face of the ingot. In the present
invention, the only limitation on the location of cast layers is that a cast layer is at least
about 1 inch thick to allow for distribution of molten metal across the width of the
ingot. The alloys which may be bonded together using the present invention are much
more numerous than those which may be reliably and/or economically roll bonded
together. Product quality is improved in the elimination of roll bonding blisters. The
productivity of a hot mill used to initially breakdown or roll an ingot produced
according to the present invention is also significantly increased as the many sealing
passes may be eliminated.
Although the invention has been described generally above, the
following particular examples give additional illustrations of the products and process
steps typical of the present invention.
EXAMPLES 1-3
In each of Examples 1-3, a sheet of AA 1350 (20 inches wide, 0.375
inch thick, and 24 inches long) was positioned in the center of 12 inch x 22 inch mold
spanning the width with a gap of about 1 inch between the edge of the sheet and the
mold walls. In each Example, a melt A of the alloy listed in Table 1 was poured into
the mold on one side of the sheet and a melt B of the alloy B listed in Table 1 was
poured into the mold on the other side of the sheet. In Example 3, flux was applied to
the side of the sheet which contacted melt A. The metals were cast on opposing sides
of the sheet while the bottom block with sheet seated thereon was lowered at a rate of
2.75 inches per minute. A 12 inch x 22 inch x about 42 inch ingot having sheet of AA
1350 bonded between a layer of alloy A and a layer of alloy B was produced.

A block was sectioned from the ingot of Example 1 and was rolled (hot
and cold) without any delaminating along the interface between the AA 1350 sheet and
the cast layers of AA 3003 and 7051. A photograph of a horizontal cut through the
ingot appears in Fig. 14. A close-up photomicrograph of the interface between the
layers of AA alloy 3003 and modified AA alloy 7051 showing minimal erosion of the
sheet appears in Fig. 15. A portion of the ingot was hot rolled to 0.250 inch (shown in
Fig. 16) and subsequently cold rolled to 0.005 inch (shown in Fig. 17).
A photograph of a horizontal cut through the ingot produced in
Example 2 appears in Fig. 18.
A photograph of a horizontal cut through the ingot produced in
Example 3 appears in Fig. 19. Example 3 was repeated without flux and a
photomicrograph of the AA3003/AA1350/AA4343 interface is shown under polarized
light in Fig. 20 after etching in barkers etch to illustrate the microstructural details of
the interface.
WE CLAIM :
1. A method of direct chill casting a multi-layered metal ingot comprising the
steps of:
(a) delivering a metallic divider member into a direct chill mold;
(b) pouring a first molten aluminum-based metal into the cirect chill mold
on one side of the divider member;
(c) pouring a second molten metal into the direct chill mold on the other
side of the divider member;
(d) allowing the first molten metal and the second molten metal to solidify
to form a multi-layer metal ingot comprising a divider metal layer disposed
between a layer of the first metal and a layer of the second metal; and
(e) withdrawing the multi-layered metal ingot from the mold, wherein the
thickness of the divider metal layer is about 0.5% to about 6% of the thickness of
the multi-layered metal ingot.
2. The method as claimed in claim 1, wherein the divider member comprises
a sheet having a thickness of about 0.07 to about 0.25 inch.
3. The method as claimed in claim 1, wherein the divider member comprises
a plate having a thickness of over about 0.25 to about 6 inches thick.
4. The method as claimed in claim 1, wherein the divider member defines a
plurality of holes therethrough.
6. The method as claimed in claim 1, wherein the divider member comprises
a screen.
7. The method as claimed in claim 5, wherein the screen comprises iron,
titanium, molybdenum or alloys thereof.
8. The method as claimed in claim 1, wherein the divider member is tubular
and one of the first and second molten metals is poured into the tubular divider
member and the other molten metal is poured between the tubular divider
member and the mold.
8. The method as claimed in claim 7. wherein the tubular divider member
defines a longitudinal slot.
9. The method as claimed in claim 1, wherein the first metal and the second
metal each comprise an aluminum alloy.
10. The method as claimed in claim 9, wherein the first metal and the second
metal are different compositions.
11. The method as claimed in claim 9, wherein the first metal and the second
metal are each an alloy of an Aluminum Association series selected from the
group consisting of 1000,2000. 3000,4000, 5000,6000. 7000 and 8000.
12. The method as claimed in claim 11, wherein the divider member has a
melting point of at least 610°C.
13. The method as claimed in claim 11, wherein the divider member
comprises an Aluminum Association 1000 series alloy.
14. The method as claimed in claim 11, wherein the divider member
comprises a composite of a plurality of layers of materials selected from the
group consisting of aluminum alloy, steel, titanium alloy, copper alloy,
magnesium alloy and nickel alloy.
15. The method as claimed in claim 1. wherein step (a) comprises delivering
another metallic divider member into the mold and step (b) comprises pouring a
third molten metal on one side of the other divider member to produce an ingot
comprising a pair of layers of divider metal interspersed between layers of the
first, second, and third metals.
16. The method as claimed in claim 15, wherein the first metal, the second
metal, and the third metal are each an alloy of an Aluminum Association series
selected from the group consisting of 1000,2000, 3000,4000, 5000,6000, 7000
and 8000.
17. The method as claimed in claim 1, wherein the ingot is withdrawn from the
mold at a rate of about 1 to about 6 inches per minute.
18. The method as claimed in claim 1. wherein the ingot is withdrawn from the
mold at a rate of about 2 to about 3 inches per minute.
19. The method as claimed in claim 1, wherein a distance from a surface of
the divider metal layer to a closest edge of the ingot is at least about 0.5 inch.
20. The method as claimed in claim 1, wherein the divider member is planar
and step (a) comprises positioning opposing edges of the divider member about
0.1 inch to about 3 inches from the mold.
21. The method as claimed in claim 1, wherein the temperature of the first
molten metal is about equal to the temperature of the second molten metal.
22. The method as claimed in claim 1, wherein the temperature of the first
molten metal differs from the temperature of the second molten metal by 150°C
or less.
23. The method as claimed in claim 1, wherein the solidus temperature of the
metal of the divider member is greater than the liquidus temperature of each of
the first metal and the second metal.
24. The method as claimed in claim 1, wherein at least one side of the divider
member is coated with a flux.
25. The method as claimed in claim 1, wherein the first molten metal and the
second molten form pools of molten metal in the mold and comprising applying
flux to the surfaces of the pools of molten metal.
26. A multi-layered metal product comprising:
a layer of a divider metal; and
a first metal layer direct chill cast onto one side of said divider metal layer,
wherein the thickness of the layer of divider metal is about 0.5 to about 6% of the
thickness of the thickness of the metal product.
27. The metal product as claimed in claim 26, comprising a second metal
layer direct chill cast onto the other side of said divider metal layer.
28. The metal product as claimed in claim 26. wherein said divider metal
comprises an alloy containing at least about 97% aluminum.
29. The metal product as claimed in claim 27, wherein said first metal layer
and said second metal layer each are an alloy of an Aluminum Association
series selected from the group consisting of 1000.2000, 3000,4000, 5000,6000,
7000 and 8000.
30. The metal product as claimed in claim 26. wherein the thickness of said
layer of divider metal is about 1 to about 3% of the thickness of said metal
product.
31. The metal product as claimed in claim 26, wherein said metal product is
an ingot or a billet.
32. The metal product as claimed in claim 31, wherein said layer of a divider
metal is about 0.07 to about 0.25 inch thick.
33. The metal product as claimed in claim 31, wherein said layer of a divider
metal is over about 0.25 to about 6 inches thick.
34. The metal product as claimed in claim 27. wherein said metal product is a
plate, a sheet or foil.
35. The metal product as claimed in claim 34, comprising an outer metal layer
roll bonded to one of said first metal layer and said second metal layer.
36. The metal product as claimed in claim 34, comprising a pair of outer metal
layers, each said outer metal layers being roll bonded to one of said first metal
layer and said second metal layer.
37. The metal product as claimed in claim 35, wherein said outer metal layer
comprises a pair of metal layers direct chill cast onto opposing sides of a divider
metal layer.
38. The metal product as claimed in claim 27, comprising at least one other
layer of divider metal and at least one other metal layer direct chill cast onto one
side of said other layer of divider metal and one of the first or second metals is
direct chill cast onto the other side of the other layer of divider metal.
39. The metal product as claimed in claim 27, wherein the melting point of the
divider metal is at least about 5°C greater than the melting points of each of the
first metal and the second metal.
40. A multi-layered metal ingot comprising:
a layer of a divider metal;
a first metal layer bonded to one side of said divider metal layer; and
a second metal layer bonded to another side of said divider metal layer,
wherein the thickness of said layer of divider metal comprises no more than
about 3% of the thickness of said ingot.
41. The ingot as claimed in claim 40, wherein said first metal layer and said
second metal layer are each direct chill cast onto said divider metal layer.
42. The ingot as claimed in claim 40. wherein said divider metal comprises an
alloy containing at least about 97% aluminum.
43. The ingot as claimed in claim 40, wherein said first metal layer and said
second metal layer each are an alloy of an Aluminum Association series
selected from the group consisting of 1000,2000, 3000,4000, 5000.6000, 7000
and 8000.
44. The ingot as claimed in claim 40, wherein said layer of a divider metal is
about 0.07 to about 0.25 inch thick.
45. The ingot as claimed in claim 40, wherein said layer of a divider metal is
over about 0.25 to about 6 inches thick.
46. The ingot as claimed in claim 40, comprising an outer metal layer roll
bonded to one of said first metal layer and said second metal layer.
47. The ingot as claimed in claim 46, wherein said outer metal layer
comprises a pair of metal layers direct chill cast onto opposing sides of a divider
metal layer.
48. The ingot as claimed in claim 40, comprising a pair of outer metal layers,
each said outer metal layers being roll bonded to one of said first metal layer and
said second metal layer.
49. The ingot as claimed in claim 40, comprising at least one other layer of
divider metal and at least one other metal direct chill cast onto one side of said
other layer of divider metal with one of the first or second metals direct chill cast
onto the other side of the other layer of divider metal.
50. The ingot as claimed in claim 49, wherein said first metal, said second
metal, and said at least one other metal are each an alloy of an Aluminum
Association series selected from the group consisting of 1000.2000. 3000,4000,
5000,6000. 7000 and 8000.
51. The method as claimed in claim 1, wherein inherent oxides of the divider
layer are located within the multi-layered metal product, and wherein these
inherent oxides are at least proximal a surface of the divider layer.
52. The multi-layered metal product as claimed in claim 26, wherein inherent
oxides of the layer of divider metal are located within the multi-layered metal
product, and wherein these inherent oxides are at least proximal a surface of the
divider metal layer.
53. The multi-layered metal product as claimed in claim 40, wherein inherent
oxides of the layer of divider metal are located within the multi-layered metal
product, and wherein these inherent oxides are at least proximal a surface of the
divider metal layer.
A method of casting a multi-layered metal ingot comprising the steps of
delivering a metallic divider (14) member into a direct chill mold (4), pouring a
first molten metal into the mold on one side of the divider member, and pouring a
second molten metal into the mold on the other side of the divider member, and
allowing the first molten metal and the second molten metal solidify to form a
metal ingot (10) which includes the divider metal layer disposed there between.

Documents:

480-KOLNP-2004-CORRESPONDENCE.pdf

480-KOLNP-2004-FORM 27.pdf

480-KOLNP-2004-FORM-27.pdf

480-kolnp-2004-granted-abstract.pdf

480-kolnp-2004-granted-assignment.pdf

480-kolnp-2004-granted-claims.pdf

480-kolnp-2004-granted-correspondence.pdf

480-kolnp-2004-granted-description (complete).pdf

480-kolnp-2004-granted-drawings.pdf

480-kolnp-2004-granted-examination report.pdf

480-kolnp-2004-granted-form 1.pdf

480-kolnp-2004-granted-form 13.pdf

480-kolnp-2004-granted-form 18.pdf

480-kolnp-2004-granted-form 3.pdf

480-kolnp-2004-granted-form 5.pdf

480-kolnp-2004-granted-gpa.pdf

480-kolnp-2004-granted-reply to examination report.pdf

480-kolnp-2004-granted-specification.pdf

480-kolnp-2004-granted-translated copy of priority document.pdf

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Patent Number

224986

Indian Patent Application Number

480/KOLNP/2004

PG Journal Number

44/2008

Publication Date

31-Oct-2008

Grant Date

29-Oct-2008

Date of Filing

12-Apr-2004

Name of Patentee

ALCOA INC.

Applicant Address

ALCOA CORPORATE CENTER, 201 ISABELLA STREET, PITTSBURGH PA

Inventors:

#	Inventor's Name	Inventor's Address
1	KIRBY JAMES L.	ALCOA TECHNICAL CENTER, 100 TECHNICAL DRIVE, ALCOA CENTER, PA 15069-0001
2	KILMER RAYMOND J.	1480 MANHEIM PIKE, LANCASTER, PA 17601

PCT International Classification Number

B22D 11/00

PCT International Application Number

PCT/US02/33915

PCT International Filing date

2002-10-22

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10/004,041	2001-10-23	U.S.A.