CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from Provisional Patent Application No. 62/142,753, filed on April 3, 2015, the disclosure of which is relied upon and incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to a metallic laminate composite having multiple layers clad in an edge-to-edge arrangement.

BACKGROUND OF THE INVENTION

[0003] Single metal products rarely exhibit all of the properties that are desired. As a result, it is often necessary to combine or clad metals together to achieve a product having the desired properties. Through the roll cladding of metals, it is possible to put disparate metals together in a process that opens the door for design of exciting new products. Cladding is generally provided by compressing metal strips together with heat and/or pressure, through the use of a roll cladding mill or a press. However, conventional cladding has limitations with respect to edge-to-edge cladding. These limitations are addressed in the process described herein.

SUMMARY OF THE INVENTION

[0004] A process for edge-to-edge cladding of two or more strips of different metals (such as aluminum and copper) is described herein. The metal strips are joined next to each other to form an edge-to-edge or side-by-side clad bimetal. In one embodiment, nine metals strips are used to create the desired clad metal composite. The design includes strips of metal that have industry standard cut edges. The clad metal composite may include multiple layers of metals positioned edge-to-edge for cladding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a perspective view of a clad metal composite formed according to the edge-to-edge bimetal cladding process.

[0006] Figure 2 is a perspective view of individual strips of metal to form a clad metal composite using the edge-to-edge bimetal cladding process.

[0007] Figure 3 is an end view of the clad metal composite.

[0008] Figure 4 is a chart providing a summary of the theoretical copper-aluminum intermetallic compound thickness as a function of time and temperature.

[0009] Figure 5A is an end view of a basic bond configuration of nine layers of metals to be clad using the edge-to-edge bimetal cladding process.

[0010] Figure 5B is an end view of the combined layers of the bonded clad metal composite illustrated in Figure 5A, the combined layers being split into left and right slit-cuts.

[0011] Figure 6 A is an end view of two single core layer clad metal composites, a top layer and a bottom layer as prepared to produce a dual-core bonded configuration.

[0012] Figure 6B is an end view of the clad metal composite having a double layer clad metal composite as shown in Figure 6A, being split into left and right slit-cuts.

[0013] Figure 7A is an end view of three single core layer clad metal composites, a top layer, a middle layer, and a bottom layer as prepared to produce a triple-core bonded configuration. [0014] Figure 7B is an end view of the bonded clad metal composite having a triple layer clad metal composite as showing in Figure 7 A, being split into left and right slit-cuts.

[0015] Figure 8 A is an end view of a basic bond configuration of nine layers of metals to be clad using the edge-to-edge bimetal cladding process as shown in Figure 5A, with two additional metal strengtheners added as additional layers.

[0016] Figure 8B is an end view of the combined layers of the bonded clad metal composite illustrated in Figure 8A.

[0017] Figure 9A is an end view of a double layer clad metal composite having a dual-core, with a top layer, a bottom layer, and a metal strengthener positioned between the top layer and bottom layer as prepared for bonding.

[0018] Figure 9B is an end view of the bonded clad metal composite having a double layer clad metal composite with a metal strengthener as showing in Figure 9A.

[0019] Figure 10A is an end view of a triple layer clad metal composite having a triple-core, with a top layer, a middle layer, and a bottom layer, and a first metal strengthener between the top and middle layers and a second metal strengthener between the middle and bottom layers as prepared for bonding.

[0020] Figure 10B is an end view of the bonded clad metal composite having a triple layer clad metal composite with metal strengthener layers as showing in Figure 10A.

[0021] Figure 11 A is an end view of a clad metal composite of five layers of metals to be clad using the edge-to-edge bimetal cladding process.

[0022] Figure 11B is an end view of the combined layers of the clad metal composite illustrated in Figure 11 A. [0023] Figure 11C is an end view of the bonded clad metal composite as illustrated in Figures 11 A and 1 IB.

[0024] Figure 12A is an end view of an inlay clad metal composite of four layers of metals to be clad using the edge-to-edge bimetal cladding process.

[0025] Figures 12B is an end view of the combined layers of the bonded clad metal composite illustrated in Figure 12 A.

[0026] Figures 12C is an end view of the combined layers of the bonded clad metal composite illustrated in Figure 12 A, the combined layers being split into left and right cuts.

[0027] Figures 13A and 13B are end views of an inlay clad metal composite of seven layers of metals to be clad using the edge-to-edge bimetal cladding process.

[0028] Figure 13C is an end view of the combined layers of the bonded clad metal composite illustrated in Figure 13 A.

[0029] Figure 13D is an end view of the combined layers of the clad metal composite illustrated in Figure 13 A, the combined layers being split into left and right slit-cuts.

[0030] Figures 14A, 14B, 14C and 14D illustrate an embodiment of the clad material that includes four metal layers.

[0031] Figure 15 is a process flow chart illustrating the process steps for bonding the metal strips made from a first metal and a second metal.

[0032] Figure 16 is an illustration of the layers of metals being clad using two rollers.

[0033] Figure 17 is a diagram of a bonding mill assembly used to clad nine layers of a metal into a single clad metal composite.

[0034] Figure 18 is a photomicrograph of the double core copper-aluminum at the transition from copper to aluminum. DETAILED DESCRIPTION OF THE INVENTION

[0035] A new process for edge-to-edge cladding of metals is described herein. Essentially, two or more different metals (such as aluminum and copper, although other combinations may be used) are joined next to each other to form an edge-to-edge or side-by-side clad bimetal 10 (see Figures 1 - 3).

[0036] Looking at Figures 2, 5A, and 5B, nine strips of metals are used to create the desired clad metal composite 10. The strips of metal have non-profiled, substantially straight strip edges, such as industry standard slit edges. In the embodiment described herein, the strips of metal are made of copper and aluminum; however, a variety of metal combinations may be implemented to provide the clad metal composite 10. For example, the combination could include a first metal of the following metals including, but not limited to, aluminum, nickel, steel and/or stainless steel joined with copper, steel and/or stainless steel joined with aluminum, or other multiple metal combinations.

[0037] Referring to Figures 5A and 5B, the clad metal composite 10 of a first embodiment includes three layers LI, L2, L3, with each layer LI, L2, L3 having three strips of metal. That is, the first layer LI includes first and second side strips 12, 16 positioned on opposite sides of first center strip 14, the second layer L2 includes third and fourth side strips 18, 22 positioned on opposite sides of second center strip 20, and the third layer L3 includes fifth and sixth side strips 24, 28 positioned on opposite sides of third center strip 26. In the illustrated embodiment, each layer LI, L2, L3 has two side strips of a first metal (such as solid aluminum) and one strip of a second metal (such as copper). The side strips of the first metal are labeled 12, 16, 18, 22, 24 and 28, and the center strips of the second metal are labeled 14, 20, 26. In this embodiment, each individual strip of the second metal (e.g., copper) is centrally positioned between two strips of the first metal (e.g., aluminum), with the side strips abutting the center strip. The side strips of the first metal are clad or bonded alongside the center strips of the second metal. However, it is foreseen that the composition of the metal strips could be reversed. That is, each layer could include two strips of copper on two sides of a strip of aluminum.

[0038] Continuing to view Figure 5A, each layer LI, L2, L3 substantially has a composite width CW. Referring to the first layer LI, the width W2 of the center strip 14 is substantially the same as the width of the center strip 26 in the third layer L3. In comparison, the width W4 of the center interlayer strip 20 in the second or middle layer L2 is substantially greater than the width W2 of the center strips 14, 26 in the first and third layers LI, L3. Likewise, the width Wl of the first and second side strips 12, 16 is substantially commensurate with the width of the fifth and sixth side strips 24, 28, while the width W3 of the third and fourth side strips 18, 22 in the second layer L2 is less than the width Wl of the side strips 12, 16, 24, 28 in the first and third layers LI, L3. The differences in the width W4 of the center interlayer strip 20 and the width W2 of the upper and lower center strips 14 and 26 will result in an "overlapping" stepped clad bond zone in the central region of the clad metal composite 10. This metal strip width overlap can be controlled to vary bond zone region as may be required for custom applications. Figures 5A and 5B show the center interlayer strip 20 touching each of the eight other strips 12, 14, 16, 18, 22, 24, 26, 28, with the aluminum surrounding sides of the center interlayer strip 20 and copper strips 14 and 26 adjacent the top and bottom of the center interlayer strip 20 as the metals to be clad enter the bonding mill 299. The present clad metal composite utilizes a "stepped" or staggered inner layer(s) to provide the basis of the bonded joint configuration of the clad metal composite 10. [0039] The metal strips 12 - 28 can be bonded utilizing heated or non-heated bonding mill rolls 300, 302, 304, 306 in a bonding mill 299. Multiple core layer configurations can be produced with or without intermediate heat treatment. Avoiding intermediate heat treatments can be beneficial by minimizing the formation of possibly harmful copper-aluminum intermetallics as described herein. Clad metal composite properties of the bonded composite 10 can be optimized during the heat treatment cycle. Heat treatment cycle can be achieved by batch or continuous heat treatment.

[0040] Figure 4 is a chart that provides a summary of the theoretical copper-aluminum intermetallic compound (IMC) thickness comparison between the expected temperature and time cycles for both a Batch Sinter Heat Treatment and a Strand Sinter Heat Treatment. The expected IMC growth for the 450°F/4 Hr Batch Sinter is -1.52 microns. The expected IMC Growth for the 750°F/3 Min Strand Sinter is -3.09 microns. Therefore, the batch sinter process is preferred in the present design, and is expected to result in essentially half the IMC thickness of the Strand Sinter process. The importance of this IMC Growth is the negative effect it has on bond strength, formability, thermal and electrical conductivity. Increased IMC thickness reduces bond strength, formability, thermal and electrical conductivity.

[0041] Figures 5A and 5B illustrate one exemplary embodiment of the clad metal composite 10. While not limited to the illustrated configuration, this embodiment shows nine independent copper and aluminum strips bonded as one single clad metal composite 10. That is, the single clad assembly 10 includes three top strips, three middle strips, and three bottom strips. Other embodiments are described herein. [0042] Looking to Figures 5B, 6B, 7B, 9B, 10B, 13C, 14D, 15D, and 16D, the bonded clad metal composite 10 can be slit to produce a left and right strip profiles that could then be stamped into the formed stamp parts, as depicted in Figure 1.

[0043] The process for bonding the various strips into a clad metal composite 10 is illustrated in Figure 15. Initially, the metals to be used in the clad metal composite 10 are selected in steps 200, 202, 204. In the illustrated embodiment, there are metal strips in each layer that are comprise aluminum and copper (as well as other potential embodiments). The design includes strips of metal that have industry standard cut edges. The various metal strips are prepared for bonding via cleaning in steps 206, 208, 210. Cleaning dirt and oils from the strip surface is necessary to ensure clad bond integrity. In the present embodiment, cleaning is performed to ensure the surface of each strip is properly prepared for clad bonding.

[0044] Once the metals are prepared, the multiple metal strips are aligned (step 212) so that the industry standard cut edges in each layer LI, L2, L3 are positioned as desired. In the nine- strip embodiment shown in Figures 5A and 5B, each of the respective three layers LI, L2, L3 are aligned according to the desired embodiment and application. Referring to Figure 5A, metal strips 12, 14, 16 in the top layer LI are aligned so that the central metal strip 14 abuts strips 12, 16; metal strips 18, 20, 22 in the middle layer L2 are aligned so that the central metal strip 20 abuts strips 18, 22, and metal strips 24, 26, 28 in the bottom layer L3 are aligned so that the central metal strip 26 abuts strips 24, 28. The metal strips are aligned in each layer LI, L2, L3, and each layer LI, L2, L3 is aligned with respect to the other layers LI, L2, L3 to achieve the desired overlapping step clad metal composite.

[0045] The alignment of the metal strips may be performed using custom guides that are known in the art and not specifically illustrated in the attached figures. These guides align the various individual metal strip widths simultaneously as they are drawn into the bonding mill rolls 300, 302, 304, 306. For example, Figure 16 provides a schematic illustrating nine various individual metal strip widths 12 - 28 simultaneously being drawn into the rolls 300, 302, 304, 306 of the bonding mill 299. However, the number of layers and strips may be varied according to the desired use by the producer.

[0046] The next step is the roll bond (step 214). This is the process step where the individual metal strips are "clad" into one piece comprising a portion made of the first metal 6 and a portion made of the second metal 8. Looking to Figure 17, this step is performed on a roll cladding mill 299 specifically design and built to withstand the separating force and heat generated during the heavy metal thickness reduction.

[0047] The bonded layers LI, L2, L3 may then treated through sintering (step 216). Sintering is a heat treatment step which promotes the metallurgical bond between the clad layers. This heating process can be done using a continuous strand annealing furnace or a batch annealing furnace. The bonded layers may be processed using either option, and the processing option is selected according to the best method known in the art based on the metal requirements and final mechanical properties as specified by the end user.

[0048] For the copper-aluminum metal system the formation of "intermetallic" compounds can be detrimental to the bond integrity (bond strength), formability, thermal and electrical conductivity. Figure 4 includes a graph that provides a theoretical comparison of the calculated copper-aluminum intermetallic (IMC) thickness values as a function of time and temperature.

[0049] The producer will determine best manufacturing practices to meet final customer specifications. The clad metal composite 10 is then slit (step 218) and readied for inspection and shipment (step 220). [0050] Furthermore, one set of bonded metal strips of the clad metal composite 10 may be combined with a separate clad metal composite 10, with the resulting clad metal composite 30 having additional clad composite layers CL1, CL2. Such an embodiment is illustrated in Figures 6B and 7B. In Figures 6A and 6B, a clad metal composite 30 having a double core layer bond configuration is shown. In this embodiment, two independent sets or composite layers CL1, CL2 of bonded strips 10 are combined to achieve a clad metal composite 30 having a desired thickness with two copper core extensions. That is, once each set of clad metal composite 10 has been bonded as described above, the two sets will then be aligned and roll cladded together to produce the clad metal composite 30. A photomicrograph of the double core copper- aluminum at the transition from copper to aluminum is provided in Figure 18, and this photograph illustrates the stair step configuration. Referring to Figure 6B, the clad metal composite 30 may then be slit into two clad halves 30A and 30B.

[0051] Figures 7A and 7B illustrate a triple layer bond configuration, with three layers CL1, CL2, CL3 of multilayer bonded strips 10. The process to prepare a triple layer bond is to first form three independent sets of multilayer bonded strips 10, align each of the sets with each other, and then roll clad the three sets of bonded strips 10 to achieve the desired triple core layer clad material 40. The clad material 40 may then be slit into two clad material halves 40A and 40B.

[0052] Looking to Figures 8A and 8B, an additional embodiment is illustrated. In this embodiment, the set of bonded layers LI, L2, L3 illustrated in Figure 5A additionally includes one or more supplemental metal strengthener layers 50, 52 positioned between the multi-metal strip layer LI, L2, L3 and bonded to for the clad metal composite 54. The sets of bonded metal strips are prepared as described above, simply with the additional supplemental metal strengthener layers 50, 52 positioned in between the layers LI, L2, L3. That is, one strengthener layer 50 may be positioned between the first layer LI and the second layer L2, and a second strengthener layer 52 may be positioned between the second layer L2 and the third layer L3. As an example, the additional metal strengthener layer 50, 52 can be from the group of nickel, aluminum, copper, steel, stainless steel or other similar material in the copper-aluminum configuration. The metal strengthener layer 50, 52 will increase the bulk metal strength and alter the thermal and electrical resistivity of the cladded metals 54.

[0053] Looking to Figures 9A and 9B, an additional embodiment of the invention is illustrated in which a supplemental strengthener layer 60 of an additional metal is positioned between two clad metal composites 10 having composite layers CL1, CL2. In this embodiment, each clad metal composite 10 is prepared as described above and are prepared to be bonded together to create a double core layer bond clad composite 30, but an additional metal strengthener layer 60 is positioned between the clad metal composites 10. The clad metal composites 10 and strengthener layer 60 are roll bonded to achieve a strengthened double core layer bond clad composite 62. The clad material 62 may then be slit into two clad metal composite halves 62A and 62B (see Figure 9B).

[0054] Figures 10A and 10B illustrate a similar embodiment to the one illustrated in Figures 9 A and 9B, with this embodiment including three layers CL1, CL2, CL3 of bonded core layers 10 that are combined together with two additional metal layers 70, 72 positioned between each set of bonded metal strips 10. The sets 10 are bonded together to create a triple core layer bond clad metal composite 74, but the additional metal layer 72 is positioned between the sets that are roll bonded to achieve a desired result. The clad material 74 may then be slit into two clad metal composite halves 74A and 74B. [0055] Finally, looking to Figures 12 A - 14D, additional embodiments of independent sets of bonded layers prepared according to the steps described above. These embodiments illustrate that other combinations of layer configurations may be prepared in addition to the three layers of three strips of metals as described above. The common element to each design is that there is a stair step arrangement of strips of differing metals that are positioned in an edge-to-edge arrangement.

[0056] Figure 11A, 1 IB and 11C illustrate an embodiment that includes three metal layers: a base layer L3, a primary layer L2, and a top layer LI. However, in this embodiment, the top layer LI and the base layer L3 have single metal strips 90, 94, respectively, of aluminum. The metal strips 92, 94, 96 in the middle metal layer include a single metal strip of copper 94 with metal strips 92, 96 of aluminum on both sides of the copper strip 94. As a result, there is a single layer 94 of copper in the center of the clad material 100, with the stair step configuration, as shown in Figure 11C. When bonded, the aluminum layers combine into a single layer 6 with the independent copper layer 94 in a locked connection in the layer 6.

[0057] Figures 12A and 12B illustrate embodiments related to the one shown in Figures 11 A, 1 IB, and 11C, with the top aluminum layer shown in Figures 11A, 1 IB, 11C removed from the bonded set of layers to achieve the clad metal composite 116. Therefore, there is a base layer 116 of aluminum with the top layer having three metal strips - a center strip 112 of copper positioned between two side strips 110, 114 of aluminum. This embodiment is further shown in Figure 12C with a central cut to create two split strips of bonded metals 116.

[0058] Figures 12 A, 12B and 12C illustrate the two layer embodiment. The base layer L2 is a single metal strip 115 of aluminum. A primary or top layer LI positioned on the base layer L2 includes a copper strip 112 with aluminum strips 110, 114 of aluminum edge to edge to both sides of the copper strip 112. The combined width of the three metal strips 110, 112, 114 in top layer LI is substantially equivalent to the width of the base layer L2. The strips 110, 112, 114, 115 are bonded together to create the clad metal composite 116 comprising the first metal 6 cradling the second metal 112. The clad metal composite 116 may then be slit into two clad metal composite halves 116A and 116B.

[0059] Figures 13 A, 13B, 13C and 13D illustrate an embodiment that includes three metal layers LI, L2, L3. However, in this embodiment, the top layer LI has two metal strips 140, 144 of a first metal (e.g., aluminum) and a central metal strip 142 of a second metal (e.g., copper) and the base layer L3 has a single metal strip 152 of the first metal. The metal strips 146, 148, 150 in the center metal layer L2 include a single metal strip 148 of the second metal with metal strips 146, 150 of the second metal on both sides of the central metal strip 148. As a result, there is a double layer of the second metal (e.g., copper) in the center of the clad metal composite 154. When the layers LI, L2, L3 are bonded, a core metal strip 8 is formed as an inlay with a stair step configuration. This embodiment is further shown in Figure 13D with a central slit-cut to create two split strips of bonded clad metal composites 154A, 154B.

[0060] Figures 14A, 14B, 14C and 14D illustrate an embodiment that includes four metal layers LI, L2, L3, L4. In this embodiment, the first layer LI, second layer L2 and third layer L3 are the same as the clad metal composite 10 illustrated in Figures 5A and 5B. The layers LI, L2, L3 all have two aluminum metal strips and a central copper metal strip and the base layer has a single metal strip of aluminum as illustrated in Figure 5A. The metal strips in the first, second and third metal layers LI, L2, L3 include a single central metal strip 14, 20, 26 of copper with metal strips of aluminum on both sides. However, the copper metal strip in the second layer is wider than the copper metal strip in the first and third metal layers. The three layers LI, L2, L3 are bonded so that there is a triple layer of copper in the center of the clad metal composite 10. Once bonded, the fourth layer L4 of a supplemental base metal strip 160 is added, wherein the supplemental base metal strip 160 is a single metal strip of aluminum. This fourth layer L4 is then bonded with the clad metal composite 10 to produce a bonded clad metal composite 162 having three layer core copper metal strip as an inlay with a stair step configuration. This embodiment is further shown in Figure 14D with a central slit-cut to create two split strips of the clad metal composite 162A, 162B.

[0061] Having thus described exemplary embodiments of a method to produce metallic composite metal, it should be noted by those skilled in the art that the within disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of this disclosure. Accordingly, the invention is not limited to the specific embodiments as illustrated herein, but is only limited by the following claims.