Enhanced in-furnace brazing cycle

Abstract

A method for reducing cycle time of a brazing process is provided, the method including: placing together first and second pairs of brazing components, each of the first and second pairs having a brazing material interposed therebetween, stacking the first and second pairs of brazing components to form a stack, interposing pyrolytic graphite (PG) between the first and second pairs of brazing components in the stack, and heating the first and second pairs of brazing components to a brazing temperature to braze together the first and second pairs of brazing components.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Patent Application No. 17 / 992,322, filed on November 22, 2022, the entire content of which is incorporated herein by reference.

Background Art

[0002] Exemplary embodiments of the present disclosure generally relate to vacuum brazing, and in one embodiment, relate to enhancing the vacuum brazing cycle using pyrolytic graphite (PG).

[0003] PG is a general term including pyrolytic graphite (TPG), annealed pyrolytic graphite (APG), and highly oriented pyrolytic graphite (HOPG). Similarly, there are other materials having a high thermal diffusivity exceeding about 500 mm 2 / s or more. These include, but are not limited to, carbon fiber, pyrolytic carbon, diamond, and carbon - containing materials such as nitrides and carbides.

[0004] Brazing is one of the metal joining processes. Two or more metals are joined together by using a filler metal with a melting point lower than that of the adjacent metals, and the filler metal is melted and poured into the joint while flowing into it. Brazing is different from welding in that it does not involve melting the workpiece. Brazing is different from soldering in that it uses a higher temperature (liquidus temperature exceeding 450°C or 840°F). During the brazing process, the filler metal flows into the gap between adjacent parts by capillary action. The filler metal is slightly above its melting (liquidus) temperature while being protected by an appropriate atmosphere, usually a vacuum. Then, the filler metal wets and reacts with the base metal and is cooled to join the workpieces together. <​Many technologies utilize a considerable number of brazed parts. For example, one technology may require hundreds of chassis, each with multiple individual brazing points. Cold plate technology, in particular, often involves multiple parts that are brazed together to form a cold plate. [Overview of the project]

[0006] According to one aspect of the present disclosure, a method for reducing the cycle time of a brazing process is provided. The method includes: arranging each of a first pair and a second pair of brazing parts integrally, wherein each of the first pair and the second pair of brazing parts has a brazing material interposed between the brazing parts; laminating the first pair and the second pair of brazing parts to form a laminate; interposing pyrolytic graphite (PG) between the first pair and the second pair of brazing parts in the laminate; and heating the first pair and the second pair of brazing parts to a brazing temperature in order to braze each of the first pair and the second pair of brazing parts integrally.

[0007] According to additional or alternative embodiments, the PG increases the effective thermal diffusivity of the laminate and, accordingly, reduces the cycle time required to braze each of the first pair and second pair of brazed parts together.

[0008] According to additional or alternative embodiments, PG increases the effective thermal diffusivity of the laminate by approximately 3.0 times or more.

[0009] According to additional or alternative embodiments, the PG has a thermal diffusivity of about 500 mm² / s or more.

[0010] According to additional or alternative embodiments, the brazing temperature is approximately 1050–1200°F.

[0011] According to additional or alternative embodiments, the method further includes interposing a first stop-off layer and a second stop-off layer between the PG and each of the first and second pairs of brazed parts, respectively.

[0012] According to additional or alternative embodiments, the method further includes covering the PG with a metal housing.

[0013] According to additional or alternative embodiments, the method further includes providing a layer of PG on at least one of the top and bottom of the laminate.

[0014] According to additional or alternative embodiments, the method further includes bending the PG around at least one outer edge of a first pair and a second pair of brazed parts, and attaching an additional PG piece to the PG to abut against at least one outer edge of a first pair and a second pair of brazed parts.

[0015] According to one aspect of the present disclosure, a method for reducing the cycle time of a brazing process is provided. The method includes: arranging each of a plurality of pairs of brazing parts integrally, each of the plurality of pairs of brazing parts having a brazing material interposed between the brazing parts; stacking the plurality of pairs of brazing parts to form a laminate; interposing pyrolytic graphite (PG) between adjacent pairs of brazing parts; and heating the plurality of pairs of brazing parts to a brazing temperature in order to braze each of the brazing parts of the plurality of pairs of brazing parts integrally.

[0016] According to additional or alternative embodiments, the PG increases the effective thermal diffusivity of the laminate and, accordingly, reduces the cycle time required to braze each of multiple pairs of brazed parts together.

[0017] According to additional or alternative embodiments, PG increases the effective thermal diffusivity of the laminate by approximately 3.0 times or more.

[0018] According to additional or alternative embodiments, the PG has a thermal diffusivity of about 500 mm² / s or more.

[0019] According to additional or alternative embodiments, the brazing temperature is approximately 1050–1200°F.

[0020] According to additional or alternative embodiments, the method further includes interposing a stop-off layer between the PG and each of the corresponding pairs of brazed parts.

[0021] According to additional or alternative embodiments, the method further includes covering the PG with a metal housing.

[0022] According to additional or alternative embodiments, the method further includes providing a layer of PG on at least one of the top and bottom of the laminate.

[0023] According to additional or alternative embodiments, the method further includes bending the PG around at least one outer edge of a plurality of pairs of brazed parts, and attaching an additional PG piece to the PG to abut against at least one outer edge of the first pair and second pair of brazed parts.

[0024] According to one aspect of the present disclosure, a method for shortening the cycle time of a brazing process. The method includes forming a first laminate and a second laminate, each comprising a plurality of pairs of brazing parts; arranging the first laminate and the second laminate adjacent to each other; interposing pyrolytic graphite (PG) between at least one adjacent pair of the plurality of pairs of brazing parts in the first laminate; providing a layer of PG on at least one of the top and bottom of the first laminate and the second laminate; bending the ends of PG to extend between the first laminate and the second laminate along one or more of the plurality of pairs of brazing parts in the first laminate and the second laminate; and heating the plurality of pairs of brazing parts of the first laminate and the second laminate to a brazing temperature to integrally braze each brazing part of the first laminate and the second laminate.

[0025] According to additional or alternative embodiments, the PG has a thermal diffusivity of about 500 mm2 / s or more, and increases the effective thermal diffusivity of at least the first laminate by about 3.0 times or more, and accordingly, shortens the cycle time required to integrally braze each brazing part of the first laminate and the second laminate.

[0026] These and other advantages and features will become more apparent from the following description in conjunction with the drawings. The following description should in no way be construed as limiting. With reference to the accompanying drawings, like elements are numbered alike.

Brief Description of the Drawings

[0027] [Figure 1] It is a flowchart showing a method for shortening the cycle time of a brazing process according to an embodiment. [Figure 2] It is a schematic diagram of a laminate of brazing parts in which layers of pyrolytic graphite (PG) are alternately arranged according to an embodiment. [Figure 3] It is an enlarged view of the portion surrounded by the broken line 3 in FIG. 2 according to an embodiment. [Figure 4]This is a schematic diagram of a brazed component laminate in which layers of PG shown in Figure 2 are arranged alternately inside a brazing furnace, according to an embodiment. [Figure 5] This is an enlarged schematic diagram of a brazed part according to an embodiment, in which layers of PG having edges with increased surface area are arranged alternately. [Figure 6] This is an enlarged schematic diagram of a brazed part according to an embodiment, in which layers of PG having mounting portions with increased surface area are arranged alternately. [Figure 7] This flowchart illustrates a method for reducing the cycle time of a brazing process according to a further embodiment. [Figure 8] This is a schematic diagram of a brazed component laminate in which layers of PG are arranged alternately, illustrating a method for reducing the cycle time of the brazing process according to an embodiment.

[0028] These and other advantages and features will become clearer from the following description in conjunction with the drawings. [Modes for carrying out the invention]

[0029] In technical fields involving the brazing of multiple parts, it has recently become clear that brazing cycle time can be a problem. For example, when parts are brazed to form a cold plate, the brazing cycle time can be very long. In these and other cases, each part may be supplied as a metal layer to be brazed to an adjacent metal layer. Each pair of adjacent layers is stacked together with alternating layers of material having a thermal conductivity equal to or less than that of the base material (such as steel), and placed in the brazing furnace. Operating the brazing furnace and raising the temperature of the laminate to the brazing temperature often takes a long time. This is because the materials of the laminate have a relatively low thermal diffusivity, and the center of the laminate heats up very slowly. For large laminates, the brazing cycle time can be up to 12 hours or more. Therefore, there is a need for methods to reduce the brazing cycle time of large laminates of parts.

[0030] Therefore, a method is provided to reduce the cycle time of the brazing process for large laminates of parts, as described below, which involves replacing the alternating layers of material in the large laminate of parts with graphite sheets made of pyrolytic graphite (PG), which has a relatively high thermal diffusivity and thus transfers heat to the center of the large laminate at a faster rate than possible with other methods.

[0031] Referring to Figures 1 and 2-5, a method 100 for reducing the cycle time of the brazing process is provided.

[0032] Method 100 first includes arranging each of the first pair of brazed parts 110 and the second pair of brazed parts 120 integrally (block 101), laminating the first pair of brazed parts 110 and the second pair of brazed parts 120 to form a laminate 130 (block 102), and interposing PG 140 between the first pair of brazed parts 110 and the second pair of brazed parts 120 within the laminate 130 (block 103). Additional PG 145 may be provided or layered on one or both of the top and bottom of the laminate 130 (block 1035). The laminate 130 in Figures 2 and 4 shows only the first pair of brazed parts 110 and the second pair of brazed parts 120 for clarity and brevity, but it will be understood that additional pairs of brazed parts and layers may be included in the laminate 130. The first pair of brazed parts 110 may include a filler or brazing material 111 interposed between the brazed parts 112. The brazed parts 112 may generally be provided as a block or layer of flat, planar metallic material. The second pair of brazed parts 120 may similarly include a filler or brazing material 121 interposed between the brazed parts 122. The brazed parts 122 may generally be provided as a block or layer of flat, planar metallic material.

[0033] Method 100 may further include placing the laminate 130 containing PG140 in a brazing furnace 401 (see Figure 4) and heating the first pair 110 and the second pair 120 of the brazing parts to a brazing temperature of approximately 1050–1200°F (block 104). This effectively brazes the brazing parts 112 of the first pair of brazing parts 110 together and the brazing parts 122 of the second pair of brazing parts 120 together. While this process would require a considerable amount of time to fully heat the center of the laminate 130, the presence of PG140 and additional PG145 in the laminate 130 increases the effective thermal diffusivity of the laminate 130 and, accordingly, reduces the cycle time required to braze the brazing parts 112 and 122 of the first pair 110 and the second pair 120 together. According to one embodiment, PG140 and additional PG145 can increase the effective thermal diffusivity of the laminate 130 by several times (i.e., by about 3.0 times or more), and accordingly reduce the cycle time required to integrally braze the brazed parts 112, 122 of the first pair 11 and the second pair 120 of brazed parts by several times (i.e., by about 3.0 times or more). According to a further embodiment, PG140 and additional PG145 can have a relatively high thermal diffusivity of about 500 mm² / s or more.

[0034] The reduction in cycle timing is determined at least by the structure of PG140. PG140 (and additional PG145) comprises multiple sheets 141 of PG material or other similar material. The relatively high thermal diffusivity of PG140 is partly due to the structure of the multiple sheets 141, generally represented by the plane P of PG140. Therefore, when heat is applied to the laminate 130 containing PG140 in the brazing furnace 401, the heat is transferred along the plane P of PG140 at a relatively faster rate than any other part of the laminate 130. This transferred heat is then conducted from PG140 into at least the central portion 131 of the laminate 130, and from there outward.

[0035] Method 100 in Figure 1 may further include covering PG140 (and additional PG145) with a metal housing 300 (block 105), and interposing a first stop-off layer 301 and a second stop-off layer 302 between PG140 and each of the first pair 110 and second pair 120 of brazed parts, respectively (block 106). As seen in Figure 3, the metal housing 300 may be formed from aluminum or another similar metallic material or alloy and may be aligned with at least the top and bottom surfaces of PG140. In some cases, the metal housing 300 may completely cover the entire PG140. In some or all cases, the metal housing 300 may be provided as a solid sheet with few or no openings, or as a frame with one or more relatively large openings. The first stop-off layer 301 and the second stop-off layer 302 can be formed from metal oxide powder such as aluminum oxide, titanium oxide, yttrium oxide, or magnesium oxide, or from another similar material, and prevent the PG140 or the metal housing 300 (in areas where the metal housing 300 is not provided, or in openings of the metal housing 300 provided as a frame) from adhering to either the first pair 110 or the second pair 120 of the brazed parts during or after heating / brazing.

[0036] According to one embodiment, as shown in Figure 4, heating may be performed inside the brazing furnace 401.

[0037] Method 100 in Figure 1 also includes at least one or more of the following: bending the end 142 of PG140 around at least one outer edge of brazed parts 112, 122 of at least one of the first pair 110 and second pair 120 of brazed parts (block 108); and attaching an additional PG piece to the end 142 of PG140 to abut against at least one outer edge of brazed parts 112, 122 of at least one of the first pair 110 and second pair 120 of brazed parts (block 109). Bending may be performed if there is extra length in PG140, as shown in Figure 5. As long as the bend 501 is smooth and free from twists and folds, the multiple sheets 141 of PG140 will remain intact and undamaged, and heat will be able to be transferred longitudinally. Thus, heat applied from the side, as shown in Figure 5, is transferred along the plane P of PG140 toward the bend 501. At the bent portion 501, heat is transferred along and around the bent portion 501, and then perpendicularly along the length of the end 142, where the plane P is oriented perpendicularly. The heat transferred to the end 142 can then be conducted into at least one proximal portion of at least one brazed part 112, 122 of the first pair 110 and second pair 120 of the brazed parts. As shown in Figure 6, the PG 140 is effectively lengthened by attaching an additional PG piece. Thus, as shown in Figure 6, heat applied from the side is transferred along the plane P of the PG 140 toward the additional PG piece 601. At the additional PG piece 601, heat is transferred perpendicularly along the length of the additional PG piece 601 and the perpendicularly oriented additional PG piece 601. The heat transferred to the additional PG piece 601 can then be conducted into at least one proximal portion of at least one of the brazed parts 112, 122 of the first pair 110 and the second pair 120 of the brazed parts. Bending and attaching the additional PG piece can be carried out in the same manner with respect to the additional PG 145.

[0038] Referring to Figure 7, a method 700 for reducing the cycle time of the brazing process is provided. Method 700 is substantially the same as Method 100 and does not need to be described in detail. Method 700 includes arranging each of a plurality of pairs of brazing parts integrally, each of the plurality of pairs of brazing parts having brazing material interposed between the brazing parts (block 701); stacking the plurality of pairs of brazing parts to form a laminate (block 702); interposing PG between adjacent of the plurality of pairs of brazing parts (block 703); providing additional PG 145 as a layer on one or both of the top and bottom of the laminate 130 (block 703); and heating the plurality of pairs of brazing parts to a brazing temperature (block 704). Method 700 may further include covering the PG with a metal housing (block 705) and interposing a first stop-off layer and a second stop-off layer between the PG and each of the corresponding pairs of brazed parts (block 706). Furthermore, Method 700 may further include bending the ends of the PG around the outer edge of at least one brazed part (block 708).

[0039] Referring to Figure 8, a method 800 for reducing the cycle time of a brazing process is provided. Referring to Figure 8, the method comprises forming a first laminate 810 and a second laminate 820, each of which comprises a plurality of pairs 811, 821 of brazed parts. The method further comprises arranging the first laminate 810 and the second laminate 820 adjacent to each other, interposing a PG 830 between at least one adjacent pair of the plurality of pairs 811 of brazed parts in the first laminate 810, and bending at least one end 831 of the PG 830 to extend between the first laminate 810 and the second laminate 820, along one or more of the plurality of pairs 811, 821 of brazed parts in the first laminate 810 and the second laminate 820. The end 831 of PG830 is elongated and actually extends along the substantial height of the first laminate 810 and the second laminate 820, and optionally between at least one adjacent pair of a plurality of pairs 821 of brazed parts within the second laminate 820. An additional PG layer 832 may also be provided as a layer on at least one of the top and bottom of at least one of the first laminate 810 and the second laminate 820. Furthermore, the method includes heating the plurality of pairs 811, 821 of brazed parts of the first laminate 810 and the second laminate 820 to a brazing temperature in order to braze the respective brazed parts 811, 821 of the first laminate 810 and the second laminate 820 together. As described above, PG830 has a thermal diffusivity of approximately 500 mm² / s or more, and increases the effective thermal diffusivity of at least the first laminate 810 (and the second laminate 820 in the illustrated case) by several times (i.e., by approximately 3.0 times or more), and accordingly shortens the cycle time required to integrally braze the brazed parts of the first laminate 810 and the second laminate 820.

[0040] In other words, in the case shown in Figure 8, when heat is applied to the first laminate 810 and the second laminate 820, the heat is transferred along the surface of the PG830 and along the surface of the portion of the PG830 between the first laminate 810 and the second laminate 820 at a relatively faster rate than any other portion of the first laminate 810 and the second laminate 820. This transferred heat is then conducted outward from the (perpendicular) portion of the PG830 between the first laminate 810 and the second laminate 820 (here, the surface of the PG830 is vertically oriented) to the proximal side of the first laminate 810 and the second laminate 820.

[0041] Therefore, it is clear that multiple stacks of brazed parts can be brazed simultaneously in a brazing furnace, while shortening the cycle time.

[0042] The advantage of the features described herein is that it provides a method for reducing the cycle time of the brazing process for large laminates of parts, including, for example, replacing alternating material layers in a large laminate of parts with graphite sheets made of PG. Because PG has a relatively high thermal diffusivity, it transfers heat to the center of the large laminate faster than would be possible by other methods.

[0043] The term "approximately" is intended to include the degree of error associated with the measurement of a particular quantity by an instrument available at the time of filing.

[0044] The terms used herein are for the sole purpose of describing specific embodiments and are not intended to limit the disclosure. Where used herein, the singular forms “a,” “an,” and “the” are intended to include the plural form unless the context clearly indicates otherwise. It will be further understood that the terms “equipment / contains” and / or “equipment / contains,” when used herein, identify the presence of the described feature, component, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, components, steps, operations, elements, components, and / or groups thereof.

[0045] While this disclosure is described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various modifications may be made without departing from the scope of this disclosure, and that equivalents may be substituted for some of its elements. Furthermore, many modifications may be made without departing from the essential scope of this disclosure in order to adapt the teachings of this disclosure to specific circumstances or materials. Thus, this disclosure is not limited to any particular embodiment disclosed as the best possible form conceived for carrying out this disclosure, but is intended to include all embodiments that fall within the “claims.”

Claims

1. A method for shortening the cycle time of the brazing process, The first pair and the second pair of brazed parts are arranged integrally, wherein each of the first pair and the second pair of brazed parts has a brazing material interposed between the brazed parts. The first pair of brazed parts are stacked to form a first laminate, The second pair of brazed parts is stacked to form a second laminate, Interposing multiple sheets of pyrolytic graphite (PG) between the first laminate and the second laminate, In order to braze the first pair and the second pair of brazed parts together, the first pair and the second pair of brazed parts are heated to the brazing temperature, Methods that include...

2. The method according to claim 1, wherein the PG increases the effective thermal diffusivity of the laminate, and accordingly reduces the cycle time required to integrally braze each of the first pair and the second pair of brazed parts of the brazed parts.

3. The method according to claim 2, wherein the PG increases the effective thermal diffusivity of the laminate by about 3.0 times or more.

4. The aforementioned PG is approximately 500 mm ２ The method according to claim 1, having a thermal diffusivity of / s or more.

5. The method according to claim 1, wherein the brazing temperature is approximately 1050 to 1200°F.

6. The method according to claim 1, further comprising interposing a first stop-off layer and a second stop-off layer between the PG and each of the first pair and second pair of the brazed parts, respectively.

7. The method according to claim 1, further comprising covering the PG with a metal housing.

8. The method according to claim 1, further comprising providing a PG layer on at least one of the upper and lower parts of the laminate.

9. The PG is bent around at least one outer edge of the first pair and the second pair of the brazed part, The method according to claim 1, further comprising attaching an additional PG piece to the PG so as to abut against the outer edge of at least one of the first pair and second pair of the brazed part, or at least one of the PG pieces.

10. A method for shortening the cycle time of the brazing process, The method involves arranging each of a plurality of pairs of brazed parts together, wherein each of the plurality of pairs of brazed parts has a brazing material interposed between the brazed parts. The process involves stacking multiple pairs of the brazed parts to form multiple laminates, The method involves interposing multiple sheets of pyrolytic graphite (PG) between adjacent laminates of the aforementioned multiple laminates, In order to braze each of the plurality of pairs of brazed parts together, the plurality of pairs of brazed parts are heated to a brazing temperature, Methods that include...

11. The method according to claim 10, wherein the PG increases the effective thermal diffusivity of the laminate, and accordingly reduces the cycle time required to braze each of the plurality of pairs of brazed parts together.

12. The method according to claim 11, wherein the PG increases the effective thermal diffusivity of the laminate by about 3.0 times or more.

13. The aforementioned PG is approximately 500 mm ２ The method according to claim 10, having a thermal diffusivity of / s or more.

14. The method according to claim 10, wherein the brazing temperature is approximately 1050 to 1200°F.

15. The method according to claim 10, further comprising interposing a stop-off layer between the PG and each of the corresponding pairs of the brazed parts.

16. The method according to claim 10, further comprising covering the PG with a metal housing.

17. The method according to claim 10, further comprising providing a PG layer on at least one of the upper and lower parts of the laminate.

18. The PG is bent around at least one outer edge of the plurality of pairs of brazed parts, To bring an additional PG piece into contact with the PG of at least one of the first pair and second pair of brazed parts, The method according to claim 10, further comprising at least one or more of the following.

19. A method for shortening the cycle time of the brazing process, Forming a first laminate and a second laminate, each comprising multiple pairs of brazed parts, The first laminate and the second laminate are arranged adjacent to each other, Interposing pyrolysis graphite (PG) between at least one adjacent pair of the plurality of brazed components within the first laminate, A layer of PG is provided on at least one of the upper and lower parts of the first laminate and the second laminate. The end of the PG is bent along one or more of the plurality of pairs of brazed parts within the first laminate and the second laminate so as to extend between the first laminate and the second laminate, To integrally braze the plurality of pairs of brazed components of the first laminate and the second laminate to the respective brazed components of the first laminate and the second laminate, the heating is performed to a brazing temperature. Methods that include...

20. The aforementioned PG is approximately 500 mm ２ The method according to claim 19, having a thermal diffusivity of 1 / s or more, increasing the effective thermal diffusivity of at least the first laminate by about 3.0 times or more, and accordingly shortening the cycle time required to integrally braze the brazed parts of the first laminate and the second laminate.

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