Method for joining dissimilar materials by using both hip and brazing

Abstract

The present invention relates to a method for joining dissimilar materials by using both hot isostatic pressing (HIP) and brazing, and, more specifically, to a method for joining dissimilar materials by using both HIP and brazing, the method being for ensuring uniform quality of a joined surface when dissimilar materials and similar materials are joined. In order to accomplish the objective, the present invention provides the method for joining dissimilar materials by using both HIP and brazing, the method including a step in which joining components are joined by means of HIP, wherein the joining components include a brazing filler metal.

Description

A method for joining dissimilar materials using both HIP and BRAZING methods.

[0001] The present invention relates to a method for joining dissimilar materials using a HIP method and a brazing method at the same time, and more specifically, to a method for joining dissimilar materials using a HIP method and a brazing method at the same time to secure uniform quality of a joining surface when joining dissimilar materials and similar materials.

[0002]

[0003] Thermal shields used in high-temperature applications, such as nuclear power or nuclear fusion, often use materials that are joined together, often with high melting points and high thermal conductivity for cooling. Tungsten, with its high melting point (3,422°C), is often combined with copper, which has high thermal conductivity for cooling efficiency, or with copper alloys with improved high-temperature properties. However, these materials have different coefficients of thermal expansion. In particular, when joining dissimilar metals, such as tungsten and copper, with significantly different coefficients of thermal expansion, the difference in expansion and contraction during heating and cooling can lead to failure in the high-temperature process, or residual internal stress after the joining process can cause defects during subsequent processes. Therefore, products that require joining materials with significantly different coefficients of thermal expansion, or that are used in environments with repeated heating and cooling, requiring different joining methods, require different joining methods. Diffusion bonding techniques, such as hot isostatic pressing (HIP) and brazing, are being developed to join these materials.

[0004] Brazing basically uses a brazing filler to form a diffusion bond between dissimilar materials to be joined, but the characteristic of high-temperature isostatic pressing (HIP) is that it forms a diffusion bond in a high-temperature, high-pressure environment without a brazing filler.

[0005] Figure 1 is an example showing the result of joining dissimilar materials using a conventional brazing method.

[0006] Referring to Figure 1, the brazing method has the advantage of being able to secure a certain level of bonding strength by using a solder when bonding dissimilar materials, causing little deformation, and being able to be processed using a general vacuum furnace.

[0007] However, brazing is difficult to apply to large areas, and as shown, it suffers from defects caused by the brazing material, such as partial brazing flow, uneven bonding, and voids. Furthermore, brazing is sensitive to the condition of the joint surface, such as surface roughness and cleaning conditions, and there are also limitations on the load per area depending on equipment capacity.

[0008] Figure 2 is an example showing the result of bonding different materials using a conventional HIP method.

[0009] Referring to Figure 2, the HIP method can be applied to large areas through isotropic pressing, and offers excellent bonding adhesion due to high-temperature and high-pressure bonding. However, compared to the brazing method, the bonding strength of the joint is lower, the process is longer, and only equipment capable of heating and pressurizing can be used.

[0010] In addition, as shown, the HIP process is prone to causing defects such as cracks in areas with high internal stress when the deformation is large, although the bonding surface is small.

[0011] Therefore, a method for joining dissimilar materials that can solve these problems is needed.

[0012] <Prior Art Literature>

[0013] Korean Patent Publication No. 10-2007-0108496

[0014]

[0015] The purpose of the present invention to solve the above problems is to provide a method for joining dissimilar materials using a HIP method and a Brazing method simultaneously to ensure uniform quality of the joining surface when joining dissimilar materials and similar materials and to prevent deformation even when stress, etc. occurs.

[0016] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0017]

[0018] The present invention for achieving the above object comprises a step of preprocessing a joining component; a step of assembling the preprocessed joining component; a step of canning the joining component; a step of vacuum testing the canned joining component; and a step of joining the joining component in a vacuum state by hot isostatic pressing (HIP) and brazing, wherein the joining component includes a brazing filler metal. The present invention provides a method for joining dissimilar materials using both the HIP method and the brazing method.

[0019] In an embodiment of the present invention, in the step of performing pretreatment on the bonding component, the bonding component may include a tungsten base material, and the tungsten base material may be heat-treated for 3 hours or more at a temperature of 950 to 1050 degrees in a vacuum atmosphere.

[0020] In an embodiment of the present invention, it may be characterized in that, in the step of performing pretreatment on the bonding component, cleaning of the bonding component is performed.

[0021] In an embodiment of the present invention, in the step of assembling the preprocessed joining component, the joining component may be assembled by sequentially stacking a copper alloy block, a copper plate, a brazing filler, a tungsten block, a molybdenum sheet, and a canning cover.

[0022] In an embodiment of the present invention, in the step of assembling the preprocessed joining component, the canning cover may be positioned at a step portion of the copper alloy block.

[0023] In an embodiment of the present invention, the brazing filler metal may be characterized as being a nickel-copper (Ni-Cu) alloy.

[0024] In an embodiment of the present invention, the tungsten base material may be provided in multiple pieces.

[0025] In an embodiment of the present invention, it may be characterized in that, in the step of canning the bonding component, the inside of the bonding component is sealed so as to maintain a vacuum atmosphere.

[0026] In an embodiment of the present invention, in the step of joining the above-described joining component in a vacuum state by hot isostatic pressing (HIP) and brazing, the above-described joining component may be characterized in that it is heat-treated for 3 hours or more at a temperature of 950 to 1,050 degrees in an argon (Ar) atmosphere, and at the same time, an isostatic pressure of 900 to 1,100 bar is applied.

[0027] In an embodiment of the present invention, after the step of performing bonding by hot isostatic pressing (HIP) and brazing on the bonding component in the vacuum state, a step of performing shape processing on the bonded bonding component may be included.

[0028]

[0029] The effect of the present invention according to the above configuration is that the adhesion of the joint surface by high temperature and high pressure is excellent, and thus the joint strength is superior compared to the conventional example in which only the brazing method and the HIP method were performed.

[0030] In addition, according to the present invention, application to a large area is possible due to isotropic pressing, and deformation of the bonding surface can be minimized.

[0031] In addition, according to the present invention, the brazing filler fills the joint interface without any gaps during the HIP and brazing processes, thereby increasing the joint area and enhancing the joint strength.

[0032] In addition, according to the present invention, cracking and breaking of the tungsten base material can be prevented, and bonding soundness against thermal shock after bonding can be secured.

[0033] In addition, according to the present invention, the phenomenon of filler agglomeration and spreading that occurs during the HIP and brazing processes is eliminated, thereby reducing defects.

[0034] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0035]

[0036] Figure 1 is an example showing the result of joining dissimilar materials using a conventional brazing method.

[0037] Figure 2 is an example showing the result of bonding different materials using a conventional HIP method.

[0038] Figure 3 is an exemplary diagram showing the result of bonding different materials according to an embodiment of the present invention.

[0039] Figure 4 is a flow chart of a method for joining dissimilar materials using the HIP method and the Brazing method simultaneously according to an embodiment of the present invention.

[0040] Figure 5 is a process diagram illustrating a method for joining dissimilar materials using the HIP method and the Brazing method simultaneously according to one embodiment of the present invention.

[0041] FIG. 6 is an exemplary diagram of a canned bonding component according to one embodiment of the present invention.

[0042] FIG. 7 is a graph showing pressure and temperature changes over time in a step of joining a vacuum-state joining component by hot isostatic pressing (HIP) and brazing according to one embodiment of the present invention.

[0043] Figure 8 is a graph comparing the bonding strength and bonding area based on the shear strength of the copper material.

[0044]

[0045] A most preferred embodiment according to the present invention comprises a step of pre-treating a joining component; a step of assembling the pre-treated joining component; a step of canning the joining component; a step of vacuum testing the canned joining component; and a step of joining the joining component in a vacuum state by hot isostatic pressing (HIP) and brazing, characterized in that the joining component includes a brazing filler metal.

[0046]

[0047] Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar parts have been designated with similar reference numerals throughout the specification.

[0048] Throughout the specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another part in between. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that it may include other components, unless otherwise specifically stated.

[0049] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0050] Additionally, terms such as “... part,” “... unit,” and “... module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software.

[0051] Additionally, when a step is said to be located "before" or "after" another step in this specification, this includes not only cases where the step is in a direct time-series relationship with the other step, but also cases where the two steps are in an indirect time-series relationship where the time-series order may be changed, such as a mixing step after each step.

[0052] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0053] FIG. 3 is an exemplary diagram showing the result of joining different materials according to an embodiment of the present invention, and FIG. 4 is a flowchart of a method for joining different materials using the HIP method and the Brazing method simultaneously according to an embodiment of the present invention.

[0054] FIG. 5 is a process diagram illustrating a method for joining dissimilar materials using a HIP method and a brazing method simultaneously according to an embodiment of the present invention, and FIG. 6 is an exemplary diagram illustrating a canned joining component according to an embodiment of the present invention.

[0055] Referring to FIGS. 3 to 6, a method for joining dissimilar materials using both the HIP method and the Brazing method may include a step (S10) in which pretreatment is performed on the joining parts, a step (S20) in which the pretreated joining parts are assembled, a step (S30) in which the joining parts are canned, a step (S40) in which a vacuum test is performed on the canned joining parts, a step (S50) in which joining is performed by hot isostatic pressing (HIP) and brazing on the joining parts in a vacuum, and a step (S60) in which shape processing is performed on the joined joining parts.

[0056] In the step (S10) where pretreatment of the parts for joining is performed, pretreatment such as cleaning and heat treatment of the parts for joining may be performed.

[0057] Specifically, the above-described joining component according to the embodiment includes a copper alloy block (1), a copper plate (2), a brazing filler (3), a tungsten block (4), a molybdenum sheet (5), and a canning cover (6), and in the step (S10) of preprocessing the joining component, the joining component may be provided with a preprocessing process of being cleaned and dried.

[0058] In addition, in the step (S10) where pretreatment of the bonding part is performed, the tungsten block (4) may be provided to be heat-treated at a temperature of 950 to 1,050 degrees for 3 hours or more in a vacuum atmosphere.

[0059] The above copper alloy block (1) may be provided in the form of a box with an open top surface so that other materials can be stacked on the inside. The copper alloy block (1) may be provided with the upper surface corners in the form of steps so that the materials can be sealed in a sequentially stacked state.

[0060] The above copper plate (2) is provided to be inserted into the inner lowest part of the above copper alloy block (1), and can be provided in the shape of a plate made of a copper (Cu) material.

[0061] The above brazing filler (3) is provided in a shape corresponding to the shape of the copper plate (2) so that it can be laminated on top of the copper plate (2) for brazing, and can be provided as a nickel-copper (Ni-Cu) alloy.

[0062] The above tungsten block (4) may be arranged to be stacked on top of the brazing filler (3) and may be made of tungsten (W) material.

[0063] The above molybdenum sheet (5) is made of molybdenum (Mo) material and can be arranged to be laminated on top of the tungsten block (4).

[0064] The above canning cover (6) is provided to be laminated on the upper portion of the molybdenum sheet (5), and may be provided to cover the entire upper portion of the molybdenum sheet (5). The above canning cover (6) may be provided to be positioned on the step-shaped portion of the copper alloy block (1).

[0065] The above-mentioned bonding components prepared in this manner can be arranged to be assembled by sequentially stacking a copper alloy block (1), a copper plate (2), a brazing filler (3), a tungsten block (4), a molybdenum sheet (5), and a canning cover (6) in that order in a step (S20) in which the preprocessed bonding components are assembled.

[0066] At this time, the canning cover (6) may be positioned on the step portion of the copper alloy block (1).

[0067] The above tungsten block (4) and the above molybdenum sheet (5) can provide an effect of preventing cracks in tungsten.

[0068] Specifically, molybdenum, along with tungsten, possesses a very high melting point, inhibiting atomic diffusion at temperatures where other metals readily diffuse. Furthermore, its vapor pressure is low at high temperatures. Therefore, during high-temperature and high-pressure diffusion bonding, molybdenum does not release gas. Instead, it combines with surrounding oxygen, absorbing oxygen released from the parent material and enhancing bonding performance.

[0069] The above tungsten block (4) may be provided as a plurality of blocks and stacked to form a plurality of rows and columns.

[0070] In the step (S30) where the jointing parts are canned, the canning can be arranged so that the assembled jointing parts are sealed while maintaining a vacuum atmosphere.

[0071] Specifically, in the step (S30) where the bonding component is canned, the canning cover (6) may be provided so that a portion extending over the stepped portion of the copper alloy block (1) is welded to form a welded portion (10). In addition, by being sealed in this manner, the interior of the copper alloy block (1) whose upper portion is covered by the canning cover (6) may be provided to be in a vacuum state.

[0072] Next, a vacuum test of the canned joint part is performed (at step S40, a vacuum test can be performed on the inside of the copper alloy block (1) that has been vacuumed in this way.

[0073] FIG. 7 is a graph showing pressure and temperature changes over time in a step of joining a vacuum-state joining component by hot isostatic pressing (HIP) and brazing according to one embodiment of the present invention.

[0074] Referring further to Fig. 7, in the step (S50) of performing joining by hot isostatic pressing (HIP) and brazing on the joining parts in a vacuum state, the joining can be performed by simultaneously performing hot isostatic pressing and brazing on the joining parts in a vacuum atmosphere.

[0075] At this time, the above-mentioned bonding component is prepared to be heat-treated at a temperature of 950 to 1050 degrees for 3 hours or more in an argon (Ar) atmosphere, and at the same time, an isotropic pressure of 900 to 1100 bar is applied so that bonding can be achieved.

[0076] Next, in the step (S60) where shape processing is performed on the jointed parts, post-processing such as shape processing may be performed on the jointed parts, whereby a post-processing portion (20) may be formed.

[0077] Figure 8 is a graph comparing the bonding strength and bonding area based on the shear strength of the copper material.

[0078] Referring to Fig. 8, based on the shear strength (100%) of the copper material, the materials joined by the brazing method have a shear strength at the joining site of 100 to 120%, and the materials joined by the HIP method have a shear strength at the joining site of approximately 70 to 90%.

[0079] However, it can be confirmed that the material bonded according to the present invention has a shear strength approaching 130 to 150%.

[0080] In addition, as shown in Fig. 8, the materials joined by the brazing method have a bonding area of ​​90% or less at the bonding site based on the defect-free bonding area (100%), and the materials joined by the HIP method have a bonding area of ​​100% at the bonding site.

[0081] In comparison, it can be confirmed that the material bonded according to the present invention has a bonding area of ​​100%.

[0082] In this way, it can be confirmed that the present invention can secure necessary bonding properties while complementing the shortcomings of the brazing method, which is unstable with a bonding area of ​​less than 90%, or the HIP method, which has low bonding strength.

[0083] In addition, according to the present invention, application to a large area is possible due to isotropic pressing, and deformation of the bonding surface can be minimized.

[0084] And, according to the present invention, cracking and breaking of the tungsten block (4) can be prevented, bonding soundness against thermal shock after bonding can be secured, and defects due to clumping and spreading of the filler occurring during the brazing process can be eliminated.

[0085] Although the description of the present invention has been illustrated with limited drawings, it is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed manner, and likewise, components described as distributed may be implemented in a combined form. Furthermore, the described techniques may be performed in a different order than the described method.

[0086] The embodiments described in this specification and the accompanying drawings merely illustrate some of the technical concepts encompassed by the present invention. Therefore, the scope of the present invention is defined by the claims below, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

[0087]

[0088] <Explanation of symbols>

[0089] 1: Copper alloy block

[0090] 2: Copper plate

[0091] 3: Brazing filler

[0092] 4: Tungsten block

[0093] 5: Molybdenum sheet

[0094] 6: Canning cover

[0095] 10: Welding

[0096] 20: Post-processing

Claims

1. A step in which preprocessing is performed on parts for joining; A step of assembling the above preprocessed joining parts; A step in which the above-mentioned joining parts are canned; A step of vacuum testing the canned joint parts; and It includes a step of joining the above-mentioned joining parts in a vacuum state by hot isostatic pressing (HIP) and brazing, A method for joining dissimilar materials using both the HIP method and the brazing method, characterized in that the above-mentioned joining parts include a brazing filler metal.

2. In paragraph 1, At the stage where preprocessing of the above-mentioned joining parts is performed, The above bonding component includes a tungsten block, A method for joining dissimilar materials using the HIP method and the Brazing method at the same time, characterized in that the above tungsten block is heat treated at a temperature of 950 to 1,050 degrees for 3 hours or more in a vacuum atmosphere.

3. In paragraph 1, At the stage where preprocessing of the above-mentioned joining parts is performed, A method for joining dissimilar materials using the HIP method and the Brazing method simultaneously, characterized in that cleaning is performed on the above-mentioned joining parts.

4. In paragraph 1, At the stage where the above preprocessed joining parts are assembled, The above-mentioned joining components are assembled by laminating in order a copper alloy block, a copper plate, a brazing filler, a tungsten block, a molybdenum sheet, and a canning cover, a method for joining dissimilar materials using the HIP method and the Brazing method at the same time.

5. In paragraph 4, At the stage where the above preprocessed joining parts are assembled, A method for joining dissimilar materials using both the HIP method and the Brazing method, characterized in that the canning cover is positioned on the stepped portion of the copper alloy block.

6. In paragraph 4, The above brazing filler metal is, A method for joining dissimilar materials using both the HIP method and the Brazing method, characterized by being a nickel-copper (Ni-Cu) alloy.

7. In paragraph 4, The above tungsten base material, A method of joining dissimilar materials using the HIP method and the Brazing method simultaneously, characterized by being provided in multiple pieces.

8. In paragraph 1, At the stage where the above-mentioned joint parts are canned, A method for joining dissimilar materials using the HIP method and the Brazing method at the same time, characterized in that the inside of the above-mentioned joining parts is sealed so that a vacuum atmosphere is maintained.

9. In paragraph 1, In the step where the joining is performed by hot isostatic pressing (HIP) and brazing of the above-mentioned joining parts in a vacuum state, A method for joining dissimilar materials using the HIP method and the Brazing method at the same time, characterized in that the above-mentioned joining parts are heat-treated at a temperature of 950 to 1,050 degrees for 3 hours or more in an argon (Ar) atmosphere, and an isotropic pressure of 900 to 1,100 bar is applied at the same time.

10. In paragraph 1, After the step of joining the above-mentioned vacuum-state joint parts by hot isostatic pressing (HIP) and brazing, A method for joining dissimilar materials using the HIP method and the Brazing method simultaneously, characterized in that it includes a step of performing shape processing on the above-mentioned joining parts where joining has been performed.

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