Diffusion welding process for large-area thin plate structural member

Abstract

The invention relates to the technical field of diffusion welding, in particular to a diffusion welding process for a large-area thin-plate structural member, which comprises the following steps of: additionally arranging flexible plates on contact surfaces of an upper welding tool and a corresponding to-be-welded plate as well as a lower welding tool and the corresponding to-be-welded plate respectively; and during diffusion welding, welding pressure is transmitted to the to-be-welded plate through the flexible plate. The diffusion welding process for the large-area thin-plate structural member aims to solve the problem that random and irregular defects are generated due to the fact that the surface of a plate of the large-area thin-plate structural member is uneven.

Description

Technical Field

[0001] The invention relates to the technical field of diffusion welding, and in particular to a diffusion welding process for large-area thin-plate structural parts. Background Art

[0002] With the continuous development of aerospace technology, the speed of aircraft is getting higher and higher, which puts higher requirements on the temperature resistance of aircraft. However, the temperature resistance of materials is an inherent property of materials. In order to increase the use temperature of materials, it is necessary to optimize the structural design. There are two main solutions. One is to design cooling channels in the structure and use active cooling, passive cooling and other methods to cool the high-temperature side, thereby reducing the temperature of the high-temperature side to ensure the normal use of components. Its structure is as follows Figure 1 In order to realize the manufacture of such a structure, it is necessary to weld the high-temperature side plate and the low-temperature side plate together by welding. As shown in the figure, the weld position is the welding surface to be welded. Compared with the cooling channel, the area to be welded is very large; the second is to use the heat resistance of different materials, the high-temperature side uses a material with high heat resistance, and the low-temperature side uses a material with low heat resistance. The structure is as follows Figure 2 As shown, two different materials are connected by welding. It can be seen from the figure that the entire surface of the plate is the area to be welded.

[0003] For the above structure, diffusion welding is adopted, that is, the high temperature side plate and the low temperature side plate are brought into contact and welded under pressure. The quality of welding directly affects the use and life of the component. Figure 3 It can be seen that during the welding process, the welding pressure is applied to the surface of the sheet to be welded through the welding tooling, and is transmitted to the weld through the sheet itself to achieve the connection of the two sheets. In the actual welding process, the end face of the sheet to be welded that contacts the tooling is not completely flat, and there may be unevenly distributed depressions and protrusions in some parts, resulting in the surface of the tooling and the sheet not being in complete contact. In welding, since the welding pressure is calculated according to the entire welding surface, the pressure is very large relative to the protrusions. During the welding process, the protrusions can be flattened, and then a good connection can be achieved at the protrusions. However, for the depressions, since the depressions are relatively small relative to the entire welding surface, the pressure value of the surface to be welded is less affected. Therefore, it can be basically considered that the pressure value at the welding interface is close to the theoretical value. During the welding process, since the welded plate is a thin plate, the overall deformation is very small. When the deformation is lower than the depth of the depression, the pressure of the tooling is not transmitted to the welding surface corresponding to the depression. That is, during the welding process, no pressure is applied to the welding surface corresponding to the depression, and an unwelded area is formed here. Since the position, size and depth of the depression of the actual plate are uncertain, the unwelded area also appears random.

[0004] Therefore, the inventor provides a diffusion welding process for large-area thin-plate structural parts. Summary of the invention

[0005] (1) Technical issues to be solved

[0006] The embodiment of the present invention provides a diffusion welding process for a large-area thin plate structural member, which solves the technical problem of random and irregular defects of the large-area thin plate structural member caused by the concave and convex unevenness of the plate surface.

[0007] (2) Technical solution

[0008] The present invention provides a diffusion welding process for a large-area thin plate structural member, comprising the following steps:

[0009] Adding flexible plates to the contact surfaces of the upper welding tool, the lower welding tool and the corresponding plates to be welded;

[0010] During diffusion welding, welding pressure is transmitted to the plate to be welded through the flexible plate.

[0011] Furthermore, the deformation of the flexible plate at the welding temperature is greater than that of the plate to be welded.

[0012] Furthermore, the first yield strength δ of the flexible plate is s1 Less than the second yield strength δ of the plate to be welded s2 .

[0013] Furthermore, the first yield strength δ s1 The second yield strength δ s2 0.4 to 0.8 times.

[0014] Furthermore, the thickness of the flexible board is less than or equal to the thickness of the board to be welded.

[0015] Furthermore, the thermal expansion coefficient of the flexible plate is the same as that of the plate to be welded.

[0016] Furthermore, there is no adverse reaction between the two flexible plates and the corresponding plates to be welded.

[0017] Furthermore, the thickness of the plate to be welded is ≥0.3 mm.

[0018] Furthermore, the thickness of the plate to be welded is ≤2.5 mm.

[0019] Furthermore, there is no adverse reaction between the two flexible plates and the corresponding upper welding tooling and lower welding tooling.

[0020] (3) Beneficial effects

[0021] In summary, the present invention achieves diffusion connection of large-area thin plate structures by adding flexible plates, and the unwelded area is significantly reduced. This method can improve the welding quality of large-area thin plate structures and ensure the development quality of components during the production process. At the same time, the operation process is simple, and only the flexible plate is laid in the conventional diffusion welding process, which has the effects of high efficiency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 It is a structural schematic diagram of a large-area thin-walled structural part;

[0024] Figure 2 It is a schematic diagram of the structure of another large-area thin-walled structural part;

[0025] Figure 3 It is a schematic diagram of the diffusion welding structure of existing large-area thin-walled structural parts;

[0026] Figure 4 It is a schematic flow chart of a diffusion welding process for a large-area thin-walled structural part provided by an embodiment of the present invention;

[0027] Figure 5 It is a structural schematic diagram of diffusion welding of a large-area thin-walled structural part provided by an embodiment of the present invention;

[0028] Figure 6 This is a diagram of ultrasonic nondestructive testing results of a large-area thin-walled structural member using a non-flexible plate to transmit pressure, provided by an embodiment of the present invention;

[0029] Figure 7 This is a diagram of ultrasonic nondestructive testing results of a large-area thin-walled structural part that does not use a non-flexible plate to transmit pressure.

[0030] In the figure:

[0031] 1-upper welding tool; 2-lower welding tool; 3-plate to be welded; 4-flexible plate; 5-low-temperature side plate; 6-high-temperature side plate; 7-cooling channel; 8-weld. DETAILED DESCRIPTION

[0032] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0033] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0035] Figure 4 is a flow chart of a diffusion welding process for a large-area thin plate structural member provided by an embodiment of the present invention, see Figure 4 , the welding process may include the following steps:

[0036] S100, a flexible plate 4 is added to the contact surfaces of the upper welding tool 1, the lower welding tool 2 and the corresponding plate 3 to be welded.

[0037] Specifically, Figure 5 As shown, two flexible plates 4 are added to the contact surfaces of the upper welding fixture 1, the lower welding fixture 2 and the plate 3 to be welded, respectively. The function of the flexible plate 4 is to produce a large deformation during the welding process, and then embed into the concave part of the plate 3 to be welded, so that the plate 3 to be welded, the flexible plate 4, the upper welding fixture 1, and the lower welding fixture 2 are completely in contact on the plane. In order to achieve the above purpose, the following designs are made to the flexible plate 4:

[0038] 1. There should be no adverse reaction between the flexible board 4 and the sheet 3 to be welded, otherwise the performance of the sheet 3 to be welded will be affected; that is, the main component of the flexible board 4 cannot react chemically with the sheet 3 to be welded to generate a low-melting-point eutectic. At the same time, the material composition of the flexible board should be reasonably selected according to the composition and use environment of the sheet to be welded. For example, when there is no Al, Fe and other elements in the sheet to be welded, the Al, Fe and other elements in the flexible board material also need to be reasonably controlled. It is recommended to use materials that do not contain Al and Fe elements.

[0039] 2. The melting point of the flexible board 4 is higher than the welding temperature of the board 3 to be welded. At the same time, at this welding temperature, the yield strength δ of the flexible board 4 is s柔性板 Less than the yield strength δ of the plate to be welded 3 s待焊板材, that is, it can be deformed greatly to make up for the depression of the plate 3 to be welded; however, the deformation of the flexible plate 4 cannot be too large. Since the plate 3 to be welded is a thin plate, the gap between the upper welding fixture 1 and the lower welding fixture 2 is small. When the flexible plate 4 is greatly deformed, it is easy to directly contact with the upper welding fixture 1 and the lower welding fixture 2, affecting the welding process. Therefore, the design δ s柔性板 =(0.4~0.8)δ s待焊板材 .

[0040] 3. The thickness of the flexible board 4 should not be too large. This is because once the thickness of the flexible board 4 is too large, the deformation during welding is mainly concentrated on one side of the flexible board 4, and no plastic deformation occurs between the two sheets 3 to be welded, and the void cannot be bridged, which affects the welding quality. Therefore, the thickness of the flexible board 4 should not be greater than the thickness of the sheets 3 to be welded;

[0041] When the flexible board 4 is too thin, it is impossible to achieve complete contact between the surface to be welded, the flexible board, and the tooling surface on the plane. Therefore, it is necessary to reasonably select the thickness of the flexible board. Due to the uneven thickness of the material itself and the difference in the flatness of the tooling plane, the minimum thickness of the flexible board 4 is D = (d1 + d2) * (3 ~ 5). Among them, d1 is the thickness deviation value of the plate to be welded, d2 is the tooling plane deviation value, and the deviation of d1 + d2 is required to be around 0.1mm, so the minimum thickness of the flexible board 4 should reach 0.3 ~ 0.5mm;

[0042] Therefore, this patent is mainly applicable to thin plates with a thickness of not less than 0.3 mm. When the thickness of the plate to be welded is less than 0.3 mm, this solution can also be adopted, but it is recommended that the thickness of the flexible plate be controlled within 0.1 to 0.3 mm;

[0043] When the thickness of the plate to be welded is 0.3-0.8mm, the thickness of the flexible plate is 0.3-0.6mm;

[0044] When the thickness of the plate to be welded is 0.8-1.5mm, the thickness of the flexible plate is 0.6-1.2mm;

[0045] When the thickness of the plate to be welded is 1.5-2.5 mm, the thickness of the flexible plate is 1.2-1.8 mm;

[0046] When the thickness of the plate to be welded is greater than 2.5mm, it is generally not necessary to use a flexible plate. If used, the thickness is recommended not to exceed 2.5mm;

[0047] The thickness of the above-mentioned flexible board is selected when the deviation requirement of d1+d2 is about 0.1mm. As the area of ​​the board to be welded increases, the deviation value of d1+d2 may increase. The thickness of the flexible board can be increased proportionally according to the deviation value according to the above requirements.

[0048] 4. The thermal expansion coefficient of the selected flexible board 4 material should be as close as possible to that of the plate 3 to be welded, in order to ensure that the deformation degree deviation of the flexible board 4 and the plate 3 to be welded is small during the temperature rise and fall stages, thereby reducing the shear force between the two and ensuring that the plate 3 to be welded is not deformed after welding. However, it is difficult to ensure that the thermal expansion coefficient of the flexible board 4 is consistent with that of the material to be welded in actual material selection, so it is necessary to control the deviation value of the thermal expansion coefficient of the two. The specific requirements are as follows:

[0049] |α 柔性板 -α 待焊接板 |≤3×10 -6 / K;

[0050] In the formula, α 柔性板 is the thermal expansion coefficient of the flexible board, α 待焊接板 is the thermal expansion coefficient of the plate to be welded.

[0051] 5. There is no adverse reaction between the flexible board 4 and the welding tooling, that is, the main component of the material of the flexible board 4 cannot chemically react with the materials of the upper welding tooling 1 and the lower welding tooling 2 to generate a low-melting point eutectic, causing failure of the upper welding tooling 1, the lower welding tooling 2 and the flexible board 4.

[0052] S200 , during diffusion welding, welding pressure is transmitted to the plate 3 to be welded via the flexible plate 4 .

[0053] Specifically, the diffusion welding process was used to weld high-temperature alloy plates. The dimensions of the components were 240*700mm, and the thickness was 0.4+0.6mm. After welding, the plates were subjected to ultrasonic nondestructive testing. The test results showed that the welding interface was well connected, and the welding rate was greater than 95%. Compared with the components without the addition of flexible plates (welding rate of about 90%), the welding rate was significantly improved, and the unwelded area was significantly reduced. That is, the diffusion welding process was used to achieve a one-time high-quality connection of large-area thin plate structural parts. Compared with the thin plates that did not use the diffusion welding process, the welding quality was significantly improved. At the same time, due to the overall heating of the parts, the flatness of the parts after welding was good, and there was no effect on the developed thin plate structural parts.

[0054] Example 1

[0055] This embodiment uses high-temperature alloy GH3536 as a flexible plate to diffusely connect high-temperature alloy thin plates, and the diffusion welding material is GH3128. The thickness of the GH3128 thin plates is 0.6×240×240mm, 0.8×240×240mm, and 0.6×240×240mm, respectively. In order to verify that the proposed method can achieve high-quality connection of large-area thin plate structural parts, there is no groove on the GH3128 plate, and the diffusion connection of the entire plate is directly carried out. The welding area is 57600mm 2The flexible board is made of a material close to the base material to be welded, and its high temperature strength is lower than that of the material of GH3128. In summary, GH3536 is selected (the material of the flexible board is not unique, it only needs to meet the flexible board selection requirements mentioned above). The thickness of the GH3536 board is 1mm, and it is welded using a radiation heating vacuum diffusion welding equipment. When the vacuum degree is lower than 8×10 -3 Pa, and the process parameters of the welding process can be program-controlled and manually controlled. Conventional mechanical grinding, pickling and other methods are used to remove the oxide film on the surface to be welded, and then it is cleaned with acetone or alcohol. Apply solder stopper evenly on the upper and lower surfaces of the flexible board, place a piece of flexible board on the lower welding fixture, then place the material to be welded on the upper surface of the flexible board, and then place another flexible board on the upper surface of the sheet to be welded, and finally place the upper welding fixture on the upper surface of the flexible board to achieve the final assembly. The assembled weldment is placed in a diffusion device, and the thermocouple contacts the weldment to ensure real-time monitoring of the weldment temperature during the welding process. After the weldment is installed, close the vacuum chamber and turn on the vacuum pump. When the vacuum degree is lower than 8×10 -3 Pa, welding temperature 1160 ℃, pressure 8MPa, welding time 180min. After welding, cut off the power supply, cool the weldment to room temperature under the original vacuum condition, and take out the weldment from the vacuum chamber to prevent oxidation of the weldment at high temperature. After taking out the sample, remove the upper and lower flexible boards, polish the surface of the parts, and perform ultrasonic nondestructive testing. The test results are as follows: Figure 6 As shown, the white area is the unwelded area. It can be seen from the figure that the overall component welding quality is good, and only some unwelded areas exist in the outer edge margin area of ​​the parts.

[0056] In order to further verify the effect of the diffusion welding process of the present invention, the same operation process and process parameters are used, and the materials are consistent with the above test. The non-flexible plate is used to carry out diffusion connection of the thin plate structure. After the connection, ultrasonic non-destructive testing is carried out. The test results are as follows Figure 7 As shown in the figure, it can be seen that there are a large number of irregularly distributed defects in the welded parts. Figure 6 and Figure 7 By comparison, it can be clearly found that the method proposed in this patent significantly improves the welding quality of large-area thin-plate structural parts.

[0057] In summary, the diffusion welding process of the present invention can achieve high-quality connection of large-area thin plates, and the operation process is simple and efficient, and has no adverse effects on the welded parts.

[0058] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of brevity, a detailed description of known methods and technologies is omitted here.

[0059] The above are only embodiments of the present application and are not limited to the present application. For those skilled in the art, the present application may have various changes and variations without departing from the scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A diffusion welding process for large-area thin plate structural parts, characterized in that: The process includes the following steps: A flexible plate (4) is respectively provided on the contact surfaces of the upper welding tool (1), the lower welding tool (2) and the corresponding plate material to be welded (3); During diffusion welding, welding pressure is transmitted to the plate (3) to be welded via the flexible plate (4).

2. The diffusion welding process for large-area thin plate structural parts according to claim 1, characterized in that: The deformation amount of the flexible plate (4) at the welding temperature is greater than that of the plate (3) to be welded.

3. The diffusion welding process for large-area thin plate structural parts according to claim 2, characterized in that: The first yield strength δ of the flexible plate (4) s1 Less than the second yield strength δ of the plate to be welded (3) s2 .

4. The diffusion welding process for large-area thin plate structural parts according to claim 3 is characterized in that: The first yield strength δ s1 The second yield strength δ s2 0.4 to 0.8 times.

5. The diffusion welding process for large-area thin plate structural parts according to claim 1, characterized in that: The thickness of the flexible plate (4) is less than or equal to the thickness of the plate (3) to be welded.

6. The diffusion welding process for large-area thin plate structural parts according to claim 1, characterized in that: The thermal expansion coefficient of the flexible plate (4) is the same as that of the plate to be welded (3).

7. The diffusion welding process for large-area thin plate structural parts according to claim 1, characterized in that: There is no adverse reaction between the two flexible plates (4) and the corresponding plates (3) to be welded.

8. The diffusion welding process for large-area thin plate structural parts according to claim 1, characterized in that: The thickness of the plate (3) to be welded is ≥0.3 mm.

9. The diffusion welding process for large-area thin plate structural parts according to claim 8, characterized in that: The thickness of the plate (3) to be welded is ≤2.5 mm.

10. The diffusion welding process for large-area thin plate structural parts according to claim 1, characterized in that: There is no adverse reaction between the two flexible plates (4) and the corresponding upper welding tool (1) and lower welding tool (2).

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