Diffusion welding sheath and preparation method thereof

Abstract

The invention discloses a diffusion welding sheath and a preparation method thereof, and relates to the technical field of sheaths, and the preparation method comprises the following steps: two wafers and a strip plate are dried after alkali washing, and the length of the strip plate is the same as the perimeter of the wafers; then cutting a graphite flake with the same shape as the two wafers and the long strip plate, correspondingly attaching and pressing the graphite flake on the two wafers and the long strip plate, spraying a layer of nano ZrO2 sol on the graphite flake, and sintering and molding; rolling a long strip plate into a cylinder by using a rolling machine, wherein the graphite flake and the nano ZrO2 layer are positioned on the inner side; putting the cylinder and one of the wafers into a clamp, carrying out electron beam welding, and welding the wafer at one end of the cylinder to form a sheath precursor; a to-be-welded product is put into the sheath precursor, and then electron beam welding is conducted on the other wafer and the unclosed end of the cylinder, so that a complete sheath is formed; the sheath is good in quality, good in compactness at the welding seam, small in thermal deformation degree, not prone to cracking, high in manufacturing efficiency and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of sheaths, and particularly relates to a diffusion welding sheath and a preparation method thereof. Background Art

[0002] In semiconductor manufacturing, aerospace, and nuclear power industries, as a key sealing component, the diffusion welding sheath is widely used for encapsulating and protecting precision components in vacuum or high-temperature and high-pressure environments. The sheath needs to have high sealing performance, excellent corrosion resistance, and long-term thermal stability. The core of its preparation process lies in achieving high-quality connection of the weld seam.

[0003] However, there are many limitations in traditional sheath preparation technologies. For example, in the existing technology, connection is achieved by filling with low-melting-point metals, but the solder is prone to forming brittle phases, resulting in low weld strength and poor high-temperature resistance. In high-temperature cyclic working conditions, the brazed joint is prone to cracking, and the leakage rate is difficult to meet the semiconductor-level sealing requirements. At the same time, in the existing technology, when degassing the inside of the sheath, usually a degassing pipe is connected to the surface of the sheath, and then the whole sheath is placed in a degassing furnace to evacuate and heat. After reaching the vacuum degree, the end of the degassing pipe is clamped off and melted to achieve sealing. However, the entire degassing process is manually controlled, the operation is cumbersome, the duration is as long as more than 3 to 4 hours, the efficiency is extremely low, and the sealing effect of the degassing pipe cannot be accurately controlled during the clamping-off process, and the sealing performance of the obtained sheath is difficult to guarantee. Summary of the Invention

[0004] The purpose of the present invention is to provide a diffusion welding sheath and a preparation method thereof, and solve the following technical problems:

[0005] How to improve the quality and preparation efficiency of the diffusion welding sheath.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In the first aspect, the present invention discloses a preparation method of a diffusion welding sheath, including the following steps:

[0008] Step 1: Ultrasonically alkali-wash two round wafers and a long strip plate and then dry them. The length of the long strip plate is the same as the circumference of the round wafer. Then cut graphite sheets with the same shapes as the two round wafers and a long strip plate, and press them correspondingly on the two round wafers and a long strip plate. Then spray a layer of nano-ZrO 2 sol on the graphite sheets and sinter them into shape;

[0009] Step 2: Roll a long strip plate into a cylinder with a rolling machine. The graphite sheet and the nano-ZrO 2 layer are located on the inner side;

[0010] Step 3: Place the cylinder and one of the circular plates in a fixture and perform electron beam welding to weld the circular plate to one end of the cylinder, forming a preform of the cladding.

[0011] Step 4: Place the product to be welded in the preform of the cladding, and then perform electron beam welding on the other circular plate and the unclosed end of the cylinder to form a complete cladding.

[0012] Further, in Step 1, the materials of the circular plates and the long strip plates are aluminum or stainless steel.

[0013] Further, in Step 1, the specific method of ultrasonic alkali cleaning is as follows: Place two circular plates and a long strip plate in a sodium hydroxide solution with a mass fraction of 5-8%, and clean them with ultrasonic waves at 40 Hz for 5 minutes.

[0014] Further, in Step 1, the thickness of the graphite sheet is 0.1-0.3 mm, its thermal conductivity is 100-150 W / (m·K), and the compression ratio is ≥30%.

[0015] Preferably, the thickness of the graphite sheet is 0.2 mm, its thermal conductivity is 125 W / (m·K), and the compression ratio is 50%.

[0016] Further, in Step 1, the method of correspondingly laminating and pressing the graphite sheet on two circular plates and a long strip plate is as follows: Roughen both sides of the graphite sheet, then correspondingly stack it on the circular plate or the long strip plate, and then apply a pressure of 0.5-1.0 MPa to make the graphite sheet closely combine with the circular plate or the long strip plate.

[0017] Preferably, a stamping machine is used for pressing, and the applied pressure is preferably 0.8 MPa.

[0018] Further, in Step 1, the nano-ZrO 2 sol has a thickness of 50-100 nm; preferably 80 nm.

[0019] Further, in Step 1, the specific conditions for sintering and forming the nano-ZrO 2 sol are as follows: Sinter at 1200-1400 °C for 3-5 s.

[0020] Preferably, the specific conditions for sintering and forming the nano-ZrO 2 layer are as follows: Sinter at 1300 °C for 4 s.

[0021] Further, in Step 3, the electron beam welding adopts a three-stage welding process, which is specifically as follows:

[0022] Process 1: At a vacuum degree of 5×10 -3Under a pressure of [[Pa]], with an accelerating voltage of 60 Kv, a beam current of 10 - 15 mA, and a speed of 1000 - 1200 mm / min, the cylinder and the wafer are preliminarily welded.

[0023] Process Step 2: The vacuum degree is increased to 1×10 -3 Pa, with an accelerating voltage of 60 Kv, a beam current of 30 - 50 mA, and a speed of 600 - 800 mm / min to complete deep penetration welding.

[0024] Process Step 3: With an accelerating voltage of 60 Kv, a beam current of 15 - 20 mA, and a speed of 1200 - 1500 mm / min, surface finishing is carried out.

[0025] Furthermore, in Step 4, the method of electron beam welding is the same as that in Step 3.

[0026] Based on this, a preferred method for preparing a diffusion welding jacket is obtained, including the following steps:

[0027] Step 1: Place two wafers and a long strip of plate in a sodium hydroxide solution with a mass fraction of 5 - 8%, clean them with ultrasonic waves at 40 Hz for 5 min, and dry them with a hair dryer; then cut graphite sheets with the same shape as the two wafers and the long strip of plate, a thickness of 0.2 mm, a thermal conductivity of 125 W / (m·K), and a compression ratio of 50%, and stack them correspondingly on the two wafers or the long strip of plate, and use a stamping machine to apply a pressure of 0.8 MPa to fix and stack the graphite sheets with the corresponding two wafers and the long strip of plate; then coat a layer of nano - ZrO 2 sol with a thickness of 80 nm on the graphite sheet, and place it in a sintering furnace to sinter at 1300 °C for 4 s to fix the nano - ZrO 2 layer on the graphite sheet.

[0028] Step 2: Roll a long strip of plate into a cylinder with a rolling machine, and the graphite sheet and the nano - ZrO 2 layer are located inside.

[0029] Step 3: Place the cylinder and one of the wafers in a fixture and perform electron beam welding to weld the wafer to one end of the cylinder to form a pre - jacket; the electron beam welding process is divided into three stages:

[0030] (1) Under a vacuum degree of 5×10 -3 Pa, with an accelerating voltage of 60 Kv, a beam current of 12 mA, and a speed of 1100 mm / min, the cylinder and the wafer are preliminarily welded.

[0031] (2) The vacuum degree is increased to 1×10 -3 Pa, with an accelerating voltage of 60 Kv, a beam current of 40 mA, and a speed of 700 mm / min to complete deep penetration welding.

[0032] (3) Perform surface finishing at an accelerating voltage of 60 Kv, a beam current of 18 mA, and a speed of 1350 mm / min;

[0033] (4) Place the product to be welded into the pre - body of the cladding, then perform electron beam welding on the unclosed end of the cylinder with another wafer. The electron beam welding method is the same as that in step three, thereby forming a complete cladding.

[0034] In a second aspect, the present invention also discloses a diffusion - welded cladding, which is prepared by the preparation method of the diffusion - welded cladding as described above.

[0035] Advantages of the present invention:

[0036] 1. During the preparation of the diffusion - welded cladding of the present invention, the electron beam welding method is used to weld the weld of the cladding in a vacuum environment, eliminating the degassing pipe in the traditional cladding preparation and the subsequent vacuum - closing operation. This reduces the preparation time. Electron beam welding is an automatic welding process, replacing manual welding with a machine, improving the consistency and coherence of welding. Multiple claddings can be welded simultaneously, improving work efficiency, reducing work intensity, and greatly saving production costs. At the same time, during the electron beam welding process, by controlling the welding parameters and vacuum degree in a segmented manner, in the first stage, the residual stress of the materials at the weld is eliminated first to avoid cracks caused by sudden heating. In the second stage, deep penetration welding is achieved through a high - energy density to ensure the density of the weld. In the third stage, surface finishing is carried out to reduce pores and thermal deformation. At the same time, the vacuum degree is moderately increased in the second stage to reduce gas interference, further improving the welding performance, resulting in a better welding effect at the weld, ensuring a good weld morphology, uniform forming without defects, and improving the sealing vacuum degree of the cladding weld and the quality of the weld.

[0037] 2. During the preparation of the diffusion - welded cladding of the present invention, graphite sheets and nano - ZrO 2 sol are provided on the inner side of the cladding. Among them, the graphite sheets can effectively absorb the thermal expansion difference of the outer - layer metal, prevent the cladding from cracking in a thermal environment, and have no volatile substances released in a vacuum environment, not polluting the cavity of the welded cladding. They can also enhance the mechanical strength of the cladding. The nano - ZrO 2 sol removes the solvent after sintering, leaving a nano - ZrO 2 layer. Through electron beam in - situ high - temperature sintering, the high - temperature resistance and corrosion resistance can be enhanced, realizing the protection of the product to be welded inside the cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] Figure 1It is a schematic structural diagram of two stainless - steel circular wafers and a stainless - steel long strip in Step 1 of Embodiment 1 of the present invention;

[0040] Figure 2 It is a schematic structural diagram of the complete diffusion - welded jacket prepared in Step 4 of Embodiment 1 of the present invention. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and are carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. The materials used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0043] Embodiment 1

[0044] Prepare a diffusion - welded jacket:

[0045] Step 1. Refer to Figure 1 , place two stainless - steel circular wafers (circumference 50 cm, thickness 5 mm) and a stainless - steel long strip (length 50 cm, width 30 cm, thickness 5 mm) in an ultrasonic cleaning machine. The ultrasonic cleaning machine is filled with a sodium hydroxide solution with a mass fraction of 7%. Then, clean with ultrasonic waves at 40 Hz for 5 min and dry with a hair dryer. Then, cut graphite sheets with the same shape as the two circular wafers and the long strip, with a thickness of 0.2 mm, a thermal conductivity of 125 W / (m·K), and a compression ratio of 50%, and stack them correspondingly on the two circular wafers or the long strip. Use a stamping machine to apply pressure at 0.8 MPa to fix and stack the graphite sheets with the corresponding two circular wafers and the long strip. Then, use an atomizing spray gun to spray a layer of nano - ZrO 2 sol with a thickness of 80 nm on the graphite sheets, and place them in a sintering furnace to sinter at 1300 °C for 4 s to fix the nano - ZrO 2 layer on the graphite sheets;

[0046] Step 2. Roll a long strip into a cylinder with a rolling machine, and the graphite sheets and the nano - ZrO 2 layer are located inside;

[0047] Step 3. Put the cylinder and one of the circular wafers into a fixture, and the nano - ZrO 2 layer is located inside; perform electron - beam welding. First, at a vacuum degree of 5×10 -3Under a pressure of -3 Pa, with an accelerating voltage of 60 kV, a beam current of 12 mA, and a speed of 1100 mm / min, the cylinder and the wafer are preliminarily welded. After welding one circle, the vacuum degree is then increased to 1×10

[0048] Step Four. Please refer to Figure 2 and place the product to be welded into the pre-form of the jacket. Then, electron beam welding is performed on the other wafer and the unclosed end of the cylinder, and the nano-ZrO 2 layer is located on the inner side. The welding method is the same as the electron beam welding method in Step Three, thereby forming a complete diffusion welding jacket with a total duration of <0.5 h.

[0049] Example 2

[0050] Preparation of the diffusion welding jacket:

[0051] Compared with Example 1, the only difference is that in Step Three and Step Four, the process of electron beam welding is as follows: First, under a vacuum degree of 5×10 -3 Pa, with an accelerating voltage of 60 kV, a beam current of 10 mA, and a speed of 1000 mm / min, the cylinder and the wafer are preliminarily welded. After welding one circle, the vacuum degree is then increased to 1×10 -3 Pa, with an accelerating voltage of 60 kV, a beam current of 30 mA, and a speed of 600 mm / min to complete the keyhole welding. After welding one circle, finally, surface finishing is performed at an accelerating voltage of 60 kV, a beam current of 15 mA, and a speed of 1200 mm / min. Other steps and conditions remain the same, and finally a complete diffusion welding jacket is obtained with a total duration of <0.5 h.

[0052] Example 3

[0053] Compared with Example 1, the only difference is that in Step Three and Step Four: the process of electron beam welding is as follows: First, under a vacuum degree of 5×10 -3 Pa, with an accelerating voltage of 60 kV, a beam current of 15 mA, and a speed of 1200 mm / min, the cylinder and the wafer are preliminarily welded. After welding one circle, the vacuum degree is then increased to 1×10 -3 Pa, with an accelerating voltage of 60 kV, a beam current of 50 mA, and a speed of 800 mm / min to complete the keyhole welding. After welding one circle, finally, surface finishing is performed at an accelerating voltage of 60 kV, a beam current of 20 mA, and a speed of 1500 mm / min. Other steps and conditions remain the same, and finally a complete diffusion welding jacket is obtained with a total duration of <0.5 h.

[0054] Example 4

[0055] Compared with Example 1, the only difference is that in Step 1: the thickness of the graphite sheet used is 0.1 mm, the thermal conductivity is 100 W / (m·K), and the compression ratio is 50%; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration of 0.5 h.

[0056] Example 5

[0057] Compared with Example 1, the only difference is that in Step 1: the thickness of the graphite sheet used is 0.3 mm, the thermal conductivity is 150 W / (m·K), and the compression ratio is 50%; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration of 0.5 h.

[0058] Example 6

[0059] Compared with Example 1, the only difference is that in Step 1: the thickness of the nano-ZrO 2 layer is 50 nm, and the sintering condition is sintering at 1200 °C for 5 s; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration < 0.5 h.

[0060] Example 7

[0061] Compared with Example 1, the only difference is that in Step 1: the thickness of the nano-ZrO 2 layer is 100 nm, and the sintering condition is sintering at 1400 °C for 3 s; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration < 0.5 h.

[0062] Comparative Example 1

[0063] Compared with Example 1, the only difference is that in Step 1: no graphite sheet is provided on the two wafers and one long strip plate, and nano-ZrO 2 is directly coated and sintered into shape; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration < 0.5 h.

[0064] Comparative Example 2

[0065] Compared with Example 1, the only difference is that in Step 1: nano-ZrO 2 is not coated on the graphite sheet; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration < 0.5 h.

[0066] Comparative Example 3

[0067] Compared with Example 1, the only difference is that in Step 1: a graphite sheet and nano-ZrO 2; Other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration of <0.5 h.

[0068] Comparative Example 4

[0069] Compared with Example 1, the only difference is that in Steps 3 and 4: when performing electron beam welding, segmented welding is not carried out. Instead, directly under a vacuum of 5×10 -3 Pa, with an acceleration voltage of 60 Kv, a beam current of 15 mA, and a speed of 1200 mm / min, the cylinder and the wafer are welded in three circles; other steps and conditions remain the same, and finally a complete diffusion welding sheath is obtained, with a total duration of <0.5 h.

[0070] Comparative Example 5

[0071] The diffusion welding sheath is prepared by the prior art, and the specific steps are as follows:

[0072] Preparation of the diffusion welding sheath:

[0073] Step 1: Place two stainless steel wafers (circumference 50 cm, thickness 5 mm), a stainless steel long strip plate (length 50 cm, width 30 cm, thickness 5 mm, with a degassing port on its surface), and a degassing tube in an ultrasonic cleaner. The ultrasonic cleaner is filled with a sodium hydroxide solution with a mass fraction of 7%, and then ultrasonically cleaned for 5 min at 40 Hz, and dried with a hair dryer;

[0074] Step 2: Roll a long strip plate into a cylinder with a rolling machine, and the graphite sheet and the nano-ZrO 2 layer are located on the inner side;

[0075] Step 3: Place the product to be welded in the cylinder, then weld the two wafers to the two ends of the cylinder by argon arc welding, and then weld the degassing tube to the degassing port on the surface of the cylinder by argon arc welding to form a pre-sheath;

[0076] Step 4: Place the pre-sheath in a degassing furnace, heat and evacuate to a vacuum of 5×10 -3 Pa, and then use a pair of tongs to cut off the head of the degassing tube, and the head of the degassing tube is melted and sealed, thereby forming a complete diffusion welding sheath, with a total duration of 4.5 h.

[0077] Perform performance tests on the diffusion welding sheaths prepared in Examples 1-5 and Comparative Examples 1-5, including the detection of the compactness, leakage rate, and thermal deformation amount at the weld. The detection methods are as follows:

[0078] Compactness at the weld: Refer to ISO 17640 "Weld Ultrasonic Testing Code";

[0079] Leakage rate: Using the helium mass spectrometry leak detection method, connect the shroud to a helium gas spray gun, spray helium gas on the weld surface, and the mass spectrometer monitors the helium ion current signal in real time. The leakage rate calculation formula is: Q = I / S; where I is the ion current intensity and S is the calibration sensitivity.

[0080] Thermal deformation: Referring to digital image correlation (DIC) technology, capture the displacement of the speckle pattern on the shroud surface at high temperature through a high-resolution camera: Spray a high-temperature heat-resistant speckle coating on the shroud surface, take images during the thermal cycle in real time, and the software analyzes the strain distribution and outputs the maximum strain value.

[0081] The test results of the diffusion-welded shrouds of Examples 1-5 and Comparative Examples 1-5 are listed in Table 1 as follows:

[0082] Table 1

[0083]

[0084]

[0085] Analyzing the data in Table 1, it can be known that compared with Comparative Examples 1-5, the diffusion-welded shrouds prepared in Examples 1-5 have higher density, lower leakage rate and smaller thermal deformation. This shows that the diffusion-welded shrouds of the present invention have better quality.

[0086] Next, compare the production time of Examples 1-5 and Comparative Examples 1-5. It can be found that compared with Comparative Example 5 (4.5 h), the production time of Examples 1-5 and Comparative Examples 1-4 (<0.5 h) is shortened by more than 9 times. This shows that the diffusion-welded shrouds of the present invention not only have good quality, but also the production time is greatly shortened, which can improve the production efficiency of the shrouds and greatly reduce the production cost.

[0087] A detailed description of an embodiment of the present invention has been given above, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for preparing a diffusion welding sheath, characterized in that: The steps include: Step 1: ultrasonically clean two discs and a long strip of plate and then dry them, wherein the length of the long strip is the same as the circumference of the disc; then cut a graphite sheet with the same shape as the two discs and the long strip, and press them on the two discs and the long strip accordingly, and then spray a layer of nano ZrO2 sol on the graphite sheet and sinter it into shape; Step 2: Roll a long strip into a cylinder using a rolling machine, with the graphite sheet and the nano ZrO2 layer located on the inside; Step 3: Place the cylinder and one of the discs into a fixture, perform electron beam welding, and weld the disc to one end of the cylinder to form a sheath precursor; Step 4: Place the product to be welded into the package precursor, and then electron beam weld another disc to the unsealed end of the cylinder to form a complete package.

2. The method for preparing a diffusion welding sheath according to claim 1, characterized in that: In step 1, the disc and the long plate are made of aluminum or stainless steel.

3. The method for preparing a diffusion welding sheath according to claim 1, characterized in that: In step 1, the specific method of ultrasonic alkaline cleaning is: placing two discs and a long strip of plate in a sodium hydroxide solution with a mass fraction of 5-8%, and cleaning them with 40 Hz ultrasonic waves for 5 minutes.

4. The method for preparing a diffusion welding sheath according to claim 1, characterized in that: In step 1, the graphite sheet has a thickness of 0.1-0.3 mm, a thermal conductivity of 100-150 W / (m·K), and a compression rate of ≥30%.

5. The method for preparing a diffusion welding sheath according to claim 4, characterized in that: In step one, the method of pressing the graphite sheet onto two discs and a long plate is as follows: roughening both sides of the graphite sheet respectively, and then superimposing it onto the disc or the long plate accordingly, and then applying a pressure of 0.5-1.0 MPa to tightly bond the graphite sheet to the disc or the long plate.

6. The method for preparing a diffusion welding sheath according to claim 1, characterized in that: In step 1, the thickness of the nano ZrO2 sol is 50-100 nm.

7. The method for preparing a diffusion welding sheath according to claim 6, characterized in that: In step 1, the specific conditions for sintering the nano ZrO2 sol are: sintering at 1200-1400°C for 3-5s.

8. The method for preparing a diffusion welding sheath according to claim 1, characterized in that: In step three, electron beam welding uses a three-stage welding process, as follows: Process 1: At a vacuum degree of 5×10 -3 Pa, with an accelerating voltage of 60 Kv, a beam current of 10-15 mA, and a speed of 1000-1200 mm / min, the cylinder and the wafer were preliminarily welded; Process 2: Vacuum degree increased to 1×10 -3 Pa, accelerating voltage 60Kv, beam current 30-50mA, speed 600-800mm / min to complete deep penetration welding; Process 3: Surface finishing is performed at an accelerating voltage of 60Kv, a beam current of 15-20mA, and a speed of 1200-1500mm / min.

9. The method for preparing a diffusion welding sheath according to claim 8, characterized in that: In step 4, the method of electron beam welding is the same as the method of electron beam welding in step 3.

10. A diffusion welding sleeve, characterized in that: The diffusion welding sheath is prepared by the preparation method of any one of claims 1 to 9.

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