A welding fixture for pulse current assisted brazing of thin sheet parts

Abstract

The application provides a welding tool for pulse current assisted thin plate brazing, which is composed of an arc-shaped base, an L-shaped positioning baffle, a ceramic pressing plate, a ceramic backing plate, a screw, a nut and a clamping screw. The ceramic backing plate is placed on the platform under the arc-shaped base. The L-shaped positioning baffle is fixed on the inner side of the arc-shaped base through the screw, and the lower end surface is matched with the ceramic backing plate in a gap. The to-be-welded sample is placed on the ceramic backing plate, and the ceramic pressing plate is placed on the to-be-welded sample. At this time, the to-be-welded sample and the ceramic pressing plate are in contact with the two inner sides of the L-shaped positioning baffle. The clamping screw is inserted through the threaded hole on the arc-shaped base, and after passing through the threaded hole, the nut is first installed, and then the clamping screw is pressed downward until it contacts the ceramic pressing plate and is pressed tightly. After the clamping screw is pressed tightly, the nut is tightened. The threaded reaction force on one hand makes the clamping screw further pressed tightly, and on the other hand prevents the brazing pressure from being reduced due to the rotation of the clamping screw in the heating process.

Description

Technical Field

[0001] This invention provides a welding fixture for pulse current-assisted brazing of thin plates. It is suitable for brazing thin plates and used to verify the weldability of brazing filler metals. It can also be used for verifying the performance of brazing filler metals before brazing thin-walled capillary tubes made of high-temperature alloys. This invention belongs to the field of aerospace science and technology. Background Technology

[0002] With the advancement of my country's aerospace technology, high-efficiency precooling hypersonic flight propulsion technology has become a hot research area both domestically and internationally in recent years. A highly efficient high-efficiency precooler is a key technology for hypersonic flight propulsion. The high-efficiency precooler mainly consists of an array of high-temperature alloy thin-walled capillary tubes arranged on a diode that carries a cooling medium, forming the core heat exchange module. The connection between the high-temperature alloy thin-walled capillary tubes and the diode is primarily achieved through brazing. Therefore, the solderability of the brazing filler metal and the strength performance testing after brazing have become crucial issues for the heat exchange module. Due to the structural characteristics of the thin-walled capillary tubes and diodes, it is not possible to directly test the post-weld strength performance of the brazing filler metal using the brazed joint between the thin-walled capillary tubes and the diode. Therefore, a full lap joint of thin plates is required for brazing to verify the joint performance of the brazing filler metal.

[0003] Based on the specific operating conditions required for brazing thin-walled capillary tubes in a precooled hypersonic flight propulsion system, a brazing fixture for thin plates needs to be designed to verify the weldability of the brazing filler metal and the strength of the brazed joint. This ensures that the weldability of the filler metal and the strength of the brazed joint meet the usage requirements. Simultaneously, the device should also provide sufficient pressure and stability for the specimen during the brazing process. Currently, no brazing fixture meets these requirements. This invention provides a brazing fixture for thin plates to solve the existing problems. Summary of the Invention

[0004] (1) Purpose

[0005] To ensure that the joint strength of thin-walled capillary welds meets practical requirements, weldability tests and post-weld strength performance tests are conducted on the brazing filler metal. A special tooling for brazing thin plates needs to be designed. This invention provides a welding tooling for pulse current-assisted brazing of thin plates.

[0006] (2) Technical solution

[0007] The present invention provides a welding fixture for pulse current-assisted brazing of thin plate parts, the technical solution of which is as follows:

[0008] Figure 1This is an assembly drawing of a welding fixture for pulse current-assisted brazing of thin plates. It mainly consists of an arc-shaped base 1, an L-shaped positioning baffle 2, a ceramic pressure plate 3, a ceramic pad 4, screws 5, nuts 6, and set screws 7. Their relationship is as follows: the ceramic pad 4 is placed on a platform below the arc-shaped base 1; the L-shaped positioning baffle 2 is fixed to the inner side of the arc-shaped base 1 by screws 5, with its lower end face clearance-fitted to the ceramic pad 4; the test piece to be welded is placed on the ceramic pad 4, and the ceramic pressure plate 3 is placed on the test piece, at which point the test piece and the inner sides of the ceramic pressure plate 3 and the L-shaped positioning baffle 2 are in contact; the set screw 7 is inserted through a threaded hole above the arc-shaped base 1, and after passing through the threaded hole, the nut 6 is installed first, then the set screw 7 is pressed downwards until it contacts and tightens the ceramic pressure plate 3. After the set screw 7 is tightened, the nut 6 is tightened. The reaction force of the threaded connection further tightens the set screw 7 and prevents the set screw 7 from rotating back during the heating process, thus preventing a decrease in brazing pressure.

[0009] The bow-shaped base 1 has the following structural form: Figure 2 As shown, it is made by processing and modifying a block of sheet metal. The material is niobium-tungsten alloy. The whole piece of material is processed into a U-shaped frame with an outer contour of 120mm x 120mm x 100mm and a thickness of 20mm. The inner height of the frame is 80mm and the width is 100mm, which provides enough space to place the test piece to be welded and other parts on the platform below the frame. An M20x2.5 threaded hole is machined in the middle of the upper part of the frame. The set screw 7 is pressed into the ceramic pressure plate 3 through the threaded hole, thereby applying welding pressure to the test piece to be welded. A through hole with a diameter of 16mm is machined on the left side of the frame. The function of this hole is to fix the L-shaped positioning baffle 2 to the inside of the bow-shaped base 1 through the screw 5, and at the same time cooperate with the ceramic pad 4 to allow the L-shaped positioning baffle 2 to rotate.

[0010] The L-shaped positioning baffle 2 has the following specific structural form: Figure 3 It is manufactured from block-shaped plates and is made of niobium-tungsten alloy. The L-shaped positioning baffle is 100mm long on each side, 10mm thick on each side, and 70mm high. An M16x2 threaded hole is machined on one side of the L-shape for fixing it to the bow-shaped base 1 with screw 5. The main function of the L-shaped positioning baffle 2 is to constrain the freedom of the test piece under the pressure applied by the set screw 7, preventing the test piece from rotating and shifting under the pressure of the set screw, thus reducing the welding surface area and causing solder loss. The 90mmx90mm area inside the L-shaped positioning baffle 2 is the space where the test piece can be placed.

[0011] The ceramic pressure plate 3 and ceramic pad 4 are zirconia ceramic plates of 80mm x 80mm x 10mm and 100mm x 100mm x 10mm respectively. Their main function is to isolate the test piece to be welded, preventing the test piece from being diffusely welded to the tooling after being heated. The ceramic pressure plate 3 also disperses the pressure applied by the set screw 7, ensuring that the surface of the test piece to be welded is evenly stressed.

[0012] The screw 5 is a standard M16x30 screw, the nut 6 is a standard M20 coarse-thread nut, and the set screw 7 is a standard M20x70 set screw; all three are made of niobium-tungsten alloy. The main function of screw 5 is to fix the L-shaped positioning block 2. The main function of set screw 7 is to provide vertically downward welding pressure on the ceramic pressure plate 3. The main function of nut 6 is to prevent set screw 7 from loosening during heating, thus preventing unstable welding pressure.

[0013] (3) Advantages and benefits

[0014] This invention addresses the specific requirements of brazing thin-walled capillary tubes in precoolers of hypersonic flight propulsion systems with strong precooling. To verify the weldability of the brazing filler metal and the strength of the joint, a welding fixture for pulsed current-assisted brazing of thin-plate components is provided. The advantages are mainly reflected in: 1. The baffles on both sides of the fixture constrain the horizontal freedom of the workpiece, preventing rotational misalignment under the pressure of the set screws; 2. The addition of nuts solves the problem of loosening of the set screws due to high-temperature absorption; 3. The dimensions of the fixture are designed according to the workpiece, ensuring stable placement, and the thickness of the arc-shaped base is also designed based on the thread clamping force. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] Figure 2 This is a schematic diagram of the bow-shaped base 1 of the present invention.

[0017] Figure 3 This invention relates to the L-shaped positioning baffle 2.

[0018] Figure 1 The serial numbers and symbols in the text are explained as follows:

[0019] 1. Bow-shaped base 2. L-shaped positioning baffle 3. Ceramic pressure plate 4. Ceramic pad

[0020] 5. Screws 6. Nuts 7. Set screws Detailed Implementation

[0021] Please see Figures 1-3As shown, this invention discloses a welding fixture for pulse current-assisted brazing of thin plates, mainly composed of an arc-shaped base 1, an L-shaped positioning baffle 2, a ceramic pressure plate 3, a ceramic pad 4, screws 5, nuts 6, and set screws 7. Their relationship is as follows: the ceramic pad 4 is placed on a platform below the arc-shaped base 1; the L-shaped positioning baffle 2 is fixed to the inner side of the arc-shaped base 1 by screws 5, with its lower end face clearance-fitted to the ceramic pad 4; the test piece to be welded is placed on the ceramic pad 4, and the ceramic pressure plate 3 is placed on the test piece, at which point the test piece to be welded contacts the two inner sides of the ceramic pressure plate 3 and the L-shaped positioning baffle 2; the set screw 7 is inserted through a threaded hole above the arc-shaped base 1, and after passing through the threaded hole, the nut 6 is first installed, then the set screw 7 is pressed downwards until it contacts and tightens the ceramic pressure plate 3. After the set screw 7 is tightened, the nut 6 is tightened. The reaction force of the threaded connection further tightens the set screw 7 and prevents the set screw 7 from rotating back during the heating process, thus reducing the brazing pressure.

[0022] The bow-shaped base 1 has the following structural form: Figure 2 As shown, it is made by processing and modifying a block of sheet metal. The material is niobium-tungsten alloy. The whole piece of material is processed into a U-shaped frame with an outer contour of 120mm x 120mm x 100mm and a thickness of 20mm. The inner height of the frame is 80mm and the width is 100mm, which provides enough space to place the test piece to be welded and other parts on the platform below the frame. An M20x2.5 threaded hole is machined in the middle of the upper part of the frame. The set screw 7 is pressed into the ceramic pressure plate 3 through the threaded hole, thereby applying welding pressure to the test piece to be welded. A through hole with a diameter of 16mm is machined on the left side of the frame. The function of this hole is to fix the L-shaped positioning baffle 2 to the inside of the bow-shaped base 1 through the screw 5, and at the same time cooperate with the ceramic pad 4 to allow the L-shaped positioning baffle 2 to rotate.

[0023] The L-shaped positioning baffle 2 has the following specific structural form: Figure 3 It is manufactured from block-shaped plates and is made of niobium-tungsten alloy. The L-shaped positioning baffle is 100mm long on each side, 10mm thick on each side, and 70mm high. An M16x2 threaded hole is machined on one side of the L-shape for fixing it to the bow-shaped base 1 with screw 5. The main function of the L-shaped positioning baffle 2 is to constrain the freedom of the test piece under the pressure applied by the set screw 7, preventing the test piece from rotating and shifting under the pressure of the set screw, thus reducing the welding surface area and causing solder loss. The 90mmx90mm area inside the L-shaped positioning baffle 2 is the space where the test piece can be placed.

[0024] The ceramic pressure plate 3 and ceramic pad 4 are zirconia ceramic plates of 80mm x 80mm x 10mm and 100mm x 100mm x 10mm respectively. Their main function is to isolate the test piece to be welded, preventing the test piece from being diffusely welded to the tooling after being heated. The ceramic pressure plate 3 also disperses the pressure applied by the set screw 7, ensuring that the surface of the test piece to be welded is evenly stressed.

[0025] The screw 5 is a standard M16x30 screw, the nut 6 is a standard M20 coarse-thread nut, and the set screw 7 is a standard M20x70 set screw; all three are made of niobium-tungsten alloy. The main function of screw 5 is to fix the L-shaped positioning block 2. The main function of set screw 7 is to provide vertically downward welding pressure on the ceramic pressure plate 3. The main function of nut 6 is to prevent set screw 7 from loosening during heating, thus preventing unstable welding pressure.

[0026] When brazing thin sheet metal parts using welding fixtures, place the ceramic backing plate 4 on the platform below the bow-shaped base 1, and insert the screw 5 through the side of the bow-shaped base 1 to the inside of the L-shaped positioning baffle 2; the thin sheet metal parts are as follows: Figure 1 The brazing process involves full overlap, with foil sheets of equal thickness to the brazing gap placed at the four corners of the overlap to control the brazing gap. The overlapped workpiece is placed on the ceramic pad 4, close to the inside of the L-shaped positioning baffle 2, to prevent rotation when pressure is applied by the set screw 7. After covering with the ceramic pressure plate 3, the set screw 7 is passed through the platform above the bow-shaped base 1 and the nut 6 is installed. Finally, the set screw 7 and nut 6 are tightened to press the foil sheets around the interlayer of the brazing workpiece so that they cannot be pulled out. The entire workpiece is then placed in a vacuum furnace for brazing. After welding, the brazing gap is first measured. If it passes the test, a brazing shear test is performed to test the brazing strength.

Claims

1. A welding fixture for pulse current-assisted brazing of thin plates, characterized in that: It consists of an arc-shaped base, an L-shaped positioning baffle, a ceramic pressure plate, a ceramic pad, screws, nuts, and set screws. Their relationship is as follows: the ceramic pad is placed on a platform below the arc-shaped base; the L-shaped positioning baffle is fixed to the inner side of the arc-shaped base with screws, its lower end face fitting with the ceramic pad; the test piece to be welded is placed on the ceramic pad, and the ceramic pressure plate is placed on the test piece, at which point the test piece to be welded is in contact with the two inner sides of the ceramic pressure plate and the L-shaped positioning baffle; the set screw is inserted through a threaded hole above the arc-shaped base, and after passing through the threaded hole, the nut is installed first, then the set screw is pressed downwards until it contacts and tightens the ceramic pressure plate. After the set screw is tightened, the nut is tightened, and the reaction force of the thread further tightens the set screw, while also preventing the set screw from rotating back during the heating process, which would reduce the brazing pressure. The L-shaped positioning baffle is made of block plate material and is made of niobium-tungsten alloy. A threaded hole is machined on one side of the L-shape and fixed to the bow-shaped base with screws. The L-shaped positioning baffle, together with the pressure applied by the set screw, constrains the degree of freedom of the test piece to be welded, preventing the test piece to be welded from rotating and misaligning under the pressure of the set screw, which would reduce the welding surface and cause the brazing filler metal to be lost. When brazing thin plate components using welding fixtures, place a ceramic backing plate on the platform below the bow-shaped base, and pass screws through the side of the bow-shaped base to the inside of the L-shaped positioning baffle. The thin plate components are fully overlapped, and foil sheets of equal thickness to the brazing gap are placed at the four corners of the overlap to control the brazing gap. The overlapped component is placed on the ceramic backing plate and close to the inside of the L-shaped positioning baffle to prevent rotation when pressure is applied by the set screws. After covering with the ceramic pressure plate, the set screws are passed through the platform above the bow-shaped base and nuts are installed. Finally, the set screws and nuts are tightened to compress the foil sheets around the brazing interlayer, preventing them from being pulled out. The entire component is then placed in a vacuum furnace for brazing. After welding, the brazing gap is measured first, followed by a brazing shear test to test the brazing strength.

2. The welding fixture for pulse current-assisted brazing of thin plates according to claim 1, characterized in that: The bow-shaped base is made by processing and modifying block plates, and the material is niobium-tungsten alloy; it is processed into a U-shaped frame, and there is enough space inside the U-shaped frame to place the test piece to be welded.

3. The welding fixture for pulse current-assisted brazing of thin plates according to claim 2, characterized in that: A threaded hole is machined at the middle of the upper part of the U-shaped frame. The set screw presses the ceramic pressure plate through the threaded hole, thereby applying welding pressure to the test piece to be welded. A through hole is machined on the left side of the U-shaped frame. The L-shaped positioning baffle is fixed to the inside of the bow-shaped base by screws through the through hole, and at the same time, the ceramic pad prevents the L-shaped positioning baffle from rotating.

4. The welding fixture for pulse current-assisted brazing of thin plates according to claim 1, characterized in that: The ceramic pressure plate and ceramic pad are made of zirconia ceramic plates. Their function is to isolate the test piece to be welded and prevent the test piece from being diffusely welded together with the tooling after being heated. The ceramic pressure plate can also distribute the pressure applied by the set screw, so that the surface of the test piece to be welded is evenly stressed.

5. A welding fixture for pulse current-assisted brazing of thin plates according to claim 1, characterized in that: The screws fix the L-shaped positioning block, and the set screws provide vertical downward welding pressure on the ceramic pressure plate. The nuts prevent the set screws from loosening during heating, which would lead to unstable welding pressure.

6. A welding fixture for pulse current-assisted brazing of thin plates according to claim 1 or 5, characterized in that: The screws are standard M16x30 screws, the nuts are standard M20 coarse thread nuts, and the set screws are standard M20x70 set screws. All three are made of niobium-tungsten alloy.

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