Scanning electron beam-brazing composite welding method suitable for closed cavity structure

Abstract

The invention provides a scanning electron beam-brazing composite welding method suitable for a closed cavity structure. The scanning electron beam-brazing composite welding method comprises the steps that S1, test welding is conducted; determining electron beam critical penetration welding parameters; determining scanning parameters of scanning electron beam critical penetration welding; determining scanning electron beam-brazing composite welding parameters; s2, welding seam machining and cleaning treatment; s3, brazing filler metal is selected and filled; s4, tool fixing and spot welding are carried out; s5, scanning electron beam-brazing composite welding is carried out; and the part fixed by the tool is placed in a vacuum chamber of an electron beam welding machine, then the part is welded through the electron beam welding and scanning parameters determined in the step S1 of test welding, and scanning electron beam-brazing composite welding of the part is achieved. The defect that in the electron beam welding process of the closed cavity structure, electron beams easily flow through large burns of metal opposite to a weld joint or are too small to cause non-welding is overcome, and therefore high-quality welding of the closed cavity structure is achieved.

Description

Technical Field

[0001] The invention provides a scanning electron beam-brazing composite welding method suitable for a closed cavity structure, belonging to the field of electron beam welding processing. Background Art

[0002] In engineering manufacturing, there are often some closed cavity welding structures (such as Figure 1a , Figure 1b As shown in the figure, when electron beam welding is used, since the weld is in the form of butt welding and has no stop, if the beam current is slightly larger, it will easily burn the metal on the opposite side of the weld, reducing the performance of the welded joint; if the beam current is too small, unwelded gaps will be generated. During operation, these unwelded gaps will become the cause of bending cracks and fatigue fractures, which will greatly reduce the service life of the part. In actual welding production, it is difficult to adjust and control the size of the electron beam current just enough to penetrate the weld without burning the opposite metal. Therefore, during weld formation inspection, welding defects such as unwelded gaps and workpiece metal burns can often be seen in the weld area, which seriously affect the welding quality of such closed cavity structure parts. Therefore, how to solve the problems of excessive beam current burning the opposite metal or too small beam current causing unwelded gaps is the key to achieving high-quality welding of closed cavity structures.

[0003] The conventional solution is to use a slightly larger beam current than penetration welding to ensure complete fusion of the weld. At the same time, a metal pad is pre-placed under the weld to absorb the penetrating beam to prevent the beam from burning the opposite metal. However, after welding, the workpiece is in a fully closed state and the pre-placed metal pad cannot be removed. Another solution is to design the weld of the closed cavity structure into a stop structure (such as Figure 2 During welding, the size of the electron beam current is adjusted through process tests so that the electron beam penetrates the weld instead of the stopper, thereby ensuring that the opposite metal is not burned. However, the stopper structure not only increases the thickness of the parts and makes the welding joint processing more complicated, but also most of the stopper structures have unwelded gaps after welding. These unwelded gaps may also become the cause of cracks, seriously affecting the quality of the welding joint.

[0004] The scanning electron beam-brazing composite welding process refers to the use of electron beam flow to melt the weld, while controlling the electron beam to perform high-frequency scanning in the direction perpendicular to the weld, and using the heat generated by electron beam welding and scanning to perform brazing, so that the brazing filler metal pre-filled on the back of the weld melts and fills the weld gap. In this way, when electron beam welding a closed cavity structure, the brazing filler metal can be pre-filled on the back of the weld of the closed cavity structure, and then a beam slightly smaller than the penetration weld is used for welding, and brazing is achieved at the same time as electron beam welding. After the brazing filler metal melts, it can fill the unfused gap after electron beam welding, thereby improving the welding quality of the closed cavity structure.

[0005] Therefore, the present invention proposes a scanning electron beam-brazing composite welding process suitable for closed cavities, which adopts an electron beam current slightly smaller than that of penetration welding for welding, and controls the electron beam to perform high-frequency scanning in the direction perpendicular to the weld. The heat generated during the electron beam scanning welding process is used to melt the brazing material pre-filled on the back of the weld and fill the unwelded gap, thereby completing the brazing of the closed cavity structure, thereby obtaining a closed cavity structure with high welding quality. Summary of the invention

[0006] 1. Purpose: The present invention proposes a scanning electron beam-brazing composite welding method to solve the problems of too large beam current burning the opposite metal or too small beam current causing unwelded gaps during electron beam welding of closed cavity structures. When welding a closed cavity structure, an electron beam current slightly smaller than that of penetration welding is selected to weld the workpiece, and the electron beam is controlled to perform high-frequency scanning in the direction perpendicular to the weld. The heat generated during the scanning electron beam welding process is used to melt the brazing material pre-filled on the back of the weld and fill the unwelded gap, thereby completing the brazing of the closed cavity structure, thereby achieving high-quality welding of the closed cavity structure. Since the electron beam has a small beam spot, concentrated energy and a fast welding speed, when critical penetration welding is used, the high-temperature zone on the back of the weld that can melt the brazing material is narrow and the high-temperature duration is short. Therefore, the purpose of high-frequency scanning of the electron beam in the direction perpendicular to the weld while welding is to increase the heat input of the pre-filled brazing material area on the back of the weld, increase the temperature, and allow the brazing material to have a sufficiently high temperature and time to melt, wet and fill the unwelded gap.

[0007] 2. Technical solution: The objective of the present invention is achieved through the following technical solution.

[0008] Based on the above purpose, the present invention provides a scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure, which mainly includes trial welding, weld processing and cleaning, tooling fixing, brazing material selection and filling, scanning electron beam-brazing hybrid welding, etc. Among them, the brazing material should be selected according to the material of the parts to be welded.

[0009] The specific steps are as follows.

[0010] S1: Test welding

[0011] S1-01: Determine the critical penetration welding parameters of electron beams. Prepare a test plate with the same material and thickness as the parts to be welded, and use different electron beam welding process parameters for test welding. Select appropriate welding process parameters through a large number of process tests, mainly including welding beam current, welding speed, etc. The principle for determining critical penetration welding parameters is: weld the test plate with the current welding process parameters, the test plate has not been fully penetrated, but slightly change the welding parameters (such as increasing the welding beam current or reducing the welding speed), the test plate is then welded through, so the current welding parameters can be preliminarily determined to be critical penetration welding parameters, which can be used for the critical penetration welding parameters of subsequent parts;

[0012] S1-02: Determine the scanning parameters of the critical penetration welding of the scanning electron beam. Use the welding test plate with the critical penetration welding parameters determined in step S1-01, and control the electron beam to perform high-frequency scanning in the direction perpendicular to the weld. Through a large number of process tests, determine the critical penetration welding parameters such as the scanning waveform, scanning amplitude and scanning speed during critical penetration welding.

[0013] S1-03: Determine scanning electron beam-braze hybrid welding parameters. Apply brazing filler metal to the back area of ​​the test plate weld position, and then use the electron beam critical penetration welding parameters and scanning parameters determined in steps S1-01 and S1-02 to carry out scanning electron beam-braze hybrid welding process tests, optimize welding process parameters, so that the brazing filler metal applied on the back of the weld can fully melt and wet the test plate, thereby determining the appropriate scanning electron beam-braze hybrid welding process parameters for the parts.

[0014] The scanning electron beam-brazing composite welding process parameters mainly include acceleration voltage, electron beam current, welding speed, scanning speed, scanning amplitude, brazing temperature and other main parameters. Among them, the acceleration voltage is determined according to the selected electron beam welding equipment, and 60kV medium-voltage electron beam welding equipment or 150kV high-voltage electron beam welding equipment can be selected; the electron beam current and welding speed are mainly determined according to the material, thickness and structure of the workpiece to be welded, and the relevant electron beam welding process manual can be consulted; the electron beam scanning speed, scanning amplitude and brazing temperature and other parameters need to be determined according to the brazing temperature and wetting effect of the selected brazing material; all the above scanning electron beam-brazing composite welding process parameters need to be determined through trial welding to determine the best welding parameters.

[0015] S2: Welding seam processing and cleaning

[0016] S2-01: Butt weld processing. According to the assembly accuracy requirements of the butt weld of the parts, the butt position of the parts is processed by mechanical processing methods, and a 0.1mm×45° chamfer is processed on the back of the butt weld to fill the brazing material.

[0017] S2-02: Cleaning. Use acetone to remove oil stains from the weld and nearby areas of the parts, use sandpaper to remove the oxide film, and then use anhydrous ethanol to clean.

[0018] S3: Brazing material selection and filling

[0019] S3-01: Select solder. The specific solder should be selected according to the material of the parts to be welded. Taking TC4 titanium alloy as an example, you can choose silver-based solder, titanium-based solder or aluminum-based solder.

[0020] S3-02: Add solder. Fill the selected solder into the chamfer on the back of the weld, and select an appropriate method to fix the solder on the back of the weld to ensure that it does not fall off during subsequent assembly and welding. Paste solder and powder solder can be bonded to the workpiece with a binder; powder solder can also be connected to the workpiece by sintering; sheet solder can be bonded, spot welded, etc.

[0021] S4: Fixing and spot welding. Assemble the parts filled with solder and fix them with special tooling (the closed cavity structure is diverse, and the same tooling cannot be applied to all closed cavity structures. Therefore, it is necessary to design a special tooling according to the closed cavity structure to be welded. For example, for the rotating structure weld shown in Figure 1, you can choose Figure 6 It is a special tooling for the turntable structure), and then it is spot welded and fixed by electron beam.

[0022] S5: Scanning electron beam-braze hybrid welding. Put the parts fixed by the tooling into the vacuum chamber of the electron beam welding machine, and then weld the parts using the electron beam welding and scanning parameters determined in the S1 test welding step to achieve scanning electron beam-braze hybrid welding of the parts.

[0023] 3. Advantages and effects:

[0024] 1) A scanning electron beam-brazing hybrid welding method suitable for closed cavity structures is proposed, which can solve the problem that the electron beam current is too large to burn the metal on the opposite side of the weld or the beam current is too small to cause unwelded joints during the electron beam welding process of closed cavity structures. This method selects an electron beam current slightly smaller than that of penetration welding to weld the workpiece, and at the same time controls the electron beam to perform high-frequency scanning in the direction perpendicular to the weld. The heat generated during the scanning electron beam welding process is used to melt the brazing material pre-filled on the back of the weld and fill the unwelded gap, completing the brazing of the closed cavity structure, thereby achieving high-quality welding of the closed cavity structure.

[0025] 2) During the welding process, using butt joints instead of lock-bottom structural joints can simplify the process and reduce costs.

[0026] 3) Using a scanning electron beam as a welding heat source can greatly increase the welding speed. At the same time, the scanning of the electron beam can increase the heated area, which is more conducive to the melting of the solder, ensuring that the solder can fully wet the base material and fill the gap in the welding joint.

[0027] 4) This process has wide applicability and can be widely used in welding TC4 workpieces of various thicknesses and shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1a , Figure 1b It is a schematic diagram of a closed cavity structure in the background technology.

[0029] Figure 2 It is a schematic diagram of the stop of a butt joint in the background technology.

[0030] Figure 3 It is a schematic diagram of chamfering processing at the docking position of closed cavity structure parts.

[0031] Figure 4 This is a schematic diagram of the pre-filled brazing filler metal at the chamfer on the back side of the weld.

[0032] Figure 5 It is a schematic diagram of the scanning electron beam-brazing composite welding method.

[0033] Figure 6 It is a schematic diagram of a special tooling for a closed cavity structure in a specific implementation scheme. DETAILED DESCRIPTION

[0034] The present invention provides a scanning electron beam-brazing composite welding method for a closed cavity structure, wherein a typical 3 mm thick TC4 titanium alloy cylindrical closed cavity structure is taken as an example. Figure 1a , Figure 1b As shown (the specific implementation scheme is Figure 1a , Figure 1b The closed cavity structure shown in the figure, but there are many types of closed cavity structures. This patent is aimed at the closed cavity structure used, but only takes the closed cavity structure shown in the figure as an example), and its specific implementation method is:

[0035] S1: Test welding

[0036] S1-01: Determine the critical penetration welding parameters of electron beam. Prepare a 3mm thick TC4 titanium alloy test plate, use different electron beam welding process parameters for trial welding, and select appropriate welding process parameters through a large number of process tests, mainly including welding beam, welding speed, etc. The principle of determining the critical penetration welding parameters is: the test plate is welded with the current welding process parameters, and the test plate has not been fully penetrated, but the welding parameters are slightly changed (such as increasing the welding beam or reducing the welding speed), and the test plate is immediately welded through. From this, the current welding parameters can be preliminarily determined as the critical welding parameters, which can be used for the critical penetration welding parameters of subsequent parts. After trial welding, the critical welding parameters of the 3mm thick TC4 titanium alloy closed cavity structure parts are an acceleration voltage of 60kV, an electron beam current of 8mA, and a welding speed of 500mm / min.

[0037] S1-02: Determine the scanning parameters of the critical penetration welding of the scanning electron beam. The critical penetration welding parameters determined in step S1-01 were used to weld the TC4 test plate, and the electron beam was controlled to perform high-frequency scanning in the direction perpendicular to the weld. The critical penetration welding parameters such as the scanning waveform, scanning amplitude, and scanning speed during critical penetration welding were determined through a large number of process tests. Finally, it was determined that the scanning waveform during critical penetration welding was circular, the scanning amplitude was 1.05 mm, and the scanning speed was 420 mm / s.

[0038] S1-03: Determine scanning electron beam-braze composite welding parameters. Apply brazing filler metal to the back area of ​​the test plate weld position, and then use the electron beam critical penetration welding parameters and scanning parameters determined in steps S1-01 and S1-02 to carry out scanning electron beam-braze composite welding process tests, optimize welding process parameters, so that the brazing filler metal coated on the back of the weld can fully melt and wet the test plate, thereby determining the scanning electron beam-braze composite welding parameters of 3mm thick TC4 titanium alloy closed cavity structure parts as 60kV acceleration voltage, 9mA electron beam current, 500mm / min welding speed, circular scanning waveform, 1.05mm scanning amplitude, and 420mm / s scanning speed.

[0039] S2: Welding seam processing and cleaning

[0040] S2-01: Butt weld processing. According to the assembly accuracy requirements of the butt weld of parts, the butt position of the 3mm thick TC4 closed cavity structure parts is processed by mechanical processing methods, and a chamfer of about 0.1mm×45° is processed on the back of the butt weld to fill the brazing material, such as Figure 3 shown.

[0041] S2-02: Cleaning. Use acetone to remove oil stains from the weld and nearby areas of the parts, use sandpaper to remove the oxide film, and then use anhydrous ethanol to clean.

[0042] S3: Brazing material selection and filling

[0043] S3-01: Select the brazing filler metal. The specific brazing filler metal should be selected according to the material of the parts to be welded. For the brazing of TC4 titanium alloy, silver-based brazing filler metal, titanium-based brazing filler metal or aluminum-based brazing filler metal can be selected. For 3mm thick TC4 titanium alloy parts, the paste AgCuInTi brazing filler metal is selected for scanning electron beam-brazing composite welding. The brazing temperature of this brazing filler metal is about 750℃.

[0044] S3-02: Add solder. Fill the selected AgCuInTi solder to the chamfer on the back of the weld and fix the solder to the back of the weld by adhesive bonding or sintering to ensure that the solder will not fall off during the subsequent assembly and welding process. Figure 4 shown.

[0045] S4: Fixing with tooling. Assemble the parts filled with solder neatly, and then fix them with special tooling (such as Figure 6 The parts are then spot welded using an electron beam.

[0046] S5: Scanning electron beam-braze hybrid welding. Put the parts fixed by the tooling into the vacuum chamber of the electron beam welding machine, and then weld the parts using the electron beam welding and scanning parameters determined in the S1 test welding step to achieve scanning electron beam-braze hybrid welding of the parts, such as Figure 5 shown.

[0047] The present invention will be further described below in conjunction with the accompanying drawings.

[0048] Fig. 1 is a schematic diagram of the closed cavity structure part. Referring to Fig. 1, the weld of the closed cavity structure part is in the form of butt welding, and the electron beam flow slightly smaller than that of penetration welding is used for welding. At the same time, the electron beam is controlled to perform high-frequency scanning in the direction perpendicular to the weld. The heat generated during the electron beam scanning welding process is used to melt the brazing material pre-filled on the back of the weld and fill the unwelded gap, thereby completing the brazing of the closed cavity structure and obtaining a well-welded closed cavity structure.

[0049] Figure 2 Schematic diagram of the stop structure of the weld. Figure 2 The stopper structure can ensure that the electron beam does not penetrate the stopper and burn the opposite metal during welding. However, the stopper structure increases the thickness of the parts, making the welding joint processing more complicated. Moreover, there is usually an unwelded gap after welding in the stopper structure, which can easily become a cause of cracks and seriously affect the quality of the welding joint.

[0050] Figure 3 This is a schematic diagram of the processing of the docking position of the closed cavity structure parts. Figure 3According to the assembly requirements of the butt weld of the parts, the butt position of the parts is processed by mechanical processing method, and a chamfer of about 0.1mm×45° is processed on the back of the butt weld to fill the brazing material.

[0051] Figure 4 Schematic diagram of the solder filling and tooling of the closed cavity structure parts. Figure 4 , fill the selected brazing filler metal into the chamfer on the back of the weld, and select appropriate methods such as bonding, sintering, spot welding, etc. to fix the brazing filler metal on the back of the weld to ensure that the brazing filler metal will not fall off during the subsequent assembly and welding of the parts. Paste brazing filler metal can be bonded with a binder, powder brazing filler metal can be bonded with sintering or a binder, and other sheet brazing filler metals can be spot welded, bonded, etc.

[0052] Figure 5 This is a schematic diagram of the scanning electron beam-brazing hybrid welding of the closed cavity structure parts. Figure 5 , the parts filled with brazing material and assembled are placed in the vacuum chamber of the electron beam welding machine to complete the scanning electron beam-brazing composite welding.

[0053] Figure 6 Schematic diagram of a special tooling for a typical closed cavity structure in the specific implementation scheme. Figure 6 The special tooling adopts a three-jaw chuck 1 on a fixed support 1 and a chuck 2 on a fixed support 2 to fix the workpiece to be welded, and adjusts the distance between the two chucks through a guide rail to fix the workpiece to be welded. The motor is installed inside the fixed support 2 to drive the chuck 2 to rotate, and drives the workpiece to be welded and the chuck 1 to rotate, thereby achieving high-quality welding of the annular weld of the closed cavity structure.

[0054] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A scanning electron beam-brazing hybrid welding method suitable for closed cavity structures, It is characterized in that The steps include: S1: Test welding; including: S1-01: Determine the electron beam critical penetration welding parameters; S1-02: Determine scanning parameters for critical penetration welding of scanning electron beam; S1-03: Determine scanning electron beam-brazing hybrid welding parameters; S2: Weld processing and cleaning; including: S2-01: Butt weld processing: According to the assembly accuracy requirements of the butt weld of parts, the butt position of the parts is processed by mechanical processing methods, and a 0.1mm×45° chamfer is processed on the back of the butt weld to fill the brazing filler metal; S2-02: Cleaning: Use acetone to remove oil stains from the weld and nearby areas of the parts, use sandpaper to remove the oxide film, and then use anhydrous ethanol to clean; S3: Brazing material selection and filling; including: S3-01: Select solder; the specific solder should be selected according to the material of the parts to be welded; S3-02: Add solder; fill the selected solder to the chamfer on the back of the weld, and select an appropriate method to fix the solder on the back of the weld to ensure that subsequent assembly and welding will not fall off; S4: Fixing and spot welding: Assemble the parts filled with solder, fix them with special tooling, and then fix them with electron beam spot welding; S5: Scanning electron beam-brazing composite welding: Place the parts fixed by the tooling into the vacuum chamber of the electron beam welding machine, and then weld the parts using the electron beam welding and scanning parameters determined in the S1 trial welding step to achieve scanning electron beam-brazing composite welding of the parts.

2. A scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure according to claim 1, Features: In step S1-01, the critical penetration welding parameters are determined: the test plate is welded with the current welding process parameters, and the test plate has not been fully penetrated, but the welding parameters are changed, that is, the welding beam is increased or the welding speed is reduced, and the test plate is then welded through, thereby determining the current welding parameters as the critical penetration welding parameters, which are used for the critical penetration welding parameters of subsequent parts.

3. A scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure according to claim 2, Features: In step S1-02, the scanning parameters of the scanning electron beam critical penetration welding are determined; the welding test plate with the critical penetration welding parameters determined in step S1-01 is used, and the electron beam is controlled to perform high-frequency scanning in a direction perpendicular to the weld to determine the critical penetration welding parameters of the scanning waveform, scanning amplitude and scanning speed during critical penetration welding.

4. A scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure according to claim 3, Features: In step S1-03, the scanning electron beam-brazing composite welding parameters are determined; the brazing filler metal is applied to the back area of ​​the weld position of the test plate, and then the electron beam critical penetration welding parameters and scanning parameters determined in steps S1-01 and S1-02 are used to allow the brazing filler metal applied on the back of the weld to fully melt and wet the test plate, thereby determining the scanning electron beam-brazing composite welding process parameters of the part.

5. A scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure according to claim 1, Features: In step S3-01, silver-based solder, titanium-based solder or aluminum-based solder is selected.

6. A scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure according to claim 1, Features: In step S3-02, the paste solder and the powder solder are bonded to the workpiece by an adhesive; the powder solder is connected to the workpiece by sintering; and the sheet solder is bonded or spot welded.

7. A scanning electron beam-brazing hybrid welding method suitable for a closed cavity structure according to claim 1, Features: In step S4, a dedicated tooling uses a three-jaw chuck 1 on a fixed support 1 and a chuck 2 on a fixed support 2 to fix the workpiece to be welded, and adjusts the distance between the two chucks through a guide rail to fix the workpiece to be welded; a motor is installed inside the fixed support 2 to drive the chuck 2 to rotate, and drives the workpiece to be welded and the chuck 1 to rotate, thereby realizing the welding of the annular weld of the closed cavity structure.

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