Method and system for repairing zm6 magnesium alloy by mechanical ultrasonic welding

Abstract

The present application relates to ZM6 magnesium alloy mechanical ultrasonic welding repair method and system, the repair method includes the following steps: step one: according to the defect size of the repair site cutting patch;Step two: the workpiece to be repaired is fixed on the tooling table, the patch is covered on the repair site and fixed;Step three: the welding of the patch and the workpiece to be repaired is carried out by ultrasonic welding;Step four: the repair site of the workpiece to be repaired is polished, and the repair of the workpiece to be repaired is completed.The system includes tooling table and vibration generator, the tooling table is used to carry the workpiece to be repaired, the vibration generator is used to generate high-frequency vibration for ultrasonic welding repair, and the vibration output end is provided with a vibration transmission rod, and the tail end of the vibration transmission rod is provided with a tungsten electrode.The present application can accurately inhibit welding oxidation during the repair process, reduce welding defects, realize the matching of the mechanical properties of the repaired workpiece and the base material, and improve the accuracy and reliability of the welding repair.

Description

Technical Field

[0001] This invention relates to a method and system for ultrasonic welding repair of ZM6 magnesium alloy, belonging to the field of welding repair technology. Background Technology

[0002] ZM6 magnesium alloy is widely used in aerospace, automotive manufacturing, and other fields due to its low density, high specific strength, and good vibration damping properties. However, its components are prone to cracking and damage during service, requiring welding repair. Because ZM6 magnesium alloy has high chemical reactivity, high thermal conductivity, and a large coefficient of linear expansion, traditional argon arc welding and brazing repair techniques easily produce cracks, porosity, and oxide inclusions, leading to a significant decrease in the mechanical properties of the repaired components, making it difficult to meet service requirements.

[0003] Existing ultrasonic-assisted welding technologies primarily introduce ultrasonic vibrations into the base material and arc region, with limited coupling with tungsten electrodes. Tungsten electrodes possess characteristics such as high temperature resistance, high strength, and good chemical stability. Furthermore, ultrasonic action on the tungsten electrode promotes electron emission and improves the arc state. However, its targeted application in vibration welding repair of ZM6 magnesium alloys has not yet been realized. There is an urgent need for a highly efficient welding repair technology adapted to the characteristics of ZM6 magnesium alloys to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art, this invention provides a method and system for ultrasonic mechanical welding repair of ZM6 magnesium alloy, which can precisely suppress welding oxidation during the repair process, reduce welding defects, achieve mechanical property matching between the repaired workpiece and the base material, and improve the accuracy and reliability of welding repair.

[0005] The technical solution adopted in this invention is: a mechanical ultrasonic welding repair method for ZM6 magnesium alloy, comprising the following steps: Step 1: Based on the defect size of the ZM6 magnesium alloy workpiece to be repaired, cut a patch of the same material as the ZM6 magnesium alloy workpiece to be repaired. Step 2: Fix the ZM6 magnesium alloy workpiece to be repaired on the tooling table, cover the repaired part of the ZM6 magnesium alloy workpiece with the patch and fix it. Step 3: Use ultrasonic welding to weld the patch to the ZM6 magnesium alloy workpiece to be repaired. First, pre-weld in sections along the edge of the patch and the direction of the part of the ZM6 magnesium alloy workpiece to be repaired. Then, with the center of the patch as the origin, weld outward in a spiral manner to the edge of the patch. Step 4: Grind and polish the repaired area of ​​the ZM6 magnesium alloy workpiece to complete the repair.

[0006] Preferably, before cutting the patch, the part to be repaired of the ZM6 magnesium alloy workpiece is first ground. After grinding, the part to be repaired and its surrounding area are cleaned with anhydrous ethanol and then air-dried.

[0007] Furthermore, the grinding process covers the area to be repaired on the ZM6 magnesium alloy workpiece and its surrounding 20mm~30mm area.

[0008] Preferably, in step one, the thickness of the cut patch is not greater than the thickness of the ZM6 magnesium alloy workpiece to be repaired, that is, the thickness of the patch is the same as the thickness of the ZM6 magnesium alloy workpiece to be repaired, or the thickness of the patch is less than the thickness of the ZM6 magnesium alloy workpiece to be repaired. When the thickness of the patch is less than the thickness of the ZM6 magnesium alloy workpiece to be repaired, typically, the thickness of the patch is 0.1mm to 0.3mm smaller than the thickness of the ZM6 magnesium alloy workpiece to be repaired.

[0009] Preferably, the edges of the patch are chamfered.

[0010] Furthermore, the chamfering process is a 45° chamfer.

[0011] Preferably, in step two, the bonding gap between the patch and the ZM6 magnesium alloy workpiece to be repaired is no greater than 0.05 mm.

[0012] Preferably, in step two, the ZM6 magnesium alloy workpiece to be repaired and the patch are fixed on the tooling table by negative pressure adsorption.

[0013] Preferably, in step three, ultrasonic welding uses a tungsten electrode as the welding head. The tungsten electrode is a thorium tungsten electrode (purity ≥99.95%), and the end of the tungsten electrode is conical with a cone angle of 30°~45°.

[0014] Preferably, during ultrasonic welding, the distance between the end of the tungsten electrode and the surface of the patch is 0.1 mm to 0.3 mm.

[0015] Preferably, during ultrasonic welding, the vibration frequency of the tungsten electrode is 15kHz~35kHz, the welding pressure is 0.2MPa~0.7MPa, and the amplitude is 25μm~55μm.

[0016] Preferably, during ultrasonic welding, argon is used as a protective gas, and the protective gas is sprayed onto the welding area in a ring-shaped manner.

[0017] The ZM6 magnesium alloy mechanical ultrasonic welding repair system uses any of the ZM6 magnesium alloy mechanical ultrasonic welding repair methods disclosed in this invention to repair the ZM6 magnesium alloy workpiece to be repaired. The ZM6 magnesium alloy mechanical ultrasonic welding repair system includes a tooling table and a vibration generator. The tooling table is provided with a workpiece bearing station for bearing the ZM6 magnesium alloy workpiece to be repaired. The vibration generator is used to generate high-frequency vibration to perform ultrasonic welding between the ZM6 magnesium alloy workpiece to be repaired and the patch. The vibration output end of the vibration generator is provided with a vibration transmission rod, and the end of the vibration transmission rod is provided with a tungsten electrode.

[0018] Preferably, the vibration transmission rod is made of tungsten carbide.

[0019] The beneficial effects of this invention are: (1) The ultrasonic welding repair of the present invention uses a high-purity thorium tungsten electrode with a tungsten carbide vibration transmission rod and an axial high-frequency vibration design to accurately transmit vibration energy, efficiently remove oxide film at the interface of the molten pool, avoid cracks and porosity defects caused by high-temperature melting, and ensure that the interface bonding strength of the ZM6 magnesium alloy after repair is not less than 88% of the strength of the base material; (2) In the welding repair process, the present invention uses an argon gas protection mechanism of an annular jet hood combined with the high chemical stability of tungsten electrodes, which can effectively suppress the oxidation reaction in the welding process of ZM6 magnesium alloy, reduce the electrode wear rate, and improve the stability of welding quality. (3) The pretreatment of the ZM6 magnesium alloy workpiece to be repaired, the parameter setting during the welding process, and the standardized design of the welding process of the present invention can flexibly adjust the process parameters according to the defect size of the ZM6 magnesium alloy to be repaired. The repair efficiency can be increased by more than 35% compared with the traditional argon arc welding repair, and it is especially suitable for the local precision repair of ZM6 magnesium alloy workpieces with complex shapes. Attached Figure Description

[0020] Figure 1 This is a flowchart of the ZM6 magnesium alloy mechanical ultrasonic welding repair method of the present invention; Figure 2 This is a schematic diagram of one embodiment of the ZM6 magnesium alloy mechanical ultrasonic welding repair system of the present invention. Detailed Implementation

[0021] See Figure 1 This invention discloses a mechanical ultrasonic welding repair method for ZM6 magnesium alloy, applicable to the precise repair of cracks, defects, and other faults in ZM6 magnesium alloy (a magnesium-zirconium-neodymium alloy of grade ZM6) workpieces, including the following steps: Step 1: Based on the defect size of the ZM6 magnesium alloy workpiece to be repaired, cut a patch of the same material as the ZM6 magnesium alloy workpiece to be repaired. Step 2: Fix the ZM6 magnesium alloy workpiece to be repaired on the tooling table, cover the repaired part of the ZM6 magnesium alloy workpiece with the patch and fix it. Step 3: Use ultrasonic welding to weld the patch to the ZM6 magnesium alloy workpiece to be repaired. First, pre-weld in sections along the edge of the patch and the direction of the part of the ZM6 magnesium alloy workpiece to be repaired. Then, with the center of the patch as the origin, weld outward in a spiral manner to the edge of the patch. Step 4: Grind and polish the repaired area of ​​the ZM6 magnesium alloy workpiece to complete the repair.

[0022] Before cutting the patch, the part of the ZM6 magnesium alloy workpiece to be repaired is first ground to remove the surface oxide film, oil and impurities. After grinding, the part to be repaired and its surrounding area are cleaned with anhydrous ethanol and then air-dried.

[0023] The grinding process should preferably cover the area to be repaired on the ZM6 magnesium alloy workpiece and the surrounding area within 20mm to 30mm.

[0024] In step one, the thickness of the cut patch is preferably no greater than the thickness of the ZM6 magnesium alloy workpiece to be repaired. That is, the thickness of the patch is the same as the thickness of the ZM6 magnesium alloy workpiece to be repaired, or the thickness of the patch is less than the thickness of the ZM6 magnesium alloy workpiece to be repaired. When the thickness of the patch is less than the thickness of the ZM6 magnesium alloy workpiece to be repaired, the thickness of the patch is usually 0.1mm to 0.3mm smaller than the thickness of the ZM6 magnesium alloy workpiece to be repaired.

[0025] The edges of the patch are preferably chamfered, with a 45° chamfer.

[0026] In step two, the fit gap between the patch and the ZM6 magnesium alloy workpiece to be repaired is preferably no greater than 0.05 mm, for example, 0.02 mm, 0.03 mm or 0.05 mm.

[0027] In step two, the ZM6 magnesium alloy workpiece and patch to be repaired are preferably fixed on the tooling table by negative pressure adsorption to avoid displacement during the welding repair process.

[0028] In step three, ultrasonic welding preferably uses a tungsten electrode as the welding head. The tungsten electrode is a thorium tungsten electrode (purity ≥99.95%), and the end of the tungsten electrode is conical (which can be formed by grinding), with a cone angle of 30°~45°.

[0029] During ultrasonic welding, the distance between the end of the tungsten electrode and the surface of the patch is preferably 0.1mm to 0.3mm, for example, 0.1mm, 0.2mm or 0.3mm.

[0030] During ultrasonic welding, the preferred vibration frequency of the tungsten electrode is 15kHz to 35kHz, such as 15kHz, 20kHz, or 35kHz; the preferred welding pressure is 0.2MPa to 0.7MPa, such as 0.2MPa, 0.5MPa, or 0.7MPa; the preferred vibration time is 1s to 4s, such as 1s, 2s, or 4s; and the preferred amplitude is 25μm to 55μm, such as 25μm, 40μm, or 55μm. In actual operation, the process parameters can be flexibly adjusted according to the defect size of the ZM6 magnesium alloy to be repaired to improve repair efficiency and effectiveness.

[0031] In the ultrasonic welding process, argon is used as the shielding gas. The shielding gas is preferably sprayed into the welding area in a ring-shaped manner, and the gas flow rate is preferably 6L / min to 12L / min, such as 6L / min, 10L / min or 12L / min.

[0032] In step three, ultrasonic welding is performed in segments. During pre-welding, the preferred welding length of each segment is 5mm, and the overlap between two adjacent segments is ≥2mm, to achieve the sealing of the damaged area and the initial fixation of the patch. The purpose of welding to the edge of the patch in a spiral manner with the center of the patch as the origin is to ensure that the welding area completely covers the damaged area. During the welding process, the protective effect of the protective gas is monitored in real time. If signs of oxidation are found at the welding area, the gas flow rate is adjusted in time.

[0033] In step four, grinding and polishing are used to remove excess weld beads, ensuring that the flatness of the repaired area is no more than 0.02mm.

[0034] After the repair of the ZM6 magnesium alloy workpiece is completed, the bonding strength of the repaired area can be tested by tensile testing. The repair effect of the current repair welding position is compared with the benchmark repair standard. If the bonding strength is less than 85% of the strength of the base material, the repair is deemed unqualified and the repaired part of the ZM6 magnesium alloy workpiece can be re-welded.

[0035] See Figure 2 The present invention also discloses a ZM6 magnesium alloy mechanical ultrasonic welding repair system. The ZM6 magnesium alloy workpiece to be repaired is repaired using any of the ZM6 magnesium alloy mechanical ultrasonic welding repair methods disclosed in the present invention. The ZM6 magnesium alloy mechanical ultrasonic welding repair system includes a tooling table 1 and a vibration generator (device for generating high-frequency vibration) 2. The tooling table is provided with a workpiece bearing station for bearing the ZM6 magnesium alloy workpiece to be repaired. The vibration generator is used to generate high-frequency vibration for ultrasonic welding of the ZM6 magnesium alloy workpiece to be repaired and the patch. The vibration output end of the vibration generator is provided with a vibration transmission rod 3, and the end of the vibration transmission rod is coaxially provided with a tungsten electrode 4.

[0036] The workpiece bearing station of the tooling table is preferably provided with an elastic buffer layer 5, which is used to buffer the force on the ZM6 magnesium alloy workpiece to be repaired during the ultrasonic welding repair process, so as to avoid damage to the ZM6 magnesium alloy workpiece to be repaired. The elastic buffer layer can be made of silicone material with a thickness of 2mm~5mm.

[0037] The tooling table can be equipped with a negative pressure suction cup. The negative pressure suction cup is horizontally positioned and penetrates the elastic buffer layer, meaning the opening of the suction cup is on the same horizontal plane as the upper surface of the elastic buffer layer. The suction cup is connected to a negative pressure source. During the welding repair process, the negative pressure suction of the suction cup is used to fix the ZM6 magnesium alloy workpiece and patch to be repaired. In practical applications, the negative pressure suction cup can also be replaced by a negative pressure adsorption hole penetrating the tooling table and the elastic buffer layer.

[0038] The vibration transmission rod is preferably made of tungsten carbide to ensure efficient transmission of vibration energy. The tungsten electrode is a thorium-tungsten electrode (purity ≥99.95%), and its end is conical (which can be ground), with a cone angle of 30°~45°. During welding, the vibration generator is activated, and the vibration transmission rod drives the tungsten electrode to perform axial high-frequency vibration, completing the welding between the ZM6 magnesium alloy workpiece to be repaired and the patch.

[0039] The ZM6 magnesium alloy mechanical ultrasonic welding repair system may also include an annular jet hood 6, which is coaxially disposed on the outside of the vibration transmission rod, so that the protective gas can be sprayed onto the welding area in an annular jet manner to provide all-round protection for the welding area. The distance between the jet nozzle of the annular jet hood and the tip of the tungsten electrode (equivalent to the distance between the jet nozzle of the annular jet hood and the welding area) is preferably 5mm to 10mm.

[0040] The ZM6 magnesium alloy mechanical ultrasonic welding repair system may further include a robotic arm 7, preferably a multi-degree-of-freedom robotic arm, such as a six-degree-of-freedom robotic arm. The vibration generator is fixedly mounted on the actuator end of the robotic arm to automate the welding repair process. The robotic arm can be programmed with control according to existing technology. The ZM6 magnesium alloy mechanical ultrasonic welding repair system may be appropriately configured with transducers, energy concentrators, and / or amplitude transformers according to the needs of the welding repair process and based on existing technology.

[0041] Example (taking a 5mm thick ZM6 magnesium alloy plate with a through crack as an example, the crack length is 30mm, the width is 0.2mm, and the bond strength is 270MPa): Pre-treatment of the ZM6 magnesium alloy workpiece to be repaired: Grind the cracked area and the surrounding 20mm area with 120-grit sandpaper until the base material is exposed; Wipe the ground area with a cloth soaked in anhydrous ethanol to remove residual impurities and let it air dry; Cut a 40mm×40mm ZM6 magnesium alloy patch with a thickness of 5mm, and chamfer the edges of the patch at 45°.

[0042] To fix the ZM6 magnesium alloy workpiece and patch to be repaired: Fix the workpiece to be repaired on a tooling table with a silicone elastic buffer layer (3mm thick), cover the cracked area with the patch, adjust the position of the patch so that the fit gap is 0.03mm, and start the negative pressure suction cup to fix the workpiece to be repaired and the patch.

[0043] Set welding repair parameters: Select a thorium tungsten electrode with a cone angle of 35° and fix it coaxially to the end of the tungsten carbide vibration transmission rod; set the system parameters as follows: vibration frequency is set to 28kHz, welding pressure is set to 0.4MPa, vibration time is set to 2.5s, amplitude is set to 40μm, argon flow rate is set to 9L / min, and the distance between the tip of the tungsten electrode and the surface of the patch is adjusted to 0.2mm.

[0044] Welding repair implementation: Start the vibration generator, first pre-weld along the crack direction in sections (the welding length of each section is 5mm, and the overlap between two adjacent sections is 3mm), and then weld outwards in a spiral manner from the center of the patch to the edge of the patch. During the welding process, keep the welding area evenly covered by argon gas.

[0045] Post-processing and inspection: After welding, turn off the vibration generator and negative pressure suction cup, cool the plate to be repaired to room temperature, remove the tooling (remove the plate to be repaired from the tooling table), grind the repair area with 200-grit sandpaper to remove weld beads, and ensure flatness ≤0.02mm; perform a tensile test on the repair area to test the bonding strength and determine whether the repair is qualified.

[0046] In this embodiment, the tested bonding strength was 240 MPa, with no oxide inclusions or defects, and the repair was deemed qualified. If the test found that the bonding strength was lower than 230 MPa or that there were porosity defects, the welding pressure could be readjusted to 0.5 MPa and the vibration time to 3 seconds, and the welding repair could be performed again.

[0047] Unless otherwise specified or further limited to one preferred or optional technical means being another, the preferred and optional technical means disclosed in this invention can be arbitrarily combined to form several different technical solutions.

Claims

1. A method for mechanical ultrasonic welding repair of ZM6 magnesium alloy, characterized in that... Includes the following steps: Step 1: Based on the defect size of the ZM6 magnesium alloy workpiece to be repaired, cut a patch of the same material as the ZM6 magnesium alloy workpiece to be repaired. Step 2: Fix the ZM6 magnesium alloy workpiece to be repaired on the tooling table, cover the repaired part of the ZM6 magnesium alloy workpiece with the patch and fix it. Step 3: Use ultrasonic welding to weld the patch to the ZM6 magnesium alloy workpiece to be repaired. First, pre-weld in sections along the edge of the patch and the direction of the part of the ZM6 magnesium alloy workpiece to be repaired. Then, with the center of the patch as the origin, weld outward in a spiral manner to the edge of the patch. Step 4: Grind and polish the repaired area of ​​the ZM6 magnesium alloy workpiece to complete the repair.

2. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 1, characterized in that... Before cutting the patch, the part to be repaired of the ZM6 magnesium alloy workpiece is first ground. After grinding, the part to be repaired and its surrounding area are cleaned with anhydrous ethanol and then air-dried.

3. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 1, characterized in that... In step one, the thickness of the cut patch shall not exceed the thickness of the ZM6 magnesium alloy workpiece to be repaired.

4. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 1, characterized in that... The edges of the patch are chamfered.

5. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 1, characterized in that... In step two, the gap between the patch and the ZM6 magnesium alloy workpiece to be repaired is no more than 0.05 mm.

6. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 1, characterized in that... In step two, the ZM6 magnesium alloy workpiece to be repaired and the patch are fixed on the tooling table by negative pressure adsorption.

7. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 1, characterized in that... In step three, ultrasonic welding uses a tungsten electrode as the welding head. The tungsten electrode is a thorium tungsten electrode, and the end of the tungsten electrode is conical with a cone angle of 30° to 45°.

8. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 7, characterized in that... During ultrasonic welding, the distance between the end of the tungsten electrode and the surface of the patch is 0.1mm~0.3mm.

9. The method for mechanical ultrasonic welding repair of ZM6 magnesium alloy according to claim 8, characterized in that... During ultrasonic welding, the vibration frequency of the tungsten electrode is 15kHz~35kHz, the welding pressure is 0.2MPa~0.7MPa, and the amplitude is 25μm~55μm.

10. A ZM6 magnesium alloy mechanical ultrasonic welding repair system, characterized in that... The ZM6 magnesium alloy mechanical ultrasonic welding repair method according to any one of claims 1-9 is used to repair the ZM6 magnesium alloy workpiece to be repaired. The ZM6 magnesium alloy mechanical ultrasonic welding repair system includes a tooling table and a vibration generator. The tooling table is provided with a workpiece bearing station for bearing the ZM6 magnesium alloy workpiece to be repaired. The vibration generator is used to generate high-frequency vibration to perform ultrasonic welding between the ZM6 magnesium alloy workpiece to be repaired and the patch. The vibration output end of the vibration generator is provided with a vibration transmission rod, and the end of the vibration transmission rod is provided with a tungsten electrode.

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