Method for repairing zm6 magnesium alloy by mechanical ultrasonic variable-angle welding

Abstract

The application relates to a ZM6 magnesium alloy mechanical ultrasonic variable-angle welding repair method and belongs to the technical field of welding repair. In the process of ultrasonic welding repair, ultrasonic energy is applied along a direction with a certain angle with the normal line of the repair surface of the part to be repaired. With the movement of the welding head along the repair path, the angle of the certain angle is gradually increased, the ultrasonic energy is uniformly covered along the defect interface of the part to be repaired, and stress concentration is avoided. The application can effectively improve the bonding strength of the repair area, reduce the secondary defect occurrence rate and ensure the consistency and stability of the performance of the workpiece after repair by dynamically matching the defect characteristics to adjust the application direction of the ultrasonic energy and combining ultrasonic parameter collaborative control.

Description

Technical Field

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

[0002] ZM6 magnesium alloy is widely used in high-end equipment fields such as aerospace and automobile manufacturing due to its low density, high specific strength, good shock absorption, and excellent corrosion resistance. However, these components are prone to defects such as cracks and surface damage during service due to stress and wear, requiring welding repair to restore their performance.

[0003] Existing ultrasonic welding repair techniques for ZM6 magnesium alloys often employ a fixed approach, applying ultrasonic energy perpendicular to the normal direction of the repair surface. This approach presents several significant problems: First, ZM6 magnesium alloys have poor plasticity, and applying ultrasonic energy perpendicular to the normal direction of the repair surface can easily lead to stress concentration in the repair area, resulting in secondary cracks. Second, due to variations in defect extension directions and cross-sectional shapes, applying ultrasonic energy in a fixed direction cannot ensure sufficient energy transfer along the defect interface, leading to inadequate repair bonding. Third, the mechanical properties of the repaired joint are uneven, making it difficult to match the original properties of the base material and affecting the reliability of the component during service. Summary of the Invention

[0004] To overcome the above-mentioned defects in the prior art, the present invention provides a mechanical ultrasonic variable angle welding repair method for ZM6 magnesium alloy. By dynamically matching the defect characteristics and adjusting the direction of ultrasonic energy application, combined with the coordinated control of ultrasonic parameters, the bonding strength of the repair area can be effectively improved, the occurrence rate of secondary defects can be reduced, and the performance of the repaired workpiece can be guaranteed to be consistent and stable.

[0005] The technical solution adopted in this invention is: a mechanical ultrasonic variable angle welding repair method for ZM6 magnesium alloy. During the ultrasonic welding repair process, ultrasonic energy is applied along a direction that forms a certain angle with the normal of the repair surface of the part to be repaired. As the welding head moves along the repair path, the angle gradually increases to ensure that the ultrasonic energy is evenly covered along the defect interface of the part to be repaired, thus avoiding stress concentration.

[0006] Preferably, the included angle is 15° to 30°.

[0007] Preferably, the angle of the included angle increases gradually by an increment of 1° to 5°.

[0008] Preferably, during the gradual increase of the included angle, the increment of the included angle is the same each time.

[0009] Preferably, when the defect in the part to be repaired is a crack, the repair path is along the direction of crack extension, and the included angle increases gradually by one time as the welding head travels a set distance along the repair path; when the defect in the part to be repaired is a wear defect, the repair path is a plurality of concentric circles with the center of the wear area as the center, and the included angle increases gradually by one time as the welding head changes to a circular path from the inside to the outside along the repair path of the plurality of concentric circles.

[0010] Preferably, the set distance is 3mm to 5mm.

[0011] Preferably, the difference in radius between any two adjacent concentric circles is 2mm to 3mm.

[0012] Preferably, the amplitude of the ultrasound increases by 5% to 15% with each increase in the included angle.

[0013] Preferably, during ultrasonic welding repair, the direction of mechanical pressure and ultrasonic energy application remains consistent, and the mechanical pressure changes linearly with the depth of the defect in the part to be repaired.

[0014] Furthermore, for every 1 mm increase in the defect depth of the area to be repaired, the mechanical pressure increases linearly by 20 N.

[0015] Preferably, the ultrasonic frequency of the ultrasonic welding repair is 20kHz~40kHz, the amplitude is 30μm~80μm, the mechanical pressure is 50N~200N, and the welding temperature (controlled by ultrasonic self-heating) is 200℃~350℃.

[0016] Preferably, during the ultrasonic welding repair process, the welding temperature of the repair area is monitored in real time. If the welding temperature exceeds the preset temperature range, the direction of ultrasonic energy application and mechanical pressure are adjusted in a timely manner to ensure the stability of the ultrasonic welding repair process.

[0017] Preferably, the ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method includes the following steps: Step 1: Perform ultrasonic testing on the part of the ZM6 magnesium alloy workpiece to be repaired to obtain data on the direction of defect extension, depth and cross-sectional shape. Step 2: Based on the acquired data on the extension direction, depth, and cross-sectional shape of the defect, plan the repair path for ultrasonic welding repair according to the type of defect; Step 3: Based on the planned repair path, set the direction of ultrasonic energy application and the gradual increment of the included angle; Step 4: Set the ultrasonic parameters for ultrasonic welding repair; Step 5: Based on the direction of ultrasonic energy application, the gradual increase of the included angle, and the ultrasonic parameters, perform ultrasonic welding repair on the part of the ZM6 magnesium alloy workpiece to be repaired.

[0018] After ultrasonic welding repair is completed on the ZM6 magnesium alloy workpiece to be repaired, ultrasonic flaw detection technology can be used to detect the bonding state inside the repair area. Tensile test is used to test the bonding strength to ensure that there are no defects such as incomplete penetration or secondary cracks, and that the bonding strength is not less than 90% of the strength of the base material.

[0019] The beneficial effects of this invention are as follows: In the ultrasonic welding repair process of ZM6 magnesium alloy, this invention employs a variable-angle ultrasonic energy application strategy to ensure uniform distribution of ultrasonic energy along the defect interface. Compared to the traditional repair process that applies ultrasonic energy in a fixed direction, the bonding strength of the ZM6 magnesium alloy repair area can be increased by 20%~35%. It also effectively avoids stress concentration caused by applying ultrasonic energy perpendicular to the normal direction of the repair surface, reducing the secondary crack incidence rate by more than 90%, and the fatigue life of the repaired component is close to that of the original substrate. This invention is adapted to the low plasticity of ZM6 magnesium alloy, reducing the width of the heat-affected zone to 0.8mm~1.5mm, effectively improving the uniformity of the repair area's performance. It is suitable for repairing different types of defects and has strong versatility. This invention uses a parameter-coordinated control and real-time monitoring mechanism to ensure the stability and reliability of the repair process and reduce operational difficulty. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of one embodiment of the ultrasonic welding repair system used in implementing the present invention. Detailed Implementation

[0021] See Figure 1 This invention discloses a mechanical ultrasonic variable-angle welding repair method for ZM6 magnesium alloy, applicable to the precise repair of cracks, wear, and other defects in ZM6 magnesium alloy (a magnesium-zirconium-neodymium alloy of grade ZM6) workpieces, including the following steps: Step 1: Defect feature detection of the ZM6 magnesium alloy workpiece to be repaired Ultrasonic testing was used to detect the defects in the ZM6 magnesium alloy workpieces to be repaired, obtaining data on the endpoint location, extension direction, depth, and cross-sectional shape of the defects, and generating a three-dimensional model of the defect contour.

[0022] Ultrasonic flaw detectors are typically used to perform ultrasonic flaw detection on the parts of ZM6 magnesium alloy workpieces to be repaired.

[0023] Step 2: Repair Path Planning Based on the three-dimensional model of the defect contour generated in step one, the defect type of the ZM6 magnesium alloy workpiece to be repaired is determined. The defect types include crack defects and wear defects. The repair path of ultrasonic welding repair is planned according to the defect type.

[0024] When the defect in the part to be repaired is a crack, the repair path is preferably along the direction of crack extension; when the defect in the part to be repaired is a wear defect, the repair path is preferably multiple concentric circles with the center of the wear area as the center.

[0025] Step 3: Set the direction of ultrasonic energy application The direction of ultrasonic energy application is set according to the planned repair path. During ultrasonic welding repair, ultrasonic energy is applied along a direction that forms a certain angle with the normal of the repair surface of the part to be repaired. As the welding head moves along the repair path, the angle gradually increases to ensure that the ultrasonic energy uniformly covers the defect interface of the part to be repaired, avoiding stress concentration. An initial angle can be set at the beginning of the ultrasonic welding repair, and the angle can be dynamically adjusted (gradually increasing) as the welding head moves along the repair path.

[0026] The included angle is preferably 15° to 30°, for example, 15°, 20°, 25° or 30°. The increment of the included angle is preferably 1° to 5°, for example, 1°, 2°, 3° or 5°. During the gradual increase of the included angle, the increment of the included angle is preferably the same each time.

[0027] When the defect at the repair site is a crack, the preferred method for gradually increasing the included angle is that the included angle increases once every time the welding head travels a set distance along the repair path. The set distance is preferably 3mm to 5mm, for example, 3mm, 4mm, or 5mm. When the defect at the repair site is a wear defect, the preferred method for gradually increasing the included angle is that the included angle increases once every time the welding head changes to a circular path from the inside to the outside along a repair path of multiple concentric circles. The difference in radius between any two adjacent concentric circles is preferably 2mm to 3mm, for example, 2mm, 2.5mm, or 3mm, to ensure that the welding head always forms an optimal working angle with the defect interface.

[0028] Step 4: Set the ultrasonic parameters for ultrasonic welding repair The frequency of the ultrasonic welding repair is preferably set to 20kHz~40kHz, for example, 20kHz, 30kHz or 40kHz; the amplitude is preferably set to 30μm~80μm, for example, 30μm, 40μm, 50μm, 60μm or 80μm. During the ultrasonic welding repair process, the amplitude of the ultrasonic wave is preferably increased by 5%~15% for each increase in the included angle; the mechanical pressure is preferably set to 50N~200N, for example, 50N, 100N, 150N or 200N. During the ultrasonic welding repair process, the mechanical pressure and the direction of ultrasonic energy application are always consistent, and the mechanical pressure changes linearly with the defect depth of the part to be repaired. For every 1mm increase or decrease in the defect depth of the part to be repaired, the mechanical pressure is preferably linearly increased or decreased by 20N; the welding temperature (controlled by ultrasonic self-heating) is preferably set to 200℃~350℃, for example, 200℃, 250℃, 300℃ or 350℃, to avoid oxidation and grain coarsening of ZM6 magnesium alloy.

[0029] Step 5: Perform ultrasonic welding repair Based on the ultrasonic energy application direction, the gradually increasing angle of the included angle, and the ultrasonic parameters set in steps three and four, ultrasonic welding is performed on the part of the ZM6 magnesium alloy workpiece to be repaired along the repair path planned in step two to complete the defect repair.

[0030] During ultrasonic welding repair, it is preferable to monitor the welding temperature of the repair area in real time (which can be done using a temperature sensor) and the ultrasonic energy conduction efficiency. If the welding temperature exceeds the preset temperature range or the energy conduction is abnormal, the direction of ultrasonic energy application and mechanical pressure parameters should be adjusted in a timely manner to ensure the stability of the ultrasonic welding repair process.

[0031] After ultrasonic welding repair is completed on the ZM6 magnesium alloy workpiece to be repaired, ultrasonic flaw detection technology can be used to detect the bonding state inside the repair area. Tensile test is used to test the bonding strength to ensure that there are no defects such as incomplete penetration or secondary cracks, and that the bonding strength is not less than 90% of the strength of the base material.

[0032] The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method is implemented using an ultrasonic welding repair system. A preferred embodiment of the ultrasonic welding repair system is as follows: See Figure 2 The ultrasonic welding repair system includes a tooling table 1 and a vibration generator (a device that generates 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 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 3, and the end of the vibration transmission rod is coaxially provided with a welding head 4.

[0033] The welding head is preferably made of tungsten electrode, which is thorium tungsten electrode (purity ≥99.95%). The end of the tungsten electrode is conical (which can be formed by grinding), and the cone angle is 30°~45°.

[0034] 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.

[0035] 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.

[0036] The vibration transmission rod is preferably made of tungsten carbide to ensure efficient transmission of vibration energy. 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.

[0037] The 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 (e.g., argon) 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.

[0038] The 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 execution end of the robotic arm to automate the welding repair process. The ZM6 magnesium alloy 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 technologies.

[0039] The ultrasonic welding repair system may further include a central control unit, used to generate a three-dimensional model of the defect contour based on the ultrasonic flaw detection results of the ultrasonic flaw detector, plan a repair path based on the three-dimensional model of the defect contour, and generate a control program for the robotic arm based on the set ultrasonic energy application direction, the progressively increasing angle of the included angle, and the repair path. The program controls the robotic arm to carry the welding head (including the vibration generator) to perform ultrasonic welding repair on the ZM6 magnesium alloy workpiece to be repaired. The above-described operation of the central control unit can be implemented based on existing technology.

[0040] Example 1 (taking crack-type defects as an example): Step 1: Defect feature detection of the ZM6 magnesium alloy workpiece to be repaired A 5MHz ultrasonic flaw detector was used to perform ultrasonic flaw detection scanning on the ZM6 magnesium alloy workpiece to be repaired, and the endpoint position, extension direction, depth data and cross-sectional morphology data of the defect were obtained to generate a three-dimensional model of the defect contour. Step 2: Repair Path Planning Based on the three-dimensional model of the defect contour, the repair path is taken according to the extension direction of the crack defect; Step 3: Set the direction of ultrasonic energy application The initial angle between the direction of ultrasonic energy application and the normal of the repair surface of the part to be repaired is set to 20°. The angle increases by 3° for every 5mm that the welding head travels along the repair path. Step 4: Set the ultrasonic parameters for ultrasonic welding repair The ultrasonic frequency for ultrasonic welding repair is set to 30kHz, the amplitude is set to 50μm, and the amplitude is increased or decreased synchronously with the angle adjustment. The mechanical pressure is set to 80N, and the mechanical pressure is increased by 10N for every 0.5mm increase in defect depth. The welding temperature is set to be maintained between 280℃ and 320℃. Step 5: Perform ultrasonic welding repair Based on the ultrasonic energy application direction, the gradually increasing angle of the included angle, and the ultrasonic parameters set in steps three and four, ultrasonic welding is performed on the part of the ZM6 magnesium alloy workpiece to be repaired along the repair path planned in step two to complete the defect repair.

[0041] Example 2 (taking wear-related defects as an example): Step 1: Defect feature detection of the ZM6 magnesium alloy workpiece to be repaired A 5MHz ultrasonic flaw detector was used to perform ultrasonic flaw detection scanning on the ZM6 magnesium alloy workpiece to be repaired, and the endpoint position, extension direction, depth data and cross-sectional morphology data of the defect were obtained to generate a three-dimensional model of the defect contour. Step 2: Repair Path Planning Based on the 3D model of the defect contour, multiple concentric circles with the center of the wear area as the center are used as the repair path, and the number of concentric circles is set to 3. Step 3: Set the direction of ultrasonic energy application The initial angle between the direction of ultrasonic energy application and the normal of the repair surface of the part to be repaired is set to 15°. When the welding head changes to a circular path from the inside to the outside along multiple concentric repair paths, the angle increases by 5°. Step 4: Set the ultrasonic parameters for ultrasonic welding repair The ultrasonic frequency for ultrasonic welding repair is set to 25kHz, the amplitude is set to 40μm, and the amplitude is increased or decreased synchronously with the angle adjustment. The mechanical pressure is set to 100N. For every 0.5mm increase in defect depth, the mechanical pressure is increased by 10N. The welding temperature is set to be maintained between 250℃ and 300℃. Step 5: Perform ultrasonic welding repair Based on the ultrasonic energy application direction, the gradually increasing angle of the included angle, and the ultrasonic parameters set in steps three and four, ultrasonic welding is performed on the part of the ZM6 magnesium alloy workpiece to be repaired along the repair path planned in step two to complete the defect repair.

[0042] 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 mechanical ultrasonic variable-angle welding repair method for ZM6 magnesium alloy, characterized in that... During ultrasonic welding repair, ultrasonic energy is applied along a direction that forms a certain angle with the normal of the repair surface of the part to be repaired. As the welding head moves along the repair path, the angle gradually increases to ensure that the ultrasonic energy is evenly covered along the defect interface of the part to be repaired, thus avoiding stress concentration.

2. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 1, characterized in that... The included angle is 15°~30°.

3. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 2, characterized in that... The angle of the included angle gradually increases by an increment of 1° to 5°.

4. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 3, characterized in that... During the gradual increase of the included angle, the increment of the included angle is the same each time.

5. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 1, characterized in that... When the defect in the part to be repaired is a crack, the repair path is along the direction of crack extension, and the included angle increases gradually by increasing once for each set distance the welding head travels along the repair path. When the defect in the part to be repaired is a wear defect, the repair path is a series of concentric circles with the center of the wear area as the center, and the included angle increases gradually by increasing once for each circular path the welding head changes from the inside to the outside along the repair path of the multiple concentric circles.

6. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 1, characterized in that... For each increase in the included angle, the amplitude of the ultrasound increases by 5% to 15%.

7. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 1, characterized in that... During ultrasonic welding repair, the direction of mechanical pressure and ultrasonic energy application remains consistent, and the mechanical pressure changes linearly with the depth of the defect in the area to be repaired.

8. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 1, characterized in that... The ultrasonic welding repair uses an ultrasonic frequency of 20kHz~40kHz, an amplitude of 30μm~80μm, a mechanical pressure of 50N~200N, and a welding temperature of 200℃~350℃.

9. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to claim 1, characterized in that... During ultrasonic welding repair, the welding temperature of the repair area is monitored in real time. If the welding temperature exceeds the preset temperature range, the direction of ultrasonic energy application and mechanical pressure are adjusted in a timely manner to ensure the stability of the ultrasonic welding repair process.

10. The ZM6 magnesium alloy mechanical ultrasonic variable angle welding repair method according to any one of claims 1-9, characterized in that... Includes the following steps: Step 1: Perform ultrasonic testing on the part of the ZM6 magnesium alloy workpiece to be repaired to obtain data on the direction of defect extension, depth and cross-sectional shape. Step 2: Based on the acquired data on the extension direction, depth, and cross-sectional shape of the defect, plan the repair path for ultrasonic welding repair according to the type of defect; Step 3: Based on the planned repair path, set the direction of ultrasonic energy application and the gradual increment of the included angle; Step 4: Set the ultrasonic parameters for ultrasonic welding repair; Step 5: Based on the direction of ultrasonic energy application, the gradual increase of the included angle, and the ultrasonic parameters, perform ultrasonic welding repair on the part of the ZM6 magnesium alloy workpiece to be repaired.

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