A method of stitch-in dual pin friction stir repair

Abstract

The application provides a double-needle plunge friction stir repair method, and steps include: processing a preformed hole near a defect site on a workpiece and a filler plate and cleaning; clamping the workpiece and the filler plate; running a friction stir welding machine to drive a stirring needle of a repair tool to press into the preformed hole from above and move horizontally along a defect direction, during the movement, a first needle body of the stirring needle always penetrates the workpiece, and a second needle body of the stirring needle always locates in the filler plate; after the defect site on the workpiece is repaired and the stirring needle is withdrawn, the workpiece is cooled. The application greatly improves the mechanical properties of a repair area, can control surface forming of the repair area, the surface forming is smooth and beautiful, metallurgical bonding is good, the repair quality is improved, the irregular defect site does not need to be processed into a regular-shaped recess, the solid-phase friction stir repair process flow is greatly simplified, the repair process is more flexible, and the breadth and depth of the friction stir welding are widened.

Description

Technical Field

[0001] This invention belongs to the field of friction stir welding technology, specifically relating to an insertion-type double-needle friction stir repair method. Background Technology

[0002] Solid-state repair technology is a type of defect repair technology developed based on solid-state bonding technology. It mainly includes friction stir processing (FSP), friction plug welding (FPW), and filler friction stir welding (FFSW). FSP is primarily used to repair surface or near-surface cracks and weak bonding defects within components. However, for large-sized defects such as tunnels and trenches, FSP is difficult to effectively repair. Furthermore, repeated friction stir processing of the repair area can lead to residual stress and changes in surface condition, affecting performance. FPW is a solid-state repair technology for point defects, keyholes, or smaller volume defects. During repair, the defect needs to be manually removed, and then filled with a plug of the same or different metal. However, the repair process is cumbersome and cannot repair large defects such as tunnels and trenches. FFSW uses a filler metal tool head instead of a traditional welding tool head to fill defects, enabling the filling and repair of larger defects. However, the application of FFSW is also limited by the complexity of the filler tool head and the handling and control during repair.

[0003] In the prior art, document CN101670483 discloses a solid-state repair technology for defects in friction stir welding. This technology uses a filling stirring needle made of the same material as the weld. After pre-drilling a hole in the weld at the defect location, a consumable stirring head is used to frictionally fill the hole, thus repairing the defect. However, this technology requires the design of consumable stirring needles of different specifications for defects of different sizes before repair, making the welding process cumbersome and difficult to apply to large-volume tunnel-like defects.

[0004] Document CN108788504A discloses a method for repairing large-sized defects left by friction stir welding. This method is designed specifically for large-sized defects left by friction stir welding. During repair, a groove is first cut at the weld defect, then metal is filled into the groove using a fusion welding method. Finally, a retractable friction stir welding method is used to weld the fused filler metal, thereby repairing the defect. While this method can effectively repair large-sized defects, the heat input during fusion welding may expand the heat-affected zone, deteriorate the joint microstructure, and affect its performance. Furthermore, the repeated friction stir process may also adversely affect joint formation and performance. Summary of the Invention

[0005] To address the technical problems mentioned in the background section, this invention provides a penetrating double-needle friction stir repair method suitable for large-sized defects. This method involves placing a filler plate under the workpiece (the plate to be repaired) and using a specific repair tool to guide the filler plate into the defect area for repair. This not only yields a high-quality repair area with a smooth and aesthetically pleasing surface, good metallurgical bonding, and excellent performance, but also allows for rapid and precise removal of the filler plate and its excess. In this invention, the large-sized defect refers to a defect that can be repaired by friction stir welding and has a defect coverage area in the range of 3mm*3mm to 6mm*6mm.

[0006] The present invention adopts the following technical solution.

[0007] A method for repairing friction by inserting a double needle, comprising the following steps:

[0008] Step 1: Select a filler plate of the same material as the workpiece, and machine pre-drilled holes near the defective parts of the workpiece and on the filler plate. Then clean the workpiece and the filler plate.

[0009] Step 2: Attach the filler plate tightly to the lower wall of the workpiece and align the pre-drilled holes of the two. Then, clamp and fix the workpiece and the filler plate under the repair tool of the friction stir welding machine. The support surface supporting the lower end face of the filler plate is a plane.

[0010] Step 3: Run the friction stir welding machine and drive the stirring needle of the repair tool to press into the pre-drilled hole from above and move horizontally along the defect direction. During this movement, the first needle body of the stirring needle always penetrates the workpiece, and the second needle body of the stirring needle always remains inside the filler plate.

[0011] Step 4: After the defective parts on the workpiece are repaired and the stirring needle is removed, turn off the friction stir welding machine and let the workpiece cool to room temperature.

[0012] In this invention, the repair tool includes a stationary shoulder, a clamping member is inserted on the stationary shoulder, and a stirring needle is fixedly installed at the lower end of the clamping member. The clamping member and the stirring needle are arranged coaxially. The stirring needle includes an integrally formed first needle body and a second needle body. The diameter of the first needle body is smaller than the diameter of the second needle body. The first needle body includes a rod and a first thread provided on the rod, and an assembly thread is provided at the tail of the rod. The second needle body includes a column and a spiral groove provided on the side wall of the column, and a vortex groove is provided at the lower end of the column.

[0013] As a preferred option, the diameter of the pre-drilled hole is 1-2 mm larger than the diameter of the second needle body.

[0014] As a preferred option, during the horizontal movement of the stirring needle, the distance between the upper surface of the second needle body and the lower surface of the workpiece is controlled to be 1-5mm.

[0015] As a preferred embodiment, the diameter of the first needle body is 4-6mm, the pitch of the first thread is 0.5mm-1.5mm, the depth of the spiral groove is 0.3-1mm, and the width is 1-5mm; the diameter of the second needle body is 5-10mm, and the pitch of the spiral groove is 1-1.5mm.

[0016] As a preferred option, when the workpiece is a lightweight alloy such as aluminum or magnesium with a thickness of 3-15mm; the angle between the axis of the repair tool and the normal of the workpiece surface is 1-3°; the rotational speed of the repair tool is 800-1800rpm, the forward speed is 50-500mm / min, and the downward pressure of the repair tool is 0.1-0.2mm.

[0017] In order to quickly and accurately remove the excess filler material while repairing workpiece defects, the friction stir welding machine is operated in step 3, and the wire cutting equipment is also operated at the same time. The working segment of the wire cutting equipment is always parallel to the workpiece surface and passes through the interface area between the workpiece and the filler material. The friction stir welding machine and the wire cutting equipment are respectively mounted on their respective translation mechanisms, and the wire and the repair tool can be translated synchronously.

[0018] As a preferred embodiment, the distance between the wire and the outer wall of the second needle in the wire EDM machine is controlled to be 10-20mm, and the wire feed speed of the wire EDM machine is controlled to be 6000-1000mm. 2 / h.

[0019] Furthermore, after implementing step 2, step 30 is also included: first, place the wire of the wire cutting equipment on the outer end of the workpiece and face the junction area between the workpiece and the filler plate; after the stirring needle is pressed into the pre-made hole, control the operation of the wire cutting equipment and the operation of the translation mechanism of the wire cutting equipment. When the wire of the wire cutting equipment moves to a distance of 10-20mm between itself and the outer wall of the second needle, control the operation of the friction stir welding machine and the operation of the translation mechanism of the friction stir welding machine so that the wire and the repair tool can be translated synchronously.

[0020] To ensure a smooth reset of the wire EDM equipment, the equipment should be shut down after the stirring needle is withdrawn and the wire reaches the needle withdrawal area. Then, the equipment should be reset after the workpiece is removed.

[0021] Beneficial effects: In the process of repairing large-sized defects, the lower needle (second needle) penetrates into the filling plate, and under the extrusion of the lower needle and the guidance of the spiral groove, the plasticized material is extruded upwards and moves upwards to the defect, ultimately achieving solid-phase filling repair of the large-sized defect. This invention eliminates the melting and filling process in traditional large-volume defect repair, greatly improving the mechanical properties of the repaired area. It also allows for control of the surface formation of the repaired area, resulting in a smooth and aesthetically pleasing surface with good metallurgical bonding, thus improving repair quality. Furthermore, it eliminates the need to process irregular defect areas into regular-shaped concave holes, greatly simplifying the solid-phase friction stir repair process and making the repair process more flexible, expanding the breadth and depth of friction stir welding. More importantly, the solution of this invention allows for rapid and precise removal of the filling plate and excess filling material, completing the removal of the filling plate almost simultaneously with the completion of the large-sized defect repair, eliminating the tedious subsequent cutting of the filling plate and significantly simplifying the workload of cutting the filling plate. Attached Figure Description

[0022] Figure 1 This is a cross-sectional schematic diagram of the repair tool in use in Example 1;

[0023] Figure 2 This is a schematic diagram of the clamping component of the repair tool in the embodiment;

[0024] Figure 3 This is a schematic diagram of the stirring needle of the repair tool in the embodiment;

[0025] Figure 4 , Figure 5 This is a partial cross-sectional schematic diagram of the repair tool in use in Example 2. Detailed Implementation

[0026] The technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] Example 1

[0028] First, the repair tools for the friction stirrer in this embodiment will be described, such as... Figures 1 to 3As shown, the repair tool includes a stationary shoulder 4, on which a clamping member 5 is inserted. A stirring needle 13 is fixedly installed at the lower end of the clamping member 5, and the clamping member 5 and the stirring needle 13 are arranged coaxially. The stirring needle 13 includes an integrally formed first needle body and a second needle body. The diameter of the first needle body is smaller than that of the second needle body. The first needle body includes a rod 10 and a first thread 9 provided on the rod 10, and an assembly thread 11 is provided at the tail of the rod 10. The assembly thread 11 fits into the screw hole 6 at the lower part of the clamping member 5. The second needle body includes a column and a spiral groove 8 provided on the side wall of the column, and a vortex groove 7 is provided at the lower end of the column. The diameter of the first needle body is 5mm, and the pitch of the first thread 9 is 1mm; the depth of the vortex groove 7 is 0.8mm and the width is 2mm; the diameter of the second needle body is 8mm, the pitch of the spiral groove 8 is 1.2mm, and the lower edge of the second needle body is flush with the lower end face of the stationary shoulder 4.

[0029] A method for repairing friction by inserting a double needle, comprising the following steps:

[0030] Step 1: Select a filler plate 3 of the same material as workpiece 1 (aluminum alloy sheet with a wall thickness of 10mm), and machine pre-drilled holes near the defect location (defect length of 5.5mm) on workpiece 1 and on filler plate 3. Then clean workpiece 1 and filler plate 3. The diameter of the pre-drilled holes is 1.5mm larger than the diameter of the second needle body.

[0031] The pre-drilled hole is a round hole opened behind the defective part (relative to the forward movement direction of the repair tool). The position of the pre-drilled hole is kept at a certain distance from the defective part. This distance should be greater than the radius of the second needle body. This can ensure that the second needle body is smoothly pressed into the filler plate and generate heat to make the material reach a plasticized state.

[0032] During cleaning, mechanical grinding is used to remove the oxide film on the surface of the workpiece 1 in contact with the filling plate 3. Then, organic solvents or cleaning agents are used to wipe the contact surfaces to remove oil and metal powder adhering to the surface. The organic solvents used are anhydrous ethanol or acetone solution.

[0033] Step 2: Attach the filler plate 3 tightly to the lower wall of the workpiece 1 and align the pre-drilled holes of the two. Then, clamp and fix the workpiece 1 and the filler plate 3 under the repair tool of the friction stir welding machine. The support surface supporting the lower end face of the filler plate 3 is a plane. Adjust the working angle of the repair tool so that the angle between the axis of the repair tool and the normal of the surface of the workpiece 1 is 2°.

[0034] Step 3: Run the friction stir welding machine, driving the stirring pin of the repair tool to rotate while pressing it into the pre-drilled hole from above, so that the stationary shoulder 4 contacts and presses against the upper surface of the workpiece 1. Then, control the repair tool to move horizontally along the defect direction. During this movement, the clamping part 5 and the stirring pin rotate synchronously. The first needle body of the stirring pin always penetrates the workpiece 1, and the second needle body of the stirring pin always remains within the filler plate 3 (this state is as follows). Figure 1 As shown), the rotational speed of the repair tool is controlled at 1200 rpm, the forward speed is 200 mm / min, and the downward pressure of the repair tool is 0.15 mm; during the horizontal movement of the stirring needle, the distance between the upper surface of the second needle body and the lower surface of the workpiece 1 is controlled at 2 mm.

[0035] Step 4: After the defective parts on workpiece 1 are repaired and the stirring needle is removed, turn off the friction stir welding machine and let workpiece 1 cool to room temperature.

[0036] Example 2

[0037] The repair tools and supporting equipment for the friction stirrer in this embodiment will be described first, with reference to the numbers in the accompanying drawings. Figures 1 to 3 As shown, the repair tool includes a stationary shoulder 4, a clamping member 5 passing through the stationary shoulder 4, and a stirring needle 13 fixedly installed at the lower end of the clamping member 5. The clamping member 5 and the stirring needle 13 are arranged coaxially. The stirring needle 13 includes an integrally formed first needle body and a second needle body. The diameter of the first needle body is smaller than that of the second needle body. The first needle body includes a rod 10 and a first thread 9 provided on the rod 10, and an assembly thread 11 is provided at the tail of the rod 10. The second needle body includes a column and a spiral groove 8 provided on the side wall of the column, and a vortex groove 7 is provided at the lower end of the column. The diameter of the first needle body is 6mm, the pitch of the first thread 9 is 1.5mm, the depth of the vortex groove 7 is 1mm, and the width is 3mm. The diameter of the second needle body is 10mm, the pitch of the spiral groove 8 is 1.5mm, and the lower edge of the second needle body is flush with the lower end face of the stationary shoulder 4. In this embodiment, a wire cutting device is also included. The wire cutting device is installed on the first translation mechanism. When the first translation mechanism translates, it drives the wire cutting device to translate. The wire 14 of the wire cutting device and the repair tool can translate synchronously.

[0038] A method for repairing friction by inserting a double needle, comprising the following steps:

[0039] Step 1: Select a filler plate 3 of the same material as workpiece 1 (magnesium alloy plate with a wall thickness of 5mm), and machine pre-drilled holes near the defect location (defect length of 4.8mm) on workpiece 1 and on filler plate 3. Then clean workpiece 1 and filler plate 3. The width of filler plate 3 shall not exceed 30mm. The diameter of the pre-drilled hole is 2mm larger than the diameter of the second needle body.

[0040] The pre-drilled hole is a round hole opened behind the defective part (relative to the forward movement direction of the repair tool). The position of the pre-drilled hole is kept at a certain distance from the defective part. This distance should be greater than the radius of the second needle body. This can ensure that the second needle body is smoothly pressed into the filler plate and generate heat to make the material reach a plasticized state.

[0041] During cleaning, mechanical grinding is used to remove the oxide film on the surface of the workpiece 1 in contact with the filling plate 3. Then, organic solvents or cleaning agents are used to wipe the contact surfaces to remove oil and metal powder adhering to the surface. The organic solvents used are anhydrous ethanol or acetone solution.

[0042] Step 2: Attach the filler plate 3 tightly to the lower wall of the workpiece 1 and align the pre-drilled holes of the two. Then, clamp and fix the workpiece 1 and the filler plate 3 under the repair tool of the friction stir welding machine. The support surface supporting the lower end face of the filler plate 3 is a plane. Adjust the working angle of the repair tool so that the angle between the axis of the repair tool and the normal of the surface of the workpiece 1 is 1.5°.

[0043] Step 30: First, place the wire 14 of the wire EDM equipment on the outer end of the workpiece 1, directly facing the interface between the workpiece 1 and the filler plate 3. Adjust the wire 14 of the wire EDM equipment so that its working segment (the segment performing wire cutting) is always parallel to the surface of the workpiece 1. This state is as follows: Figure 4 As shown;

[0044] Step 3: Run the friction stir welding machine, drive the stirring pin of the repair tool to rotate while pressing it into the pre-drilled hole from above, so that the stationary shoulder 4 contacts and presses against the upper surface of the workpiece 1. Then control the repair tool to move horizontally along the defect direction. During this movement, the clamping part 5 and the stirring pin rotate synchronously. The first needle body of the stirring pin always penetrates the workpiece 1, and the second needle body of the stirring pin always remains within the filling plate 3. The rotation speed of the repair tool is controlled at 1500 rpm, the forward speed is 300 mm / min, and the downward pressure of the repair tool is 0.1 mm. During the horizontal movement of the stirring pin, the distance between the upper surface of the second needle body and the lower surface of the workpiece 1 is controlled at 1 mm.

[0045] In step 3, after the stirring needle is pressed into the pre-drilled hole, the wire cutting equipment and the first translation mechanism are controlled to operate (the cutting equipment is mounted on the first translation mechanism, and the moving speed of the first translation mechanism is the translation speed of the wire 14, which is 300 mm / min). The wire feed speed of the wire cutting equipment is controlled to be 8000 mm / min. 2 / h, when the wire 14 of the wire cutting equipment moves to a distance of 10-20mm between itself and the outer wall of the second needle, control the operation of the friction stir welding machine and its translation mechanism to synchronize the wire 14 and the repair tool. This state is as follows: Figure 5As shown; when the cutting equipment is running, the working segment of the wire 14 is always parallel to the surface of the workpiece 1 and passes through the junction area between the workpiece 1 and the filler plate 3.

[0046] Figure 4 and Figure 5 In the diagram, the arrows indicate the forward movement direction of the repair tool and the translation direction of the wire cutting equipment;

[0047] Step 4: After the defective parts on workpiece 1 are repaired and the stirring pin is withdrawn, turn off the friction stir welding machine and let workpiece 1 cool to room temperature. When the stirring pin is withdrawn and the wire 14 of the wire EDM equipment reaches the pin withdrawal area, turn off the wire EDM equipment, then control the wire EDM equipment to reset after removing workpiece 1, and finally remove the cut filler plate 3.

[0048] In this embodiment, the lower end face of the filler plate 3 is supported by a plane. The wire 14 of the wire cutting device passes through the (cutting) area, leaving a very narrow gap 16 (i.e., wire cutting gap) at the junction of the workpiece 1 and the filler plate 3. This gap 16 will not cause the workpiece to fall / shift downwards and will not affect the operation of the repair tool. During use, the stirring needle 13 moves forward while rotating, plasticizing the material around the stirring needle 13. The wire 14 moves forward behind the stirring needle 13. With the help of the wire 14, the junction area between the newly formed workpiece 1 and the filler plate 3 (the metallurgical bonding area in this state has just completed the metallurgical bonding but is still in a thermal state, making it very easy and smooth to cut) is wire cut, thereby flexibly, quickly and accurately separating the junction area between the workpiece 1 and the filler plate 3. This solution is also one of the key points / ingenious points of this invention.

[0049] In the process of repairing large-sized defects, the lower needle (second needle) is inserted into the filling plate 3, and under the extrusion of the lower needle and the guidance of the spiral groove, the plasticized material is extruded upwards and moved to the defect, ultimately achieving solid-phase filling repair of the large-sized defect. This method eliminates the melting and filling process in the traditional large-volume defect repair process, greatly improving the mechanical properties of the repaired area. It also allows for control of the surface formation of the repaired area, resulting in a smooth and aesthetically pleasing surface with good metallurgical bonding, thus improving repair quality. Furthermore, it eliminates the need to process irregular defect areas into regular-shaped concave holes, greatly simplifying the solid-phase friction stir repair process and making the repair process more flexible, expanding the breadth and depth of friction stir welding. More importantly, this scheme allows for the rapid and precise removal of the filling plate 3 and the removal of any excess filling plate 3. The removal of the filling plate is completed almost simultaneously with the completion of the large-sized defect repair, eliminating the tedious subsequent cutting of the filling plate 3 and significantly reducing the workload of cutting the filling plate 3.

Claims

1. A method for repairing metallized double-needle agitation friction, characterized in that the steps include... include: Step 1: Select a filler plate (3) of the same material as the workpiece (1), and process pre-drilled holes near the defective part of the workpiece (1) and the filler plate (3). Then clean the workpiece (1) and the filler plate (3). Step 2, attach the filler plate (3) tightly to the lower wall of the workpiece (1) and align the pre-drilled holes of the two. Then, clamp and fix the workpiece (1) and the filler plate (3) under the repair tool of the friction stir welding machine. The support surface supporting the lower end face of the filler plate (3) is a plane. Step 3: Run the friction stir welding machine and drive the stirring needle of the repair tool to press into the pre-made hole from above and move horizontally along the defect direction. During this movement, the first needle body of the stirring needle always penetrates the workpiece (1), and the second needle body of the stirring needle always resides inside the filler plate (3). Step 4: After the defective parts on the workpiece (1) are repaired and the stirring needle is removed, turn off the friction stir welding machine and place the workpiece (1) to cool to room temperature. The repair tool includes a stationary shoulder (4), a clamping member (5) is inserted on the stationary shoulder (4), and a stirring needle (13) is fixedly installed at the lower end of the clamping member (5). The clamping member (5) and the stirring needle (13) are arranged coaxially. The stirring needle (13) includes an integrally formed first needle body and a second needle body. The diameter of the first needle body is smaller than that of the second needle body. The first needle body includes a rod body (10) and a first thread (9) provided on the rod body (10), and an assembly thread (11) is provided at the tail of the rod body (10). The second needle body includes a column body and a spiral groove (8) provided on the side wall of the column body, and a vortex groove (7) is provided at the lower end of the column body.

2. The method for repairing by inserting a double-needle agitation friction according to claim 1, characterized in that: The diameter of the pre-drilled hole is 1-2 mm larger than the diameter of the second needle body.

3. The method for repairing by inserting a double-needle agitation friction according to claim 2, characterized in that: During the horizontal movement of the stirring needle, the distance between the upper surface of the second needle body and the lower surface of the workpiece (1) is controlled to be 1-5mm.

4. The method for repairing by inserting a double-needle agitation friction according to claim 3, characterized in that: The diameter of the first needle body is 4-6mm, and the pitch of the first thread (9) is 0.5mm-1.5mm; the depth of the spiral groove (7) is 0.3-1mm and the width is 1-5mm; the diameter of the second needle body is 5-10mm, and the pitch of the spiral groove (8) is 1-1.5mm.

5. The method for repairing by inserting a double-needle agitation friction according to claim 4, characterized in that: When the workpiece (1) is an aluminum alloy or magnesium alloy with a thickness of 3-15mm; the angle between the axis of the repair tool and the normal of the surface of the workpiece (1) is 1-3°; the rotation speed of the repair tool is 800-1800rpm, the forward speed is 50-500mm / min, and the downward pressure of the repair tool is 0.1-0.2mm.

6. The method for repairing by inserting a double-needle agitation friction according to any one of claims 1-5, characterized in that: In step 3, the friction stir welding machine is operated while the wire cutting equipment is also operated. The working segment of the wire (14) of the wire cutting equipment is always parallel to the surface of the workpiece (1) and passes through the junction area between the workpiece (1) and the filler plate (3). The friction stir welding machine and the wire cutting equipment are respectively installed on their respective translation mechanisms, and the wire (14) and the repair tool can be translated synchronously.

7. The method for repairing by inserting a double-needle agitation friction according to claim 6, characterized in that: The distance between the wire (14) of the wire cutting equipment and the outer wall of the second needle is controlled to be 10-20mm, and the wire feeding speed of the wire cutting equipment is controlled to be 6000-1000mm² / h.

8. The method for repairing by inserting a double-needle agitation friction according to claim 7, characterized in that, The steps following step 2 are as follows: First, place the wire (14) of the wire cutting equipment on the outer end of the workpiece (1) and face the junction area between the workpiece (1) and the filler plate (3); After the stirring needle is pressed into the pre-made hole, control the operation of the wire cutting equipment and the operation of the translation mechanism of the wire cutting equipment. When the wire (14) of the wire cutting equipment moves to a distance of 10-20mm between itself and the outer wall of the second needle, control the operation of the friction stir welding machine and the operation of the translation mechanism of the friction stir welding machine so that the wire (14) and the repair tool can be translated synchronously.

9. The method for repairing by inserting a double-needle agitation friction according to claim 8, characterized in that: When the stirring needle is withdrawn and the wire (14) of the wire EDM device runs to the needle withdrawal area, the wire EDM device is turned off, and then the wire EDM device is reset after the workpiece (1) is removed.

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