Friction stir welding device and method driven by a penetrative double shoulder

Abstract

The present invention relates to the field of welding technology, and provides a friction stir welding device and method driven by a penetrative double shoulder, the device comprising a stirring tool, a lower shoulder spacer, a rotating head, a moving assembly, a positioning platform and a workbench; the positioning platform and the moving assembly are both arranged on the workbench, the lower shoulder spacer is arranged on the moving assembly through the rotating head, the positioning platform is used for positioning the workpiece to be welded, the stirring tool and the lower shoulder spacer are respectively located above and below the workpiece to be welded, and the lower shoulder spacer can rotate under the drive of the rotating head and the upper end surface thereof is in close contact with the lower surface of the workpiece to be welded. In the present invention, the lower shoulder spacer rotates to generate heat by friction with the back of the workpiece to be welded, softening the material, reducing the forward resistance of the stirring tool and the lower shoulder spacer during the welding process, avoiding contact wear between the stirring pin and the hole of the lower shoulder during welding, improving the welding efficiency, and realizing a stable and efficient welding process.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, and particularly to a friction stir welding device and method driven by a penetrating double shoulder. Background Art

[0002] As a new type of solid-phase welding technology, friction stir welding is widely used in large-scale manufacturing fields such as rockets, ships, and trains due to its advantages of environmental protection and high automation. Traditional friction stir welding usually does not penetrate the workpiece, so it is easy to cause defects such as incomplete penetration at the root of the weld. This defect is difficult to detect and will reduce the performance of the welded joint. Therefore, there are relatively large potential risks.

[0003] To solve this problem, the prior art mainly realizes penetrating double shoulder friction stir welding through two methods: long pin stirring tool welding and lower shoulder auxiliary support. Patent document CN105382405A discloses a static shoulder-assisted support inclined penetration friction stir welding device and method, which realizes friction stir penetration welding by using the method of synchronously moving a long pin stirring tool and a static shoulder with a blind hole. This welding method can effectively avoid incomplete penetration. However, when welding high-strength thick plate workpieces, the stirring pin is overloaded and deformed, and due to the large forward resistance, it is easy to cause the stirring tool and the static shoulder to move out of sync along the welding direction. Therefore, during the welding process, the stirring pin is prone to contact with the static shoulder, resulting in a certain degree of wear and reducing the life of the stirring tool. In addition, when welding thick plates, the rotation of a single shoulder will cause the joint morphology to be uneven, with too much heat input at the upper end of the weld and decreasing downward. The joint morphology presents a "conical shape", ultimately resulting in uneven weld tissue performance. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide a friction stir welding device and method driven by a penetrating double shoulder.

[0005] A friction stir welding device driven by a penetrating double shoulder according to the present invention includes a stirring tool, a lower shoulder pad, a rotating head, a moving component, a positioning platform, and a workbench.

[0006] The positioning platform and the moving component are both arranged on the workbench. The lower shoulder pad is arranged on the moving component through the rotating head. The positioning platform is used to position the workpiece to be welded. Among them, the stirring tool and the lower shoulder pad are respectively located above and below the workpiece to be welded and are arranged opposite to each other. The stirring tool can be driven to rotate. During welding, the stirring tool and the lower shoulder pad can move synchronously along the welding direction and always remain on the same axis. The lower shoulder pad can be rotated under the drive of the rotating head, and its upper end surface is in close contact with the lower surface of the workpiece to be welded.

[0007] Preferably, the positioning platform includes a first positioning member and a second positioning member, and both the first positioning member and the second positioning member are installed on the workbench;

[0008] The moving assembly includes a linear guide rail and a moving platform. The two linear guide rails are arranged along the welding direction and are both installed between the first positioning member and the second positioning member. The moving platform is installed on the linear guide rail and can slide along the length direction of the linear guide rail.

[0009] Preferably, the rotating head is detachably fixed on the moving platform, the lower shoulder pad is detachably fixed on the rotating head, and the workpiece to be welded is assembled on the positioning platform and fixed by a fixture so that the back surface of the workpiece to be welded is in close contact with the shoulder surface of the lower shoulder pad.

[0010] Preferably, the lower shoulder pad is of a cylindrical structure and has a circular hole in the center. The stirring tool has an upper shoulder and a stirring pin disposed at the bottom of the upper shoulder, and the length of the stirring pin is greater than the thickness of the workpiece to be welded;

[0011] During welding, the upper shoulder contacts the upper surface of the workpiece to be welded.

[0012] Preferably, the diameter of the circular hole on the lower shoulder pad is greater than the maximum diameter of the stirring pin, and the depth of the circular hole is greater than the difference between the thickness of the workpiece to be welded and the length of the stirring pin.

[0013] Preferably, there is a double rotating head, and both the stirring tool and the lower shoulder pad can be independently driven, and any one of the parameters of the shoulder diameter, rotation speed, and rotation direction of the lower shoulder pad can be set to be the same as or different from those of the stirring tool.

[0014] Preferably, when the rotating head does not rotate, the lower shoulder pad can be used as a stationary lower shoulder pad.

[0015] A friction stir welding method with a penetrating double shoulder drive according to the present invention includes the following steps:

[0016] Preparatory step: Assemble the stirring tool on the friction stir welding machine, install the lower shoulder pad on the rotating head so that the shoulder surface of the lower shoulder pad is on the same horizontal plane as the upper surface of the positioning platform, place the center of the stirring pin of the stirring tool coaxially with the center of the circular hole of the lower shoulder pad, record the X and Y direction coordinates, drive the stirring tool and the lower shoulder pad to move along the welding direction in an unloaded state, and adjust them to move synchronously;

[0017] Positioning welding steps: Use a positioning welding tool for positioning welding. Fix the workpieces to be welded on the positioning platform with a fixture so that the butt joint of the workpieces to be welded is located on the axis of the positioning welding tool, and the shoulder surface of the lower shoulder pad is in close contact with the back of the workpiece to be welded; Input the selected welding process parameters into the control system and adjust the inclination angle of the positioning welding tool. Start the friction stir welding machine for positioning welding. During positioning welding, the rotating head is not started, the lower shoulder pad is relatively stationary, and the welding method is that the workpiece to be welded is fixed, and the positioning welding tool and the lower shoulder pad move synchronously along the welding direction;

[0018] Formal welding steps: Replace the positioning welding tool with a stirring tool, and move the stirring tool to the initial position. Change the welding process parameters of the friction stir welding machine in the first control system, and input the process parameters of the rotating head in the second control system. After centering again, start the two system programs simultaneously for formal welding. The welding method is that the workpiece to be welded is fixed, and the stirring tool and the lower shoulder pad move synchronously along the welding direction.

[0019] Preferably, the inclination angle of the stirring tool on the friction stir welding machine is 2.5°.

[0020] Preferably, during the welding process, the linear guide rail, the positioning platform, the fixture, and the workpiece to be welded are stationary. The stirring pin of the stirring tool penetrates the workpiece to be welded and inserts into the round hole of the lower shoulder pad, and the shoulder surface of the lower shoulder pad is in contact with the lower surface of the workpiece to be welded.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the present invention, the lower shoulder pad rotates and generates heat by friction with the back of the workpiece to be welded, softening the material, reducing the forward resistance of the stirring tool and the lower shoulder pad during the welding process, avoiding contact wear between the stirring pin and the hole of the lower shoulder during welding, improving the welding efficiency, forming a "dumbbell-shaped" welding joint, extending the service life of the stirring tool, and realizing a stable and efficient welding process.

[0023] 2. The rotating head in the present invention can independently control the rotation of the lower shoulder pad, can achieve the same speed or different speeds of rotation of the upper and lower shoulders, and can also achieve the same direction or opposite direction of rotation, which is also helpful for improving the welding efficiency. Description of the Drawings

[0024] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, purposes, and advantages of the present invention will become more obvious:

[0025] Figure 1 It is a schematic central cross-sectional view of the device in the present invention;

[0026] Figure 2 It is a schematic top view of the structure of the lower shoulder pad;

[0027] Figure 3 Structural sectional view of the lower shoulder pad

[0028] Figure 4 is Figure 1 Partially enlarged view of the stirring tool and the lower shoulder pad in

[0029] As shown in the figure:

[0030] Stirring tool 1

[0031] Lower shoulder pad 2

[0032] Workpiece to be welded 3

[0033] Rotating head 4

[0034] Linear guide 5

[0035] Moving platform 6

[0036] Fixture 7

[0037] Positioning platform 8

[0038] Workbench 9 Specific implementation mode

[0039] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0040] The present invention provides a friction stir welding device driven by a penetrating double shoulder, including a stirring tool 1, a lower shoulder pad 2, a rotating head 4, a moving component, a positioning platform 8 and a workbench 9. The positioning platform 8 and the moving component are both arranged on the workbench 9. The lower shoulder pad 2 is arranged on the moving component through the rotating head 4. The positioning platform 8 is used to position the workpiece to be welded 3. Among them, the stirring tool 1 and the lower shoulder pad 2 are respectively located above and below the workpiece to be welded 3 and are arranged opposite to each other and can move synchronously, that is, the stirring tool 1 is arranged directly above the lower shoulder pad 2. The lower shoulder pad 2 can rotate under the drive of the rotating head 4 and the upper end surface is in close contact with the lower surface of the workpiece to be welded 3. The stirring tool 1 and the lower shoulder pad 2 move synchronously along the welding direction during welding and always keep the two on the same axis.

[0041] The positioning platform 8 includes a first positioning member and a second positioning member. Both the first positioning member and the second positioning member are installed on the workbench 9. The moving assembly includes a linear guide rail 5 and a moving platform 6. Two linear guide rails 5 are arranged along the welding direction and are both installed between the first positioning member and the second positioning member. The moving platform 6 is installed on the linear guide rail 5 and can slide along the length direction of the linear guide rail 5. The rotating head 4 is fixed on the moving platform 6. The lower shoulder spacer 2 is detachably fixed on the rotating head 4. The stirring tool 1 is installed on the friction stir welding machine. The workpiece to be welded 3 is assembled on the positioning platform 8 and fixed by a fixture 7 to ensure that the back surface of the workpiece to be welded 3 is in close contact with the shoulder surface of the lower shoulder spacer 2.

[0042] As Figure 2 , Figure 3 shown, the lower shoulder spacer 2 is a double-layer cylindrical structure. A round hole is machined in the center of the upper cylinder, and four through holes are evenly distributed on the lower cylinder for assembly on the rotating head 4.

[0043] The stirring tool 1 consists of a stirring pin and an upper shoulder, and the stirring pin and the upper shoulder rotate coaxially. The stirring pin has three cutting surfaces and is located in the middle of the upper shoulder. The length of the stirring pin is greater than the thickness of the workpiece to be welded 3. Preferably, the length of the stirring pin of the stirring tool 1 is 1 mm greater than the thickness of the workpiece to be welded 3.

[0044] In practical applications, the shoulder diameter of the lower shoulder spacer 2 (which can be understood as Figure 4 M in Figure 4 ) can be equal to the shoulder diameter of the stirring tool 1 (which can be understood as Figure 4 L in Figure 4 ), or it can be not equal to the shoulder diameter of the stirring tool 1. The diameter of the round hole on the lower shoulder spacer 2 (which can be understood as Figure 4 N in Figure 4 ) is greater than the root diameter of the stirring pin of the stirring tool 1 (which can be understood as Figure 4 K in

[0045] ), and the hole depth is greater than the difference between the thickness of the workpiece to be welded 3 and the length of the stirring pin. Preferably, the diameter of the lower shoulder spacer 2 is the same as the diameter of the upper shoulder of the stirring tool 1. The diameter of the round hole of the lower shoulder spacer 2 is 4 mm larger than the root diameter of the stirring pin of the stirring tool 1, and the depth of the round hole of the lower shoulder spacer 2 is 1.5 mm larger than the difference between the thickness of the workpiece to be welded 3 and the length of the stirring pin.

[0045] During the welding process, the workpiece to be welded 3 remains stationary, and the stirring tool 1 and the lower shoulder spacer 2 move synchronously and rotate simultaneously along the welding direction to achieve the welding process.

[0046] The present invention also provides a friction stir welding method, which includes the following steps:

[0047] Preparatory steps, positioning welding steps, and formal welding steps.

[0048] Taking the welding of 10-mm-thick 2219 aluminum alloy as an example, the steps of the penetration-type double-shoulder driven friction stir welding method are described by using the stirring tool 1 and the lower shoulder spacer 2. In this example, the shoulder diameter, rotation direction, and rotation speed of the lower shoulder spacer 2 are the same as those of the stirring tool 1.

[0049] In this example, the upper shoulder diameter of the stirring tool 1 is 26 mm, the stirring pin is a conical stirring pin with three cutting surfaces and a right-handed thread, the pin length is 11 mm, and the root diameter is 6 mm; the lower shoulder spacer 2 has a round hole, the lower shoulder diameter is 26 mm, the round hole is located at the center of the lower shoulder spacer 2, and the size is 10 mm (diameter) × 2.5 mm (depth).

[0050] A friction stir welding method in the present invention includes the following steps:

[0051] Preparatory steps: Assemble the stirring tool 1 on the friction stir welding machine, install the lower shoulder spacer 2 on the rotating head 4, the shoulder surface of the lower shoulder spacer 2 and the upper surface of the positioning platform 8 are on the same horizontal plane, the center of the stirring pin of the stirring tool 1 is placed coaxially with the center of the round hole of the lower shoulder spacer 2, record the coordinates in the X and Y directions, start the device to make the stirring tool 1 and the lower shoulder spacer 2 move along the welding direction in the no-load state, and observe whether they move synchronously. If they do not move synchronously, adjust until they move synchronously;

[0052] Positioning welding steps: After ensuring that the stirring tool 1 and the lower shoulder spacer 2 move synchronously, use the positioning welding tool for positioning welding, the pin length is 2 - 2.5 mm, fix the workpiece 3 to be welded on the positioning platform 8 by using the fixture 7, ensure that the butt joint of the workpiece 3 to be welded is located at the axis center of the positioning welding tool, the shoulder surface of the lower shoulder spacer 2 is in close contact with the back of the workpiece 3 to be welded, input the selected welding process parameters into the control system (for example, set the rotation speed of the positioning welding tool to 600 r / min, rotate counterclockwise, the welding speed is 200 mm / min, and the penetration amount is 0.1 mm - 0.2 mm), and adjust the inclination angle of the positioning welding tool (for example, set the positioning welding tool to 2.5°), start the friction stir welding machine for positioning welding. During positioning welding, the rotating head 4 does not start, the lower shoulder spacer 2 is relatively stationary (for example, set the rotation speed of the lower shoulder spacer to 0 r / min, and the penetration amount is 0 mm), and the welding method is that the workpiece 3 to be welded is fixed and the positioning welding tool and the lower shoulder spacer 2 move synchronously along the welding direction;

[0053] Formal welding steps: Remove the tack welding tool, replace it with the stirring tool 1, and move it to the initial position. Change the welding process parameters in the first control system of the friction stir welding machine (for example, set the rotation speed of the stirring tool to 500 r / min, rotate counterclockwise, the welding speed to 150 mm / min, the penetration amount to 0.1 mm - 0.2 mm, and the inclination angle of the stirring tool 1 to 2.5°). Input the process parameters in the second control system of the rotating head 4 (for example, set the rotation speed of the lower shoulder pad to 500 r / min, rotate counterclockwise, the travel speed of the rotating head 4 to 150 mm / min, and the penetration amount to 0 mm). After centering again, start the two system programs simultaneously for formal welding. The welding method is that the workpiece to be welded 3 remains stationary, and the stirring tool 1 and the lower shoulder pad 2 move synchronously along the welding direction.

[0054] The penetration - type double - shoulder driven friction stir welding method provided in the present invention has the following beneficial effects compared with the prior art:

[0055] Firstly, it solves the problem of contact wear between the stirring pin and the lower shoulder: By rotating the lower shoulder pad 2, heat is generated by friction with the workpiece to be welded 3, softening the material, reducing the forward resistance, and ensuring the synchronous movement of the stirring tool and the lower shoulder pad, thus avoiding the risk of contact wear between the stirring pin and the lower shoulder.

[0056] Secondly, it improves the welding efficiency: When driven by double shoulders, both the upper and lower shoulders generate heat by friction with the workpiece to be welded. Therefore, the heat input will increase. At this time, the welding speed can be increased to reduce the heat input, saving the welding time and improving the welding efficiency.

[0057] Thirdly, it improves the quality of the welded joint: In double - shoulder driven friction stir welding, both the upper and lower shoulders generate heat, and the heat distribution in the joint is uniform up and down. The degree of tissue evolution is close, and the joint presents a "dumbbell shape". For thick plates, the joint performance can be significantly improved.

[0058] Finally, it realizes a multi - functional welding method: When welding thin plates, it is required that the heat input should not be too high. At this time, without turning on the rotating head of the lower shoulder, the penetration - type stationary - shoulder friction stir welding can be realized; when welding thick plates, turning on the rotating head can realize the penetration - type double - shoulder driven friction stir welding.

[0059] The above advantages can achieve a high - efficiency welding process and obtain high - quality welded joints.

[0060] The penetration - type double - shoulder driven friction stir welding method of the present invention can solve the problem that the stirring pin is prone to mutual wear with the lower shoulder pad during the existing penetration - type friction stir welding process, and form a "dumbbell - shaped" welded joint.

[0061] A set of rotating heads 4 is built under the lower shoulder pad 2 of the present invention, enabling the lower shoulder pad 2 to rotate independently without relying on the welding head, achieving friction stir welding with a penetrating dual-shoulder drive. Since heat is generated by friction between the lower shoulder pad 2 and the back surface of the workpiece 3 during rotation, the welding heat input can be increased to a certain extent, softening the workpiece to be welded, reducing the forward resistance between the stirring tool and the lower shoulder pad 2 during welding, and effectively avoiding mutual wear between the stirring pin and the lower shoulder pad 2 during the welding of high-strength thick-plate workpieces. In addition, the dual-shoulder drive can increase the heat generation during welding and evenly distribute the weld seam, with the joint presenting a "dumbbell shape" and the joint performance being improved. The dual-shoulder drive can also increase the welding speed and improve the welding efficiency. Thus, a more stable and efficient welding process is achieved, and finally, a high-quality welded joint is obtained.

[0062] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0063] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other.

Claims

1. A penetrating double-shoulder driven friction stir welding device, characterized in that: It comprises a stirring tool (1), a lower shoulder pad (2), a rotating head (4), a moving component, a positioning platform (8) and a workbench (9); The positioning platform (8) and the moving assembly are both arranged on the workbench (9); the lower shoulder pad (2) is arranged on the moving assembly via a rotating machine head (4); the positioning platform (8) is used to position the workpiece (3) to be welded; wherein the stirring tool (1) and the lower shoulder pad (2) are respectively located above and below the workpiece (3) to be welded and are arranged opposite to each other; the stirring tool (1) can be driven to rotate; during welding, the stirring tool (1) and the lower shoulder pad (2) can move synchronously along the welding direction and both are always kept on the same axis; the lower shoulder pad (2) can rotate under the drive of the rotating machine head (4) and the upper end surface is in close contact with the bottom of the workpiece (3) to be welded; The positioning platform (8) comprises a first positioning member and a second positioning member, and the first positioning member and the second positioning member are both mounted on a workbench (9); The moving assembly comprises a linear guide rail (5) and a moving platform (6), wherein the two linear guide rails (5) are arranged along the welding direction and are both installed between the first positioning member and the second positioning member, and the moving platform (6) is installed on the linear guide rail (5) and is capable of sliding along the length direction of the linear guide rail (5); The lower shoulder pad (2) is a cylindrical structure with a circular hole at the center, the stirring tool (1) has an upper shoulder and a stirring needle arranged at the bottom of the upper shoulder, and the length of the stirring needle is greater than the thickness of the workpiece (3) to be welded; During welding, the upper shoulder contacts the upper surface of the workpiece (3) to be welded; The diameter of the circular hole on the lower shoulder pad (2) is greater than the maximum diameter of the stirring needle, and the depth of the circular hole is greater than the difference between the thickness of the workpiece (3) to be welded and the length of the stirring needle.

2. The penetrating double-shoulder driven friction stir welding device according to claim 1, characterized in that: The rotating machine head (4) is detachably fixed on the moving platform (6), the lower shoulder pad (2) is detachably fixed on the rotating machine head (4), and the workpiece (3) to be welded is assembled on the positioning platform (8) and fixed by a clamp (7) so that the back surface of the workpiece (3) to be welded is in close contact with the shoulder surface of the lower shoulder pad (2).

3. The through-type double-shoulder driven friction stir welding device according to claim 1, characterized in that: The invention has a double rotating head, the stirring tool (1) and the lower shoulder pad (2) can be driven independently, and any one parameter of the shoulder diameter, rotation speed and rotation direction of the lower shoulder pad (2) can be set to be the same as or different from that of the stirring tool (1).

4. The penetrating double-shoulder driven friction stir welding device according to claim 1, characterized in that: When the rotary machine head (4) does not rotate, the lower shoulder pad (2) can be used as a stationary lower shoulder pad.

5. A penetrating double-shoulder driven friction stir welding method, characterized in that: The through-type double-shoulder driven friction stir welding device according to any one of claims 1 to 4 comprises the following steps: Preliminary preparation steps: assemble the stirring tool (1) on the friction stir welding machine, install the lower shoulder pad (2) on the rotating head (4) so ​​that the shoulder surface of the lower shoulder pad (2) and the upper surface of the positioning platform (8) are on the same horizontal plane, the center of the stirring needle of the stirring tool (1) is placed at a position coaxial with the center of the circular hole of the lower shoulder pad (2), record the X and Y coordinates, drive the stirring tool (1) and the lower shoulder pad (2) to move along the welding direction in a no-load state, and adjust the stirring tool (1) and the lower shoulder pad (2) to move synchronously; Positioning welding steps: using a positioning welding tool to perform positioning welding, using a clamp (7) to fix the workpiece (3) to be welded on a positioning platform (8) so that the butt joint of the workpiece (3) to be welded is located at the axis of the positioning welding tool, and the shoulder surface of the lower shoulder pad (2) is in close contact with the back of the workpiece (3) to be welded; inputting the selected welding process parameters into the control system and adjusting the inclination angle of the positioning welding tool, starting the friction stir welding machine to perform positioning welding, during positioning welding, the rotating head (4) is not started, the lower shoulder pad (2) is relatively stationary, and the welding method is that the workpiece (3) to be welded is fixed, and the positioning welding tool and the lower shoulder pad (2) move synchronously along the welding direction; Formal welding steps: replace the positioning welding tool with the stirring tool (1), and move the stirring tool (1) to the initial position, change the welding process parameters of the friction stir welding machine in the first control system, input the process parameters of the rotating head (4) in the second control system, and after centering again, start the two system programs at the same time to perform formal welding. The welding method is that the workpiece (3) to be welded is fixed, and the stirring tool (1) and the lower shoulder pad (2) move synchronously along the welding direction.

6. The through-type double-shoulder driven friction stir welding method according to claim 5, characterized in that: The inclination angle of the stirring tool (1) on the friction stir welding machine is 2.5°.

7. The through-type double-shoulder driven friction stir welding method according to claim 5, characterized in that: During the welding process, the linear guide rail (5), the positioning platform (8), the fixture (7), and the workpiece (3) to be welded are stationary, the stirring needle of the stirring tool (1) penetrates the workpiece (3) to be welded and is inserted into the circular hole of the lower shoulder pad (2), and the shoulder surface of the lower shoulder pad (2) contacts the bottom of the workpiece (3) to be welded.

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