Penetration-type double-shaft-shoulder-driven friction stir welding device and method thereof

Abstract

The invention relates to the technical field of welding, and provides a penetration type friction stir welding device driven by double shaft shoulders and a method thereof.The device comprises a stirring tool, a lower shaft shoulder cushion block, a rotating machine 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 shaft shoulder cushion block is arranged on the moving assembly through the rotating machine head, the positioning platform is used for positioning a welded workpiece, and the stirring tool and the lower shaft shoulder cushion block are located above and below the welded workpiece respectively. The lower shaft shoulder cushion block can be driven by the rotating machine head to rotate, and the upper end face of the lower shaft shoulder cushion block makes close contact with the lower face of the welded workpiece. The lower shaft shoulder cushion block rotates and rubs with the back of a welded workpiece to generate heat, materials are softened, forward resistance of a stirring tool and the lower shaft shoulder cushion block in the welding process is reduced, contact abrasion of a stirring needle and a lower shaft shoulder hole in the welding process is avoided, the welding efficiency is improved, and the stable and efficient welding process is achieved.

Description

Technical Field

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

[0002] As a new solid phase welding technology, friction stir welding is widely used in large-scale manufacturing fields, such as rockets, ships, trains, etc., due to its advantages of green environmental protection and high degree of 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 is a greater potential risk.

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

[0004] In view of the defects in the prior art, an object of the present invention is to provide a penetrating double-shoulder driven friction stir welding device and method thereof.

[0005] According to the present invention, a penetrating double-shoulder driven friction stir welding device comprises a stirring tool, a lower shoulder pad, 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, and the lower shoulder pad is arranged on the moving assembly through a rotating machine head. The positioning platform is used to position the workpiece to be welded, wherein 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, and the stirring tool can be driven to rotate, and during welding, the stirring tool and the lower shoulder pad can move synchronously along the welding direction and both of them always remain on the same axis, and the lower shoulder pad can rotate under the drive of the rotating machine head and the upper end surface is in close contact with the bottom of the workpiece to be welded.

[0006] Preferably, the positioning platform comprises a first positioning member and a second positioning member, and the first positioning member and the second positioning member are both installed on the workbench; 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.

[0007] Preferably, the rotating head is detachably fixed on the mobile platform, the lower shoulder pad is detachably fixed on the rotating head, the workpiece to be welded is assembled on the positioning platform and fixed by a clamp so that the back side of the workpiece to be welded is in close contact with the shoulder surface of the lower shoulder pad.

[0008] Preferably, the lower shoulder pad is a cylindrical structure with a circular hole in the center, the stirring tool 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 to be welded; During welding, the upper shoulder contacts the upper surface of the workpiece to be welded.

[0009] Preferably, the diameter of the circular hole on the lower shoulder pad is larger than the maximum diameter of the stirring needle, and the depth of the circular hole is larger than the difference between the thickness of the workpiece to be welded and the length of the stirring needle.

[0010] Preferably, it has a double rotating head, the stirring tool and the lower shoulder pad can be driven independently, and any one parameter 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 the stirring tool.

[0011] Preferably, when the rotary head does not rotate, the lower shoulder pad can be used as a stationary lower shoulder pad.

[0012] A penetrating double-shoulder driven friction stir welding method provided by the present invention comprises the following steps: Preliminary preparation steps: 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 and the upper surface of the positioning platform are on the same horizontal plane, the center of the stirring needle of the stirring tool is placed at a position coaxial with the center of the circular hole of the lower shoulder pad, record the X and Y coordinates, drive the stirring tool and the lower shoulder pad to move along the welding direction under no-load condition, and adjust them to synchronize the movement of the stirring tool and the lower shoulder pad; Positioning welding steps: Use the positioning welding tool to perform positioning welding, use the fixture to fix the workpiece to be welded on the positioning platform so that the butt joint of the workpiece to be welded is located at 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 static, 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; 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, input the process parameters of the rotating head in the second control system, and after centering again, start the two system programs at the same time 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.

[0013] Preferably, the inclination angle of the stirring tool on the friction stir welding machine is 2.5°.

[0014] Preferably, during the welding process, the linear guide rail, positioning platform, fixture, and workpiece to be welded are stationary, the stirring needle of the stirring tool penetrates the workpiece to be welded and is inserted into the circular hole of the lower shoulder pad, and the shoulder surface of the lower shoulder pad contacts the bottom of the workpiece to be welded.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. In the present invention, the lower shoulder pad rotates and rubs against the back of the workpiece to be welded to generate heat, soften the material, reduce the forward resistance of the stirring tool and the lower shoulder pad during welding, avoid contact and wear between the stirring needle and the lower shoulder hole during welding, improve welding efficiency, form a "dumbbell-shaped" welding joint, extend the service life of the stirring tool, and achieve a stable and efficient welding process.

[0016] 2. The rotating head in the present invention can independently control the rotation of the lower shoulder pad, so that the upper and lower shoulders can rotate at the same speed or at a different speed, and can also rotate in the same direction or in the opposite direction, which is also helpful to improve the welding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a schematic diagram of the central section of the device of the present invention; Figure 2 It is a schematic top view of the structure of the lower shoulder pad; Figure 3 It is a schematic diagram of the structural section of the lower shoulder pad; Figure 4 for Figure 1 A partial enlarged schematic diagram of the middle stirring tool and the lower shoulder pad.

[0018] The figure shows: Stirring tool 1 Lower shoulder pad 2 Workpiece to be welded3 Rotating head 4 Linear guide 5 Mobile Platform 6 Fixture 7 Positioning platform 8 Workbench 9 DETAILED DESCRIPTION The present invention is 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 are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0019] The present invention provides a penetrating double-shoulder driven friction stir welding device, comprising a stirring tool 1, a lower shoulder pad 2, a rotating head 4, a moving assembly, a positioning platform 8 and a workbench 9, wherein 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 through the rotating head 4, and the positioning platform 8 is used to position a 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 arranged oppositely and can move synchronously, that is, the stirring tool 1 is arranged directly above the lower shoulder pad 2, and the lower shoulder pad 2 can rotate under the driving of the rotating head 4 and the upper end surface is in close contact with the lower side of the workpiece 3 to be welded. 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.

[0020] The positioning platform 8 includes a first positioning member and a second positioning member, both of which are installed on the workbench 9. The moving assembly includes a linear guide rail 5 and a moving platform 6. The two linear guide rails 5 are arranged along the welding direction and are 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 pad 2 is detachably fixed on the rotating head 4. The stirring tool 1 is installed on the friction stir welding machine. The workpiece 3 to be welded is assembled on the positioning platform 8 and fixed by the clamp 7 to ensure that the back of the workpiece 3 to be welded is in close contact with the shoulder surface of the lower shoulder pad 2.

[0021] like Figure 2 , Figure 3As shown, the lower shoulder pad 2 is a double-layer cylindrical structure, a circular hole is processed in the center of the upper cylinder, and four through holes are evenly distributed on the lower cylinder for assembly on the rotating machine head 4.

[0022] The stirring tool 1 consists of a stirring needle and an upper shoulder, and the stirring needle rotates coaxially with the upper shoulder. The stirring needle has three sections and is located in the middle of the upper shoulder. The length of the stirring needle is greater than the thickness of the workpiece 3 to be welded. Preferably, the length of the stirring needle of the stirring tool 1 is 1 mm greater than the thickness of the workpiece 3 to be welded.

[0023] In practical applications, the shoulder diameter of the lower shoulder pad 2 (which can be understood as Figure 4 M in the figure can be equal to the diameter of the stirring tool shoulder 1 (which can be understood as Figure 4 L in the figure may not be equal to the diameter of the shaft shoulder of the stirring tool 1, the diameter of the circular hole on the lower shaft shoulder pad 2 (which can be understood as Figure 4 N in the stirring tool 1) is larger than the root diameter of the stirring needle of the stirring tool 1 (which can be understood as Figure 4 K in the figure), the hole depth is greater than the difference between the thickness of the workpiece 3 to be welded and the length of the stirring needle. Preferably, the diameter of the lower shoulder pad 2 is the same as the diameter of the upper shoulder of the stirring tool 1, the diameter of the circular hole of the lower shoulder pad 2 is 4 mm larger than the diameter of the root of the stirring needle of the stirring tool 1, and the depth of the circular hole of the lower shoulder pad 2 is 1.5 mm larger than the difference between the thickness of the workpiece 3 to be welded and the length of the stirring needle.

[0024] During the welding process, 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 and rotate simultaneously to realize the welding process.

[0025] The present invention also provides a friction stir welding method, comprising the following steps: Preliminary preparation steps, positioning welding steps and formal welding steps.

[0026] Taking the welding of 10 mm thick 2219 aluminum alloy as an example, the steps of the penetrating double shoulder driven stir friction welding method are explained using a stirring tool 1 and a lower shoulder pad 2. In this example, the shoulder diameter, rotation direction, and rotation speed of the lower shoulder pad 2 are consistent with those of the stirring tool 1.

[0027] In this example, the upper shoulder diameter of the stirring tool 1 is 26 mm, the stirring needle is a conical stirring needle with three sections and right-handed threads, the needle length is 11 mm, and the root diameter is 6 mm; the lower shoulder pad 2 has a circular hole, the lower shoulder diameter is 26 mm, the circular hole is located in the center of the lower shoulder pad 2, and the size is 10 mm (diameter) × 2.5 mm (depth).

[0028] A friction stir welding method in the present invention 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, 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 direction coordinates, start the device to move the stirring tool 1 and the lower shoulder pad 2 along the welding direction under no-load state, and observe whether the two move synchronously. If not, adjust them to move synchronously; Positioning welding steps: after ensuring that the stirring tool 1 and the lower shoulder pad 2 move synchronously, use the positioning welding tool for positioning welding, the needle length is 2 to 2.5 mm, and the workpiece 3 to be welded is fixed on the positioning platform 8 by the clamp 7, ensuring 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, and the selected welding process parameters are input into the control system (for example, the positioning welding tool speed is set to 600r / min, counterclockwise rotation, the welding speed is 200 mm / min, and the pressing amount is 0.1 mm to 0.2 mm), and the inclination angle of the positioning welding tool is adjusted (for example, the positioning welding tool is set to 2.5°), and the friction stir welding machine is started for positioning welding. During positioning welding, the rotating head 4 is not started, and the lower shoulder pad 2 is relatively stationary (for example, the lower shoulder pad speed is set to 0r / min, and the pressing amount is 0mm). 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: remove the positioning 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 stir friction welding machine (for example, set the stirring tool speed to 500r / min, counterclockwise rotation, the welding speed to 150 mm / min, the pressing amount to 0.1 mm~0.2 mm, and the inclination angle of the stirring tool 1 to 2.5°), and enter the process parameters in the second control system of the rotating head 4 (for example, set the lower shoulder pad speed to 500r / min, counterclockwise rotation, the rotating head 4 speed to 150 mm / min, and the pressing amount to 0mm). After centering again, start the two system programs at the same time for 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.

[0029] The penetrating double-shoulder driven friction stir welding method provided in the present invention has the following beneficial effects compared with the prior art: Firstly, the problem of contact wear between the stirring needle and the lower shoulder is solved: the lower shoulder pad 2 rotates and generates heat through friction with the workpiece 3 to soften the material, reduce the forward resistance, ensure the synchronous movement of the stirring tool and the lower shoulder pad, and avoid the risk of contact wear between the stirring needle and the lower shoulder.

[0030] Secondly, the welding efficiency is improved: when the double shoulders are driven, the upper and lower shoulders generate heat by friction with the workpiece to be welded, so the heat input will increase. At this time, the welding speed can be increased to reduce the heat input, saving welding time and improving welding efficiency.

[0031] Secondly, the quality of welded joints is improved: in double-shoulder driven friction stir welding, both the upper and lower shoulders generate heat, the heat distribution above and below the joint is even, the degree of microstructure evolution is close, and the joint is "dumbbell-shaped", which can significantly improve the joint performance for thick plates.

[0032] Finally, a multifunctional welding method is realized: when welding thin plates, the heat input should not be too high. At this time, the lower shoulder rotating head is not turned on, and penetrating static shoulder friction stir welding can be achieved; when welding thick plates, the rotating head is turned on to achieve penetrating double shoulder driven friction stir welding.

[0033] The above advantages can realize a high-efficiency welding process and obtain high-quality welding joints.

[0034] The penetrating double-shoulder driven friction stir welding method of the present invention can solve the problem that the stirring needle and the lower shoulder pad are easily worn against each other during the existing penetrating friction stir welding process, thereby forming a "dumbbell-shaped" welding joint.

[0035] The present invention builds a set of rotating machine heads 4 under the lower shoulder pad 2, so that the lower shoulder pad 2 can rotate independently without relying on the welding machine head, thereby realizing penetrating double-shoulder driven friction stir welding. Since the lower shoulder pad 2 will generate heat by friction with the back of the workpiece 3 to be welded when rotating, it can increase the welding heat input to a certain extent, soften the workpiece to be welded, and reduce the forward resistance of the stirring tool and the lower shoulder pad 2 during the welding process, effectively avoiding the mutual wear between the stirring needle and the lower shoulder pad 2 during the welding of high-strength thick plate workpieces; in addition, the double-shoulder drive can increase the heat generation during the welding process and evenly distribute the weld seam, the joint presents a "dumbbell shape", and the joint performance is improved; the double-shoulder drive can also increase the welding speed and improve the welding efficiency, thereby achieving a more stable and efficient welding process and finally obtaining a high-quality welded joint.

[0036] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0037] The above describes the specific embodiments of the present invention. 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. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

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; the stirring tool (1) and the lower shoulder pad (2) are respectively located above and below the workpiece (3) to be welded and arranged opposite 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.

2. The penetrating double-shoulder driven friction stir welding device according to claim 1, characterized in that: 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); the two linear guide rails (5) are arranged along the welding direction and are both installed between a first positioning member and a second positioning member; 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).

3. The through-type double-shoulder driven friction stir welding device according to claim 2, 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).

4. The penetrating double-shoulder driven friction stir welding device according to claim 1, characterized in that: 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) being welded.

5. The penetrating double-shoulder driven friction stir welding device according to claim 4, characterized in that: 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.

6. The penetrating 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).

7. 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.

8. A through-type double-shoulder driven friction stir welding method, characterized in that: The steps include: 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.

9. The through-type double-shoulder driven friction stir welding method according to claim 8, characterized in that: The inclination angle of the stirring tool (1) on the friction stir welding machine is 2.5°.

10. The through-type double-shoulder driven friction stir welding method according to claim 8, 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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