Penetrating double shoulder friction stir welding device and method thereof

Abstract

The present invention relates to the field of welding technology, and provides a penetration type double shoulder friction stir welding device and method. The welding device includes a headstock, a tailstock, an external fixture, an internal support tooling, an external welding head, and a retractable lower shoulder system. The headstock and the tailstock are arranged on the machine tool bed and are respectively configured on both sides of the workpiece to be welded, and are both used for clamping the workpiece to be welded. The internal support tooling is configured between the headstock and the tailstock and is used to expand the workpiece to be welded from the inside. The external fixture is arranged along the circumference of the workpiece to be welded and is used to clamp the workpiece to be welded. The external welding head and the retractable lower shoulder system jointly perform circumferential seam penetration type double shoulder friction stir welding on the workpiece to be welded. By means of the stirring pin penetrating the workpiece to be welded, the present invention eliminates defects such as incomplete penetration and weak bonding of the circumferential seam, and improves the quality of the circumferential seam.

Description

Technical Field

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

[0002] Friction stir welding technology has been widely applied in the welding production of carrier fuel tanks at first. The main material of the fuel tank is aluminum alloy, and there are many circumferential seams in the production process of the tank, such as the bottom ring seam of the tank, the bottom-barrel section ring seam, the barrel section-barrel section ring seam, the bottom-short shell ring seam, etc. The weld quality is directly related to the quality of the tank product. At present, conventional friction stir welding is generally used for tank welding. However, since the length of the stirring pin in conventional friction stir welding is less than the thickness of the welded part, defects such as incomplete penetration and weak bonding are likely to occur at the root of the weld.

[0003] Double-shoulder friction stir welding connects the upper and lower shoulders into a stirring tool through the stirring pin, which can penetrate the base material and avoid defects at the root of the weld. At present, this technology has been applied by SpaceX, a space technology company in the United States, in the production of circumferential seams of rocket fuel tanks. However, double-shoulder friction stir welding has high precision requirements for the stirring tool and the base material, and the stirring pin cannot use an inclination angle. After welding, holes will be left at the end of the weld, and it is necessary to cooperate with friction plug welding to form a complete circumferential seam, which cannot be obtained by one-time processing, resulting in low production efficiency, and the performance of the joint obtained by friction plug welding is lower than that of the friction stir weld.

[0004] In addition to conventional double-shoulder friction stir welding, penetration-type friction stir welding can also be achieved by using a long stirring pin greater than the thickness of the base material and auxiliary support of the lower shoulder. For example, patent document CN105382405B discloses a welding method that uses a long stirring pin and a stationary shoulder with a blind hole to synchronously weld to achieve friction stir penetration welding. This welding method can effectively avoid defects such as incomplete penetration. However, due to the existence of a blind hole in the stationary shoulder, keyholes and back protrusions will exist at the end of the weld. Although a complete weld can be obtained by leaving upper and lower margins and cutting off the margins after welding. But this method wastes materials on the one hand and is not suitable for the circumferential seam welding of fuel tanks on the other hand. Summary of the Invention

[0005] Aiming at the defects in the prior art, the purpose of the present invention is to provide a penetration-type double-shoulder friction stir welding device and method thereof.

[0006] According to a penetration-type double-shoulder friction stir welding device provided by the present invention, it includes a headstock, a tailstock, an external fixture, an internal support tooling, an external welding head, and a retractable lower shoulder system;

[0007] The headstock and the tailstock are arranged on the bed body and are respectively disposed on both sides of the welded part, and are both used for clamping the welded part. The inner support tooling is disposed between the headstock and the tailstock and is used to expand the diameter of the welded part from the inside of the welded part. The outer fixture is arranged along the circumferential direction of the welded part and is used to clamp the welded part;

[0008] The external welding head is arranged outside the welded part and the retractable lower shoulder system is arranged inside the welded part, so that the external welding head and the retractable lower shoulder system jointly perform circumferential penetration double shoulder friction stir welding on the welded part.

[0009] Preferably, the headstock and the tailstock adopt the same structure, and both include a gear disk, a fixed seat, a movable seat and a mandrel;

[0010] The gear disk is rotatably disposed on one side of the fixed seat. The movable seat is disposed below the fixed seat and can move on the bed body to realize the movement of the headstock and / or the tailstock. The mandrel is disposed at the center of the fixed seat and penetrates through the fixed seat for installing the inner support tooling and the retractable lower shoulder system. Among them, the gear disk can rotate around the fixed seat, the mandrel does not rotate with the gear disk, and can independently move along the axial direction of the fixed seat.

[0011] Preferably, the outer fixture includes two symmetrically arranged fixture components, and each fixture component includes a fixture base, a centering gear disk, a claw and a slip ring;

[0012] The fixture base is disposed on the bed body. The centering gear disk is installed on one side of the fixture base. A plurality of the claws are circumferentially distributed on the inner side surface of the centering gear disk and are used to synchronously clamp the welded part.

[0013] Preferably, the outer fixture is equipped with a rotation system so as to be able to drive the outer fixture to drive the welded part to rotate.

[0014] Preferably, the inner support tooling is detachably disposed on the mandrel and includes a telescopic rod, an outer ring arc plate and a fixing ring. The inner ends of a plurality of the telescopic rods are connected to the fixing ring and are arranged along the circumferential direction of the fixing ring. The outer end of each telescopic rod is connected to an outer ring arc plate. All the outer ring arc plates form an annular structure, and the diameter of the annular structure when it expands the diameter is the same as the inner diameter of the welded part.

[0015] Preferably, the external welding head is arranged outside the outer fixture and is provided with a movable base below, so that the external welding head can move horizontally and / or vertically to realize the centering of the retractable stirring pin on the external welding head;

[0016] The external welding head is equipped with a retractable system so as to be able to realize the retraction of the retractable stirring pin at the end of welding.

[0017] Preferably, the retracting lower shoulder system includes a lower shoulder spacer, a retracting spacer, a rotating head, a retracting shaft, and a telescopic connecting rod;

[0018] One end of the telescopic connecting rod is fixed on the mandrel, and the lower shoulder spacer is arranged at the other end of the telescopic connecting rod through the rotating head. By adjusting the telescopic amount of the telescopic connecting rod, the contact between the shoulder surface of the lower shoulder spacer and the inner side surface of the part to be welded can be controlled; a through hole is arranged inside the lower shoulder spacer, the retracting shaft is arranged inside the telescopic connecting rod and a retracting spacer is arranged at the end, and the retracting spacer is located inside the through hole and can retract under the drive of the retracting shaft;

[0019] A part of the through hole above the retracting spacer forms a hole for placing filling material.

[0020] Preferably, the rotating head is equipped with an independent control system and can drive the lower shoulder spacer to rotate.

[0021] A penetration type double shoulder friction stir welding method provided by the present invention includes the following steps:

[0022] Step 1: Preparation stage: Fix the telescopic connecting rod of the retracting lower shoulder system in the mandrel of the headstock, install the lower shoulder spacer on the rotating head, install the retracting spacer on the retracting shaft, manually start the retracting system, adjust the upper end surface of the retracting spacer to be flush with the shoulder surface of the lower shoulder spacer, assemble the positioning welding stirring tool on the external welding head, adjust the length of the telescopic connecting rod to ensure that the center of the stirring pin of the positioning welding stirring tool is on the same straight line as the center of the retracting spacer, restrain the telescopic connecting rod and not allow it to move along the axial direction of the part to be welded and allow it to move along the radial direction of the part to be welded together with the external welding head;

[0023] Step 2: Assembly stage: Install the corresponding tooling of the part to be welded on the gear discs of the headstock and the tailstock, assemble the part to be welded onto the tooling, move the bracket to the welding end area, and install the internal support tooling on the two mandrels so that the outer ring arc plate contacts the part to be welded. Adjust the internal support tooling to tighten the part to be welded and select the corresponding jaws to install on the centering gear disc. Start the moving seat and the bracket to move the part to be welded into the external fixture so that the butt joint of the two parts to be welded is located between the positioning welding stirring tool and the retracting spacer, and ensure that there is no gap or misalignment at the butt joint. After alignment, use the jaws to tightly press the part to be welded in a full circle. Adjust the length of the telescopic connecting rod in the axial direction of the part to be welded so that the shoulder surface of the lower shoulder spacer closely adheres to the inner surface of the part to be welded, and the assembly is completed;

[0024] Step 3: Positioning stage: After performing fusion welding and segmental positioning on the parts to be welded, move the retractable stirring tool back and align the retractable stirring needle with the butt joint of the weld seam. Input the selected positioning welding process parameters into the control system, and adjust the inclination angle of the positioning welding stirring tool. Start the external welding head for positioning welding. During positioning welding, the rotating head is not started, the retractable lower shoulder system remains stationary, and the upper end face of the retractable spacer still remains flush with the shoulder face of the lower shoulder spacer. The welding method is that the parts to be welded rotate with the equipment, and the positioning welding stirring tool and the retractable lower shoulder system remain stationary.

[0025] Step 4: Welding stage: Remove the positioning welding stirring tool and replace it with a retractable stirring tool. Determine the protruding length of the retractable stirring needle according to the thickness of the parts to be welded. Adjust the retraction amount of the retractable spacer according to the length of the retractable stirring needle. The retraction amount is recorded as the hole depth. Place the filler material in the hole of the lower shoulder spacer. Change the welding process parameters in the control system of the equipment. After inputting the process parameters into the control system of the rotating head, perform centering again. At the same time, start the two system programs for formal welding. The welding method is that the parts to be welded rotate with the equipment, and the retractable stirring tool and the retractable lower shoulder system remain stationary.

[0026] Step 5: Retraction stage: When the welding program ends, the system automatically starts the retraction program. At this time, the retractable stirring needle and the retractable spacer are retracted simultaneously at the same retraction speed. When the upper end face of the retractable spacer retracts to be flush with the shoulder face of the lower shoulder spacer, it reaches the limit position. At this time, stop retracting, but the lower shoulder spacer is still rotating. At this time, the root of the retractable stirring needle is exactly located at the bottom end of the parts to be welded. Subsequently, the retractable stirring needle continues to retract upward until it is flush with the shoulder face of the upper shoulder. At this time, the welding is completed, and the upper shoulder and the lower shoulder spacer stop rotating simultaneously, obtaining a complete weld seam.

[0027] Preferably, in step 4, the protruding length of the retractable stirring needle is the needle length. The needle length is 1 - 3 mm larger than the thickness of the parts to be welded. The retraction amount of the retractable spacer is the hole depth. The hole depth is 1.5 mm larger than the difference between the length of the retractable stirring needle and the thickness of the parts to be welded. The diameter of the filler material is 0.1 - 1 mm smaller than the diameter of the hole, and the thickness is 0.1 - 0.5 mm smaller than the hole depth.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention can eliminate the risk of incomplete penetration in the circumferential weld of the storage tank. Compared with the existing circumferential weld welding technology of the storage tank, by penetrating the parts to be welded with the stirring needle, defects such as incomplete penetration and weak bonding in the circumferential weld are eliminated, and the quality of the circumferential weld is improved.

[0030] 2. Although two internal support toolings are used in the present invention, when assembling the internal support toolings, the toolings only play the role of circular support, and the arc plates do not undertake the role of welding leakage plates, and there is no need to form a closed circle. That is, the toolings can be applied to storage tanks of various sizes, and during the assembly process, it is not necessary to strictly align the toolings with the weld center, which is more convenient for tooling assembly, improves the assembly efficiency, and saves the tooling cost.

[0031] 3. When welding the circumferential seam of the storage tank of the present invention, there will be no keyhole left like the conventional two-shoulder friction stir welding. Therefore, there is no need to perform plug welding to repair the weld, and it can be processed in one go, realizing a high-efficiency welding process and improving the production efficiency.

[0032] 4. The headstock and tailstock in the present invention adopt the same structure, and the use is not single. The retractable lower shoulder system is installed on the mandrel, which improves the convenience of installation and disassembly. When the retractable lower shoulder system is not used, conventional circumferential seam friction stir welding can be realized. Therefore, the welding mode can be switched, the multi-functional operation of the welding equipment can be realized, the welding requirements in different situations can be met, and the diversification of welding methods can be achieved.

[0033] 5. Based on the multi-parameter perception, intelligent tool shank perception and end motion detection during the laser ring-scanning friction stir welding process of the present invention, the detection and on-line intelligent control of the downward pressure / downward force, inclination angle, and weld deviation during the welding process are realized, breaking through the intelligent control technology for the friction stir welding process of complex structural parts, improving the welding stability, and obtaining high-quality welds. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 It is a schematic internal cross-sectional view of the welding device. Among them, the external fixture is hidden in the figure. In addition, for the convenience of description, the external welding head and the retractable lower shoulder system are parallel to the Z direction. The two parts to be welded are respectively fixed on the toolings of the headstock and the tailstock, and the moving device is docked. The two internal support toolings respectively support the two parts to be welded. The retractable friction stir tool is assembled on the external welding head to ensure that the center of the retractable friction stir tool, the center of the lower shoulder pad of the retractable lower shoulder system, and the weld docking position are aligned. The two parts to be welded are clamped by the claws of the external fixture. After the assembly is completed, welding is carried out. The welding method is that the headstock, the tailstock, and the external fixture drive the two parts to be welded to rotate, and the external welding head and the retractable lower shoulder system remain stationary;

[0036] Figure 2 It is a schematic diagram of a circumferential penetration type two-shoulder friction stir welding device. Among them, the headstock and the tailstock can move along the X direction on the bed, and the external fixture is fixed on the bed and does not move. The parts to be welded are driven by the headstock and the tailstock to move towards the external fixture;

[0037] Figure 3 This is a schematic diagram of the headstock and the tailstock. The headstock and the tailstock have the same composition and structure, including a gear disk, a fixed seat, a movable seat, and a mandrel. The gear disk is on one side of the fixed seat. The movable seat is located below the fixed seat and connects the bed body to the fixed seat. The mandrel is located at the center of the fixed seat and penetrates the fixed seat. The movable seat can drive the entire headstock to move horizontally. The gear disk can rotate circumferentially. The mandrel does not rotate with the gear disk and can independently move horizontally;

[0038] Figure 4 This is a schematic side view of the external fixture and the external welding head. The external fixture consists of two symmetrically distributed fixtures, including a fixture base, a centering gear disk, clamping jaws, and a slip ring. The fixture base is fixed on the bed body; the centering gear disk is installed on one side of the fixture base; eighteen clamping jaws are evenly distributed on the inner side of the centering gear disk. The centering gear disk rotates in the same direction and at the same speed as the gear disk. The external welding head is located on the right side of the external fixture and is equipped with a laser ring scanning device;

[0039] Figure 5 This is a schematic front view of the external fixture and the external welding head;

[0040] Figure 6 This is a schematic diagram of the internal support tooling. The internal support tooling is installed on the mandrel, and the telescopic rod on the tooling can be manually adjusted to adjust the diameter of the internal support tooling, which can be applicable to storage tank products with different diameters;

[0041] Figure 7 This is a schematic diagram of the retraction stirring tool. The retraction stirring tool includes an upper shoulder and a retraction stirring needle. The shoulder surface of the upper shoulder is a concave surface. The retraction stirring needle has a double - thread and three cutting surfaces. Among them, the stirring needle that does not penetrate the welded part is set with a left - hand thread, and the stirring needle that penetrates the welded part and is located in the hole of the lower shoulder spacer is set with a right - hand thread;

[0042] Figure 8 This is a schematic diagram of the retraction lower shoulder system and the placement position of the filling material. The retraction lower shoulder system includes a lower shoulder spacer, a retraction spacer, a rotating head, a retraction shaft, and a telescopic connecting rod. The lower shoulder spacer is fixed on the rotating head, the rotating head is fixed on the telescopic connecting rod, the retraction spacer is installed on the retraction shaft, and the whole retraction lower shoulder system is installed on the mandrel. The lower shoulder spacer is a cylindrical structure, and the diameter of the shoulder surface can be the same as or different from the diameter of the upper shoulder. There is a through - hole in the center. The retraction spacer is also a cylindrical structure, and the diameter of the retraction spacer is the same as the through - hole diameter of the lower shoulder spacer. The two are in clearance fit, and the depth of the round hole of the lower shoulder spacer can be adjusted. The filling material is selected to be the same as the material of the welded part and is a cylindrical block, which is placed in the hole of the lower shoulder spacer during welding.

[0043] As shown in the figure:

[0044] Bed body 1;

[0045] Headstock 2;

[0046] Tailstock 3;

[0047] External fixture 4;

[0048] Bracket 5;

[0049] Internal support tooling 6;

[0050] External welding head 7;

[0051] Retraction lower shoulder system 8;

[0052] Parts to be welded 9;

[0053] Gear disk 10;

[0054] Fixed seat 11;

[0055] Moving seat 12;

[0056] Mandrel 13;

[0057] Fixture base 14;

[0058] Centering gear disk 15;

[0059] Jaw 16;

[0060] Slip ring 17;

[0061] Retraction stirring tool 18;

[0062] Upper shoulder 19;

[0063] Retraction stirring needle 20;

[0064] Lower shoulder spacer 21;

[0065] Retraction spacer 22;

[0066] Rotating head 23;

[0067] Retraction shaft 24;

[0068] Telescopic connecting rod 25;

[0069] Filling material 26;

[0070] Laser ring scanning device 27;

[0071] Expansion rod 61;

[0072] Outer arc-shaped plate 62;

[0073] Fixed ring 63;

[0074] Movable base 71. Detailed implementation manners

[0075] 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.

[0076] Embodiment 1:

[0077] To solve the problem that the circumferential weld of the storage tank cannot be welded in one pass, the present invention provides a gantry penetration type double shoulder friction stir welding device applicable to the circumferential weld of the tank bottom and the total circumferential butt weld of the storage tank. As Figure 1 shown, it includes a headstock 2, a tailstock 3, an external fixture 4, an internal support tooling 6, an external welding head 7, and a retractable lower shoulder system 8. The headstock 2 and the tailstock 3 are used to clamp the parts to be welded 9. The internal support tooling 6 is arranged between the headstock 2 and the tailstock 3 and inside the parts to be welded 9 for supporting and rounding the parts to be welded 9. The external fixture 4 is arranged along the circumference of the parts to be welded 9 for clamping the outside of the parts to be welded 9. The external welding head 7 is arranged outside the parts to be welded 9 and the retractable lower shoulder system 8 is arranged inside the parts to be welded 9. The external welding head 7 and the retractable lower shoulder system 8 jointly perform retractable penetration type double shoulder friction stir welding on the parts to be welded 9, which is applicable to the penetration type double shoulder friction stir welding of the circumferential weld of the storage tank.

[0078] Specifically, as Figure 2 、 Figure 3 shown, the headstock 2 and the tailstock 3 have the same composition and structure and are respectively arranged on both sides of the parts to be welded 9. The headstock 2 and the tailstock 3 are symmetrically arranged and both include a gear disk 10, a fixed seat 11, a moving seat 12, and a mandrel 13. The gear disk 10 is on one side of the fixed seat 11 for fixing the flower plate, cylinder section tooling, etc. The moving seat 12 is located below the fixed seat 11 and connects the bed 1 and the fixed seat 11. The moving seat 12 can move on the bed 1 to realize the movement of the headstock 2 and the tailstock 3. The mandrel 13 is located at the center of the fixed seat 11 and penetrates the fixed seat 11 for installing the internal support tooling 6 and the retractable lower shoulder system 8. The moving seat 12 can drive other components on the headstock 2 to move horizontally as a whole. The gear disk 10 can rotate circumferentially. The mandrel 13 does not rotate with the gear disk 10 and can independently move along the axis direction of the fixed seat 11.

[0079] As Figure 2 、 Figure 4 、 Figure 5As shown in the figure, the external fixture 4 includes two symmetrically arranged fixture components. Each fixture component includes a fixture base 14, a centering gear disc 15, a jaw 16, and a slip ring 17. The fixture base 14 is fixed on the bed 1; the centering gear disc 15 is installed on one side of the fixture base 14; eighteen jaws 16 are circumferentially distributed on the inner side surface of the centering gear disc 15 for synchronously clamping the parts to be welded 9. The butt joint of the parts to be welded 9 is located in the middle of the jaws 16. The external fixture 4 is equipped with a rotation system, which can drive the external fixture 4 to drive the parts to be welded 9 to rotate, so as to realize the same-direction and same-speed rotation as the gear discs 10 of the headstock 2 and the tailstock 3.

[0080] Furthermore, the gear disc 10 can be installed with different toolings according to the parts to be welded 9 of different sizes, and at the same time, the jaws 16 can also be replaced to ensure that the equipment can be applied to the total butt circumferential penetration type two-shoulder friction stir welding device with various diameters. It should be noted that the external fixture 4 is fixed on the bed 1 without moving, and the parts to be welded 9 are driven by the headstock 2 and the tailstock 3 to move to the middle of the external fixture 4. During the welding process, the rotation of the parts to be welded 9 is driven by the synchronous rotation of the gear disc 10 and the centering gear disc 15, and the retractable stirring tool 18 and the retractable lower shoulder system are fixed axially.

[0081] As Figure 1 、 Figure 6 shown, the internal support tooling 6 is a detachable manual internal support, which is fixed on the mandrels 13 of the headstock 2 and the tailstock 3. It mainly consists of a telescopic rod 61, an outer ring arc plate 62, and a fixing ring 63. The inner ends of multiple telescopic rods 61 are connected to the fixing ring 63 and arranged circumferentially along the fixing ring 63. The outer end of each telescopic rod 61 is connected to an outer ring arc plate 62. All the outer ring arc plates 62 form an annular structure. The diameter of the annular structure when it is expanded is the same as the inner diameter of the parts to be welded 9, which plays a role in expanding the circle and will rotate with the rotation of the parts to be welded 9 during the welding process.

[0082] Furthermore, one internal support tooling 6 is assembled on each of the mandrels 13 of the headstock 2 and the tailstock 3, and the internal support tooling 6 is located at a position 100 mm on both sides of the weld seam and is not used as a welding leakage plate, only playing a role in expanding the circle. The support at the back of the weld seam is ensured by the retractable lower shoulder system 8.

[0083] As Figure 4 、 Figure 5 shown, the external welding head 7 is installed outside the external fixture 4, and there is a movable base 71 below, so that the external welding head 7 can move in the X and Y directions to realize the centering of the stirring needle. The external welding head 7 is equipped with a retractable system, and the stirring needle can be retracted at the end of welding.

[0084] As Figure 1 、 Figure 8As shown, the retracting lower shoulder system 8 includes a lower shoulder spacer 21, a retracting spacer 22, a rotating head 23, a retracting shaft 24, and a telescopic connecting rod 25. The lower shoulder spacer 21 is detachably fixed on the rotating head 23, which plays a role in supporting the inner side surface of the welded part 9 and generating heat during the welding process. The rotating head 23 is equipped with an independent control system and can drive the lower shoulder spacer 21 to rotate without interfering with the control of the external welding head 7. The retracting shaft 24 is installed inside the telescopic connecting rod 25. The retracting spacer 22 is fixed at the end of the retracting shaft 24, located inside the lower shoulder spacer 21 and capable of moving axially relative to the lower shoulder spacer 21, and starts to retract at the end of welding. The telescopic connecting rod 25 is fixed on the mandrel 13, and the contact between the shoulder surface of the lower shoulder spacer 21 and the back of the welded part 9 can be controlled by adjusting the telescopic amount.

[0085] The present invention can realize a circumferential seam penetration type double shoulder friction stir welding device for the welded part 9. With the retracting technology of the retracting stirring pin 20 and the retracting spacer 22, a complete circumferential seam without keyhole and back bulge can be finally obtained.

[0086] Specifically, the retracting stirring tool 18 includes an upper shoulder 19 and a retracting stirring pin 20. The shoulder surface of the upper shoulder 19 is a concave surface. The retracting stirring pin 20 is fixed on the external welding head 7 equipped with a retracting system. The length of the retracting stirring pin 20 is 1 - 3 mm larger than the thickness of the welded part 9. The retracting stirring pin 20 has a double - threaded and three - cut surface. Among them, the stirring pin that does not penetrate the welded part 9 has a left - hand thread, and the stirring pin that penetrates the welded part 9 and is located in the hole of the lower shoulder spacer 21 has a right - hand thread.

[0087] As Figure 7 、 Figure 8 shown, the lower shoulder spacer 21 is a cylindrical structure. The diameter of the shoulder surface can be the same as or different from the diameter of the upper shoulder 19. A through - hole is opened at the center of the shoulder of the lower shoulder spacer 21. The retracting spacer 22 is also a cylindrical structure, and the diameter of the retracting spacer 22 is the same as the diameter of the through - hole of the lower shoulder spacer 21, both of which are 4 mm larger than the root diameter of the retracting stirring pin 20. They are in clearance fit to ensure that the retracting spacer 22 can freely expand and contract in the through - hole of the lower shoulder spacer 21. Placing the retracting spacer 22 in the through - hole of the lower shoulder spacer 21 can form a hole at the top of the through - hole, and the hole can be used to place the filling material 26. The depth of the hole on the lower shoulder spacer 21 is 1.5 mm larger than the difference between the thickness of the welded part 9 and the length of the retracting stirring pin 20. It should be noted that the filling material 26 is made of the same material as the welded part 9, is a cylindrical block, its diameter is 0.1 - 1 mm smaller than the diameter of the retracting spacer 22, and its thickness is 0.1 - 0.5 mm smaller than the depth of the hole on the lower shoulder spacer 21, and is placed in the hole on the lower shoulder spacer 21 during welding.

[0088] Specifically, the welding device in the present invention has two retraction systems and can control the retraction of the retractable stirring pin 20 and the retractable spacer 22 at the same retraction speed respectively. At the same time, the welding device also has two welding heads, which respectively control the rotation of the retractable stirring tool 18 and the lower shoulder spacer 21. Their rotation speeds and rotation directions can be the same or different, depending on different situations. When the rotating head 23 does not rotate, the lower shoulder spacer 21 can be used as a stationary lower shoulder spacer; when the upper end surface of the retractable spacer 22 and the shoulder surface of the lower shoulder spacer 21 are at the same horizontal plane, the lower shoulder spacer 21 can be used as a flat spacer, and this position is the limit position for the upward retraction of the retractable spacer 22; when the stirring pin of the retractable stirring tool 18 does not retract, it can be used as an ordinary stirring tool, and when the stirring pin is fully retracted, it can be used as a needleless stirring tool, and the length of the stirring pin can be adjusted to weld welded parts 9 with different thicknesses.

[0089] It should be noted that when the device is welding, the welded part 9 is driven to rotate by the headstock 2, the tailstock 3 and the external fixture 4, and the retractable stirring tool 18 and the retractable lower shoulder system 8 are fixed; the rotation speeds and rotation directions of the external welding head 7 and the rotating head 23 can be the same or different; after welding, the retractable stirring pin 20 and the retractable spacer 22 both retract upward, and their retraction speeds must be kept consistent throughout the process. At the same time, a laser ring scanning device 27 is equipped on the external welding head 7. A laser ring scanning type friction stir welding process detection system is adopted. The laser distance sensor rotates around the retractable stirring tool 18, and the three-dimensional spatial coordinates of the monitoring point are obtained through the encoder in the servo motor and the height of the detection point. An algorithm for extracting parameters such as the inclination angle of the retractable stirring tool 18, the shoulder penetration amount, and the weld deviation during the welding process is designed.

[0090] Furthermore, the laser ring scanning device 27 equipped on the external welding head 7 adopts a multi-parameter detection system for weld seam position and pose with end motion detection, realizes the synchronous detection of multiple parameters such as weld deviation, penetration amount, and pose, restores the three-dimensional morphology of the surface of the welded part 9 near the retractable stirring tool 18, and adopts an adaptive PID controller based on reinforcement learning to realize the adaptive tracking control of the welding process.

[0091] Even further, the external welding head 7 is equipped with a laser ring scanning device 27, which adopts a pressure detection elastomer. The strain signal is converted into an electrical signal by using a strain gauge group bridge, and the theoretical relationship between the signal and the upsetting force is established to detect, analyze and perform constant pressure adaptive control on the upsetting force information during the welding process.

[0092] The present invention also provides a penetration type double-shoulder friction stir welding method applicable to the circumferential weld of a storage tank. It uses a penetration type double-shoulder friction stir welding device, and includes the following steps:

[0093] Step 1: Preparation stage: Fix the telescopic connecting rod 25 of the back-drawing lower shoulder system 8 in the mandrel 13 of the headstock 2, install the lower shoulder spacer 21 on the rotating head 23, install the back-drawing spacer 22 on the back-drawing shaft 24, manually start the back-drawing system, and adjust the upper end face of the back-drawing spacer 22 to be flush with the shoulder face of the lower shoulder spacer 21 (i.e., the hole depth is 0 mm). Assemble the positioning welding stirring tool (with a needle length of 3 mm) on the external welding head 7, adjust the length of the telescopic connecting rod 25 to ensure that the center of the stirring needle of the positioning welding stirring tool is on the same straight line as the center of the back-drawing spacer 22, and restrict the movement of the telescopic connecting rod 25 in the X direction so that it can only move in the Y direction with the external welding head 7, then the back-drawing lower shoulder system 8 is installed;

[0094] Step 2: Assembly stage: Install the corresponding tooling for the welded part 9 on the gear disks 10 of the headstock 2 and the tailstock 3, loosen the clamping air circuit of the tooling, cooperate with the overhead crane and the bracket 5 to lift the welded part 9 onto the tooling, move the bracket 5 to the welding end area. Subsequently, install the internal support tooling 6 on the two mandrels 13, requiring that the internal support tooling 6 is located 100 mm at the butt joint, and the outer arc plate 62 contacts the welded part 9. Adjust the tightening device of the internal support tooling 6, select the corresponding claw 16 and install it on the centering gear disk 15, start the moving seat 12 and the bracket 5 to move the welded part 9 into the external fixture 4, requiring that the butt joint is located in the middle of the positioning welding stirring tool and the back-drawing spacer 22, and ensure that there is no gap or misalignment at the butt joint. After alignment, start the pressing device and use the claw 16 to press the welded part 9 in a full circle. Adjust the length of the telescopic connecting rod 25 in the Y direction to make the shoulder face of the lower shoulder spacer 21 closely adhere to the inner surface of the welded part 9, then the assembly is completed.

[0095] Step 3: Positioning stage: First, perform fusion welding segmented positioning on the welded part 9, then move the back-drawing stirring tool 18 and align the back-drawing stirring needle 20 with the weld butt joint. Input the selected positioning welding process parameters into the control system, and adjust the inclination angle of the positioning welding stirring tool. Start the external welding head 7 for positioning welding. During positioning welding, the rotating head 23 does not start, the back-drawing lower shoulder system 8 remains stationary, and the upper end face of the back-drawing spacer 22 is still flush with the shoulder face of the lower shoulder spacer 21. The welding method is that the welded part 9 rotates with the equipment, and the positioning welding stirring tool and the back-drawing lower shoulder system 8 are fixed;

[0096] Step 4: Welding stage: Remove the positioning welding stirring tool and replace it with the retraction stirring tool 18. Determine the protruding length of the retraction stirring pin 20 (i.e., the pin length) according to the thickness of the welded part 9. The pin length is usually 1 - 3 mm larger than the thickness of the welded part 9. Adjust the retraction amount of the retraction spacer 22 (i.e., the hole depth) according to the length of the retraction stirring pin 20. The hole depth is usually set 1.5 mm larger than the difference between the length of the retraction stirring pin 20 and the thickness of the welded part 9. Select a filling material 26 with a suitable size. The filling material 26 is usually selected with a diameter 0.1 - 1 mm smaller than the hole diameter and a thickness 0.1 - 0.5 mm smaller than the hole depth. Place it in the hole of the lower shoulder spacer 21. Change the welding process parameters in the control system of the equipment. After inputting the process parameters (rotation speed, rotation direction) in the control system of the rotating head 23, perform centering again. At the same time, start the two system programs for formal welding. The welding method is that the welded part 9 rotates with the equipment, and the retraction stirring tool 18 and the retraction lower shoulder system 8 remain stationary.

[0097] Step 5: Retraction stage: When the welding program ends, the system automatically starts the retraction program. At this time, the retraction stirring pin 20 and the retraction spacer 22 retract simultaneously at the same retraction speed. When the retraction spacer 22 retracts to the position where its upper end face is flush with the shoulder face of the lower shoulder spacer 21, it reaches the limit position and stops retracting at this time, but the lower shoulder spacer 21 is still rotating. At this time, the root of the retraction stirring pin 20 is exactly located at the bottom end of the welded part 9. Subsequently, the retraction stirring pin 20 continues to retract upward until it is flush with the shoulder face of the upper shoulder 19. At this time, the welding is completed, and the upper shoulder 19 and the lower shoulder spacer 21 stop rotating simultaneously, obtaining a complete weld seam.

[0098] Specifically, the inclination angle of the retraction stirring tool 18 assembled on the external welding head 7 is preferably 2.5°. During the welding process, the equipment does not move, and the welded part 9, the headstock 2, the tailstock 3, and the external fixture 4 rotate. The retraction stirring pin 20 penetrates the welded part 9 and pierces into the hole of the lower shoulder spacer 21. The shoulder face of the lower shoulder spacer 21 just contacts the back of the welded part 9 (without pressing-in amount). The shoulder diameters, rotation directions, and rotation speeds of the retraction stirring tool 18 and the lower shoulder spacer 21 are not fixed, but the two must start rotating simultaneously.

[0099] Furthermore, the retraction stirring tool 18 and the retraction lower shoulder system 8 always remain on the same axis during welding, and the retraction speeds and the start retraction times of the retraction stirring pin 20 and the retraction spacer 22 are consistent.

[0100] The present invention can realize a penetration - type double - shoulder friction stir welding device for the circumferential seam of the storage tank, which can be applied to the circumferential seam of the tank bottom and the total circumferential butt joint seam of the storage tank. With the retraction technology of the stirring pin and the spacer, the risk of root defects in the weld seam is eliminated, and a complete circumferential seam without keyhole and back bulge is obtained, greatly improving the welding quality.

[0101] Example 2:

[0102] This example is an optimized example of Example 1.

[0103] Taking the total butt joint of two 8-mm-thick 2219 aluminum alloy cylinder segments as an example, this example demonstrates the penetration double-shoulder friction stir welding device for the tank girth weld. The steps of the penetration double-shoulder friction stir welding device for the tank girth weld are described using the above equipment and tools. In this example, the shoulder diameter, rotation direction, and rotation speed of the lower shoulder pad 21 are the same as those of the retractable stirring tool 18.

[0104] In this example, the tooling assembled on the gear disk 10 is applicable to cylinder segments with a diameter of 3350 mm. The parts to be welded 9 are two cylinder segments with dimensions of 3350 mm (diameter) × 1945 mm (height) × 8 mm (thickness). The shoulder diameter of the upper shoulder 19 is 27 mm; the retractable stirring pin 20 is a conical stirring pin with three cutting surfaces and double-threaded. The pin length is 10 mm, with 8 mm of the upper part of the stirring pin having a left-handed thread and 2 mm of the lower part having a right-handed thread. The root diameter of the stirring pin is 7 mm; the lower shoulder pad 21 is a cylindrical structure with a through hole in the center. Its diameter is the same as that of the upper shoulder 19, which is 27 mm, and the diameter of the through hole is 11 mm; the retractable pad 22 is a cylindrical structure with a diameter of 11 mm, which has a clearance fit with the through hole of the lower shoulder pad 21. The length of the retractable pad 22 is 30 mm; the filler material 26 is a cylindrical structure with a diameter of 10 mm and a thickness of 3 mm.

[0105] The upper shoulder 19 and the retractable stirring pin 20 are combined into the retractable stirring tool 18 and assembled on the external welding head 7; the lower shoulder pad 21 is fixed on the rotating head 23, and the retractable pad 22 is fixed on the retractable shaft 24. The two together form the retractable lower shoulder pad 21; the filler material 26 is placed in the hole of the lower shoulder pad 21.

[0106] The working principle of the penetration double-shoulder friction stir welding device for the tank girth weld in the present invention is as follows:

[0107] I. Preparation stage: Fix the telescopic connecting rod 25 of the retractable lower shoulder system 8 in the mandrel 13 of the headstock 2. Install the lower shoulder pad 21 on the rotating head 23 and install the retractable pad 22 on the retractable shaft 24. Manually start the retractable system and adjust the upper end face of the retractable pad 22 to be flush with the shoulder face of the lower shoulder pad 21 (i.e., the hole depth is 0 mm). Assemble the positioning welding stirring tool (with a pin length of 3 mm) on the external welding head 7. Adjust the length of the telescopic connecting rod 25 to ensure that the center of the stirring pin of the positioning welding stirring tool is on the same horizontal line as the center of the retractable pad 22. Restrain the movement of the telescopic connecting rod 25 in the X direction so that it can only move in the Y direction with the external welding head 7. This completes the installation of the retractable lower shoulder system 8.

[0108] II. Assembly Stage: Select the 3350 cylinder section tooling and install it on the gear discs 10 of the headstock 2 and the tailstock 3. Loosen the clamping air circuit of the tooling, and cooperate with the overhead crane and the bracket 5 to lift the cylinder section onto the tooling. Move the bracket 5 to the welding end area. Subsequently, install the internal support tooling 6 suitable for the 3350 cylinder section on the two mandrels 13. It is required that the internal support tooling 6 is located 100 mm from the weld butt joint, and the arc-shaped plate is in contact with the cylinder section. Adjust the tightening device of the internal support tooling 6. Select the jaws 16 suitable for the 3350 cylinder section and install them on the centering gear disc 15. Start the moving seat 12 and the bracket 5 to move the cylinder section into the external fixture 4. It is required that the butt joint is located between the positioning welding stirring tool and the retracting pad 22, and ensure that there is no gap or misalignment at the butt joint. After alignment, start the pressing device, and use the jaws 16 to tightly press the cylinder section in a full circle. Adjust the length of the telescopic connecting rod 25 in the Y direction to make the shoulder surface closely adhere to the inner surface of the cylinder section, which means the assembly is completed.

[0109] III. Positioning Stage: First, perform fusion welding segmented positioning on the cylinder section. Then, move the retracting stirring tool 18 and align the retracting stirring needle 20 with the weld butt joint. Input the selected positioning welding process parameters into the control system (rotation speed is 400 r / min, welding speed is 150 mm / min, rotate clockwise, penetration amount is 0.1 mm - 0.2 mm), and adjust the inclination angle of the positioning welding stirring tool (inclination angle is 2.9°). Start the external welding head 7 for positioning welding. First, perform 7-segment positioning, with each segment having a length of 10° of the circumference. During positioning welding, the rotating head 23 is not started, the retracting lower shoulder system 8 remains stationary, and the upper end surface of the retracting pad 22 is still flush with the shoulder surface of the lower shoulder pad 21. The welding method is that the cylinder section rotates with the equipment, and the positioning welding stirring tool and the retracting lower shoulder system 8 are fixed.

[0110] IV. Welding Stage: Remove the positioning welding stirring tool and replace it with the retracting stirring tool 18. Adjust the protruding length of the retracting stirring needle 20 to 10 mm, and adjust the retracting amount of the retracting pad 22 to 3.5 mm (hole depth). Select the filler material 26 of 2219 aluminum alloy with a size of 10 mm (diameter) × 3 mm (thickness) and place it in the hole of the lower shoulder pad 21. Change the welding process parameters in the control system of the equipment (rotation speed is 700 r / min, welding speed is 200 mm / min, rotate clockwise, penetration amount is 0.1 mm - 0.2 mm, inclination angle is 2.9°, welding length is 365° of the circumference). Input the process parameters (rotation speed is 700 r / min, rotate clockwise) into the control system of the rotating head 23 and then perform centering again. At the same time, start the two system programs for formal welding. The welding method is that the cylinder section rotates with the equipment, and the retracting stirring tool 18 and the retracting lower shoulder system 8 are fixed.

[0111] V. Withdrawal stage: When the welding process ends, the system automatically activates the withdrawal process (the withdrawal welding length is 5° of the circumference and the withdrawal speed is 2 mm / min). At this time, the withdrawal stirring pin 20 and the withdrawal spacer 22 are withdrawn simultaneously at the same withdrawal speed. When the withdrawal spacer 22 is withdrawn until its upper end face is flush with the shoulder face of the lower shaft shoulder spacer 21, it reaches the limit position. At this time, its withdrawal stops, but the lower shaft shoulder spacer 21 is still rotating. At this time, the root of the withdrawal stirring pin 20 is exactly located at the bottom end of the cylinder section. Subsequently, the withdrawal stirring pin 20 continues to be withdrawn upward until it is flush with the shoulder face of the upper shaft shoulder 19. At this time, the welding ends, and the upper shaft shoulder 19 and the lower shaft shoulder spacer 21 stop rotating simultaneously, obtaining a complete weld seam.

[0112] 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 therefore should not be construed as a limitation to the present application.

[0113] 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 do 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 friction stir welding method, characterized in that: A penetrating double-shoulder friction stir welding device is used, which comprises a head frame (2), a tail frame (3), an external clamp (4), an internal support tooling (6), an external welding machine head (7) and a retracting lower shoulder system (8); The headstock (2) and tailstock (3) are arranged on the bed (1) and are respectively disposed on both sides of the welded part (9), and are used to clamp the welded part (9); the inner support tool (6) is arranged between the headstock (2) and the tailstock (3), and is used to support the welded part (9) from the inside of the welded part (9); the outer clamp (4) is arranged along the circumference of the welded part (9) and is used to clamp the welded part (9); The external welding head (7) is arranged outside the welded part (9) and the retracting lower shoulder system (8) is arranged inside the welded part (9), so that the external welding head (7) and the retracting lower shoulder system (8) jointly perform circumferential penetration double shoulder friction stir welding on the welded part (9); The headstock (2) and tailstock (3) have the same structure, and both include a toothed disc (10), a fixed seat (11), a movable seat (12), and a core shaft (13); The toothed disc (10) is rotatably arranged on one side of the fixed seat (11); the movable seat (12) is arranged below the fixed seat (11) and is movable on the bed (1) to achieve movement of the headstock (2) and / or the tailstock (3); the mandrel (13) is arranged at the center of the fixed seat (11) and passes through the fixed seat (11) and is used to install the inner support tooling (6) and retract the lower shoulder system (8), wherein the toothed disc (10) is capable of rotating around the fixed seat (11), the mandrel (13) does not rotate with the toothed disc (10), and is capable of independently moving along the axial direction of the fixed seat (11); The retracting lower shaft shoulder system (8) comprises a lower shaft shoulder pad (21), a retracting pad (22), a rotating machine head (23), a retracting shaft (24) and a telescopic connecting rod (25); One end of the telescopic connecting rod (25) is fixed on the core shaft (13), and the lower shoulder pad (21) is arranged at the other end of the telescopic connecting rod (25) through the rotating machine head (23). By adjusting the telescopic amount of the telescopic connecting rod (25), the contact between the shoulder surface of the lower shoulder pad (21) and the inner surface of the welded part (9) can be controlled; a through hole is arranged inside the lower shoulder pad (21); the retraction shaft (24) is arranged inside the telescopic connecting rod (25) and the retraction pad (22) is arranged at the end thereof; the retraction pad (22) is located inside the through hole and can be retracted under the drive of the retraction shaft (24); A portion of the through hole located above the retraction pad (22) forms a hole, and the hole is used to place a filling material (26); The method comprises the following steps: Positioning stage: the selected positioning welding process parameters are input into the control system, and the inclination angle of the positioning welding stirring tool is adjusted, and the external welding head (7) is started for positioning welding. During positioning welding, the rotating head (23) is not started, the retracting lower shoulder system (8) is stationary, and the upper end surface of the retracting pad (22) is still flush with the shoulder surface of the lower shoulder pad (21). The welding method is that the welded part (9) rotates with the equipment, and the positioning welding stirring tool and the retracting lower shoulder system (8) are fixed; Welding stage: remove the positioning welding stirring tool and replace it with a retraction stirring tool (18). The retraction stirring tool (18) includes an upper shaft shoulder (19) and a retraction stirring needle (20). According to the thickness of the welded part (9), determine the extension length of the retraction stirring needle (20). According to the extension length of the retraction stirring needle (20), adjust the retraction amount of the retraction pad (22). The retraction amount is recorded as the hole depth. Place the filling material (26) in the hole of the lower shaft shoulder pad (21). Change the welding process parameters in the control system of the equipment. After entering the process parameters in the control system of the rotating machine head (23), perform centering again and perform formal welding. The welding method is that the welded part (9) rotates with the equipment, and the retraction stirring tool (18) and the retraction lower shaft shoulder system (8) are fixed; Retraction stage: When the welding program ends, the system automatically starts the retraction program. At this time, the retraction stirring needle (20) and the retraction pad (22) are retracted at the same retraction speed. When the retraction pad (22) is retracted until the upper end surface is flush with the shoulder surface of the lower shoulder pad (21), it reaches the limit position and stops retraction. However, the lower shoulder pad (21) is still rotating. At this time, the root of the retraction stirring needle (20) is exactly located at the bottom of the welded part (9). Then the retraction stirring needle (20) continues to retract upward until it is flush with the shoulder surface of the upper shoulder (19). At this time, the welding is completed, and the upper shoulder (19) and the lower shoulder pad (21) stop rotating at the same time to obtain a complete weld.

2. The penetrating double-shoulder friction stir welding method according to claim 1, characterized in that: The following steps are also included: Preparation stage; An assembly phase, wherein the assembly phase is performed before the positioning phase.

3. The penetrating double-shoulder friction stir welding method according to claim 1, characterized in that: During the welding stage, the extended length of the retracted stirring needle (20) is 1 to 3 mm greater than the thickness of the welded part (9), the retraction amount of the retracted pad (22) is the hole depth, the hole depth is 1.5 mm greater than the difference between the extended length of the retracted stirring needle (20) and the thickness of the welded part (9), the diameter of the filling material (26) is 0.1 to 1 mm smaller than the hole diameter, and the thickness is 0.1 to 0.5 mm smaller than the hole depth.

4. The penetrating double-shoulder friction stir welding method according to claim 1, characterized in that: The outer clamp (4) comprises two symmetrically arranged clamp assemblies, each of which comprises a clamp base (14), a centering toothed disc (15), a clamping claw (16) and a slip ring (17); The fixture base (14) is arranged on the bed (1); the centering toothed disc (15) is installed on one side of the fixture base (14); a plurality of clamping claws (16) are circumferentially distributed on the inner side surface of the centering toothed disc (15) and are used to synchronously clamp the welded part (9).

5. The penetrating double-shoulder friction stir welding method according to claim 4, characterized in that: The outer clamp (4) is equipped with a rotation system, which can drive the outer clamp (4) to drive the welded part (9) to rotate.

6. The penetrating double-shoulder friction stir welding method according to claim 1, characterized in that: The inner support fixture (6) is detachably arranged on the core shaft (13), and comprises a telescopic rod (61), an outer arc plate (62) and a fixing ring (63). The inner ends of a plurality of the telescopic rods (61) are connected to the fixing ring (63) and are arranged along the circumference of the fixing ring (63). The outer end of each telescopic rod (61) is connected to one of the outer arc plates (62). All the outer arc plates (62) form an annular structure. The diameter of the annular structure when it is supported is the same as the inner diameter of the welded part (9).

7. The penetrating double-shoulder friction stir welding method according to claim 1, characterized in that: The external welding head (7) is arranged outside the external clamp (4) and is provided with a movable base (71) below, so that the external welding head (7) can move horizontally and / or vertically to achieve the centering of the retracted stirring needle (20) on the external welding head (7); The external welding machine head (7) is equipped with a retractable system so that the stirring needle (20) can be retracted when welding is completed.

8. The penetrating double-shoulder friction stir welding method according to claim 1, characterized in that: The rotating machine head (23) is equipped with an independent control system and is capable of driving the lower shoulder pad (21) to rotate.

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