Circumferential strong pressure backfill type friction stir spot welding repair tool and method

Abstract

The invention belongs to the technical field of welding, and particularly relates to a circumferential strong pressure backfill type friction stir spot welding repairing tool and method.The repairing tool comprises a pressing ring, a sleeve and a stirring needle which are coaxially arranged, m symmetrical threads are arranged on the upper portion of the side face of the sleeve, and the left rotation direction and the right rotation direction of the symmetrical threads are changed every 90 degrees; k large-lead-angle threads are arranged at the lower part of the side surface of the sleeve; n gradient threads are uniformly arranged on the end surface of the sleeve; during repairing, a to-be-repaired workpiece is polished and filled with the T-shaped filling rod, then the repairing tool is pressed downwards to the upper surfaces of the to-be-repaired workpiece and the T-shaped filling rod, the outer diameter D4 of the sleeve is smaller than the inner diameter D2 of the T-shaped filling rod, then the stages of preheating, downward pricking, backfilling, evacuation and polishing are conducted, and therefore repairing of the whole workpiece is completed. According to the method, metallurgical bonding of a filling material / base metal interface and a sleeve exit line interface is promoted, interface bonding is further enhanced, and the connection quality of welding spots is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a circumferential strong pressure backfill type stir friction spot welding repair tool and method. Background Art

[0002] Metal structural parts in the fields of aerospace and aviation will inevitably produce various defects during use, such as corrosion pits in aircraft skins, out-of-tolerance holes in aviation structures, etc., which affect the performance of metal structural parts and even lead to product scrapping in severe cases. Therefore, it is of great significance to carry out green repair of defective metal structural parts. At present, the methods for repairing defects in metal materials mainly include traditional fusion welding, electric spark alloying, laser multi-layer coating, etc. Among them, the mechanism of fusion welding repair method is based on material melting, but excessive local heat input can easily cause coarse tissue and cannot avoid the generation of secondary defects such as pores and cracks; electric spark alloying and laser multi-layer coating are only suitable for surface defect repair of metal structural parts, and the application objects are limited. As a new type of solid phase repair technology, refilled Friction Stir Spot Welding Repairing (RFSSWR) has advantages in the green repair of volume defects. However, a certain amount of metal volume loss will inevitably occur during the refilling process, resulting in insufficient plastic metal remaining in the refilling stage to fill the gap left by the stirring tool withdrawal, which in turn produces surface ring groove defects and weak connection problems at the interface of the thermomechanical affected zone / stirring zone, affecting the welding quality. In order to solve the above problems, scholars have proposed many improvement methods and measures to improve the quality of refilling friction stir spot welding repair.

[0003] Chinese invention patent CN110640392A provides a method for repairing defects in aluminum alloy welds based on RFSSW equipment. First, a cylindrical hole is machined on the workpiece to be repaired according to the defect size and position, and the defective part is removed. At the same time, a cylindrical part with the same diameter and depth as the cylindrical hole is machined, and the cylindrical part is inserted into the cylindrical hole; then, the sleeve and the stirring needle are controlled to rotate so that they rub against the workpiece to be repaired to generate heat to soften the workpiece to be repaired; finally, the movement of the sleeve and the stirring needle of the backfill friction stir spot welding (RFSSW) equipment is controlled to complete the repair. Although this method has a certain effect in eliminating defects such as pores, cracks and inclusions, since the diameter and depth of the processed cylindrical part are consistent with the cylindrical hole, surface ring groove defects caused by material loss will be generated during the RFSSW process, which will cause serious thinning of the weld joint in the repair area and fail to guarantee the welding quality of the weld joint.

[0004] Chinese invention patent CN116197518A discloses a friction stir spot welding weld and weld repair method and device, which processes the weld cross section into an inverted Ω shape that is narrow at the top and wide at the bottom, and uses a specially designed first stirring needle structure and a second stirring needle structure to sequentially contact the groove with the stirring needle, hot melt filling, and reverse exit process, so that the weld filler is not easy to fall off after the weldment is stressed, and the surface after welding has good mechanical properties. However, this method has high requirements for the processing of the inverted Ω shape that is narrow at the top and wide at the bottom, and does not take into account the high heat generated by the two weldings, which will cause the grain size of the material in the welding area to become larger, affecting the mechanical properties and bearing capacity of the welded joint.

[0005] Chinese invention patent CN111687595A discloses a method for repairing engine disc pit damage with pre-placed materials by friction stir spot welding, which fills the engine disc pit with powder material or pre-placed block material, and then repairs the damaged area by friction stir spot welding, so as to achieve the purpose of dense tissue in the repair area and small blade deformation. However, the invention does not consider that too much pre-placed block material and high operating speed will cause bulging damage in the repair area, affect the quality of joint welding, and in severe cases, cause damage to the repaired component. Summary of the invention

[0006] In order to avoid surface ring groove defects, weak connection of welding interface and other problems during the backfilling friction stir spot welding repair process, and improve the forming quality and joint strength of the welded joint, the present invention provides a circumferential strong pressure backfilling friction stir spot welding repair tool and method, which specifically adopts the following technical solutions:

[0007] A circumferential strong pressure backfill type stir friction spot welding repair tool comprises a coaxially arranged clamping ring, a sleeve and a stirring needle, wherein the upper part of the sleeve side surface is provided with m symmetrical threads, and the symmetrical threads change the left / right rotation direction every 90 degrees; the lower part of the sleeve side surface is provided with k large lead angle threads; and the end surface of the sleeve is evenly provided with n gradual threads.

[0008] The m>2, the symmetrical thread width=depth=1.0mm~3.0mm, the symmetrical thread includes left-handed thread and right-handed thread, the inclination angle β of the left-handed thread or the right-handed thread is 20°~60°; the symmetrical thread arranged on the side of the sleeve occupies 2 / 3~4 / 5 of the entire sleeve height.

[0009] The k>2, the rotation direction of the large lead angle thread matches the rotation direction of the sleeve, when the rotation direction of the sleeve is counterclockwise, the large lead angle thread is right-handed; when the rotation direction of the sleeve is clockwise, the large lead angle thread is left-handed; the width and depth of the large lead angle thread are the same, which is 0.5mm~2mm, and the inclination angle θ is 30°~75°.

[0010] The n>2, the gradual thread rotation direction is designed from outside to inside, the width of the gradual thread = depth = 0.2mm~4mm, and the width gradually narrows from inside to outside; the gradual thread has an outward arc length b and an inward arc length c, wherein: c=A×b, A=2~3; the curvature radius of the gradual thread is adjusted according to actual process conditions.

[0011] A circumferential strong pressure backfilling friction stir spot welding repair method, specifically:

[0012] Hole making stage: Grind the defective part of the workpiece to be repaired, and make a prefabricated hole with a minimum diameter of D3 on the premise of ensuring the minimum expansion of the defective part volume;

[0013] Filling stage: preparing a T-shaped filling rod, and the height of the T-shaped filling rod is higher than the surface of the workpiece to be repaired;

[0014] Preheating stage: The stirring needle, sleeve and clamping ring are pressed down to the upper surface of the workpiece to be repaired and the T-shaped filling rod as a whole, and the workpiece to be repaired is pressed and fixed. At the same time, the outer diameter D4 of the sleeve is smaller than the inner diameter D2 of the T-shaped filling rod, and the sleeve and the stirring needle start to rotate at a speed of ω1 to preheat the surface of the workpiece to be repaired and the T-shaped filling rod;

[0015] The plunger stage: the sleeve and the stirring needle keep the same rotation speed ω1, the sleeve rotates to plunge into the T-shaped filling rod, and the stirring needle rotates and withdraws at the same time, and the welded metal is squeezed into the cavity of the sleeve. The speed of the sleeve plunger and the stirring needle withdrawal is ν1;

[0016] Backfilling stage: the sleeve and the stirring needle maintain the same rotation speed ω2, the sleeve rotates and withdraws at the speed ν1 while the stirring needle rotates and plunges downward at the speed ν2, and the plastic metal in the sleeve cavity is backfilled to the upper surface of the workpiece to be repaired;

[0017] Evacuation stage: The sleeve and the stirring needle rotate at a certain speed ω3, and the sleeve and the stirring needle are withdrawn from the surface of the workpiece to be repaired at a speed ν3 and return to the original set position;

[0018] Grinding stage: remove the workpiece to be repaired, and grind the excess metal material protruding from the upper surface of the workpiece to be repaired to ensure that the upper surface of the workpiece to be repaired is flat.

[0019] Furthermore, the material of the T-shaped filling rod is consistent with the material of the workpiece to be repaired, and the height of the T-shaped filling rod is h2=h1+t, wherein: h1 is the depth of the prefabricated hole, t=0.1mm~0.5mm; the inner diameter of the T-shaped filling rod is D2, and the outer diameter is D1, wherein: D2=D3-0.05mm, D1=1.2×D3, D3 is the diameter of the prefabricated hole; the outer diameter of the sleeve is D4=D2-0.2mm; the end face of the clamping ring is provided with a groove, the groove diameter D5=D1+0.04mm, and the depth a=t+0.01mm.

[0020] Furthermore, during the preheating stage, the speed ω1 of the sleeve and the stirring needle ranges from 600 rpm to 1200 rpm.

[0021] Furthermore, in the lower piercing stage, the sleeve piercing and stirring needle withdrawal speed ν1 ranges from 0.5 mm / min to 1.5 mm / min.

[0022] Furthermore, during the backfilling stage, the rotation speed ω2 of the sleeve and the stirring needle ranges from 900 rpm to 1500 rpm, and the downward speed ν2 of the stirring needle ranges from 3.0 mm / min to 5.0 mm / min.

[0023] Furthermore, in the withdrawal stage, the rotation speed ω3 of the sleeve and the stirring needle ranges from 600rpm to 800rpm, and the withdrawal speed ν3 of the sleeve and the stirring needle ranges from 2.0mm / min to 3.0mm / min.

[0024] The beneficial effects of the present invention are:

[0025] 1. The sleeve diameter of the present invention is smaller than the filling rod diameter. Therefore, in the repair area, there is not only the sleeve exit line interface, but also the filling material / parent material interface. The material gathered due to the change in the sleeve thread rotation direction at the symmetry center will give a greater extrusion pressure to the surrounding materials. In the backfilling stage, the symmetrical threads drive the material to flow upward and downward respectively and converge and collide at the symmetry center, giving a greater extrusion pressure to the surrounding materials; the synergistic effect of the sleeve side large lead angle thread and the end face gradual thread can strengthen the horizontal impact of the material, thereby promoting the metallurgical bonding of the filling material / parent material interface and the sleeve exit line interface, further enhancing the interface bonding and improving the connection quality of the weld.

[0026] 2. The backfill friction stir spot welding method adopted in the present invention adopts a T-shaped filling rod, and the volume of its filling material is larger than the defect volume, which can make up for the volume loss of metal during the backfill spot welding process and avoid the generation of surface ring groove defects; at the same time, since the volume of the pre-backfill material is larger than the space to be filled generated by the sleeve retraction, the internal pressure of the plastic metal inside the sleeve can be increased, which is beneficial to avoid the generation of holes and ensure the quality of joint welding.

[0027] 3. The crossbeam part of the T-shaped filling rod can not only achieve zero thinning welding and avoid annular grooves, but also ensure that the material is strongly squeezed out of the line interface after the sleeve leaves the upper surface of the workpiece during the backfilling stage, thereby improving the welding quality.

[0028] 4. Since the sleeve diameter is smaller than the filler rod diameter, a small-diameter weld spot is obtained, which can reduce the influence of heat generation on the strength of the workpiece to be welded, and achieve high-quality repair of volume defects at a lower heat input. Compared with the large-diameter sleeve of the existing conventional RFSSW repair process, the sleeve diameter is larger than the filler rod diameter. Although there is no filler material / base material interface, the increase in sleeve diameter will lead to high heat input, which is contrary to the green characteristics of the repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of the sleeve of the circumferential strong pressure backfill type stir friction spot welding repair tool of the present invention;

[0030] Figure 2 It is a schematic structural diagram of the symmetrical threads of the sleeve of the circumferential strong pressure backfill type stir friction spot welding repair tool of the present invention;

[0031] Figure 3 The figure is a layout diagram of the gradual thread on the end face of the sleeve of the backfill type friction stir spot welding repair tool with circumferential strong pressure of the present invention;

[0032] Figure 4 It is a layout diagram of the large-angle thread of the sleeve of the backfill type friction stir spot welding repair tool with circumferential strong pressure of the present invention;

[0033] Figure 5 It is a schematic diagram of the structure of the clamping ring of the backfill type friction stir spot welding repair tool with circumferential strong pressure of the present invention;

[0034] Figure 6 It is a schematic cross-sectional structure diagram of the filling stage of the backfill type stir friction spot welding repair method with circumferential strong pressure of the present invention;

[0035] Figure 7 It is a structural schematic diagram of the preheating stage of the backfill type stir friction spot welding repair method using circumferential strong pressure of the present invention;

[0036] Figure 8 It is a structural schematic diagram of the lowering stage of the backfill type stir friction spot welding repair method using circumferential strong pressure of the present invention;

[0037] Fig. 9 It is a structural schematic diagram of the backfilling stage of the backfilling type friction stir spot welding repair method using circumferential strong pressure of the present invention;

[0038] Fig.10 It is a structural schematic diagram of the evacuation stage of the backfill type stir friction spot welding repair method using circumferential strong pressure of the present invention;

[0039] Fig.11 for Fig. 9 Schematic diagram of material flow during the backfill phase;

[0040] In the attached figure: 1. workpiece to be repaired; 2. T-shaped filling rod; 3. stirring needle; 4. sleeve; 5. clamping ring; 51. groove; 6. pad; 7. sleeve withdrawal line; 8. filling material / parent material interface; 9. symmetrical thread; 91. right-hand thread; 92. left-hand thread; 10. gradual thread; 11. large lead angle thread. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0042] like Figures 1 to 5 As shown in , 7, a circumferential strong pressure backfilling type stir friction spot welding repair tool comprises a coaxially arranged clamping ring 5, a sleeve 4 and a stirring needle 3, the upper part of the side of the sleeve 4 is provided with m symmetrical threads 9, m>2, the symmetrical threads 9 include left-handed threads 92 and right-handed threads 91, the symmetrical threads 9 change the left / right rotation direction every 90°, so that the materials converge and collide at the symmetry center during the backfilling process, giving the surrounding materials a large extrusion pressure, the width of the symmetrical threads 9 = depth = 1.0mm~3.0mm, the inclination angle β of the left-handed thread or the right-handed thread = 20°~60°; the symmetrical threads 9 account for 2 / 3~4 / 5 of the height of the entire sleeve 4; the lower part of the side of the sleeve 4 is provided with k large lead angle threads 11, k>2, and the rotation direction of the large lead angle threads 11 is opposite to that of the sleeve 4 When the sleeve 4 is rotated counterclockwise, the large lead angle thread 11 is right-handed; when the sleeve 4 is rotated clockwise, the large lead angle thread 11 is left-handed, so that the material is gathered downward; the width and depth of the large lead angle thread 11 are the same, which is 0.5mm~2mm, and the inclination angle θ is 30°~75°; the end face of the sleeve 4 is evenly provided with n gradual threads 10, n>2, and the gradual threads 10 are rotated from outside to inside to achieve horizontal high-speed outflow of the end face material during the backfilling process; the width of the gradual threads 10 = depth = 0.2mm~4mm, and the width gradually narrows from inside to outside; the gradual threads 10 have an outward arc length b and an inward arc length c, wherein: c=A×b, A=2~3; the curvature radius of the gradual threads 10 is adjusted according to actual process conditions.

[0043] like Figures 6 to 11 As shown, a circumferential strong pressure backfill stir friction spot welding repair method is specifically:

[0044] Hole making stage: grinding the defective part of the workpiece 1 to be repaired, so as to form a prefabricated hole with a minimum diameter of D3 on the premise of ensuring the minimum expansion of the defective part volume;

[0045] Filling stage: prepare a T-shaped filling rod 2, the material of the T-shaped filling rod 2 is consistent with the material of the workpiece 1 to be repaired, the height of the T-shaped filling rod 2 is higher than the surface of the workpiece 1 to be repaired, and the oxides and oil stains of the area to be welded and the filling material are cleaned with acetone and ethanol to expose the fresh material surface; the height of the T-shaped filling rod 2 is h2=h1+t, where: h1 is the depth of the prefabricated hole, t=0.1mm~0.5mm, the inner diameter of the T-shaped filling rod 2 is D2, and the outer diameter is D1, where: D2=D3-0.05mm, D1=1.2×D3, D3 is the diameter of the prefabricated hole;

[0046] Preheating stage: the stirring needle 3, sleeve 4 and clamping ring 5 are pressed down as a whole to the upper surface of the workpiece 1 to be repaired and the T-shaped filling rod 2. The workpiece 1 to be repaired is placed on the pad 6 and is clamped and fixed. At the same time, the outer diameter D4 of the sleeve 4 is smaller than the inner diameter D2 of the T-shaped filling rod 2, and the outer diameter D4 of the sleeve is D2-0.2mm, so that a sleeve withdrawal line 7 and a filling material / parent material interface 8 are formed. A groove 51 is provided on the end face of the clamping ring 5. The groove 51 cooperates with the T-shaped filling rod. The groove diameter D5 is D1+0.04mm and the depth a is t+0.01mm. The sleeve 4 and the stirring needle 3 are rotated at a speed of ω1 to preheat the surface of the workpiece 1 to be repaired and the T-shaped filling rod 2. The speed ω1 of the sleeve 4 and the stirring needle 3 is in the range of 600rpm to 1200rpm.

[0047] In the lower penetration stage, the sleeve 4 and the stirring needle 3 maintain the same rotation speed ω1, the sleeve 4 rotates to penetrate into the T-shaped filling rod 2, and the stirring needle 3 rotates and withdraws at the same time, and the welded metal is squeezed into the cavity of the sleeve 4. The speeds of the sleeve 4 penetration and the stirring needle 3 withdrawal are both ν1, and the range of the sleeve 4 penetration and the stirring needle 3 withdrawal speed ν1 is 0.5mm / min~1.5mm / min;

[0048] Backfilling stage: the sleeve 4 and the stirring needle 3 maintain the same speed ω2, the sleeve 4 rotates and withdraws at the speed ν1 while the stirring needle 3 rotates and plunges at the speed ν2, so that the plastic metal in the cavity of the sleeve 4 is backfilled to the upper surface of the workpiece 1 to be repaired, the speed ω2 of the sleeve 4 and the stirring needle 3 ranges from 900rpm to 1500rpm, and the plunge speed ν2 of the stirring needle 3 ranges from 3.0mm / min to 5.0mm / min;

[0049] Evacuation stage: the sleeve 4 and the stirring needle 3 rotate at a certain speed ω3, and the sleeve 4 and the stirring needle 3 are withdrawn from the surface of the workpiece 1 to be repaired at a speed ν3 and return to the original set position. The rotation speed ω3 of the sleeve 4 and the stirring needle 3 ranges from 600rpm to 800rpm, and the withdrawal speed ν3 of the sleeve 4 and the stirring needle 3 ranges from 2.0mm / min to 3.0mm / min;

[0050] Grinding stage: remove the workpiece 1 to be repaired, and grind the excess metal material protruding from the upper surface of the workpiece 1 to be repaired. During the grinding, the grinding area needs to be cooled in real time to reduce the impact of the high temperature generated by the grinding on the performance of the welding joint and ensure that the upper surface of the workpiece to be repaired is flat.

[0051] Example 1

[0052] A circumferential strong pressure backfill type stir friction spot welding repair tool consists of three parts: a coaxially arranged clamping ring 5, a sleeve 4 and a stirring needle 3. The structural schematic diagram of the repair tool is shown in FIG. Figures 1 to 5 shown.

[0053] In this embodiment, the workpiece 1 to be repaired and the T-shaped filling rod 2 are made of 2024 aluminum alloy. The diameter of the stirring needle 3 is 3mm, the outer diameter of the sleeve 4 is D4=4.75mm, and the outer diameter of the clamping ring 5 is 15mm; there are 6 symmetrical threads 9 on the upper part of the side of the sleeve 4, among which the right-handed thread 91 and the left-handed thread 92 are alternately arranged every 90°, the width and depth of the symmetrical threads are both 2.0mm, the inclination angle β of the right-handed thread 91 and the left-handed thread 92 is 45°, and the symmetrical threads 9 account for 3 / 4 of the entire sleeve height; there are 4 large-angle threads 11 on the lower part of the side of the sleeve 4, the large-angle threads are right-handed, the width and depth are both 1.5mm, and the inclination angle θ=60°; the end face of the sleeve 4 has 5 evenly distributed gradual threads, the gradual thread width=depth=1.8mm, the outward arc length b=2mm, and the inward arc length c=4mm.

[0054] The repair process includes six stages: hole making, filling, preheating, piercing, backfilling, evacuation and grinding.

[0055] like Figures 6 to 11 As shown, a circumferential strong pressure backfill stir friction spot welding repair method is specifically:

[0056] Hole making stage: trim the defect position of the workpiece 1 to be repaired so that the defect forms a prefabricated hole with a depth of h1 = 4 mm and a diameter of D3 = 5 mm;

[0057] Filling stage: prepare a T-shaped filling rod 2, and the height of the T-shaped filling rod 2 is higher than the surface of the workpiece to be repaired, and the height of the T-shaped filling rod 2 is h2 = 4.3 mm, the inner diameter D2 = 4.95 mm, and the outer diameter D1 = 6 mm;

[0058] Preheating stage: the stirring needle 3, sleeve 4 and clamping ring 5 are pressed down to the upper surface of the workpiece 1 to be repaired and the T-shaped filling rod 2 as a whole, and the workpiece 1 to be repaired is pressed and fixed. At the same time, the outer diameter D4 of the sleeve 4 is smaller than the inner diameter D2 of the T-shaped filling rod 2, and the outer diameter D4 of the sleeve 4 is 4.75 mm. The sleeve 4 and the stirring needle 3 start to rotate counterclockwise at a speed of ω1=900 rpm to preheat the surface of the workpiece 1 to be repaired and the T-shaped filling rod 2;

[0059] In the lower penetration stage, the sleeve 4 and the stirring needle 3 maintain the same rotation speed ω1=900rpm, the sleeve 4 rotates to penetrate into the T-shaped filling rod 2, and the stirring needle 3 rotates and withdraws at the same time, and the welded metal is squeezed into the cavity of the sleeve 4. The speed of the sleeve 4 penetration and the stirring needle 3 withdrawal is ν1=1.0mm / min;

[0060] Backfilling stage: the sleeve 4 and the stirring needle 3 maintain the same rotation speed ω2 = 1000 rpm, the sleeve 4 rotates and retracts at a speed ν1 = 1.0 mm / min, while the stirring needle 3 rotates and plunges down at a speed ν2 = 3.0 mm / min, and the plastic metal in the cavity of the sleeve 4 is backfilled to the upper surface of the workpiece to be repaired;

[0061] Evacuation stage: the sleeve 4 and the stirring needle 3 rotate at a certain speed ω3 = 800 rpm, and the sleeve 4 and the stirring needle 3 are withdrawn from the surface of the workpiece 1 to be repaired at a speed ν3 = 2.0 mm / min and return to the original set position;

[0062] Grinding stage: remove the workpiece 1 to be repaired, and grind the excess metal material protruding from the upper surface of the workpiece 1 to be repaired to ensure that the upper surface of the workpiece 1 to be repaired is flat.

[0063] At this point, the entire repair process is completed; there is no thinning on the surface of the repaired workpiece. At the same time, due to the strong extrusion of the material during the repair process, the metallurgical bonding between the repair area material and the parent material can be promoted, thereby improving the molding quality and the bearing capacity after repair.

[0064] Example 2

[0065] A circumferential strong pressure backfill type stir friction spot welding repair tool consists of three parts: a coaxially arranged clamping ring 5, a sleeve 4 and a stirring needle 3. The structural schematic diagram of the repair tool is shown in FIG. Figures 1 to 5 shown.

[0066] In this embodiment, the workpiece 1 to be repaired and the T-shaped filling rod 2 are made of 5083 aluminum alloy. The diameter of the stirring needle 3 is 2mm, the outer diameter of the sleeve 4 is D4=3.75mm, and the outer diameter of the clamping ring 5 is 10mm; there are 5 symmetrical threads 9 on the upper part of the side of the sleeve 4, in which the right-handed thread 91 and the left-handed thread 92 are alternately arranged every 90°, the width and depth of the symmetrical threads are both 1.5mm, the inclination angle β of the right-handed thread 91 and the left-handed thread 92 is 60°, and the symmetrical threads 9 account for 4 / 5 of the entire sleeve height; there are 6 large-angle threads 11 on the lower part of the side of the sleeve 4, the large-angle threads are right-handed, the width and depth are both 2.0mm, and the inclination angle θ=75°; the end face of the sleeve 4 has 4 evenly distributed gradual threads, the gradual thread width=depth=3.0mm, the outward arc length b=3mm, and the inward arc length c=6mm.

[0067] The repair process includes six stages: hole making, filling, preheating, piercing, backfilling, evacuation and grinding.

[0068] like Figures 6 to 11 As shown, a circumferential strong pressure backfill stir friction spot welding repair method is specifically:

[0069] Hole making stage: trim the defect position of the workpiece 1 to be repaired so that the defect forms a prefabricated hole with a depth of h1 = 3 mm and a diameter of D3 = 4 mm;

[0070] Filling stage: prepare a T-shaped filling rod 2, and the height of the T-shaped filling rod 2 is higher than the surface of the workpiece to be repaired, and the height of the T-shaped filling rod 2 is h2 = 3.3 mm, the inner diameter D2 = 3.95 mm, and the outer diameter D1 = 4.8 mm;

[0071] Preheating stage: the stirring needle 3, sleeve 4 and clamping ring 5 are pressed down to the upper surface of the workpiece 1 to be repaired and the T-shaped filling rod 2 as a whole, and the workpiece 1 to be repaired is pressed and fixed. At the same time, the outer diameter D4 of the sleeve is smaller than the inner diameter D2 of the T-shaped filling rod, and the outer diameter D4 of the sleeve 4 is 3.75 mm. The sleeve 4 and the stirring needle 3 are rotated at a speed of ω1=800 rpm to preheat the surface of the workpiece 1 to be repaired and the T-shaped filling rod 2;

[0072] In the lower penetration stage, the sleeve 4 and the stirring needle 3 maintain the same rotation speed ω1=800rpm, the sleeve 4 rotates to penetrate into the T-shaped filling rod 2, and the stirring needle 3 rotates and withdraws at the same time, and the welded metal is squeezed into the cavity of the sleeve 4. The speed of the sleeve 4 penetration and the stirring needle 3 withdrawal is ν1=1.5mm / min.

[0073] Backfilling stage: the sleeve 4 and the stirring needle 3 maintain the same rotation speed ω2 = 1100 rpm, the sleeve 4 rotates and retracts at a speed ν1 = 1.5 mm / min, while the stirring needle 3 rotates and plunges down at a speed ν2 = 3.2 mm / min, and the plastic metal in the cavity of the sleeve 4 is backfilled to the upper surface of the workpiece to be repaired;

[0074] Evacuation stage: the sleeve 4 and the stirring needle 3 rotate at a certain speed ω3 = 700 rpm, and the sleeve 4 and the stirring needle 3 are withdrawn from the surface of the workpiece 1 to be repaired at a speed ν3 = 2.2 mm / min and return to the original set position;

[0075] Grinding stage: remove the workpiece 1 to be repaired, and grind the excess metal material protruding from the upper surface of the workpiece 1 to be repaired to ensure that the upper surface of the workpiece 1 to be repaired is flat.

[0076] At this point, the entire repair process is completed; there is no thinning on the surface of the repaired workpiece. At the same time, due to the strong extrusion of the material during the repair process, the metallurgical bonding between the repair area material and the parent material can be promoted, thereby improving the molding quality and the bearing capacity after repair.

Claims

1. A circumferential strong pressure backfill type stir friction spot welding repair tool, characterized in that: It includes a coaxially arranged clamping ring, a sleeve and a stirring needle. The upper part of the sleeve side is provided with m symmetrical threads, and the symmetrical threads change left / right rotation direction every 90 degrees; the lower part of the sleeve side is provided with k large lead angle threads; and the end face of the sleeve is evenly provided with n gradual threads.

2. A circumferential strong pressure backfill type stir friction spot welding repair tool according to claim 1, characterized in that: The m>2, the width of the symmetrical thread = depth = 1.0mm~3.0mm, the symmetrical thread includes left-handed thread and right-handed thread, the inclination angle β of the left-handed thread or the right-handed thread is 20°~60°; the symmetrical thread arranged on the side of the sleeve occupies 2 / 3~4 / 5 of the entire sleeve height.

3. A circumferential strong pressure backfill type friction stir spot welding repair tool according to claim 1, characterized in that: The k>2, the rotation direction of the large lead angle thread matches the rotation direction of the sleeve, when the rotation direction of the sleeve is counterclockwise, the large lead angle thread is right-handed; when the rotation direction of the sleeve is clockwise, the large lead angle thread is left-handed; the width and depth of the large lead angle thread are the same, which is 0.5mm~2mm, and the inclination angle θ is 30°~75°.

4. A circumferential strong pressure backfill type stir friction spot welding repair tool according to claim 1, characterized in that: The n>2, the gradual thread rotation direction is designed from outside to inside, the width of the gradual thread = depth = 0.2mm~4mm, and the width gradually narrows from inside to outside; the gradual thread has an outward arc length b and an inward arc length c, wherein: c=A×b, A=2~3; the curvature radius of the gradual thread is adjusted according to actual process conditions.

5. A circumferential strong pressure backfilling friction stir spot welding repair method, according to the repair tool of claim 1, characterized in that: Specifically: Hole making stage: Grind the defective part of the workpiece to be repaired, and make a prefabricated hole with a minimum diameter of D3 on the premise of ensuring the minimum expansion of the defective part volume; Filling stage: preparing a T-shaped filling rod, and the height of the T-shaped filling rod is higher than the surface of the workpiece to be repaired; Preheating stage: The stirring needle, sleeve and clamping ring are pressed down to the upper surface of the workpiece to be repaired and the T-shaped filling rod as a whole, and the workpiece to be repaired is pressed and fixed. At the same time, the outer diameter D4 of the sleeve is smaller than the inner diameter D2 of the T-shaped filling rod, and the sleeve and the stirring needle start to rotate at a speed of ω1 to preheat the surface of the workpiece to be repaired and the T-shaped filling rod; The plunger stage: the sleeve and the stirring needle keep the same rotation speed ω1, the sleeve rotates to plunge into the T-shaped filling rod, and the stirring needle rotates and withdraws at the same time, and the welded metal is squeezed into the cavity of the sleeve. The speed of the sleeve plunger and the stirring needle withdrawal is ν1; Backfilling stage: the sleeve and the stirring needle maintain the same rotation speed ω2, the sleeve rotates and withdraws at the speed ν1 while the stirring needle rotates and plunges downward at the speed ν2, and the plastic metal in the sleeve cavity is backfilled to the upper surface of the workpiece to be repaired; Evacuation stage: The sleeve and the stirring needle rotate at a certain speed ω3, and the sleeve and the stirring needle are withdrawn from the surface of the workpiece to be repaired at a speed ν3 and return to the original set position; Grinding stage: remove the workpiece to be repaired, and grind the excess metal material protruding from the upper surface of the workpiece to be repaired to ensure that the upper surface of the workpiece to be repaired is flat.

6. A circumferential strong pressure backfilling friction stir spot welding repair method according to claim 5, characterized in that: The material of the T-shaped filling rod is consistent with the material of the workpiece to be repaired, and the height of the T-shaped filling rod is h2=h1+t, wherein: h1 is the depth of the prefabricated hole, t=0.1~0.5mm; the inner diameter of the T-shaped filling rod is D2, and the outer diameter is D1, wherein: D2=D3-0.05mm, D1=1.2×D3, D3 is the diameter of the prefabricated hole; the outer diameter of the sleeve is D4=D2-0.2mm; a groove is provided on the end face of the clamping ring, the groove diameter D5=D1+0.04mm, and the depth a=t+0.01mm.

7. The circumferential strong pressure backfilling friction stir spot welding repair method according to claim 5 is characterized in that: During the preheating stage, the speed ω1 of the sleeve and the stirring needle ranges from 600 rpm to 1200 rpm.

8. The circumferential strong pressure backfill type stir friction spot welding repair method according to claim 5, characterized in that: During the piercing stage, the sleeve piercing and stirring needle withdrawal speed ν1 ranges from 0.5mm / min to 1.5mm / min.

9. The circumferential strong pressure backfilling friction stir spot welding repair method according to claim 5, characterized in that: During the backfilling stage, the rotation speed ω2 of the sleeve and the stirring needle ranges from 900rpm to 1500rpm, and the downward speed ν2 of the stirring needle ranges from 3.0mm / min to 5.0mm / min.

10. The circumferential strong pressure backfill type stir friction spot welding repair method according to claim 5, characterized in that: During the withdrawal stage, the rotation speed ω3 of the sleeve and the stirring needle ranges from 600rpm to 800rpm, and the withdrawal speed ν3 of the sleeve and the stirring needle ranges from 2.0mm / min to 3.0mm / min.

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