Friction head for repairing key hole through friction welding

Abstract

The utility model relates to the technical field of welding manufacturing, and discloses a friction head for a friction welding repair key hole, which comprises a shaft shoulder and a core shaft, the core shaft is arranged in the shaft shoulder, the core shaft comprises a concave arc end arranged in the shaft shoulder, and the concave arc end is provided with a spiral groove for driving a filler to rotate. Through cooperation of the shaft shoulder and the mandrel, in the downward pressing process of the mandrel in the center of the shaft shoulder, the inwards-concave arc end of the mandrel scrapes the inner wall material of the shaft shoulder to serve as a filler to fill a key hole left after conventional friction welding, the friction head is in an inwards-concave arc shape, the materials on the two sides can flow towards the middle in the downward pressing and filling process, the middle hole can be fully filled, and therefore the friction welding efficiency is improved. Meanwhile, a trisection spiral groove is formed in the inwards-concave arc end of the core shaft, in the downward pressing process of the core shaft, the spiral groove drives the filler to rotate, the friction force between the filler and the friction head is increased, and the molten state of the material is effectively filled.

Description

Technical Field

[0001] This utility model relates to the field of welding manufacturing technology, and in particular to a friction welding repair head for keyholes. Background Technology

[0002] Friction welding is suitable for rotating bodies, achieving weld strength equivalent to that of the base material. It can also be used for welding dissimilar materials, making it ideal for welding various types of pipe parts. Conventional friction welding often leaves keyholes, which are unsightly and affect the quality of the finished product. A new friction head can be designed to fill these keyholes left by conventional friction welding.

[0003] Chinese patent document CN214212577U discloses a "friction welding head". It includes a first weldment and a second weldment. The first weldment has an L-shaped stepped structure, and the second weldment is placed on the step for welding. When the end faces of the first and second weldments are welded together, the second weldment is embedded in the step of the first weldment, and the end faces of the first and second weldments are connected by friction welding. The first weldment has a flash groove to cover the inner flash during welding. This technical solution cannot solve the problem of keyholes left after conventional friction welding. Summary of the Invention

[0004] This utility model mainly solves the technical problem that existing technical solutions cannot address the keyholes left after conventional friction welding. It provides a friction welding head for repairing keyholes. Through the cooperation of a shoulder and a mandrel, during the pressing process of the mandrel at the center of the shoulder, the concave arc end of the mandrel scrapes off the material from the inner wall of the shoulder as filler to fill the keyholes left after conventional friction welding. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing process of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material to effectively fill the hole. This avoids the quality problems caused by the filler not rotating during the pressing process of the mandrel being driven into the hole like a rivet.

[0005] The above-mentioned technical problems of this utility model are mainly solved by the following technical solution: This utility model includes a shoulder and a mandrel. The mandrel is disposed inside the shoulder and includes a concave arc end disposed inside the shoulder. The concave arc end is provided with a spiral groove that drives the filler material to rotate. Through the cooperation of the shoulder and the mandrel, during the pressing process of the mandrel at the center of the shoulder, the concave arc end of the mandrel scrapes off the material from the inner wall of the shoulder as filler material to fill the keyhole left after conventional friction welding. The friction head adopts a concave arc shape, which can make the material on both sides flow to the middle during the pressing and filling process, so as to fully fill the middle hole. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing process of the mandrel, the spiral groove drives the filler material to rotate, increasing the friction between the filler material and the friction head, achieving a molten state of the material to achieve effective filling, and avoiding the filler material not rotating during the pressing process of the mandrel, which would cause quality problems if it were driven into the hole by a rivet.

[0006] Preferably, the spiral grooves gradually deepen from small to large, with the small end of the spiral groove flush with the edge of the concave arc end, and the large end close to the inner wall of the concave arc end. The mandrel adopts a concave arc shape, with the arc mechanism surface divided into three equal spiral grooves. The spiral grooves adopt a structure that gradually deepens from small to large, with the small end flush with the surface and the large end 0.5mm deep. This structure prevents the filler material from not rotating during the mandrel pressing process, which would result in the material being driven into the hole like a rivet, with the surface of the material fusing while the interior does not reach a molten state, thus affecting the hole filling quality.

[0007] Preferably, the concave arc end is provided with a clamping end at its center. The clamping end is an inverted frustum. During operation, the clamping end is aligned with the keyhole left after conventional friction welding. During the pressing of the mandrel, the concave arc end of the mandrel scrapes off the inner wall material of the shoulder as filler to fill the keyhole left after conventional friction welding. The friction head adopts a concave arc shape, which allows the material on both sides to flow towards the middle during the pressing and filling process, thus fully filling the middle hole. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material and realizing effective filling.

[0008] Preferably, the shoulder has a through hole, the diameter of which gradually decreases in the direction of movement of the mandrel during operation. Since the mandrel is cylindrical, the concave arc end of the mandrel scrapes off material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding during the downward pressing process.

[0009] Preferably, the mandrel includes a mandrel body, the diameter of which is smaller than the maximum diameter of the shoulder through hole and larger than the minimum diameter of the shoulder through hole. The mandrel body diameter being smaller than the maximum diameter of the shoulder through hole indicates that the mandrel body can be normally placed in the shoulder through hole, while the mandrel body diameter being larger than the minimum diameter of the shoulder through hole indicates that the mandrel body will not penetrate the shoulder without external pressure being applied.

[0010] Preferably, the outer surface of the shoulder is arranged in sequence according to the direction of movement of the mandrel during operation, consisting of a limiting section, a locking section, a transition section, and a positioning section. This sequential arrangement of the limiting section, locking section, transition section, and positioning section ensures that the shoulder can be aligned with the keyhole left after conventional friction welding and is effectively fixed during mandrel pressing. This ensures relative movement between the shoulder and the mandrel, allowing the spiral groove to rotate the filler material, increasing the friction between the filler material and the friction head, achieving a molten state for effective filling.

[0011] Preferably, the limiting section is cylindrical, and the diameter of the through hole in the limiting section is larger than the diameter of the mandrel body. The larger diameter of the through hole in the limiting section allows for the placement of the mandrel, and the cylindrical shape facilitates fixation.

[0012] Preferably, the locking section is cylindrical, located at the point where the shoulder diameter is at its maximum, and the through-hole diameter of the limiting section is larger than the diameter of the mandrel body. Since the locking section is at the point of maximum shoulder diameter, the connections between the locking section, the limiting section, and the transition section are at right angles. The locking section exhibits an annular protrusion, facilitating effective fixation of the shoulder during mandrel pressing, ensuring relative movement between the shoulder and the mandrel. The spiral groove drives the filler material to rotate, increasing the friction between the filler material and the friction head, achieving a molten state of the material for effective filling.

[0013] Preferably, the positioning section is cylindrical, and the diameter of the through hole in the positioning section is smaller than the diameter of the mandrel body. Because the diameter of the through hole in the positioning section is smaller than the diameter of the mandrel body, during the mandrel pressing process, the concave arc end of the mandrel scrapes off material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding.

[0014] Preferably, the transition section is an inverted frustum shape, with a through-hole diameter smaller than the mandrel diameter. The upper base diameter of the inverted frustum is the same as the positioning section diameter, while the lower base diameter is smaller than the locking section diameter. The smaller through-hole diameter allows the concave arc end of the mandrel to scrape off material from the inner shoulder wall as filler during the mandrel's downward pressing process, filling the keyhole left after conventional friction welding. The inverted frustum shape of the transition section, with its continuously decreasing diameter from the locking section to the positioning section, allows for more accurate alignment of the positioning section with the keyhole left after conventional friction welding. This allows material from both sides to flow towards the center during the pressing process, fully filling the central hole. Simultaneously, the concave arc end of the mandrel features a three-part spiral groove. During the mandrel's downward pressing process, the spiral groove rotates the filler material, increasing the friction between the filler and the friction head, achieving a molten state and effective filling.

[0015] The beneficial effects of this utility model are as follows: through the cooperation of the shoulder and the mandrel, during the pressing process of the mandrel at the center of the shoulder, the concave arc end of the mandrel scrapes off the inner wall material of the shoulder as filler to fill the keyhole left after conventional friction welding. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing process of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material to achieve effective filling, and avoiding the quality risks caused by the filler not rotating during the pressing process of the mandrel being driven into the hole by a rivet. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model.

[0017] Figure 2 This is a schematic diagram of the structure of a concave arc end of this utility model.

[0018] Figure 3 This is a force diagram of one of the working parts of this utility model.

[0019] Figure 4 This is a schematic diagram of the working state of this utility model.

[0020] In the diagram, 1 is the shoulder, 1.1 is the limiting section, 1.2 is the locking section, 1.3 is the transition section, 1.4 is the positioning section, 2 is the mandrel, 2.1 is the mandrel body, 2.2 is the concave arc end, 2.3 is the pressing end, and 2.4 is the spiral groove. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this application will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only one preferred embodiment of this application and are only used to explain this application. They do not limit the scope of protection of this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] In engineering, the main methods used to address keyhole defects and other weld flaws in friction stir welds are fusion welding and friction plug welding. Fusion welding typically uses tungsten inert gas (TIG) welding with filler wire. Friction plug welding is essentially consumable friction welding, using a rotating plug rod. Friction forces the defective weld and the plug rod into a plastic state, and then the plug rod is abruptly stopped, applying an upsetting force to form the weld. However, these two methods do not achieve excellent mechanical properties in addressing weld defects and keyholes. If traditional fusion welding is used for repair, the joint strength will be significantly reduced, directly affecting the load-bearing capacity and efficiency of the welded structure. If friction stir welding is used, the effective joint thickness will be thinned, leading to keyhole problems and affecting mechanical properties.

[0023] Common welding repair methods include:

[0024] According to the content described in [Fan Pingzhang. Research and Development and Key Issues of Friction Plug Welding. Aerospace Manufacturing Technology, 2007, 1, 34-37], fusion welding generally uses tungsten inert gas (TIG) welding with filler wire. Currently, most welding defects are repaired using traditional manual TIG welding. This method is simple to operate, but the heat input is large, which can easily cause local grain growth in the weld, reducing toughness. It can also cause significant residual stress and deformation at the repair site. In addition, manual TIG repair welding often cannot be successful in one attempt, and some aluminum alloys cannot be repaired multiple times. Excessive repair welding can cause the loss of alloy elements in the joint, seriously affecting the joint quality and even causing product scrap, thus significantly increasing product costs and extending the production cycle.

[0025] According to [P J. Hartley. Friction plug weld repair for the space shuttle external tank. Weld. Metal Fabrication, 2002, 9, 6-8], friction plug welding is a solid-state connection. During the repair welding process, metal melting does not occur, resulting in low residual stress in the weld, minimal workpiece deformation, and significantly improved mechanical properties, fatigue strength, fracture toughness, and joint plasticity. Welding parameters can be precisely controlled, and the process has high stability and reproducibility, increasing the success rate of the repair weld on the first attempt. However, this method requires secondary processing to remove excess plug rod because the entire plug rod is placed at the repair welding position. Furthermore, since the force during plug welding is limited to a localized area on the center sidewall of the shoulder, stress concentration in the repair welding area is severe, affecting the mechanical properties of the joint. Additionally, this method requires a sudden stop while applying the forging force, necessitating specialized equipment that cannot be achieved on a conventional friction stir welding machine.

[0026] According to the content described in [UEMAT SU Y, TOKAJI K, TOZAKI Y, KURITAT, MURATA S. Effect of re-filling probe kole on tensile failure and fatigue behavior of friction stirwelded j oints in Al-Mg-Si alloy. Int. J. Fat. 2008, 30, 1956-1966], the retraction-type friction stir welding is similar to conventional friction stir welding in the welding process, except that at the end of the welding, the stirring pin is gradually retracted during rotation, and the keyhole is filled by the backfilling of the plastic metal under the shoulder. However, the implementation of this technology not only requires a complex control system, power system and corresponding mechanical structure, but also, because there is not enough plastic metal to achieve backfilling, although the keyhole is eliminated, the effective thickness of the joint at the end of the weld is thinned, and the influence of the keyhole is not completely eliminated.

[0027] In contrast, this application utilizes a shoulder and a mandrel in a coordinated manner. During the pressing down of the mandrel at the center of the shoulder, the concave arc end of the mandrel scrapes off the inner wall material of the shoulder as filler to fill the keyhole left after conventional friction welding. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing down of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material and effectively filling the gap.

[0028] The technical solution of this utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0029] Example 1

[0030] This embodiment provides a friction welding repair keyhole friction head, such as... Figure 1 As shown, the device includes a shoulder 1 and a mandrel 2. The mandrel 2 is disposed inside the shoulder 1 and includes a concave arc end 2.2 disposed inside the shoulder 1. The concave arc end 2.2 has a spiral groove 2.4 for rotating the filler material. Through the cooperation of the shoulder and the mandrel, during the downward pressing of the mandrel at the center of the shoulder, the concave arc end of the mandrel scrapes off the material from the inner wall of the shoulder as filler material to fill the keyhole left after conventional friction welding. Figure 3 As shown, the friction head adopts an inwardly concave arc shape, which allows the material on both sides to flow towards the middle during the pressing and filling process, thus fully filling the middle hole. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing process of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material to achieve effective filling. This avoids the filler not rotating during the pressing process of the mandrel and being driven into the hole by a rivet, which could lead to quality problems.

[0031] like Figure 2 As shown, the spiral groove 2.4 gradually deepens from small to large. The small end of the spiral groove 2.4 is flush with the edge of the concave arc end 2.2, while the large end of the spiral groove 2.4 is close to the inner wall of the concave arc end 2.2. The mandrel adopts a concave arc shape, and the arc mechanism surface has three equally divided spiral grooves. The spiral grooves adopt a structure that gradually deepens from small to large, with the small end flush with the surface and the large end 0.5mm deep. This structure prevents the filler material from not rotating during the mandrel pressing process, which would result in the material being driven into the hole like a rivet, with the surface of the material fusing while the interior does not reach a molten state, thus affecting the hole filling quality.

[0032] The concave arc end 2.2 has a clamping end 2.3 at its center. The clamping end 2.3 is an inverted frustum. During operation, the clamping end is aligned with the keyhole left after conventional friction welding. During the pressing down of the mandrel, the concave arc end of the mandrel scrapes off the inner wall material of the shoulder as filler to fill the keyhole left after conventional friction welding. The friction head adopts a concave arc shape, which allows the material on both sides to flow towards the middle during the pressing down filling process, so as to fully fill the middle hole. At the same time, the concave arc end of the mandrel has a three-part spiral groove. During the pressing down of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, so as to achieve the molten state of the material and achieve effective filling.

[0033] The shoulder 1 has a through hole inside, the diameter of which gradually decreases according to the direction of movement of the mandrel 2 during operation. The mandrel 2 is cylindrical, so during the downward pressing process, the concave arc end of the mandrel scrapes off material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding. The mandrel 2 includes a mandrel body 2.1, the diameter of which is smaller than the maximum diameter of the through hole in the shoulder 1, and larger than the minimum diameter of the through hole. The smaller diameter of the mandrel body 2.1 indicates that it can be normally placed in the through hole of the shoulder 1, and the larger diameter indicates that the mandrel body 2.1 will not penetrate the shoulder 1 without external pressure.

[0034] like Figure 4 As shown, the outer part of the shoulder 1, in accordance with the direction of movement of the mandrel 2 during operation, consists of a limiting section 1.1, a locking section 1.2, a transition section 1.3, and a positioning section 1.4. The sequential arrangement of the limiting section 1.1, locking section 1.2, transition section 1.3, and positioning section 1.4 ensures that the shoulder 1 can be aligned with the keyhole left after conventional friction welding to be repaired, and effectively fixes the shoulder 1 during the mandrel's downward pressing process. This ensures the relative movement between the shoulder 1 and the mandrel 2, allowing the spiral groove to drive the filler material to rotate, increasing the friction between the filler material and the friction head, achieving a molten state of the material for effective filling.

[0035] The limiting section 1.1 is cylindrical, and the diameter of the through hole in the limiting section 1.1 is larger than the diameter of the mandrel 2.1. The larger diameter of the through hole in the limiting section 1.1 allows it to accommodate the mandrel 2, and the cylindrical shape facilitates fixation.

[0036] The locking section 1.2 is cylindrical and located at the point of maximum diameter of shoulder 1. The diameter of the through hole in the limiting section 1.1 is larger than the diameter of the mandrel body 2.1. Since the locking section 1.2 is at the point of maximum diameter of shoulder 1, the connections between the locking section 1.2, the limiting section 1.1, and the transition section 1.3 are at right angles. The locking section 1.2 exhibits an annular protrusion, which effectively fixes shoulder 1 during the mandrel pressing process, ensuring relative movement between shoulder 1 and mandrel 2. The spiral groove can drive the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material for effective filling.

[0037] Positioning section 1.4 is cylindrical, and the diameter of the through hole in positioning section 1.4 is smaller than the diameter of the mandrel body 2.1. The diameter of positioning section 1.4 is equal to or slightly larger than the diameter of the keyhole. Because the diameter of the through hole in positioning section 1.4 is smaller than the diameter of the mandrel body 2.1, during the mandrel pressing process, the concave arc end of the mandrel scrapes off material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding.

[0038] The transition section 1.3 is an inverted frustum shape. The diameter of the through hole in the transition section 1.3 is smaller than the diameter of the mandrel body 2.1. The upper base diameter of the inverted frustum is the same as the diameter of the positioning section 1.4, and the lower base diameter is smaller than the diameter of the locking section 1.2. The smaller diameter of the through hole in the transition section 1.3 allows the concave arc end of the mandrel to scrape off material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding during the mandrel pressing process. The inverted frustum shape of the transition section 1.3, with its continuously decreasing diameter from the locking section 1.2 to the positioning section 1.4, allows for more accurate alignment of the keyhole left after conventional friction welding. During the pressing and filling process, the material on both sides flows towards the center, fully filling the central hole. Simultaneously, the concave arc end of the mandrel has a three-part spiral groove. During the mandrel pressing process, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state and effective filling.

[0039] Example 2

[0040] A friction welding head for repairing keyholes includes a shoulder 1 with a through hole inside. The diameter of the through hole gradually decreases according to the moving direction of a mandrel 2. The through hole inside the shoulder 1 gradually decreases according to the moving direction of the mandrel 2. The mandrel 2 is cylindrical, so that during the downward pressing of the mandrel, the concave arc end of the mandrel scrapes off material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding. The outer surface of the shoulder 1, according to the moving direction of the mandrel 2, consists of a limiting section 1.1, a locking section 1.2, a transition section 1.3, and a positioning section 1.4. The sequential arrangement of the limiting section 1.1, locking section 1.2, transition section 1.3, and positioning section 1.4 ensures that the shoulder 1 can be aligned with the keyhole left after conventional friction welding to be repaired, and effectively fixes the shoulder 1 during the downward pressing of the mandrel. This ensures the relative movement between the shoulder 1 and the mandrel 2, allowing the spiral groove to drive the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material for effective filling.

[0041] The limiting section 1.1 is cylindrical, and the diameter of the through hole in the limiting section 1.1 is larger than the diameter of the mandrel body 2.1. The limiting section 1.1 is used to increase the rigidity of the arc part of the mandrel so that it does not undergo plastic deformation during forging. The diameter of the through hole in the limiting section 1.1 is larger than the diameter of the mandrel body 2.1, which can be used to place the mandrel 2, and the cylindrical shape facilitates fixation.

[0042] The locking section 1.2 is cylindrical and located at the point of maximum diameter of shoulder 1. The diameter of the through hole in the limiting section 1.1 is larger than the diameter of the mandrel body 2.1. The locking section 1.2 is used to increase axial resistance during forging to ensure that the through hole of shoulder 1 is not pulled through, while also improving the bonding quality of the upper interface of the joint. Since the locking section 1.2 is located at the point of maximum diameter of shoulder 1, the connection points of the locking section 1.2 with the limiting section 1.1 and the transition section 1.3 are at right angles. The external shape of the locking section 1.2 is a ring-shaped protrusion, which facilitates effective fixation of shoulder 1 during the pressing of the mandrel, ensuring the relative movement between shoulder 1 and mandrel 2. The spiral groove can drive the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material for effective filling.

[0043] The transition section 1.3 adopts a conical design to ensure stable and uniform deformation and flow of the material near the friction head during the contact between the filler material and the mandrel during welding, as well as in the initial stage of welding. The diameter of the through hole in the transition section 1.3 is smaller than the diameter of the mandrel body 2.1. The upper base diameter of the inverted frustum is the same as the diameter of the positioning section 1.4, and the lower base diameter of the inverted frustum is smaller than the diameter of the locking section 1.2. The small end diameter of the transition section is equal to or slightly larger than the diameter of the keyhole. The cone angle ranges from 30-45°, and the length ranges from 5-10 mm. The through hole diameter of the transition section 1.3 is smaller than the diameter of the mandrel body 2.1, so that during the mandrel pressing down, the concave arc end of the mandrel scrapes off the inner wall material of the shoulder as filler material to fill the keyhole left after conventional friction welding. The transition section 1.3 is an inverted frustum shape. During the process from the locking section 1.2 to the positioning section 1.4, the diameter continuously decreases. The positioning section 1.4 can more accurately align with the keyhole left after conventional friction welding to be repaired. During the pressing and filling process, the material on both sides can flow towards the middle, which can fully fill the middle hole. At the same time, the concave arc end of the mandrel is provided with a three-divided spiral groove. During the pressing of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, so as to achieve the molten state of the material and achieve effective filling.

[0044] Positioning section 1.4 is cylindrical, used to increase the rigidity of the mandrel's arc portion to prevent plastic deformation during forging. The diameter of the through hole in positioning section 1.4 is smaller than the diameter of the mandrel body 2.1. The positioning section is used for axial positioning of the mandrel, ensuring the concentricity of the mandrel and the keyhole. It ensures stable and uniform deformation and flow of material near the friction head during the welding process, allowing the filler material to contact the mandrel and during the initial stage of welding. The diameter of positioning section 1.4 is equal to or slightly larger than the diameter of the keyhole, while the diameter of the through hole in positioning section 1.4 is smaller than the diameter of the mandrel body 2.1. This allows the concave arc end of the mandrel to scrape off material from the inner wall of the shoulder as filler material to fill the keyhole left after conventional friction welding during the mandrel pressing process.

[0045] The assembly also includes a mandrel 2, which is disposed inside the shoulder 1. The mandrel 2 includes a mandrel body 2.1, the diameter of which is smaller than the maximum diameter of the through hole in the shoulder 1, and larger than the minimum diameter of the through hole in the shoulder 1. The smaller diameter of the mandrel body 2.1 indicates that it can be properly placed in the through hole of the shoulder 1, and the larger diameter indicates that it will not penetrate the shoulder 1 without external pressure. The mandrel 2 also includes a concave arc end 2.2 disposed inside the shoulder 1. The concave arc end 2.2 has a clamping end 2.3 at its center, which is an inverted frustum. The concave arc end 2.2 has a spiral groove 2.4 for rotating the filler material. The spiral groove 2.4 gradually deepens from small to large. The small end of the spiral groove 2.4 is flush with the edge of the concave arc end 2.2, while the large end of the spiral groove 2.4 is close to the inner wall of the concave arc end 2.2. The mandrel adopts a concave arc shape, and the arc mechanism surface has three equally divided spiral grooves. The spiral grooves adopt a structure that gradually deepens from small to large, with the small end flush with the surface and the large end 0.5mm deep. This structure prevents the filler material from not rotating during the mandrel pressing process, which would result in the material being driven into the hole like a rivet, with the surface of the material fusing while the interior does not reach a molten state, thus affecting the hole filling quality. During operation, the clamping end is aligned with the keyhole left after conventional friction welding. During the pressing process of the mandrel, the concave arc end of the mandrel scrapes off the material from the inner wall of the shoulder as filler to fill the keyhole left after conventional friction welding. The friction head is concave arc-shaped, which allows the material on both sides to flow towards the middle during the pressing and filling process, thus fully filling the middle hole. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing process of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material and effectively filling the hole.

[0046] Through the cooperation of the shoulder and the mandrel, during the pressing process of the mandrel at the center of the shoulder, the concave arc end of the mandrel scrapes off the inner wall material of the shoulder as filler to fill the keyhole left after conventional friction welding. For example... Figure 3 As shown, the friction head adopts an inwardly concave arc shape, which allows the material on both sides to flow towards the middle during the pressing and filling process, thus fully filling the middle hole. At the same time, the concave arc end of the mandrel is provided with a three-part spiral groove. During the pressing process of the mandrel, the spiral groove drives the filler to rotate, increasing the friction between the filler and the friction head, achieving a molten state of the material to achieve effective filling. This avoids the filler not rotating during the pressing process of the mandrel and being driven into the hole by a rivet, which could lead to quality problems.

[0047] The maximum welding feed rate should not allow the mandrel to touch the forming ring, while the minimum should ensure that the intersection of the mandrel and the shoulder center, and the intersection of the mandrel and the forming ring, are on the same straight line. The welding feed rate should be adjusted between these maximum and minimum values. The welding speed should ensure sufficient welding heat input during the welding process, so that the friction interface temperature meets the bonding conditions; a recommended speed in this application is 7000-7500 rpm. Axial tensile force has a significant impact on weld formation; excessive tensile force will cause the stopper to puncture, while insufficient tensile force will prevent sufficient material interaction. In this application, the welding tensile force should be in the range of 40-60 kN.

[0048] In the initial stage of welding, the mandrel rotates at high speed under the drive of the spindle and moves towards the center of the shoulder at a certain feed rate. For example... Figure 1 As shown, the minor diameter of the conical transition section serves as the initial contact position, contacting the center of the shoulder. This effectively reduces vibration generated by the mandrel when in contact with the shoulder center, allowing for more complete material flow around the shoulder center. During welding, the conical welding section of the continuously rotating and feeding mandrel primarily utilizes friction and compression with the workpiece. Figure 3 , Figure 4 As shown, the welding section is the main part of the mandrel. Under the conditions of heat input and axial tensile force, the weld formation and interface bonding quality can be obtained by adjusting the size of the conical angle of the welding section for different materials and thicknesses of the shaft shoulder center.

[0049] The purpose of the concave arc end is to effectively fill the unwelded defects at the top of the weld seam through its concave arc-shaped structure. The size of the arc should be within a reasonable range; an excessively large arc radius will not effectively fill the unwelded defects, while an excessively small arc radius will cause significant stress concentration at the top of the weld seam, resulting in uneven stress distribution throughout the weld. The fact that the mandrel is not pulled into the center of the shoulder facilitates disassembly of the joint after welding. This design expands the flow range of the plastic material, allowing for better material contact; it also expands the range of rigid support of the forming ring, ensuring uniform stress distribution throughout the weld seam. Simultaneously, it improves the quality of the bonding interface.

[0050] The specific embodiments described herein are merely illustrative examples illustrating the spirit of the invention. The above embodiments only express several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art to which this application pertains can make various modifications or additions to the described specific embodiments or use similar methods to replace them, but without departing from the spirit of this application or exceeding the scope defined by the appended claims. For those skilled in the art, multiple variations and improvements can be made without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A friction welding repair head for keyholes, characterized in that, It includes a shoulder (1) and a mandrel (2). The mandrel (2) is disposed inside the shoulder (1). The mandrel (2) includes a concave arc end (2.2) disposed inside the shoulder (1). The concave arc end (2.2) is provided with a spiral groove (2.4) for driving the filler to rotate.

2. A friction welding keyhole friction head according to claim 1, wherein, The spiral groove (2.4) gradually deepens from small to large. The depth of the small end of the spiral groove (2.4) is flush with the edge of the concave arc end (2.2), and the large end of the spiral groove (2.4) is close to the inner wall of the concave arc end (2.2).

3. A friction welding keyhole friction head according to claim 1 or 2, wherein The concave arc end (2.2) has a clamping end (2.3) at its center.

4. A friction welding keyhole friction head according to claim 1 wherein, The shoulder (1) has a through hole inside, and the diameter of the through hole gradually decreases according to the moving direction of the mandrel (2) during operation.

5. A friction welding keyhole friction head according to claim 4, wherein, The mandrel (2) includes a mandrel body (2.1), the diameter of which is smaller than the maximum diameter of the through hole of the shoulder (1) and larger than the minimum diameter of the through hole of the shoulder (1).

6. A friction welding keyhole friction head according to claim 1 wherein, The outer part of the shoulder (1) consists of a limiting section (1.1), a locking section (1.2), a transition section (1.3), and a positioning section (1.4) in the direction of movement of the spindle (2) during operation.

7. A friction welding keyhole friction head according to claim 6, wherein, The limiting section (1.1) is cylindrical, and the diameter of the through hole in the limiting section (1.1) is larger than the diameter of the mandrel body (2.1).

8. A friction welding keyhole friction head according to claim 6, wherein, The locking section (1.2) is cylindrical and is located at the maximum diameter of the shoulder (1). The diameter of the through hole in the limiting section (1.1) is larger than the diameter of the mandrel body (2.1).

9. A friction welding keyhole friction head according to claim 6, wherein, The positioning section (1.4) is cylindrical, and the diameter of the through hole in the positioning section (1.4) is smaller than the diameter of the mandrel (2.1).

10. A friction welding keyhole friction head according to claim 6, wherein The transition section (1.3) is an inverted frustum. The diameter of the through hole in the transition section (1.3) is smaller than the diameter of the mandrel (2.1). The upper diameter of the inverted frustum is the same as the diameter of the positioning section (1.4). The lower diameter of the inverted frustum is smaller than the diameter of the locking section (1.2).

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