Steel bar linear friction welding device and using method

Abstract

The invention discloses a steel bar linear friction welding device and a using method. The device comprises a machine tool platform and a power and control unit. The upset forging oil cylinder and the upset forging moving table are installed on the machine tool platform, the upset forging moving table is arranged on the upset forging moving table guide rail in a sliding mode, and the upset forging oil cylinder drives the upset forging moving table to move in the axial direction; the vibration oil cylinder fixing seat and the vibration oil cylinder are fixed on the machine tool platform, the vibration block is arranged on the vibration block guide rail in a sliding mode, and the vibration oil cylinder drives the vibration block to do reciprocating rectilinear motion. The upsetting clamping mechanism is arranged on the upsetting moving table and used for clamping a first steel bar; the vibration clamping mechanism is arranged on the vibration block and used for clamping a second steel bar; the moving direction of the upsetting oil cylinder is perpendicular to the moving direction of the vibration oil cylinder, so that linear friction is generated between the first reinforcing steel bar and the second reinforcing steel bar which are in end face contact. Efficient, precise and environment-friendly welding of large-diameter long steel bars and irregularly-shaped steel bars can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of linear friction welding technology, and specifically relates to a linear friction welding device for reinforcing bars and its usage method. Background Technology

[0002] With the rapid development of building infrastructure construction, the demand for pile foundation engineering, precast concrete beams, and large bridges and tunnels is increasing. In the production of steel reinforcement cages, automated production equipment is gradually replacing traditional manual customized operations in order to reduce labor intensity and improve efficiency. Among them, the butt welding of thick and long steel bars, especially large-diameter steel bars with a diameter ≥32mm, is a key process that restricts the efficiency and quality of automated production lines.

[0003] Currently, existing rebar connection technologies mainly exhibit the following development stages and corresponding problems: The first stage involves traditional fusion welding processes, such as flash butt welding, CO2 gas shielded welding, or manual arc welding. These processes exhibit serious drawbacks when dealing with large-diameter reinforcing bars: as the diameter of the bars increases, the risk of cold cracking due to hydrogen diffusion and residual stress rises sharply; simultaneously, due to insufficient penetration, impurities such as sulfur and phosphorus easily form low-melting-point eutectics (such as FeS), leading to slag inclusions and porosity, severely affecting joint strength. Traditional processes typically require preheating and slow cooling, resulting in long processing times at each point, high consumption of welding materials, and a high rework rate. The welding process also generates large amounts of fumes containing harmful substances such as manganese and chromium, resulting in high emissions that fail to meet increasingly stringent environmental standards.

[0004] The second stage focuses on friction welding technology to address pollution and efficiency issues. Because the high-speed rotation of long reinforcing bars generates enormous centrifugal force and causes violent swaying, direct rotational friction welding of two long reinforcing bars is extremely difficult. To solve this problem, Chinese invention patent application CN114633014A discloses a friction welding connection process and apparatus for reinforcing bars. This apparatus includes an operating platform, several moving structures, and a positioning structure. The operating platform is equipped with a first guide rail and a second guide rail. The moving structures are slidably connected to the first guide rail, and the positioning structure is slidably connected to the second guide rail. Each moving structure includes a first clamp and a first sliding plate. The first threaded long reinforcing bar is connected to the first clamp. The positioning structure includes a second rotating clamp and a second sliding plate, and the second threaded short reinforcing bar is connected to the second rotating clamp. This solution employs an intermediate transition approach, clamping two long reinforcing bars to be welded on the moving structures on both sides, and placing a short reinforcing bar that can rotate at high speed in the middle. During welding, the high-speed rotation of the middle short reinforcing bar contacts and rubs against the stationary long reinforcing bars on both sides, thereby achieving the connection.

[0005] Although the above-mentioned scheme avoids the safety hazards of directly rotating long steel bars, it still has significant limitations in practical applications: the process requires the introduction of a short steel bar from a third party as a medium, making direct butt welding of two steel bars impossible. This not only increases material consumption but also results in two weld interfaces at a single connection, doubling the risk of fracture failure. The rotational friction method limits its applicability to steel bars with circular cross-sections. For irregularly shaped steel bars or metal components such as square or hexagonal bars, the edges cannot be aligned after rotational welding, disrupting the geometric continuity of the component. The reliance on mechanical positioning with lead screws and guide rails is insufficient for thick steel bars with a diameter ≥32mm. Due to the inherent straightness error of the steel bars, simple mechanical clamping cannot guarantee micron-level concentricity, easily leading to misalignment. The lack of closed-loop control over the temperature field, upsetting pressure, and displacement during welding, and the absence of post-weld heat treatment for high-strength steel bars, makes it prone to brittle structures due to uncontrolled cooling rates. Summary of the Invention

[0006] This invention provides a linear friction welding device and method for reinforcing bars. It utilizes high-frequency linear vibration friction to generate heat, rapidly raising the end face of the reinforcing bar to a plastic state, thus achieving a metal connection without welding materials or protective gas. This invention aims to solve problems existing in current technologies, such as three-way welding, narrow applicability, and insufficient precision in welding process control.

[0007] To address the aforementioned technical problems, this invention proposes a linear friction welding device for reinforcing bars, comprising: a machine tool platform, a power and control unit, and further comprising: An upsetting cylinder and an upsetting moving table are mounted on a machine tool platform. The upsetting moving table is slidably mounted on an upsetting moving table guide rail. The upsetting cylinder drives the upsetting moving table to move axially. The vibratory cylinder mounting base and vibratory cylinder are fixed on the machine tool platform, and the vibratory block is slidably arranged on the vibratory block guide rail. The vibratory cylinder drives the vibratory block to perform reciprocating linear motion. An upsetting clamping mechanism is provided on the upsetting moving platform for clamping the first reinforcing bar; A vibration clamping mechanism is provided on the vibration block for clamping the second reinforcing bar; The movement direction of the upsetting cylinder is perpendicular to the movement direction of the vibration cylinder. The feed of the upsetting moving table causes the end faces of the first steel bar and the second steel bar to come into contact, and linear friction is generated under the drive of the vibration cylinder.

[0008] Preferably, the machine tool platform is provided with a centering detection component for aligning two sections of reinforcing bars. The centering detection component includes a laser centering instrument installed on the side of the upsetting clamping mechanism and a laser displacement sensor installed on the side of the vibration cylinder fixing seat.

[0009] Preferably, the device further includes an infrared thermometer for monitoring the temperature of the welding zone, a compressed air cooling unit for cooling the fusion zone, and an end face gap sensor for detecting the distance between the first and second reinforcing bars.

[0010] Preferably, there are two upsetting cylinders, which are connected in parallel; each upsetting cylinder is equipped with a magnetostrictive displacement sensor and an electro-hydraulic proportional valve to switch between position control mode and pressure control mode.

[0011] On the other hand, the present invention also proposes a method for linear friction welding of reinforcing bars, the method using the linear friction welding apparatus for reinforcing bars as described in the first aspect of the present invention, comprising the following steps: Clamping and alignment: The two sections of steel bars are clamped by an upsetting clamping mechanism and a vibration clamping mechanism, respectively, and the position is finely adjusted by a vibration cylinder to achieve concentric alignment; Pre-compression contact: The upsetting cylinder drives the upsetting moving table forward, so that the end faces of the two steel bars come into contact and a constant pre-compression is applied; Vibration friction heat generation: Maintain the preload and control the vibration cylinder to drive the second steel bar to perform linear reciprocating motion, thereby increasing the temperature of the contact surface by friction heat generation; Upsetting fusion: When the temperature reaches the first preset value, the vibration stops and the upsetting cylinder is controlled to apply upsetting force, so that the two steel bars are squeezed against each other to produce plastic deformation and fuse together; Pressure holding, cooling and unloading: Maintain pressure until the temperature drops to the second preset value, then release the clamping mechanism and reset the device.

[0012] Preferably, the clamping and alignment steps are as follows: The vibratory cylinder is activated and put into fine-tuning mode. The servo valve controls the vibratory cylinder to push the second reinforcing bar axially at a feed speed of 0.5 mm / s. The concentricity of the two steel bar ends is monitored in real time using a laser displacement sensor. When the axial offset is ≤0.05mm, the alignment is considered complete and the position is locked.

[0013] Preferably, the pre-compression contact step method is as follows: The forging cylinder first drives the first reinforcing bar to move rapidly at a speed of 120 mm / s; When the end face gap sensor detects a distance ≤5mm, the speed is switched to 20mm / s; When the detected distance is ≤0.3mm, the system automatically switches to pressure control mode and applies a constant pressure of 20-50MPa.

[0014] Preferably, the vibration friction heat generation step method is as follows: The vibration frequency is controlled at 40–60 Hz, and the amplitude is controlled at 0.5–3 mm. The temperature of the welding area is monitored in real time using an infrared thermometer, with the target temperature range set at 1200±30℃. If the monitored temperature is below 1170℃, the vibration time will be automatically extended by 0.5 seconds; if the monitored temperature is above 1230℃, the vibration will be terminated prematurely. At the moment the vibration stops, a laser encoder is used to confirm that the vibrating block is stationary in the mechanical center position, with the position deviation controlled within ±0.03mm.

[0015] Preferably, the upsetting and fusion step is as follows: Upsetting begins within 0.08 seconds after vibration stops, with the upsetting cylinder outputting an instantaneous high pressure of 150–300 MPa; upsetting displacement… According to the diameter of the reinforcing bar According to the formula The calculation settings are configured to form a dense metallurgical bonding layer with a width of 2-3 mm at the bonding surface.

[0016] Preferably, the pressure holding, cooling, and unloading steps employ a segmented gradient cooling strategy: First stage: When the temperature of the welding zone is in the range of 1200℃~800℃, maintain the full upsetting pressure and allow for natural cooling. Second stage: When the temperature drops to the range of 800℃ to 500℃, the upsetting pressure is reduced to 50%, and the weld is subjected to enhanced cooling. Third stage: Once the temperature drops below 500℃, completely release the pressure and loosen the clamps.

[0017] Compared with the prior art, the present invention has the following technical effects: 1. The linear friction welding device for reinforcing bars proposed in this invention adopts the principle of linear reciprocating vibration friction, requiring the reinforcing bars to undergo only micro-amplitude (0.5-3mm) high-frequency linear motion. This eliminates the enormous centrifugal force and potential for swaying generated by the rotation of long reinforcing bars, enabling direct butt welding of infinitely long reinforcing bars, reducing welding points and processes by half, and significantly improving the overall reliability of the structure. Furthermore, since it does not rely on rotational motion, this invention can also achieve high-precision alignment welding of non-circular cross-section components such as square steel, flat steel, and hexagonal steel, greatly expanding the applicability of the process.

[0018] 2. The linear friction welding device for reinforcing bars proposed in this invention addresses the pain point of large-diameter, thick reinforcing bars having large straightness deviations and being difficult to center. It introduces a centering system composed of a laser centering instrument, a laser displacement sensor, and servo hydraulic micro-motion. In the clamped state, the device can actively detect and compensate for axial and radial errors (accuracy up to 0.01mm). Through the micro-motion adjustment of the vibration cylinder, the final weld concentricity deviation is controlled within 0.05mm, significantly improving the finished product qualification rate.

[0019] 3. This invention addresses the problem of unstable welding quality in manual welding and open-loop control using the proposed linear friction welding device for reinforcing bars. By controlling vibration time with infrared thermometry feedback, controlling upsetting displacement with magnetostrictive sensors, and controlling upsetting pressure with force-displacement dual feedback, it ensures that the energy input and plastic deformation of each weld are within the optimal process window. This intelligent control results in a denser weld structure and improved welding quality.

[0020] 4. The linear friction welding device for reinforcing bars proposed in this invention employs a three-stage gradient cooling process: full-pressure natural cooling, depressurized air cooling, and depressurization. This process utilizes residual welding heat and a controllable cooling rate to improve the metallographic transformation of the weld zone, refine the grains, and fundamentally solve the industry problem of high cold cracking rate in large-diameter reinforcing bar welding.

[0021] 5. The linear friction welding device for reinforcing bars proposed in this invention requires no welding rods, welding wires, or shielding gas, and its energy consumption is only 1 / 5 to 1 / 3 of that of traditional flash butt welding. The welding process is performed in a plastic state, with no spatter, and with the help of a fume collection system, near-zero emissions can be achieved, meeting stringent environmental standards such as ISO 14046. Simultaneously, the welding time per cycle is controlled within 85 seconds, resulting in a significant improvement in production efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the device described in this invention; Figure 2 This is a front view of the device described in this invention; Figure 3 This is a flowchart illustrating the method described in this invention.

[0023] Reference numerals in the attached drawings: 1. Machine tool platform; 2. Power and control unit; 3. First reinforcing bar; 4. Upsetting cylinder; 5. Upsetting cylinder mounting base; 6. Upsetting moving table; 7. Upsetting clamping mechanism; 8. Upsetting moving table guide rail; 9. Vibration cylinder; 10. Vibration cylinder mounting base; 11. Vibration block; 12. Vibration clamping mechanism; 13. Vibration block guide rail; 14. Second reinforcing bar. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present application and with reference to the accompanying drawings.

[0025] Example 1 Please see Figure 1 , 2 This embodiment is a linear friction welding device for reinforcing bars, mainly used to realize the butt welding of large-diameter thick reinforcing bars and non-circular metal components.

[0026] The main structure of the device includes a machine tool platform 1 and a power and control unit 2 located inside or on one side of the machine tool platform. The machine tool platform 1 adopts a high-rigidity welded or cast structure, providing a stable support base for the entire welding process. The power and control unit 2 mainly consists of a hydraulic station and an electrical control cabinet, providing pressure oil and control signals to each actuator cylinder.

[0027] An upsetting cylinder 4 and an upsetting moving table 6 are mounted on a machine tool platform. The upsetting moving table 6 is slidably mounted on a guide rail 8, and the upsetting cylinder 4 drives the upsetting moving table 6 to move axially. Specifically, an upsetting unit is provided on one side of the machine tool platform 1. An upsetting cylinder mounting base 5 is fixed on the machine tool platform 1, and two upsetting cylinders 4 are mounted in parallel on the mounting base 5. The piston rod ends of the two upsetting cylinders 4 are connected to the upsetting moving table 6. The bottom of the upsetting moving table 6 is slidably mounted on the upsetting moving table guide rail 8 via a slider. In order to withstand the high load during upsetting and ensure accuracy, the upsetting moving table guide rail 8 is preferably a heavy-duty roller guide rail with a surface hardness of HRC 60 or higher. The upsetting moving table 6 itself is preferably made of QT600-3 ductile iron to obtain good vibration damping and strength. The upsetting cylinder 4 integrates a magnetostrictive displacement sensor (not shown in the figure), and the external oil circuit is equipped with an electro-hydraulic proportional valve. This configuration allows the upsetting cylinder 4 to smoothly switch between position control mode (for rapid feeding and precise alignment) and pressure control mode (for applying a constant upsetting force) within milliseconds. An upsetting clamping mechanism 7 is mounted on the upsetting moving table 6 to clamp the first reinforcing bar 3 to be welded. This clamping mechanism is hydraulically driven, and its jaws are designed as V-shaped clamps with carbide teeth to ensure that the reinforcing bar does not slip when the axial thrust is up to 300 kN.

[0028] A vibration unit is provided on the opposite side of the machine tool platform 1 from the upsetting unit. This unit includes a vibration cylinder mounting base 10 vertically fixed on the machine tool platform, and a vibration cylinder 9 mounted thereon. The vibration cylinder 9 drives the vibration block 11 below. The vibration block 11 is slidably mounted on the vibration block guide rail 13, which is fixed to the machine tool platform 1. Crucially, the movement direction of the vibration cylinder 9 is perpendicular to the axial feed direction of the upsetting cylinder 4. The vibration cylinder 9 is controlled by a high-frequency servo valve (response time ≤ 3ms), which drives the vibration block 11 to perform linear sinusoidal reciprocating motion at a frequency of 40-60Hz. The feed of the upsetting moving table 6 causes the first reinforcing bar 3 to contact the end face of the second reinforcing bar 14, generating linear friction under the drive of the vibration cylinder 9. A vibration clamping mechanism 12 is installed on the vibration block 11 to clamp the second reinforcing bar 14. To prevent the reinforcing bar from loosening due to high-frequency vibration, this mechanism is designed as a double-set hydraulic clamp, simultaneously clamping the reinforcing bar from both the top and bottom, forming a stable three-point positioning constraint structure.

[0029] The device in this embodiment is equipped with a multi-dimensional sensor assembly, which forms the basis of closed-loop control: To ensure the concentricity of the two reinforcing bars (first reinforcing bar 3 and second reinforcing bar 14), the alignment detection assembly is equipped with a laser alignment system. A laser alignment instrument is installed on the side of the upsetting clamping mechanism 7 to monitor the radial runout of the first reinforcing bar 3; a laser displacement sensor with an accuracy of ±0.01mm is installed on the side of the vibration unit (the side of the vibration cylinder fixing seat 10) to monitor the axial and radial position of the second reinforcing bar 14. By finely adjusting the vibration cylinder 9, the alignment error can be controlled within 0.05mm.

[0030] An end face gap sensor is provided at the front end of the upsetting moving table 6 or on a relatively stationary part to detect the distance between the end faces of the first steel bar 3 and the second steel bar 14 in real time, thereby controlling the timing of the upsetting cylinder switching from fast advance to slow advance to prevent rigid impact.

[0031] Above or to the side of the welding area, a dual-color infrared thermometer with a sampling rate of ≥100Hz is installed on the bracket. Its field of view covers the welding joint surface and is used to provide real-time feedback of temperature data generated by frictional heat to the control unit to determine the start and end times of vibration. A compressed air cooling unit (not shown in the figure) is also installed to cool the fusion zone. The compressed air cooling unit is activated when the temperature of the fusion zone drops to a set threshold and sprays compressed air into the fusion zone at a flow rate of 10m³ / min to enhance the cooling of the fusion zone.

[0032] A laser encoder is also provided next to the vibrating block 11 to confirm whether the vibrating block 11 is accurately positioned in the mechanical geometry (deviation < ±0.03mm) at the moment the vibration stops, ensuring that the welded steel bars are not misaligned.

[0033] To meet environmental protection and process cooling requirements, the unit is equipped with an air intake (not shown in the figure) for a fume collection system above the welding area, which controls the particulate matter concentration in the operating area within a standard range. In addition, the unit is equipped with compressed air cooling nozzles pointing towards the weld joint, which are connected to an adjustable-flow-rate air source to provide gradient air cooling during the pressure holding phase.

[0034] In one embodiment of the present invention, the upsetting clamping mechanism 7 and the vibration clamping mechanism 12 adopt a 60° V-groove structure. The groove surface is deposited with a WC-10Co cemented carbide layer (composition: 88% WC, 10% Co, 2% Cr3C2) through laser cladding. The cladding layer thickness is 0.8±0.05mm, and the surface hardness reaches HRC 67-70 (Vickers hardness test standard ISO 6507). The tooth pitch is designed to be 5mm, and the tooth tip radius is R0.2mm. Finite element analysis (ANSYS Workbench) verifies that this structure can control the rebar slippage to ≤0.08mm under a clamping force of 300kN. The hydraulic compensation unit uses a proportional relief valve (set pressure 25MPa) linked with a plunger-type compensation cylinder to offset the clamping force fluctuation caused by the thermal expansion of the rebar in real time (compensation response time ≤10ms).

[0035] Example 2 This embodiment describes a method for linear friction welding of reinforcing bars. The method uses the linear friction welding device for reinforcing bars as described in Embodiment 1. This process is fully automated and under closed-loop control via a control unit. Figure 3 As shown, it includes the following steps one through five: Step 1: Clamping and centering. The two sections of steel bars are clamped by the upsetting clamping mechanism 7 and the vibration clamping mechanism 12 respectively, and the position is finely adjusted by the vibration cylinder 9 to achieve concentric alignment.

[0036] In this embodiment, the clamping and alignment method includes the following steps S11 to S13: S11: Place the first reinforcing bar 3 and the second reinforcing bar 14 to be welded in the upsetting clamping mechanism 7 and the vibration clamping mechanism 12 respectively. The hydraulic system drives the V-shaped jaws of the upsetting clamping mechanism 7 to lock the first reinforcing bar 3 with a clamping force of 100-300kN. Simultaneously drive the double clamps of the vibration clamping mechanism 12 to clamp the second reinforcing bar 14 from the upper and lower sides with a clamping force of 100-300kN.

[0037] Specifically, with the clamping mechanism fully released, the two sections of reinforcing bars to be welded are placed parallel to each other on the V-shaped positioning frame of the machine tool platform. The diameter of the reinforcing bars (Φ16–50mm) is automatically identified by a laser diameter measuring instrument, and the tooth pitch of the upsetting clamping mechanism 7 and the vibration clamping mechanism 12 is dynamically adjusted to a reference value of 5mm according to the diameter. At the same time, the clamping force is set according to the diameter gradient (100kN for Φ16mm, 300kN for Φ50mm). Among them, the first reinforcing bar 3 is clamped by a single set of upsetting clamping mechanism 7 on the upsetting side, and the second reinforcing bar 14 is redundantly clamped by a double set of vibration clamping mechanism 12 on the vibration side. The clamping tooth surface is overlaid with a WC-10Co hard alloy layer (hardness ≥HRC 65), and the hydraulic compensation unit eliminates clamping slippage to ensure radial runout ≤0.1mm.

[0038] S12: To eliminate the coaxiality error between the two sections of reinforcing bars, the system activates the fine-tuning mode. The vibrating cylinder 9 is activated to enter the fine-tuning mode, and the servo valve controls the vibrating cylinder 9 to push the second reinforcing bar 14 to translate along the axial direction of the vibrating cylinder 9 at a feed speed of 0.5 mm / s.

[0039] S13: The concentricity of the two rebar end faces is monitored in real time using a laser displacement sensor. When the axial offset is ≤0.05mm, the alignment is considered complete and the position is locked. The laser displacement sensor installed on the side monitors the relative position of the two rebar end faces in real time. When the system detects that the axial centerline offset of the two rebars is ≤0.05mm, the alignment is considered qualified, and the system immediately locks the current position of the vibration cylinder 9, preparing to enter the next stage.

[0040] Step Two: Pre-pressing Contact. The upsetting cylinder 4 drives the upsetting moving table 6 forward, bringing the end faces of the two steel bars into contact and applying a constant pre-pressure. After alignment, the upsetting cylinder 4 drives the upsetting moving table 6 to advance the first steel bar 3 towards the second steel bar 14. To balance processing efficiency and equipment safety, this process employs segmented speed control.

[0041] In this embodiment, the pre-compression contact method includes the following steps S21 to S23: S21: The top forging cylinder 4 first drives the first reinforcing bar 3 to move rapidly at a speed of 120 mm / s to shorten the idle stroke time.

[0042] S22: When the end face gap sensor detects that the distance between the two steel bar end faces is ≤5mm, the system controls the top forging cylinder 4 to decelerate rapidly to 20mm / s to prevent high-speed impact from damaging the steel bar end faces or damaging the precision sensor.

[0043] S23: When a distance ≤ 0.3mm is detected, the system automatically switches to pressure control mode, applying a constant pressure of 20–50MPa. When the end face gap sensor detects that the two sections of steel bars are about to contact, the control system switches the upsetting cylinder 4 from position control mode to pressure control mode. At this time, the upsetting cylinder 4 applies a constant preload of 20–50MPa, making the end faces of the two sections of steel bars fit tightly together.

[0044] Step 3: Vibration and friction generate heat. Under the condition of maintaining the constant pre-pressure, control the vibration cylinder 9 to drive the second steel bar 14 to perform linear reciprocating motion, and use friction to generate heat to increase the temperature of the contact surface.

[0045] In this embodiment, the vibration friction heat generation method includes the following steps S31 to S34: S31: The high-frequency servo valve drives the vibration cylinder 9 to move the second steel bar 14 in a linear reciprocating motion. The vibration frequency is set to 40-60Hz and the amplitude is 0.5-3mm, so that the metal at the contact surface heats up rapidly and reaches a plastic state.

[0046] S32: The dual-color infrared thermometer continuously monitors the temperature of the welding interface at a sampling rate of 100Hz. The system is set to a target temperature range of 1200±30℃.

[0047] S33: If the monitored temperature is below 1170℃, the vibration time will be automatically extended by 0.5 seconds to ensure sufficient heat input; if the monitored temperature is above 1230℃, the vibration will be terminated in advance to prevent overheating from causing grain coarsening or metal loss.

[0048] S34: Upon receiving the vibration stop command, the control system uses the position feedback of the laser encoder to control the vibration block 11 to stop precisely at the mechanical geometric center. The position deviation is strictly controlled within ±0.03mm to ensure that the welded steel bars do not have misalignment.

[0049] Step 4: Upsetting and fusion. When the temperature reaches the first preset value, stop the vibration and control the upsetting cylinder 4 to apply upsetting force, so that the two steel bars are squeezed against each other to produce plastic deformation and fuse together.

[0050] Once the vibration stops, the upsetting stage begins immediately to achieve solid-state bonding. In this embodiment, the upsetting fusion method includes the following steps: Within 0.08 seconds after vibration stops (i.e., during the window period when the metal is in its optimal plastic state), upsetting is initiated, and upsetting cylinder 4 outputs an instantaneous high pressure of 150–300 MPa; at this time, upsetting cylinder 4 switches back to displacement control or pressure-displacement composite control. To ensure welding quality, the upsetting displacement... It is not a fixed value, but depends on the diameter of the reinforcing bar. According to the formula The calculation settings ensure that a dense metallurgical bond layer with a width of 2-3 mm is formed at the interface. For example, for a 32 mm diameter rebar, the upsetting displacement is automatically set to 2.76 mm. Under this high-pressure extrusion, the oxide scale and overheated metal at the interface are extruded to form flash, and the metal at both ends undergoes sufficient plastic flow and recrystallization to form a dense metallurgical bond layer with a width of approximately 2-3 mm.

[0051] Step 5: Pressure holding, cooling and unloading. Maintain pressure until the temperature drops to the second preset value, then release the clamping mechanism and reset the device.

[0052] To prevent weld cracks from forming due to rapid cooling or stress release at high temperatures, this embodiment employs a segmented gradient cooling strategy: First stage (high temperature and heavy pressure): When the temperature of the welding zone is in the range of 1200℃ to 800℃, maintain the full upsetting pressure for natural cooling, so that the weld can cool naturally under compressive stress to prevent high temperature cracking.

[0053] The second stage (medium-temperature air cooling): When the temperature drops to the range of 800℃ to 500℃, the metal has a certain strength. At this time, the upsetting pressure is linearly reduced to 50% of the original pressure, and the weld is strengthened by cooling, for example, by opening the compressed air nozzle to strengthen the air cooling of the weld, so as to improve production efficiency and refine the grain.

[0054] The third stage (low-temperature unloading): Once the temperature drops below 500℃, the pressure is completely released and the clamps are loosened. Finally, the upsetting clamping mechanism 7 and the vibration clamping mechanism 12 release simultaneously, the upsetting cylinder 4 quickly returns to its initial position, and the robot arm removes the welded steel bar, completing one welding cycle. The entire single cycle time is controlled within 85 seconds.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A linear friction welding device for reinforcing bars, comprising: The machine tool platform (1) and the power and control unit (2) are characterized in that they further include: Upsetting cylinder (4) and upsetting moving table (6) are installed on the machine tool platform. The upsetting moving table (6) is slidably arranged on the upsetting moving table guide rail (8). The upsetting cylinder (4) drives the upsetting moving table (6) to move axially. The vibration cylinder mounting base (10) and vibration cylinder (9) are fixed on the machine tool platform, and the vibration block (11) is slidably arranged on the vibration block guide rail (13). The vibration cylinder (9) drives the vibration block (11) to perform reciprocating linear motion. Upsetting clamping mechanism (7) is provided on the upsetting moving table (6) and is used to clamp the first steel bar (3); A vibration clamping mechanism (12) is provided on the vibration block (11) for clamping the second reinforcing bar (14). The movement direction of the upsetting cylinder (4) is perpendicular to the movement direction of the vibration cylinder (9). The first steel bar (3) and the end face of the second steel bar (14) are brought into contact by the feed of the upsetting moving table (6), and linear friction is generated under the drive of the vibration cylinder (9).

2. The apparatus according to claim 1, characterized in that, The machine tool platform (1) is equipped with a centering detection component for aligning two sections of steel bars. The centering detection component includes a laser centering instrument installed on the side of the upsetting clamping mechanism (7) and a laser displacement sensor installed on the side of the vibration cylinder fixing seat (10).

3. The apparatus according to claim 2, characterized in that, The device also includes an infrared thermometer for monitoring the temperature of the welding zone, a compressed air cooling unit for cooling the fusion zone, and an end face gap sensor for detecting the distance between the first reinforcing bar (3) and the second reinforcing bar (14).

4. The apparatus according to claim 3, characterized in that, The number of the upsetting cylinders (4) is two, and the two upsetting cylinders (4) are arranged in parallel; the upsetting cylinders (4) are equipped with magnetostrictive displacement sensors and electro-hydraulic proportional valves to realize the switching between position control mode and pressure control mode.

5. A method for linear friction welding of reinforcing bars, characterized in that, The method uses the apparatus as described in claim 4 and includes the following steps: Clamping and centering: The two sections of steel bars are clamped by the upsetting clamping mechanism (7) and the vibration clamping mechanism (12) respectively, and the position is finely adjusted by the vibration cylinder (9) to achieve concentric alignment; Pre-press contact: The upsetting cylinder (4) drives the upsetting moving table (6) to move forward, so that the end faces of the two steel bars contact and apply a constant pre-press; Vibration friction heat generation: Maintain pre-pressure and control the vibration cylinder (9) to drive the second steel bar (14) to perform linear reciprocating motion, and use friction heat generation to increase the temperature of the contact surface; Upsetting fusion: When the temperature reaches the first preset value, the vibration is stopped, and the upsetting cylinder (4) is controlled to apply upsetting force, so that the two steel bars are squeezed against each other to produce plastic deformation and fuse together; Pressure holding, cooling and unloading: Maintain pressure until the temperature drops to the second preset value, then release the clamping mechanism and reset the device.

6. The method according to claim 5, characterized in that, The clamping and alignment steps are as follows: Start the vibration cylinder (9) to enter the fine-tuning mode, and control the vibration cylinder (9) to push the second steel bar (14) to move axially at a feed speed of 0.5 mm / s through the servo valve; The concentricity of the two steel bar ends is monitored in real time using a laser displacement sensor. When the axial offset is ≤0.05mm, the alignment is considered complete and the position is locked.

7. The method according to claim 5, characterized in that, The method for the pre-compression contact step is as follows: The top forging cylinder (4) first drives the first steel bar (3) to move rapidly at a speed of 120 mm / s; When the end face gap sensor detects a distance ≤5mm, the speed is switched to 20mm / s; When the detected distance is ≤0.3mm, the system automatically switches to pressure control mode and applies a constant pressure of 20-50MPa.

8. The method according to claim 5, characterized in that, The method for generating heat through vibration and friction is as follows: The vibration frequency is controlled at 40–60 Hz, and the amplitude is controlled at 0.5–3 mm. The temperature of the welding area is monitored in real time using an infrared thermometer, with the target temperature range set at 1200±30℃. If the monitored temperature is below 1170℃, the vibration time will be automatically extended by 0.5 seconds; if the monitored temperature is above 1230℃, the vibration will be terminated prematurely. At the moment the vibration stops, the laser encoder is used to confirm that the vibration block (11) is stationed in the mechanical center position, and the position deviation is controlled within ±0.03mm.

9. The method according to claim 5, characterized in that, The method for the upsetting and fusion step is as follows: Upsetting begins within 0.08 seconds after vibration stops, and the upsetting cylinder (4) outputs an instantaneous high pressure of 150-300 MPa; the upsetting displacement... According to the diameter of the reinforcing bar According to the formula The calculation settings are configured to form a dense metallurgical bonding layer with a width of 2-3 mm at the bonding surface.

10. The method according to claim 5, characterized in that, The pressure holding, cooling, and unloading steps employ a segmented gradient cooling strategy: First stage: When the temperature of the welding zone is in the range of 1200℃~800℃, maintain the full upsetting pressure and allow for natural cooling. Second stage: When the temperature drops to the range of 800℃ to 500℃, the upsetting pressure is reduced to 50%, and the weld is subjected to enhanced cooling. Third stage: Once the temperature drops below 500℃, completely release the pressure and loosen the clamps.

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