Rotary rolling grain refinement type metal diffusion welding device and method

Abstract

This invention relates to the field of welding technology, specifically to a rotary rolling mill for refining grain-type diffusion welding of metals and a method thereof. The apparatus includes a rotary rolling mill, a rotary rolling head, a liquid medium fixture, and a welding fixture. The rotary rolling mill includes a bed and a power head and a two-dimensional moving platform mounted on the bed. The power head is located above the two-dimensional moving platform and has rotational and Z-axis movement degrees of freedom. The two-dimensional moving platform has X and Y-axis movement degrees of freedom. The liquid medium fixture is mounted on the two-dimensional moving platform and is used to fix the workpieces to be welded, while simultaneously providing a liquid medium to the friction interface of the workpieces. The rotary rolling head is mounted on the power head and is used to rotary roll the surface of the workpieces to be welded, achieving grain refinement of the metal surface. The welding fixture is used to clamp and fix the two workpieces to be welded after the metal surface grain refinement has been completed. This invention achieves low-temperature, low-deformation, high-weld-ratio, and low-cost diffusion bonding.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a rotary rolling mill refining grain-type metal diffusion welding apparatus and method. Background Technology

[0002] The principle of diffusion bonding is that, in a vacuum or protective atmosphere, the contact surfaces of the parts to be welded undergo microscopic plastic deformation and tightly bond under certain temperature and pressure. The interfacial atoms diffuse into each other, eventually forming a metallurgical joint. Throughout the process, the base material does not melt and the weldment is formed in a solid phase.

[0003] Diffusion welding is primarily used for welding small, precision, and complex structural components where fusion welding and brazing fail to meet quality requirements. It is suitable for joining precision aluminum alloy components with complex internal curved cavities, flow channels, micropores, and other special structures. Traditional diffusion joining requires high temperatures to achieve sufficient atomic diffusion, which negatively impacts joint strength and deformation rate, and also damages the properties of the base material. However, nanocrystals have a much higher grain boundary diffusion coefficient than polycrystalline materials, exhibiting significant diffusion even at low temperatures. Utilizing their high diffusivity can significantly reduce the temperature and time required for diffusion welding, while avoiding the adverse effects of high temperatures on material properties. Therefore, developing a device for large-area nanocrystal preparation on aluminum alloy surfaces has significant theoretical and engineering application value for achieving a new low-temperature diffusion joining process for high-strength, low-deformation aluminum alloys. Based on this, there is an urgent need for a rotary rolling grain-refining metal diffusion welding device and method to solve the aforementioned technical challenges. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a rotary rolling and refining metal diffusion welding apparatus and method to solve the defects of traditional aluminum alloy diffusion welding, such as high temperature, large heat damage, poor interface bonding at low temperature, high equipment cost, uneven welding stiffness, and insufficient grain refinement effect and efficiency, thereby achieving low temperature, low deformation, high welding rate, and low cost diffusion bonding.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The present invention provides a rotary rolling mill for refining grain-type metal diffusion welding, comprising a rotary rolling mill, a rotary rolling head, a liquid medium fixture, and a welding fixture;

[0007] The rotary rolling mill includes a bed, a power head mounted on the bed, and a two-dimensional moving platform. The power head is located above the two-dimensional moving platform and has rotational and Z-axis movement degrees of freedom. The two-dimensional moving platform has X and Y-axis movement degrees of freedom. A liquid medium fixture is mounted on the two-dimensional moving platform. The liquid medium fixture is used to fix the workpiece to be welded and to provide a liquid medium to the friction interface of the workpiece. The rotary rolling head is mounted on the power head and is used to rotary roll the surface of the workpiece to be welded, thereby refining the grain size of the metal surface.

[0008] The welding fixture is used to clamp and fix two workpieces to be welded after the metal surface grain refinement has been completed.

[0009] The rotary rolling head includes a rotating shaft and multiple round-headed pins. One end of the rotating shaft is connected to the power head, and the other end of the rotating shaft is detachably equipped with multiple round-headed pins along the circumferential direction. The head of each round-headed pin has a dome, which protrudes outside the other end face of the rotating shaft. During operation, the dome contacts the surface of the workpiece to be welded, and the multiple round-headed pins simultaneously roll to achieve efficient grain refinement of a large area of ​​the surface to be welded.

[0010] The round-headed pin is threadedly connected to the rotating shaft and is locked in place by a locking nut.

[0011] The two-dimensional mobile platform includes an X-axis mobile platform and a Y-axis mobile platform arranged sequentially from bottom to top.

[0012] The liquid medium fixture is equipped with a pressure plate fixture, which is used to press and fix the workpiece to be welded on both sides.

[0013] The liquid medium is water, which forms a water film on the surface of the workpiece to be welded.

[0014] The welding fixture includes pressure plate I, pressure plate II, C-type locking plate I, and C-type locking plate II; the two workpieces to be welded are stacked and placed between pressure plate I and pressure plate II, and then clamped and fixed on both sides by C-type locking plate I and C-type locking plate II.

[0015] The workpiece to be welded is an aluminum plate; both pressure plate I and pressure plate II are steel plates.

[0016] Another aspect of the present invention provides a welding method utilizing the rotary rolling grain refinement type metal diffusion welding apparatus described above, comprising the following steps:

[0017] Step S1, Surface pretreatment: Grind and clean the surface of the workpiece to be welded with alcohol to remove oxide film and dirt;

[0018] Step S2, Rotary Rolling Refinement: The pre-treated workpiece to be welded is clamped on a liquid medium fixture, and the surface of the workpiece to be welded is rolled multiple times by a rotary rolling head to achieve surface nano-crystallization.

[0019] Step S3, Chemical Cleaning: The workpiece to be welded with nanocrystals on the surface is sequentially subjected to alkaline washing, acid washing, and ultrasonic cleaning with anhydrous ethanol, and then dried.

[0020] Step S4, Vacuum Low-Temperature Diffusion Welding: Assemble the two workpieces to be welded into the welding fixture, and then place them in a vacuum diffusion welding furnace with a vacuum degree < 4 × 10⁻⁶. -3 Pa, heated to 480-550℃ at a heating rate of 5-15℃ / min, pressure 3-8MPa, held for 30-120min, and then cooled with the furnace to complete the diffusion connection.

[0021] In step S2, the pressing depth of the rotary compactor is less than 0.15 mm, the rotation speed is 300-400 rpm, and the travel speed is 20-30 mm / min.

[0022] The present invention has the following beneficial effects and advantages:

[0023] 1. Low-temperature welding: The nanocrystalline layer accelerates grain boundary diffusion, reducing the minimum diffusion welding temperature of aluminum alloys to 480℃, which is 50-100℃ lower than the traditional process, significantly reducing thermal damage and deformation of the base material.

[0024] 2. High efficiency in grain refinement: Water-cooled assisted rolling can refine the grains from about 59.62μm to 80nm, resulting in strong interfacial bonding and high welding rate.

[0025] 3. Excellent lubrication and operating conditions: The dynamic pressure water film achieves full-fluid lubrication, reduces vibration and noise, reduces friction and wear, extends service life, and is suitable for high-speed operating conditions.

[0026] 4. Low tooling cost: The simple temperature-controlled furnace and thermal expansion pressurization tooling are used, and the purchase cost is significantly lower than that of hydraulic pressure head pressurization and vacuum diffusion welding equipment.

[0027] 5. Stiffness uniformity: The multi-C type locking plate layout alleviates the difference in contact stiffness of the workpiece, avoids local insufficient welding or over-welding, and improves the uniformity and reliability of the joint.

[0028] 6. Advantages of rotary compaction grain refinement compared to shot peening: Based on the vertical surface compressive-tensile strain impact strain wave, tangential shear strain is introduced. Compared to the vertical surface compressive-tensile strain of shot peening, this is more conducive to dislocation multiplication and entanglement to form nanocrystals, thus promoting nanocrystal formation.

[0029] 7. Advantages of rotary compaction for grain refinement: Based on the gradual strain wave of compressive-tensile strain perpendicular to the surface, tangential shear strain is introduced. Compared with the compressive-tensile strain perpendicular to the surface of roll compaction, this is more conducive to dislocation multiplication and entanglement to form nanocrystals, and thus more conducive to nanocrystal formation.

[0030] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 This is an isometric view of the rotary roller in this invention;

[0034] Figure 2 for Figure 1 Enlarged view of a portion of point A in the middle;

[0035] Figure 3 This is a schematic diagram of the rotating compaction head in this invention;

[0036] Figure 4 This is one of the isometric views of the rotary compactor head in this invention;

[0037] Figure 5 This is the second isometric view of the rotary compactor head in this invention;

[0038] Figure 6 Comparison images of electronic lenses with and without water-cooled auxiliary surface rotation and rolling in embodiments of the present invention: (a) image of electronic lens without water-cooled auxiliary surface rotation and rolling; (b) image of electronic lens with water-cooled auxiliary surface rotation and rolling.

[0039] Figure 7 This is an isometric view of the welding fixture in this invention;

[0040] Figure 8 This is a schematic diagram of the structure of the workpiece to be welded containing an inner cavity in an embodiment of the present invention;

[0041] Figure 9 This is a schematic diagram of the mounting of a workpiece containing an inner cavity to be welded in an embodiment of the present invention;

[0042] Figure 10This is a thermal stress analysis diagram of diffusion welding assembly in an embodiment of the present invention;

[0043] Figure 11 This is a stress distribution diagram of the welding cross-section in an embodiment of the present invention.

[0044] In the diagram: 1. Rotary rolling mill; 101. Bed; 102. Power head; 103. X-axis moving platform; 104. Y-axis moving platform; 2. Rotary rolling head; 201. Rotary shaft; 202. Round head pin; 203. Locking nut; 204. Dome; 3. Liquid medium fixture; 4. Pressure plate fixture; 5. Workpiece to be welded; 501. Workpiece to be welded I; 502. Workpiece to be welded II; 7. Pressure plate I; 8. Pressure plate II; 9. C-type locking plate I; 10. C-type locking plate II. Detailed Implementation

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] See Figures 1 to 9 As shown, an embodiment of the present invention provides a rotary rolling mill for refining grain-type metal diffusion welding, including a rotary rolling mill 1, a rotary rolling head 2, a liquid medium fixture 3, and a welding fixture. The rotary rolling mill 1 includes a bed 101, a power head 102 and a two-dimensional moving platform disposed on the bed 101. The power head 102 is located above the two-dimensional moving platform and has degrees of freedom of rotation and movement along the Z direction. The two-dimensional moving platform has degrees of freedom of movement along the X and Y directions. The liquid medium fixture 3 is disposed on the two-dimensional moving platform and is used to fix the workpiece 5 to be welded, while providing a liquid medium for the friction interface of the workpiece 5 to be welded. The rotary rolling head 2 is disposed on the power head 102 and is used to rotary roll the surface of the workpiece 5 to be welded, thereby refining the grain of the metal surface. The welding fixture is used to clamp and fix the two workpieces 5 to be welded after the metal surface grain refinement is completed.

[0048] See Figures 3 to 5As shown in the embodiment of the present invention, the rotary rolling head 2 includes a rotary shaft 201 and a plurality of round-headed pins 202. One end of the rotary shaft 201 is connected to the power head 102, and the other end of the rotary shaft 201 is detachably mounted with a plurality of round-headed pins 202 in the circumferential direction. The head of the round-headed pin 202 is provided with a dome 204, and the dome 204 is exposed on the outer side of the other end face of the rotary shaft 201. During operation, the dome 204 contacts the surface of the workpiece 5 to be welded, and the plurality of round-headed pins 202 simultaneously roll to achieve efficient grain refinement of a large area of ​​the surface to be welded.

[0049] Specifically, the round-headed pin 202 is threadedly connected to the rotating shaft 201 and is locked in place by the locking nut 203.

[0050] In this embodiment, the two-dimensional moving platform includes an X-axis moving platform 103 and a Y-axis moving platform 104 arranged sequentially from bottom to top. A pressure plate fixture 4 is provided on the liquid medium fixture 3, which is used to press and fix the workpiece 5 to be welded on both sides. The liquid medium is water, forming a water film on the surface of the workpiece 5 to be welded.

[0051] Specifically, the bed 101 integrates multiple sets of transmission and drive mechanisms, each including a motor, reducer, lead screw, and guide rail slider. Their specific functions are as follows: one set drives the power head 102 to move up and down; another set drives the X-axis moving platform 103 to move horizontally along the X-axis; the X-axis moving platform 103 also integrates a set of transmission and drive mechanisms of the same specifications to drive the Y-axis moving platform 104 to move horizontally along the Y-axis. The rotation of the power head 102 is driven by a motor-reducer mechanism. Based on the above structure, the rotary rolling head 2 has four degrees of freedom relative to the workpiece 5 to be welded, enabling smooth rotary rolling. The workpiece 5 to be welded is installed inside the liquid medium fixture 3 via a pressure plate fixture 4. The pressure plate fixture 4 can be changed to multiple positions on a single welding surface in one pass, achieving comprehensive grain refinement of the welding surface.

[0052] In this embodiment, six holes are evenly distributed at the lower end of the rotating shaft 201. Each hole has a pin hole at the bottom and a thread at the top. Six round-headed pins 202 are respectively assembled into the six holes on the rotating shaft 201 through locking nuts 203. The structural features of the round-headed pins 202 are: a dome 204 at the lower end, a cylindrical structure in the middle, a thread in the middle section, and a hexagonal head at the upper tail (for fastening). The rotating shaft 201, the round-headed pins 202, and the locking nuts 203 are fastened with a double-nut anti-loosening method, and the lower vertices of all the domes 204 are uniformly distributed in the axial dimension. A sliding water film can be formed between the dome 204 and the workpiece 5 to be welded. The formation of this water film mainly depends on the water wedge effect and the adhesion of water: water is carried into the wedge-shaped convergent gap between the dome surface and the plane to be welded. As the rotation speed increases, the water pressure in the gap gradually increases, eventually forming a continuous dynamic pressure water film, realizing full fluid lubrication between the dome 204 and the workpiece 5 to be welded.

[0053] To verify the process effect, grain refinement experiments were conducted on the surface of the workpieces to be welded in both liquid and non-liquid environments. The two workpieces used in the experiment were 6061 aluminum alloy with an initial average grain size of 59.62 μm. After five passes of surface rotation and rolling, the average grain size of one of the workpieces was refined to 170 nm. (See [link to relevant documentation]). Figure 6 As shown in (a); another workpiece 5 to be welded underwent five passes of water-cooled assisted surface rotary rolling, further refining the average grain size to 80 nm, see [reference]. Figure 6 As shown in (b) of the diagram.

[0054] See Figure 7 As shown, in an embodiment of the present invention, the welding fixture includes pressure plate I7, pressure plate II8, C-type locking plate I9 and C-type locking plate II10; two workpieces 5 to be welded (workpiece I501 and workpiece II502 to be welded) are stacked and placed between pressure plate I7 ​​and pressure plate II8, and then clamped and fixed on both sides by C-type locking plate I9 and C-type locking plate II10.

[0055] Specifically, the workpiece 5 to be welded is an aluminum plate, and the pressure plates I7 and II8 are both steel plates. Since aluminum has a larger coefficient of thermal expansion than steel, it will generate the pressure used for welding.

[0056] It should be noted that the experimental data in this embodiment are the comprehensive results of multiple experiments to ensure the reliability of the process effect. The scope of protection of this invention includes, but is not limited to, the above-mentioned tooling-type diffusion welding method, and the tooling structure can be adjusted according to actual needs. The specific method of fixing the workpieces to be welded is as follows: workpieces to be welded I 501 and II 502 are respectively pressed by pressure plate I 7 and pressure plate II 8, and pressure plate I 7 and pressure plate II 8 are locked in a direction perpendicular to the welding surface by C-type locking plate I 9 and C-type locking plate II 10. Among them, pressure plate I 7, pressure plate II 8, C-type locking plate I 9 and C-type locking plate II 10 are all made of Q235B high-quality steel; since the coefficient of thermal expansion of aluminum alloy is greater than that of steel, the difference in thermal expansion between the two will naturally generate the pressure required for welding during the welding process, ensuring a tight bond at the welding interface. Diffusion friction welding with a pressure of 18.9MPa can be achieved at a temperature of 350℃.

[0057] See Figure 8 and Figure 9As shown, workpiece I501 to be welded contains an internal cavity, which leads to a difference in contact stiffness between workpiece I501 and workpiece II502. To avoid localized under-welding or over-welding during the welding process, pressure plates I7 and II8 are used to press down on workpieces I501 and II502, and multiple C-shaped locking plates I9 are used to lock the pressure plates I7 and II8 in a direction perpendicular to the welding surface. The multiple C-shaped locking plates I9 are distributed in different positions, which can effectively alleviate the difference in contact stiffness between workpieces I501 and II502, thereby achieving uniform welding contact stiffness and ensuring stable welding quality. The experimental data in this embodiment are the comprehensive results of multiple experiments to ensure the reliability of the process effect. The scope of protection of this invention includes, but is not limited to, the above-mentioned tooling-type diffusion welding method.

[0058] This invention provides a rotary rolling milling grain-refining metal diffusion welding device. Utilizing four rotary rolling degrees of freedom, the device can adapt to different workpieces and can further optimize the grain refinement effect by combining it with a liquid medium (water cooling). Employing full-fluid lubrication (dynamic pressure water film), it reduces wear between the dome and the workpiece during rotary rolling, ensuring a stable grain refinement process. Experimental data has been repeatedly verified, demonstrating high process reliability. With the aid of a pressure plate fixture, multiple positions can be changed in a single pass to achieve comprehensive grain refinement of the weldable surface, avoiding insufficient localized refinement. The joint has a high welding rate and minimal deformation, significantly reducing thermal damage to the base material. The equipment is low-cost, has uniform contact stiffness, and is suitable for efficient low-temperature diffusion bonding of light alloys such as aluminum alloys.

[0059] See Figures 1 to 9 As shown, another embodiment of the present invention provides a welding method using the rotary rolling grain refinement type metal diffusion welding apparatus as described above, comprising the following steps:

[0060] Step S1, Surface pretreatment: The surface of the workpiece 5 to be welded is sanded with sandpaper and cleaned with alcohol to remove the surface oxide film and dirt.

[0061] Step S2, Rotary Rolling Refinement: The pre-treated workpiece 5 to be welded is clamped on the liquid medium fixture 3, and the surface of the workpiece 5 to be welded is rolled in multiple passes by the rotary rolling head 2 to achieve surface nano-crystallization; the pressing depth of the rotary rolling head 2 is less than 0.15mm, the rotation speed is 300-400rpm, and the travel speed is 20-30mm / min.

[0062] Step S3, Chemical Cleaning: The workpiece 5 with nanocrystalized surface is subjected to alkaline washing, acid washing, and ultrasonic cleaning with anhydrous ethanol in sequence, and then dried.

[0063] Specifically, the processed aluminum alloy workpiece 5 is cut to size, lightly polished to remove surface processing marks, placed in a 5-15% NaOH solution for 2-5 minutes of alkaline washing, then placed in a 10-30% HNO3 solution for 1-2 minutes of acid washing, and finally ultrasonically cleaned with anhydrous ethanol for 10-15 minutes. After drying, the cleaned aluminum alloy is obtained.

[0064] Step S4, Vacuum Low-Temperature Diffusion Welding: Assemble the two workpieces 5 to be welded into the welding fixture, and then place them in a vacuum diffusion welding furnace with a vacuum degree < 4 × 10⁻⁶. -3 Pa, heated to 480-550℃ at a heating rate of 5-15℃ / min, pressure 3-8MPa, held for 30-120min, and then cooled with the furnace to complete the diffusion connection.

[0065] Remove the weldment and clean it to complete the low-temperature diffusion bonding of the aluminum alloy.

[0066] In this embodiment, the workpiece 5 to be welded is made of 6061 aluminum alloy. The diffusion welding temperature of nanocrystalline aluminum is typically 50–100°C lower than that of non-nanocrystalline aluminum, and therefore can be considered as relatively low-temperature welding. Nanocrystalline materials have higher grain boundary density and larger specific surface area, significantly improving atomic diffusion rate, and can achieve good interfacial bonding at lower temperatures. For traditional non-nanocrystalline aluminum, the diffusion welding temperature generally needs to reach 540–570°C; while nanocrystalline aluminum can achieve effective diffusion welding in the range of 400–550°C, and some experimental data are shown in Table 1.

[0067] Table 1: Comparison of diffusion welding achieved by multi-pass rolling of nanocrystalline aluminum: Rolling number Diffusion bonding temperature / °C Diffusion bonding time / min Diffusion bonding pressure / MPa Joint tensile strength / MPa Joint deformation / % Joint weld ratio / % 0 540 120 4 72 9.70 93.5 0 480 120 4 / / 0 1 480 120 4 63 0.94 86.7 3 480 120 4 74 0.93 94.3 5 480 120 4 66 0.95 90.6

[0068] This invention employs a rotary rolling device to process the surfaces of the aluminum alloys to be joined, minimizing the impact on the original surface roughness and facilitating the smooth implementation of subsequent diffusion joining processes. Rotary rolling treatment of the aluminum alloy surface before diffusion joining reduces the minimum diffusion joining temperature to 480℃, minimizing thermal damage to the base material caused by prolonged high-temperature heat treatment. The dome structure of the rotary rolling head 2 forms a sliding water film between the workpieces 5 to be welded, resulting in better grain refinement and stronger load-bearing capacity. The water film can withstand high radial and axial loads, while also providing vibration and noise reduction. The viscoelastic damping characteristics of the water film effectively absorb vibration and impact energy, improving operational stability; simultaneously, it achieves a liquid friction state, significantly reducing frictional heat generation and wear loss, and extending service life. Full-fluid lubrication avoids direct metal-to-metal contact friction, greatly improving service life and making it more suitable for high-speed conditions, with a more stable water film forming at high speeds.

[0069] This invention employs a tooling-type diffusion welding method, which, compared to hydraulic vacuum diffusion welding equipment (purchase cost approximately 150,000 RMB) and a vacuum temperature-controlled heating furnace (costing approximately 110,000 RMB), helps reduce equipment investment. This tooling-type diffusion welding structure can achieve uniform welding contact stiffness and improve welding quality stability.

[0070] See Figure 10 and Figure 11 As shown, the embodiment of the present invention uses finite element thermal and stress coupling analysis software to obtain the stress distribution diagram of the welding surface; the analysis software used is the Simulation module in SolidWorks software. Under the temperature condition of 480℃, the minimum pressure of the welding surface is 7.84MPa. According to the convention of diffusion welding industry, pressure is actually pressure intensity.

[0071] The aforementioned finite element thermal-stress coupling simulation method is used in the design of tooling fixtures. Its core purpose is to improve the welding quality by rationally designing the stiffness of the tooling fixtures, thereby making the contact stiffness of the welding surface of large hollow workpieces more uniform, while reducing the temperature and pressure parameters during the welding process and optimizing the welding process performance.

[0072] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A rotary rolling mill for refining grain-type metal diffusion welding, characterized in that, It includes a rotary rolling mill (1), a rotary rolling head (2), a liquid medium tooling (3), and welding tooling; The rotary rolling mill (1) includes a bed (101) and a power head (102) and a two-dimensional moving platform disposed on the bed (101). The power head (102) is located above the two-dimensional moving platform and has the freedom of rotation and movement along the Z direction. The two-dimensional moving platform has the freedom of movement along the X and Y directions. The liquid medium fixture (3) is disposed on the two-dimensional moving platform. The liquid medium fixture (3) is used to fix the workpiece to be welded (5) and to provide liquid medium for the friction interface of the workpiece to be welded (5). The rotary rolling head (2) is disposed on the power head (102). The rotary rolling head (2) is used to perform rotary rolling on the surface of the workpiece to be welded (5) to achieve grain refinement of the metal surface. The welding fixture is used to clamp and fix the two workpieces (5) to be welded after the metal surface grain refinement is completed.

2. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 1, characterized in that, The rotary rolling head (2) includes a rotating shaft (201) and multiple round-headed pins (202). One end of the rotating shaft (201) is connected to the power head (102), and multiple round-headed pins (202) are detachably installed on the other end of the rotating shaft (201) along the circumferential direction. The head of the round-headed pin (202) is provided with a dome (204), and the dome (204) is exposed on the outer side of the other end face of the rotating shaft (201). During operation, the dome (204) contacts the surface of the workpiece (5) to be welded, and the multiple round-headed pins (202) roll synchronously to achieve efficient grain refinement of the large area of ​​the surface to be welded.

3. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 2, characterized in that, The round-headed pin (202) is threadedly connected to the rotating shaft (201) and locked in place by a locking nut (203).

4. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 2, characterized in that, The two-dimensional mobile platform includes an X-axis mobile platform (103) and a Y-axis mobile platform (104) arranged sequentially from bottom to top.

5. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 2, characterized in that, The liquid medium fixture (3) is provided with a pressure plate fixture (4), which is used to press and fix the workpiece (5) to be welded on both sides.

6. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 2, characterized in that, The liquid medium is water, which forms a water film on the surface of the workpiece (5) to be welded.

7. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 2, characterized in that, The welding fixture includes pressure plate I (7), pressure plate II (8), C-type locking plate I (9) and C-type locking plate II (10); the two workpieces to be welded (5) are stacked and placed between pressure plate I (7) and pressure plate II (8), and then clamped and fixed on both sides by C-type locking plate I (9) and C-type locking plate II (10).

8. The rotary rolling and refining grain-type metal diffusion welding apparatus according to claim 7, characterized in that, The workpiece to be welded (5) is an aluminum plate; the pressure plate I (7) and pressure plate II (8) are both steel plates.

9. A welding method using the rotary rolling grain-refining metal diffusion welding apparatus of claim 8, characterized in that, Includes the following steps: Step S1, Surface pretreatment: Grind and clean the surface of the workpiece (5) to be welded with alcohol to remove oxide film and dirt; Step S2, Rotary rolling refinement: The pre-treated workpiece (5) to be welded is clamped on the liquid medium tooling (3), and the rotating rolling head (2) is used to roll the surface of the workpiece (5) to be welded multiple times to achieve surface nano-crystallization. Step S3, Chemical cleaning: The workpiece (5) with nanocrystalized surface is subjected to alkali washing, acid washing, and ultrasonic cleaning with anhydrous ethanol in sequence, and then dried; Step S4, Vacuum Low-Temperature Diffusion Welding: Assemble the two workpieces (5) to be welded into the welding fixture, and then place them in the vacuum diffusion welding furnace with a vacuum degree < 4 × 10⁻⁶. -3 Pa, heated to 480-550℃ at a heating rate of 5-15℃ / min, pressure 3-8MPa, held for 30-120min, and then cooled with the furnace to complete the diffusion connection.

10. The welding method according to claim 9, characterized in that, In step S2, the pressing depth of the rotary compactor (2) is less than 0.15 mm, the rotation speed is 300-400 rpm, and the travel speed is 20-30 mm / min.

Images