An electrode for friction stir welding and a friction stir welding process

Abstract

This invention discloses a welding electrode and a friction stir welding process. The welding electrode is placed at the weld joint between a first base material and a second base material to be welded. A stirring head is then used to stir the weld joint, welding the welding electrode, the first base material, and the second base material together. The welding electrode has a T-shaped cross-section, including a first side and a second side that are perpendicular to each other. The second side is positioned within the weld joint between the first and second base materials, with both sides of the second side adhering to the edges of the first and second base materials respectively. The first side is located on the surface of the first and second base materials and is in contact with their surfaces. When stirring at the weld joint of the first and second base materials, the stirring head is pressed down from the surface of the first side towards the weld joint of the first and second base materials to stir. This invention solves the problem of base material loss inherent in the friction stir welding process due to the technical principle by wearing down the first side.

Description

Technical Field

[0001] This invention belongs to the field of welding technology and relates to a welding electrode for friction stir welding and a friction stir welding process. Background Technology

[0002] Friction stir welding (FSW) effectively reduces porosity and slag inclusions generated in traditional fusion welding, featuring minimal joint deformation, automated welding process, and high joint quality. Compared to other welding processes, FSW has lower heat input, enabling high-quality joining of various materials, and is currently widely used in the field of light metals such as magnesium and aluminum. Before the FSW experiment, the workpiece to be welded is fixed, and a non-consumable tool with a stirring pin and shoulder is rotated at high speed and pressed into the workpiece. When the shoulder contacts the workpiece surface, heat is generated by friction between the workpiece and the stirring tool, and the heat input increases with increasing pressure, putting the metal material in a thermoplastic state. The stirring tool moves in a predetermined direction to complete the welding process. A key feature of the stirring head is that the stirring pin is located at the bottom of the stirring head, and its length is slightly less than the thickness of the plate. The heat generated in this process is achieved through the plastic deformation of the rotating tool and the workpiece material. This localized heating softens the workpiece before it reaches plastic deformation, and the rotation and movement of the welding tool causes the softened metal to move from the front end to the rear end of the stirring head. In this process, a solid-phase weld joint is formed.

[0003] However, this method of increasing frictional heat by adjusting the downward pressure to achieve the purpose of welding will result in severe surface wear of the weldment. This inevitable defect will seriously reduce the service performance of the workpiece. Summary of the Invention

[0004] To address the material loss inherent in friction stir welding due to its inherent technical principles, this invention proposes a welding electrode and a friction stir welding process for friction stir welding.

[0005] The technical solution adopted in this invention is as follows:

[0006] A friction stir welding process includes the following steps:

[0007] Welding rods are placed at the weld joint of the first and second base materials to be welded. Then, a stirring head is used to stir the weld joint of the first and second base materials to be welded, so as to weld the welding rods, the first and second base materials to be welded together.

[0008] The welding rod has a T-shaped cross-section, which includes a first side and a second side that are perpendicular to each other. When the welding rod is placed at the weld joint between the first base material and the second base material, the second side is placed inside the weld joint between the first base material and the second base material. The two sides of the second side are respectively attached to the edges of the first base material and the second base material. The first side is located on the surface of the first base material and the second base material and is attached to the surface of the first base material and the second base material.

[0009] When stirring at the weld joint of the first and second base materials to be welded using a stirring head, the stirring head is pressed down from the first side surface toward the weld joint of the first and second base materials to be welded and stirred.

[0010] Preferably, the thickness of the first side is 1 to 1.5 times the pressure of the stirring head, and the height of the second side is not less than the thickness of the first and second base materials to be welded.

[0011] Preferably, the cross-section of the second side is rectangular, the stirring pin of the stirring head is cylindrical, and the thickness of the second side is 0.1 to 0.95 times the diameter of the stirring pin of the stirring head.

[0012] Preferably, the cross-section of the second side is rectangular, the shape of the stirring pin of the stirring head is frustum-shaped, the thickness of the second side is 0.1 to 0.95 times the diameter of the large end of the stirring pin of the stirring head, and the thickness of the second side is 0.1 to 0.95 times the diameter of the small end of the stirring pin of the stirring head.

[0013] Preferably, the cross-section of the second side is trapezoidal, the longer base of the second side is connected to the first side, the edges of the first and second base materials to be welded that are in contact with the second side are set as inclined surfaces, the stirring needle of the stirring head is cylindrical, and the length of the longer base of the second side is 0.1 to 0.95 times the diameter of the stirring needle of the stirring head.

[0014] Preferably, the cross-section of the second side is trapezoidal, the longer base of the second side is connected to the first side, the edges of the first and second base materials to be welded that are in contact with the second side are set as inclined surfaces, the stirring pin of the stirring head is frustum shaped, the length of the longer base of the second side is 0.1 to 0.95 times the diameter of the large end of the stirring pin of the stirring head, and the length of the shorter base of the second side is 0.1 to 0.95 times the diameter of the small end of the stirring pin of the stirring head.

[0015] Preferably, the taper of the stirring needle is the same as the bottom angles at both ends of the longer bottom edge of the second side.

[0016] Preferably, the welding electrode is made of a high-entropy alloy.

[0017] Preferably, the high-entropy alloy uses metastable Fe. 40 Mn 20Co 20 Cr 15 Si5 high-entropy alloy.

[0018] The present invention also provides a welding electrode for use in the friction stir welding process described above, wherein the cross-section of the welding electrode is T-shaped and the cross-section of the welding electrode includes a first side and a second side that are perpendicular to each other.

[0019] When welding the first and second base materials to be welded by friction stir welding, the second side is placed in the weld seam between the first and second base materials to be welded, with both sides of the second side in contact with the edges of the first and second base materials to be welded, and the first side located on the surface of the first and second base materials to be welded, in contact with the surface of the first and second base materials to be welded; then the stirring head is pressed down from the surface of the first side towards the weld seam of the first and second base materials to be welded and friction stir welding is performed.

[0020] Compared with the prior art, the present invention has the following technical advantages:

[0021] In this invention, a T-shaped welding electrode is used in the friction stir welding process. The first edge of the electrode acts as a sacrificial layer, being worn down by the stirring head during the friction stir welding process, thus replacing the surface damage of the workpiece in the original friction stir welding process, which effectively ensures the workpiece accuracy. The second edge of the electrode not only fixes the first edge of the electrode, but also uses the thickness of the second edge to offset the loss of the base material along the weld width direction. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the base material, welding rod, and stirring head in the friction stir welding process of the present invention;

[0023] Figure 2(a) is a schematic diagram of one form of the base material and welding rod arrangement in an embodiment of the present invention; Figure 2(b) is a top view of Figure 2(a); Figure 2(c) is a left view of Figure 2(a); Figure 2(d) is a schematic diagram of one form of the welding rod of the present invention; Figure 2(e) is a schematic diagram of another form of the welding rod of the present invention.

[0024] Figure 3 This is a schematic diagram of the friction stir welding process using the designed welding rod in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of butt stir friction welding performed on Example 1 without the addition of "T-type welding rods";

[0026] Figure 5 These are tensile property diagrams of the welded joints obtained in Embodiment 1 and Comparative Example 1 of the present invention;

[0027] Figure 6This is a hardness distribution diagram of the welded joint obtained in Embodiment 1 and Comparative Example 1 of the present invention.

[0028] In the figure, 1-first base material to be welded, 2-welding electrode, 2-1-first side, 2-2-second side, 3-second base material to be welded, and 4-stirring head. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0030] See Figure 1 , Figures 2(a)-2(e) as well as Figure 3 The friction stir welding process of the present invention includes the following steps:

[0031] Welding rod 2 is placed at the weld joint of the first base material 1 and the second base material 3 to be welded. Then, a stirring head is used to stir the weld joint of the first base material 1 and the second base material 3 to be welded, so as to weld the welding rod 2, the first base material 1 and the second base material 3 to be welded together.

[0032] See Figures 2(a)-2(e) The welding rod 2 has a T-shaped cross section, which includes a first side 2-1 and a second side 2-2 that are perpendicular to each other. When the welding rod 2 is set at the weld between the first base material 1 and the second base material 3, the second side 2-2 is set in the weld between the first base material 1 and the second base material 3. The two sides of the second side 2-2 are respectively attached to the edges of the first base material 1 and the second base material 3. The first side 2-1 is located on the surface of the first base material 1 and the second base material 3 and is attached to the surface of the first base material 1 and the second base material 3.

[0033] When stirring at the weld seam of the first base material 1 and the second base material 3, the stirring head is pressed down from the surface of the first side 2-1 towards the weld seam of the first base material 1 and the second base material 3 and stirred.

[0034] Compared with traditional friction stir welding, the electrode prepared using this method, as a binder, effectively improves the strength of the welded joint while achieving zero underpressure and zero loss of the welded plates. The electrode preparation process is simple, and its use is convenient, requiring no complicated procedures. It effectively improves the structural properties and microstructure of the welded joint without increasing the welding cycle.

[0035] In this invention, the thickness of the first side 2-1 is 1 to 1.5 times the downward pressure of the stirring head, and the height of the second side 2-2 is not less than the thickness of the first base material 1 and the second base material 3 to be welded. The thickness of the first side 2-1 is slightly greater than the process loss, which can effectively ensure the integrity of the workpiece to be welded. Furthermore, since the selected material is metastable Fe... 40 Mn 20 Co 20 Cr 15 The Si5 high-entropy alloy effectively absorbs frictional heat during welding, thereby reducing the heat input to the aluminum alloy to be welded, minimizing the dissolution of precipitated phases, and improving the tensile strength of the weld joint. The second side, 2-2, is designed with different shapes to assist in the welding of irregular workpieces. Simultaneously, under the rotation of the stirring head, 2-2 is broken into fine high-entropy alloy particles during welding. These fine high-entropy alloy particles can serve as nucleation sites for fractal nucleation, further refining the grain size of the joint and improving its mechanical properties.

[0036] The welding electrode 2 and the weld seam of the present invention can take many forms, as detailed below:

[0037] 1. As shown in Figure 2(d), the cross-section of the second side 2-2 is rectangular, the stirring needle of the stirring head is cylindrical, and the thickness of the second side 2-2 is 0.1 to 0.95 times the diameter of the stirring needle of the stirring head.

[0038] 2. As shown in Figure 2(d), the cross-section of the second side 2-2 is rectangular, the shape of the stirring needle of the stirring head is frustum-shaped, the thickness of the second side 2-2 is 0.1 to 0.95 times the diameter of the large end of the stirring needle of the stirring head, and the thickness of the second side 2-2 is 0.1 to 0.95 times the diameter of the small end of the stirring needle of the stirring head.

[0039] 3. Referring to Figures 2(a) and 2(e), the cross-section of the second side 2-2 is trapezoidal, and the longer bottom edge of the second side 2-2 is connected to the first side 2-1. The edges of the first base material 1 and the second base material 3 that are in contact with the second side 2-2 are set as inclined surfaces. The stirring needle of the stirring head is cylindrical, and the length of the longer bottom edge of the second side 2-2 is 0.1 to 0.95 times the diameter of the stirring needle of the stirring head.

[0040] 4. Referring to Figures 2(a) and 2(e), the cross-section of the second side 2-2 is trapezoidal. The longer base of the second side 2-2 connects to the first side 2-1. The edges of the first base material 1 and the second base material 3 that are in contact with the second side 2-2 are set as inclined surfaces. The stirring pin of the stirring head is shaped like a frustum. Ideally, the taper of the stirring pin is the same as the base angles at both ends of the longer base of the second side 2-2. The length of the longer base of the second side 2-2 is 0.1 to 0.95 times the diameter of the larger end of the stirring pin of the stirring head, and the length of the shorter base of the second side 2-2 is 0.1 to 0.95 times the diameter of the smaller end of the stirring pin of the stirring head.

[0041] The electrode 2 of this invention can be made of a high-entropy alloy. Specifically, the high-entropy alloy uses metastable Fe. 40 Mn 20 Co 20 Cr 15 Si5 high-entropy alloy. High-purity Fe was prepared using a vacuum melting method. 40 Mn 20 Co 20 Cr 15 The Si5 high-entropy alloy is processed into a target T-shaped structure according to the design to obtain the aforementioned welding electrode structure. During welding, the workpiece is tightly spliced ​​onto both sides of the welding electrode, and the spliced ​​structure is subjected to friction stir welding using a stirring head. The welded joint prepared using this method has a tensile strength of 175–181 MPa.

[0042] In the preparation of Fe 40 Mn 20 Co 20 Cr 15 When alloying Si5 into high-entropy alloys, metastable Fe is prepared by vacuum melting using Fe, Mn, Co, Cr, and Si metal powders with a purity greater than 99.99%. 40 Mn 20 Co 20 Cr 15 The Si5 high-entropy alloy ingot is cut into a specially designed shape using wire electrical discharge machining. The materials to be welded are then spliced ​​together with the prepared welding rods, and a stirring head is used to perform friction stir welding on the welding rods.

[0043] Fe 40 Mn 20 Co 20 Cr 15 The preparation and application of Si5 high-entropy alloy are achieved through the following steps:

[0044] Step 1: Use Fe, Mn, Co, Cr, and Si particles with a purity greater than 99.99% as raw materials. Before weighing, use sandpaper to polish and remove the oxide film on the surface of the particles. Use anhydrous ethanol solution to clean the surface stains with ultrasonic cleaning. According to the target composition ratio, use an electronic balance to weigh the raw materials. The error range of weighing is controlled within ±0.0005g.

[0045] Step 2: Vacuum treatment is performed on the Fe, Mn, Co, Cr, and Si particles. Before vacuuming, the furnace is wiped clean with alcohol-moistened gauze to reduce contamination from impurities in the alloy. Then, the raw materials are placed into the copper flask in order of decreasing melting point to reduce the volatilization and splashing of low-melting-point metals. After the raw materials are filled, the furnace door is tightened, and then the vacuuming process begins; first, a mechanical pump is used to evacuate the furnace to 2 × 10⁻⁶. -5 Pa, then use a molecular pump to evacuate to 5 × 10 Pa. -6 Pa, and finally, high-purity hydrogen is introduced as a protective gas. Since the alloy is easily oxidized at high temperatures, a vacuum method is used for hydrogen purification, and the process is repeated three times to minimize the oxygen content in the furnace cavity.

[0046] Step 3: Adjust the current and voltage to change the furnace temperature, controlling it between 1190℃ and 1240℃ until all particles melt and flow uniformly in the crucible. To ensure uniform mixing of components and eliminate casting defects such as component segregation and shrinkage cavities, each ingot is repeatedly melted three to four times, then cooled and solidified in a water-cooled copper mold. After the water-cooled copper mold cools to room temperature, the sample is removed to obtain as-cast Fe. 40 Mn 20 Co 20 Cr 15 Si5 high-entropy alloy.

[0047] Step 4: Use wire electrical discharge machining to cut Fe 40 Mn 20 Co 20 Cr 15 Cut the Si5 high-entropy alloy ingot to the target shape, place the plates to be welded on both sides of the designed welding electrode, and select the following welding parameters: press the stirring head into the upper surface of the welding electrode (i.e., the first side 2-1) by 0.2-0.3 mm, welding speed 50-200 mm / min, stirring head rotation speed 300-500 r / min, and tilt angle of 2° (see...). Figure 3Friction stir welding is performed. During the welding process, on one hand, the stirring pins on the stirring head contact the welding electrode, forming a solid-state bond between the aluminum alloy and the welding electrode, and between aluminum alloys. On the other hand, the welding electrode, prepared using a metastable high-entropy alloy, is broken down by the stirring head during the friction stir process, forming fine high-entropy alloy particles. These fine high-entropy alloy powders provide new nucleation sites for fractal nucleation, further refining the grain size in the stirred zone. Simultaneously, the small high-entropy alloy powders are uniformly distributed within the weld joint, providing dispersion strengthening. These two factors combined improve the mechanical properties of the weld joint, achieving a high-quality connection.

[0048] The aforementioned vacuum melting method involves adding all elemental particles to a vacuum melting furnace according to their atomic ratio, and heating the furnace to the target temperature. The resulting metastable high-entropy alloy is designated Fe. 40 Mn 20 Co 20 Cr 15 The stacking fault energy of Si5 is calculated to be 6.31 mJ / m. 2 .

[0049] The designed electrode shape is based on the principle of friction stir welding, which can effectively improve the inherent defects in the friction stir welding process.

[0050] In the following embodiments and comparative examples of the present invention, both the first base material 1 and the second base material 3 to be welded are made of aluminum alloy sheet with a thickness of 3 mm and a grade of 6061. The stirring head has a shoulder diameter of 12 mm and an inclination angle of 2°. The stirring pin is frustum-shaped with an upper diameter of 5 mm, a lower diameter of 4 mm, and a length of 2.3 mm.

[0051] Example 1:

[0052] In this embodiment, Fe, Mn, Co, Cr, and Si particles with a purity greater than 99.99% are used as raw materials. Before weighing, the oxide film on the surface of the particles is removed by sanding with sandpaper. Surface stains are removed by ultrasonic cleaning with anhydrous ethanol solution. After precise weighing according to the target composition ratio, the particles are placed into the furnace. Two different pumps are used to evacuate the furnace to a vacuum level of 5 × 10⁻⁶. -6 Pa, and finally, high-purity hydrogen is introduced as a protective gas. Because the alloy is easily oxidized at high temperatures, a vacuum method is used for hydrogen purification, repeated three times to minimize the oxygen content in the furnace cavity. During melting, the temperature is controlled between 1190℃ and 1240℃ until all particles melt and flow uniformly in the crucible to obtain Fe with a homogeneous composition and no significant segregation. 40 Mn 20 Co 20 Cr 15Si5 high-entropy alloy. The high-entropy alloy ingot is machined into the required T-shaped structure. The T-shaped welding rod and the workpiece are placed on the worktable of a friction stir welding machine and fixed with a fixture. Figure 1 As shown. During the welding process, the relative positions of the welding electrodes do not change; a frustum-shaped stirring pin is used perpendicular to the friction stir electrode to perform single-pass welding; after welding is completed, the clamp is opened and the overlapping plates are removed.

[0053] The 6061 aluminum plate to be welded has a thickness of 3mm. The designed T-shaped welding rod is shown in Figures 2(a) and 2(e). The upper end of the T-shape (first side 2-1), i.e., the width parallel to the large welding section, should be consistent with the shoulder width of the selected stirring head, which is 14mm. The thickness depends on the pressure applied in the welding process. To ensure the integrity of the plate to be welded, the thickness of the first side 2-1 of the welding rod should be slightly greater than the selected pressure. The thickness used in this experiment is 4mm. The length of the welding rod is consistent with the length of the plate to be welded. Since the aluminum plate to be welded in this experiment is a regular rectangular 6061 aluminum alloy plate, the second side 2-2 of the welding rod adopts a rectangular structure with a thickness of 3mm.

[0054] This embodiment successfully employs the designed "T-shaped" Fe 40 Mn 20 Co 20 Cr 15 Two 6061 aluminum plates were welded using Si5 high-entropy alloy welding electrodes. The addition of the electrodes improved the flow of metal in the weld joint, resulting in a superior weld with no obvious micro-defects.

[0055] Comparative Example 1

[0056] The comparative example is the same as Example 1, except that: butt stir friction welding is performed on 6061 aluminum alloy sheets, and the Fe described in Example 1 is not added at the sheet joint. 40 Mn 20 Co 20 Cr 15 Si5 high-entropy alloy "T-type" welding rod. Use a frustum-shaped stirring head... Figure 4 The schematic diagram shown illustrates a single-pass machining process using friction stirring.

[0057] Figure 5 The tensile property curve of the welded joint is shown below. Figure 5 It is evident that the tensile properties of the weld joint with added high-entropy alloy welding rod (i.e., the present invention) are the same as those of the weld joint without welding rod (i.e., Comparative Example 1), exhibiting the same elongation after fracture. However, in terms of tensile strength, the weld joint with added welding rod exhibits a 20-30 MPa increase compared to the weld joint produced using the conventional process. This is due to the addition of Fe... 40 Mn20 Co 20 Cr 15 Si5 high-entropy alloy is used as a welding electrode material because it is a two-phase metastable high-entropy alloy with a specific heat capacity of 973 J / (kg·K). -1 The specific heat capacity of 6061 aluminum alloy is only 897 J / (kg·K). -1 Therefore, during the friction stir machining process, the shoulder of the hot stirring head rubs against the welding electrode, and the frictional heat mainly acts on the electrode structure, thus causing Fe... 40 Mn 20 Co 20 Cr 15 The HCP phase inside Si5 high-entropy alloy welding electrodes will transform into FCC. The heat absorption formula for the material is ΔQ = cmΔT, where ΔQ is the heat absorbed by the material during the friction stir process, c is the specific heat capacity of the alloy, m is the mass of the object, and ΔT is the temperature rise of the object after absorbing heat. This formula reveals that Fe... 40 Mn 20 Co 20 Cr 15 The Si5 high-entropy alloy absorbs a large amount of frictional heat, effectively reducing the heat input of the substrate to be welded, decreasing the dissolution of precipitated phases, and thus improving the tensile strength of the weld joint. Simultaneously, during friction stir welding, the high-entropy alloy electrode structure is broken into high-entropy alloy particles due to the rotation of the stirring head. These particles can serve as fractal nucleation sites for the dynamic recrystallization of grains within the material during welding, effectively refining the grain size of the weld joint and further improving its mechanical properties.

[0058] Figure 6 The hardness distribution diagrams of the welded joints obtained in Example 1 and Comparative Example 1 are shown below. Figure 6 It can be observed that in the weld nugget area without welding rods, the precipitated phases in the 606 aluminum alloy dissolve into the material due to heat input, resulting in a decrease in the microhardness of the weld joint. However, the microhardness of the weld joint after adding high-entropy alloy "T-type" welding rods is significantly improved in some areas. This is because high-entropy alloys themselves possess excellent microhardness; during friction stir welding, only the original structure is broken without altering its inherent properties. Therefore, since the high-entropy alloy particles are dispersed throughout the 6061 aluminum alloy weld joint, the problem of poor hardness in the 6061 aluminum alloy weld joint after friction stir welding is effectively solved.

[0059] Example 2:

[0060] Referring to Figure 2, the method of this embodiment is illustrated. In this embodiment, the selection of the welding electrode size is determined solely by the size of the stirring head and the welding specifications selected in this experiment. For different welding specifications and plate shapes, the electrode length can be varied to suit all plate materials. The θ angle ranges from 0 to 90°. Other steps are the same as in Specific Embodiment 1.

[0061] The results above demonstrate that this invention compensates for material loss caused by the amount of downward pressure by using the thickness of the welding electrode. Furthermore, the inherent characteristics of high-entropy alloys, when used as welding electrodes, significantly enhance the strength of the welded joint. This invention eliminates workpiece loss caused by the amount of downward pressure, improving the mechanical properties of the joint while ensuring the integrity of the workpiece.

[0062] Using the process of this invention, the tensile strength of the welded joint is increased by 20-30 MPa compared with the welded joint under the traditional process.

[0063] 1. Compared with existing technologies, this method effectively improves the material surface wear problem caused by large downward pressure during friction stir welding, thus effectively ensuring workpiece accuracy. It eliminates the need for designing special stirring heads, using new welding equipment, or altering the shape of the weld band, ensuring both ease of operation and improved performance.

[0064] 2. Traditional friction stir welding technology has stringent requirements on the morphology of the weldment, requiring the parts to be tightly joined together with minimal gaps. The welding electrode designed in this invention can achieve high-quality welding of irregularly shaped plates by changing the electrode's shape, which is unattainable with traditional friction welding.

[0065] 3. During friction stir welding, high-entropy alloy electrodes break into fine particles due to the high-speed rotation of the stirring head. These fine particles become fractal nucleation sites for dynamic recrystallization within the material, further refining the grain size. Simultaneously, the uniform distribution of these fine high-entropy alloy grains within the weld joint hinders dislocation movement, resulting in dispersion strengthening. Both of these phenomena significantly enhance the strength of the weld joint.

[0066] 4. Fe 40 Mn 20 Co 20 Cr 15 Compared to 6061 aluminum alloy, Si5 high-entropy alloy has a higher specific heat capacity and greater heat absorption capacity. During friction stir welding, the heat generated by the stirring head is first transferred to the high-entropy alloy. Since most of the heat is absorbed by the high-entropy alloy, less heat is transferred to the aluminum alloy, thus mitigating the dissolution of precipitated phases.

[0067] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent variations made to the content described in the claims of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A friction stir welding process, characterized in that, The process includes the following: Welding rod (2) is placed at the weld joint of the first base material (1) and the second base material (3). Then, a stirring head is used to stir at the weld joint of the first base material (1) and the second base material (3) to weld the welding rod (2), the first base material (1) and the second base material (3) together. The cross section of the welding rod (2) is T-shaped. The cross section of the welding rod (2) includes a first side (2-1) and a second side (2-2) that are perpendicular to each other. When the welding rod (2) is set at the weld seam of the first base material (1) and the second base material (3), the second side (2-2) is set in the weld seam between the first base material (1) and the second base material (3). The two sides of the second side (2-2) are respectively attached to the edges of the first base material (1) and the second base material (3). The first side (2-1) is located on the surface of the first base material (1) and the second base material (3). The first side (2-1) is attached to the surface of the first base material (1) and the second base material (3). When stirring the first base material (1) and the second base material (3) with a stirring head, press the stirring head down from the surface of the first side (2-1) towards the weld of the first base material (1) and the second base material (3) and stir. The thickness of the first side (2-1) is 1 to 1.5 times the pressure of the stirring head, and the height of the second side (2-2) is not less than the thickness of the first base material (1) to be welded and the second base material (3) to be welded; The welding rod (2) is made of a high-entropy alloy.

2. The friction stir welding process according to claim 1, characterized in that, The cross-section of the second side (2-2) is rectangular, the stirring needle of the stirring head is cylindrical, and the thickness of the second side (2-2) is 0.1 to 0.95 times the diameter of the stirring needle of the stirring head.

3. The friction stir welding process according to claim 1, characterized in that, The cross-section of the second side (2-2) is rectangular, the shape of the stirring needle of the stirring head is frustum-shaped, the thickness of the second side (2-2) is 0.1 to 0.95 times the diameter of the large end of the stirring needle of the stirring head, and the thickness of the second side (2-2) is 0.1 to 0.95 times the diameter of the small end of the stirring needle of the stirring head.

4. The friction stir welding process according to claim 1, characterized in that, The cross-section of the second side (2-2) is trapezoidal. The longer bottom edge of the second side (2-2) is connected to the first side (2-1). The edges of the first base material (1) and the second base material (3) that are in contact with the second side (2-2) are set as inclined surfaces. The stirring needle of the stirring head is cylindrical. The length of the longer bottom edge of the second side (2-2) is 0.1 to 0.95 times the diameter of the stirring needle of the stirring head.

5. The friction stir welding process according to claim 1, characterized in that, The cross-section of the second side (2-2) is trapezoidal. The longer bottom edge of the second side (2-2) is connected to the first side (2-1). The edges of the first base material (1) and the second base material (3) that are in contact with the second side (2-2) are set as inclined surfaces. The stirring needle of the stirring head is shaped like a frustum. The length of the longer bottom edge of the second side (2-2) is 0.1 to 0.95 times the diameter of the large end of the stirring needle of the stirring head. The length of the shorter bottom edge of the second side (2-2) is 0.1 to 0.95 times the diameter of the small end of the stirring needle of the stirring head.

6. The friction stir welding process according to claim 5, characterized in that, The taper of the stirring needle is the same as the bottom angles at both ends of the longer bottom edge of the second side (2-2).

7. The friction stir welding process according to claim 1, characterized in that, The high-entropy alloy adopts metastable Fe. 40 Mn 20 Co 20 Cr 15 Si5 high-entropy alloy.

8. A welding electrode for use in the friction stir welding process according to any one of claims 1-7, characterized in that, The cross-section of the welding rod (2) is T-shaped, and the cross-section of the welding rod (2) includes a first side (2-1) and a second side (2-2) that are perpendicular to each other. When welding the first base material (1) and the second base material (3) by friction stir welding, the second side (2-2) is placed in the weld between the first base material (1) and the second base material (3). The two sides of the second side (2-2) are respectively attached to the edges of the first base material (1) and the second base material (3). The first side (2-1) is located on the surface of the first base material (1) and the second base material (3). The first side (2-1) is attached to the surface of the first base material (1) and the second base material (3). Then, the stirring head is pressed down from the surface of the first side (2-1) to the weld of the first base material (1) and the second base material (3) and friction stir welding is performed.

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