Welding method of metastable austenite steel with TWIP effect

Abstract

The invention discloses a TWIP effect metastable state austenitic steel welding method, a welding device is provided with a material conveying cavity, the material conveying cavity is sequentially connected with a first-stage material conveying cavity and a second-stage material conveying cavity from top to bottom, and a spiral material conveying assembly extends into the first-stage material conveying cavity from the top; the lower end of the second-stage material conveying cavity is connected with a stirring head; a channel communicated with the second-stage material conveying cavity is embedded in the stirring head; a heating assembly is installed outside the second-stage material conveying cavity. According to the method, austenite stable elements or reinforced particles are mixed into a welding seam, the austenite stable elements are accelerated to be quickly diffused into austenite by utilizing the thermal diffusion effect and the pipe dislocation diffusion effect, and a welding joint containing the austenite is obtained through quenching partition heat treatment; in addition, the severe plastic deformation can obviously refine grains, and the austenite grain size refinement can also improve the austenite stability; meanwhile, a welding area is fully heated, so that a large number of annealing twin crystals are formed in a welding seam; based on the method, high-quality welding of the metastable-state high-strength steel is achieved.

Description

A welding method for metastable austenitic steel with TWIP effect Technical Field

[0001] This invention belongs to the field of metal plastic processing, and specifically relates to a welding method for metastable austenitic steel with TWIP effect. Background Technology

[0002] The automotive industry has become a pillar industry of the national economy. To further reduce vehicle weight, lower energy consumption, and achieve green and low-carbon development, replacing traditional low-strength steel with advanced high-strength steel has become a development trend. As representatives of advanced high-strength steel, transformation-induced plasticity steel (TRIP steel), quenched and partitioned steel (QP steel), and twinned induced plasticity steel (TWIP steel) possess excellent strength and toughness, making them the most promising and potentially applicable lightweight materials. The main reason why TRIP steel, QP steel, and TWIP steel maintain excellent strength and plasticity lies in the presence of metastable austenite within them. During plastic deformation, the metastable austenite undergoes phase transformation or twinning, coordinating the plastic deformation and producing the TRIP or TWIP effect, enabling the material to maintain high work hardening performance and exhibit excellent strength and plasticity. However, in practical applications, metastable austenitic steel inevitably faces welding requirements.

[0003] Currently, the main welding methods for metastable austenitic steels include laser welding, resistance welding, and electron beam welding. However, these methods are prone to causing solidification defects such as porosity, inclusions, and cracks within the joint. Friction stir welding (FSW), as a solid-state welding method, has low heat input, is environmentally friendly, and can effectively avoid the defects of traditional fusion welding, thus improving weld quality. However, when conventional FSW welds metastable austenitic steels, the intense plastic deformation and thermal cycling effects cause phase transformation of the metastable austenite in the joint. This leads to the formation of a large amount of brittle martensite in the weld area, inhibiting the TRIP or TWIP effect, resulting in low joint strength and ductility, which is difficult to meet the requirements of engineering applications. Summary of the Invention

[0004] To address the shortcomings and deficiencies of the aforementioned technologies, the present invention aims to provide a welding method for metastable austenitic steel with the TWIP effect.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A metastable austenitic steel friction stir welding device is provided, comprising: a feeding chamber, wherein a primary feeding chamber and a secondary feeding chamber are sequentially connected from top to bottom; a spiral feeding assembly is installed extending from the top into the primary feeding chamber; a stirring head is connected to the lower end of the secondary feeding chamber, wherein the stirring head has a channel embedded in it that communicates with the secondary feeding chamber; and a heating assembly is installed outside the secondary feeding chamber.

[0007] Optionally, the spiral conveying assembly includes a conveying bin and a conveying rod arranged from top to bottom; the conveying rod is provided with spiral blades in the circumferential direction.

[0008] Optionally, the stirring head includes a shaft shoulder and a stirring needle, with a main channel arranged axially inside the shaft shoulder and communicating with the main channel, and a branch channel arranged inside the stirring needle.

[0009] Optionally, there are multiple branch channels, and the branch channels are arranged in a centrifugal oblique direction.

[0010] Optionally, the outer diameter of the stirring head is 10-15 mm, the inner diameter of the main channel is 3-5 mm, and the inner diameter of the branch channel is 2-3 mm.

[0011] Optionally, the heating component is provided with a fixed outer shell, with an installation head at one end of the fixed outer shell, and an insulation layer, a heating tube and an array of heat dissipation holes are sequentially attached inside the fixed outer shell.

[0012] Optionally, an air blowing assembly is provided in communication with the secondary material conveying chamber. The air blowing assembly includes an air pump and an air pipe.

[0013] A method for welding TRIP-effect metastable austenitic steel, characterized by employing any of the metastable austenitic steel friction stir welding devices described in this invention, specifically including: adding an austenite stabilizing element to the weld surface of the workpiece to be welded; performing friction stir welding on the weld surface with a stirring head; providing auxiliary heating during the welding process; and performing quenching and partitioning heat treatment after welding to obtain a welded joint containing residual austenite; wherein the austenite stabilizing element is carbon or manganese with a purity greater than 99.9%; the particle size of the carbon powder is 10–1000 nm, and the particle size of the manganese powder is 0.2–50 µm; the amount of austenite stabilizing element added is 0.5%–3.0%; the heating temperature of the auxiliary heating is 200–800 °C; the rotation speed of the feed rod is 1.0–100 r / min; the gas pressure range in the secondary feed chamber is 0.4–0.8 MPa; the rotation speed of the stirring head is 200–2000 rpm, and the forward speed is 10–600 mm / min.

[0014] Optionally, the quenching and partitioning heat treatment includes: first heating to 800℃ and holding for 300s; then cooling to 260℃ and holding for 60s; finally heating to 400℃, holding for 180s, and then cooling to room temperature.

[0015] A welding method for metastable austenitic steel with TWIP effect, using any of the metastable austenitic steel friction stir welding devices described in this invention, specifically includes: pre-adding aluminum carbide reinforcing particles with a particle size of 1-2000 nm to the feed hopper; performing friction stir welding on the weld surface of the workpiece with a stirring head; during the welding process, the aluminum carbide reinforcing particles enter the welding area, while the heating assembly heats the center area of ​​the weld; the heating temperature is 200-800℃; the rotation speed of the feed rod is 1.0-100 r / min; the gas pressure range in the secondary feed chamber is 0.4-0.8 MPa; the rotation speed of the stirring head is 200-2000 rpm, and the forward speed is 10-600 mm / min.

[0016] Compared with the prior art, the present invention has the following technical effects: 1. The metastable austenitic steel friction stir welding device provided by the present invention can effectively realize the connection of metastable austenitic steel, avoid solidification defects such as porosity, inclusions, and cracks, while retaining residual austenite inside the weld joint, controlling microstructure characteristics (grain size, annealing twins), etc., and improving the welding quality and strength and plasticity of metastable austenitic steel. The technical effects are significant.

[0017] 2. The raw material method provided by this invention mainly solves the problem of easy agglomeration of nano-sized powders through physical processes such as extrusion transport, gas acceleration, and rotational dispersion, achieving uniform dispersion of nano-sized or micron-sized powders within the weld seam. This method is applicable to the addition of single or multiple powders of different particle size ranges. The method is simple, allowing for simultaneous powder addition and welding, reducing welding steps and lowering welding costs.

[0018] 3. The technical principle of this invention is novel. Targeting TRIP-effect metastable austenitic steel, it adds austenite-stabilizing elements to increase austenite stability. Typically, the intense plastic deformation during friction stir welding disrupts the original austenite element distribution characteristics, reducing austenite stability and making it difficult to retain at room temperature. This invention solves the problem of difficulty in retaining metastable austenite by adding austenite-stabilizing elements, which enrich the austenite within the austenite structure. The technical effect is significant.

[0019] 4. To address the welding problem of metastable austenitic steel due to the TWIP effect, reinforcing particles are added during the welding process. This strengthens the weld joint and hinders grain size coarsening. Simultaneously, heating the weld joint promotes annealing twin formation, ensuring excellent strength and ductility.

[0020] 5. The austenite stabilizing elements provided by this invention include carbon and manganese, among which carbon is the most economical and effective austenite stabilizing and solid solution strengthening element, achieving both austenite stabilization and strengthening. Manganese is a strong austenite stabilizing element, effectively improving the stability of austenite. Adding these austenite stabilizing elements has little impact on welding costs but provides better technical results.

[0021] 6. Compared with traditional fusion welding technology, this invention uses friction stir welding technology to achieve metastable austenitic steel welding. By adding austenite stabilizing elements, weld joints containing austenite stabilizing elements can be prepared, improving the performance of the weld joints. At the same time, this technology is a solid-state welding technology, which is green and environmentally friendly, highly automated, and can significantly reduce time and energy costs. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used in conjunction with the following detailed description and are disclosed in the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 is a structural diagram of the metastable austenitic steel friction stir welding device of the present invention; Figure 2 is a structural diagram of the stirring head in Figure 1; Figure 3 is a structural diagram of the heating assembly in Figure 1; Figure 4 is an electron backscatter diffraction detection austenite distribution diagram in Example 1 (the black part in the figure represents austenite); Figure 5 is an electron backscatter diffraction detection austenite distribution diagram in Comparative Example 1 (the black part in the figure represents austenite); Figure 6 is an electron backscatter diffraction detection austenite distribution diagram in Comparative Example 3 (the black part in the figure represents austenite); Figure 7 is an electron backscatter diffraction detection austenite distribution diagram in Comparative Example 2. Austenite distribution diagram (black parts in the diagram represent austenite); the labels in the diagram represent: 1-feeding chamber, 11-primary feeding chamber, 12-secondary feeding chamber; 2-spiral feeding assembly, 21-feeding rod, 211 spiral blade, 22-feeding bin; 3-stirring head, 31-shoulder, 311-main channel, 32-stirring needle, 321-branch channel; 4-heating assembly, 41-mounting head, 42-fixed outer shell, 421-insulation layer, 422-heating tube, 423-array heat dissipation holes; 5-air blowing assembly, 51-air pump, 52-air pipe; 6-motor. Detailed Implementation

[0023] The present invention will be further explained and described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] This invention targets two types of metastable austenitic steels: the first type is metastable high-strength steel with the TRIP effect (e.g., QP980, QP1180, TRIP800, etc.); the second type is metastable high-strength steel with the TWIP effect (e.g., Fe-Mn-C or Fe-Mn-Al-Si series TWIP steels).

[0025] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Referring to Figures 1-3, the metastable austenitic steel friction stir welding device of the present invention is used for welding. The welding device is configured as follows: a feeding chamber 1, which is connected from top to bottom to a primary feeding chamber 11 and a secondary feeding chamber 12. A spiral feeding assembly 2 is installed extending from the top into the primary feeding chamber 11. The spiral feeding assembly 2 includes a hopper and a feeding rod connected from top to bottom. The raw material is added to the feeding hopper 22 and flows into the feeding rod 21 by its own gravity. The feeding rod 21 is provided with spiral blades 211 along its circumference. The rotating feeding rod 21 conveys the raw material axially downward along the spiral blades 211. The above process is completed in the primary feeding chamber 11. After that, the raw material is conveyed to the secondary feeding chamber 12. Since the raw material used in the present invention is basically nano-sized powder, an air pump 51 is connected to the secondary feeding chamber 12 through an air pipe 52 to supply air to the secondary feeding chamber 12. High-pressure gas is introduced into the secondary conveying chamber 12. The high-pressure gas not only prevents the agglomeration of nano-sized raw materials, but also accelerates the passage of raw materials through the secondary conveying chamber 12. The lower end of the secondary conveying chamber 12 is connected to the stirring head 3, which includes a shoulder 31 and a stirring needle 32. In order to achieve simultaneous addition and stirring of raw materials, channels are set in the original stirring head and stirring needle. This allows for simultaneous addition and stirring without hindering the rotation of the stirring head. For example, a main stirring channel 311 is set along the axial direction in the stirring head 3, and a branch channel 321 is set in the stirring needle 32. The direction of the branch channel 321 can be oblique or axial, and the shape of the channel is not limited. It can be straight, wavy, etc., as long as it can facilitate the passage of raw materials. The inner diameter and number of the branch channels 321 in the stirring needle 32 can be adjusted according to different requirements such as the amount of material added. For example, as shown in the figure, there are two or more branch channels 321, and the two or more channels are obliquely arranged along the stirring centrifugal direction of the stirring needle 32. By rotating the centrifugal force, the passage of raw materials is further accelerated. The stirring head 3 is mainly driven to rotate by the motor 6, so as to realize the stirring friction welding.

[0026] The heating component 4 is connected to the secondary feeding chamber 12 and includes a power supply, heating tube, infrared temperature measuring device, etc., as shown in Figure 3. A fixed outer shell 42 is provided, with an installation head 41 at one end of the fixed outer shell 42, such as a threaded shaft or rod, for easy installation and disassembly. The shape of the fixed outer shell 42 is, for example, a rectangular bent shell. The inner shell is sequentially fitted with an insulation layer 421, a heating tube 422, and an array of heat dissipation holes 423 to achieve precise heating of the welding surface below. During operation, the raw material feeding device pushes the raw material from the hopper into the feeding channel. The air pump 51 pressurizes the raw material and quickly enters the main channel 311 and branch channel 321 of the stirring head 3. During the high-speed rotation of the stirring head 3, the raw material is added to the welding area. With the auxiliary heating of the heating component 4, the parts to be welded are connected simultaneously.

[0027] Its working principle is as follows: First, stable austenitic elements, such as carbon and manganese, are selected according to the elemental composition of the workpiece to be welded. The raw materials are added to the feeding bin 22 and flow into the feeding rod 21 by their own gravity. The spiral blades 211 drive the raw materials from the primary feeding chamber 11 into the secondary feeding chamber 12. The secondary feeding chamber 12 is an acceleration chamber. The raw materials can be accelerated by connecting the air pipe 52 and the air pump 51. The raw materials reach the cross-section of the workpiece to be welded through the main stirring channel 311 and the branch channel 321. Next, welding is carried out. During the high-speed rotation of the stirring head 3, the raw materials are mixed into the workpiece to be welded. After welding, quenching and distribution heat treatment is carried out to obtain stable austenite.

[0028] The metastable austenitic steel friction stir welding apparatus of the present invention, through the spiral feeding assembly 2, the feeding chamber 1, and the feeding channel connected to the feeding chamber, can achieve the purpose of integrated addition of austenitic stabilizing elements and welding, thereby improving welding production efficiency. The air blowing assembly 5 can accelerate the raw material, allowing it to quickly reach the workpiece to be welded; simultaneously, high-speed airflow can disperse nano-sized powder, solving the problem of easy agglomeration of nano-sized powder. This apparatus has strong applicability and can meet the addition of different types and sizes of austenitic stabilizing elements, thus expanding the application range of the metastable austenitic friction stir welding method and apparatus of the present invention. For example, the rotation speed of the feeding rod 21 is 1.0 r / min to 100 r / min; the air pump 51 mainly functions to accelerate the feeding of raw materials, break up the agglomeration of nano-powder, and ensure that the raw material is evenly distributed inside the weld. The gas pressure range is 0.4 to 0.8 MPa; the outer diameter of the stirring head 3 is 10 to 15 mm, and its internal shape is "tree-like," i.e., one channel at the top and two channels at the bottom. The main channel 311 has an inner diameter of 3–5 mm, and the branch channel 321 has an inner diameter of 2–3 mm. The stirring head 3 rotates at a speed of 200 rpm to 2000 rpm and advances at a speed of 10 mm / min to 600 mm / min. The stirring head material is a tungsten-based alloy. Metastable austenitic steel includes TRIP steel, QP steel, and TWIP steel, as well as high-strength steel with the TRIP / TWIP effect. The thickness of the metastable austenitic steel is 1–2 mm.

[0029] The method for friction stir welding of metastable austenitic steel includes the following steps: Step 1: Determine the raw materials to be added based on the composition of the material to be welded; Step 2: Add the raw materials to the raw material hopper, the extrusion rod longitudinally extrudes the raw materials downwards, and the material to be added is sent into the acceleration hopper through the raw material channel. The air pump accelerates the raw materials into the hollow stirring head through the acceleration gas. Then, the high-speed rotating stirring head is inserted into the middle of the workpiece to be welded. After rotating for a period of time, the heating components are turned on to start welding. After welding is completed, all components are turned off.

[0030] Step 3: Determine whether to perform quenching and component separation treatment on the weld joint based on the composition of the workpiece to be welded.

[0031] Based on the above-mentioned device, this invention proposes a welding method for TRIP-effect metastable austenitic steel. The method includes adding austenite-stabilizing elements such as carbon and manganese to the welding surfaces of the workpieces to be welded. Then, a stirring head 3 is used to perform friction stir welding on the weld seam of the workpieces with deposited austenite-stabilizing elements. Auxiliary heating is applied during the welding process. After welding, a quenching and partitioning heat treatment is performed to obtain a welded joint containing residual austenite. Specifically, the raw materials are mainly austenite-stabilizing elements such as carbon powder and manganese powder, with a purity greater than 99.9%. The particle size of the carbon powder is 10–1000 nm, and the particle size of the manganese powder is 0.2–50 µm. The purpose of heating is to allow the austenite-stabilizing elements to rapidly diffuse into the austenite interior, achieving the goal of stabilizing the austenite. The purpose of the quenching and partitioning heat treatment is to further increase the austenite content of the welded joint, ensuring that the welded joint has excellent strength and ductility. The heating assembly 4 is equipped with 2–4 heating tubes 422, and the heating temperature is 200–800℃.

[0032] Based on the aforementioned device, this invention proposes a welding method for metastable austenitic steel with the TWIP effect. The method includes pre-adding aluminum carbide reinforcing particles to a raw material hopper, and using a stirring head with a shoulder and stirring pin to perform friction stir welding on the workpiece. During welding, the aluminum carbide reinforcing particles enter the welding area through a feed channel and an acceleration chamber. Simultaneously, a heating assembly heats the central region of the weld to achieve austenite stabilization and microstructure control. Specifically, the raw material also includes reinforcing particles such as aluminum carbide, with a particle size of 1–2000 nm. The purpose of adding aluminum carbide reinforcing particles is twofold: first, to strengthen the weld joint performance; second, to hinder grain migration during repeated heating, preventing abnormal grain growth. The purpose of heating is twofold: first, to accelerate the formation of metallurgical bonding between the particles and the material to be welded; second, to allow annealed twins to form inside the TWIP steel weld, strengthening the joint performance while maintaining sufficient plasticity. The heating assembly includes 2–4 heating tubes, with a heating temperature of 200–800°C.

[0033] Specifically, the principle of this invention is to utilize the intense plastic flow of materials during friction stir welding to incorporate austenite stabilizing elements or reinforcing particles into the weld. Simultaneously, thermal diffusion and dislocation diffusion accelerate the rapid diffusion of austenite stabilizing elements into the austenite interior. A welded joint containing austenite is obtained through quenching and partitioning heat treatment. Furthermore, the intense plastic deformation during friction stir welding can significantly refine the grain size, and this refinement of austenite grain size also improves austenite stability. Simultaneously, the heating element fully heats the welding area, resulting in the formation of numerous annealed twins within the weld. Based on the above methods, high-quality welding of metastable high-strength steel is achieved.

[0034] Example 1: Friction stir welding was performed on QP1180 steel exhibiting the TRIP effect. Before welding, the mating surfaces of the workpieces were cleaned with acetone to remove oil stains. Carbon was added during the QP1180 steel welding process at a rate of 1.8% of the weld volume. The stirring head rotated at 800 rpm, the welding speed was 300 mm / min, the stirring pin diameter was 5 mm, and the shoulder was 12 mm. The heating temperature during welding was 200℃. After welding, a quenching and partitioning heat treatment was performed. The quenching and partitioning heat treatment process was as follows: first, heating to 800℃ and holding for 300 s; then cooling to 260℃ and holding for 60 s; finally, heating to 400℃ and holding for 180 s, and then cooling to room temperature. The joint mechanical properties were tested as follows:

[0035] The distribution of retained austenite was characterized using electron backscattering technology, as shown in Figure 4. The retained austenite content in the joint increased to 15%, which is higher than that in Comparative Examples 1-4. Compared with Comparative Examples 1-4, the joint elongation in Example 1 was significantly improved, fully demonstrating the significant improvement effect of this solution.

[0036] Example 2: Friction stir welding was performed on QP1180 steel exhibiting the TRIP effect. Before welding, the mating surfaces of the workpieces were cleaned with acetone to remove oil stains. During welding, the stirring head rotated at 1400 rpm, and the welding speed was 40 mm / min. Carbon was added during welding at 1.5% of the weld volume, the gas pressure was 0.3 MPa, and the heating temperature was 200℃. After welding, a quenching and fractional heat treatment was performed. The heat treatment process was as follows: heating to 800℃, holding for 300s, rapidly cooling to 260℃, holding for 60s, heating to 400℃, holding for 180s, and then cooling to room temperature. The joint mechanical properties were tested as follows:

[0037] The distribution of retained austenite was characterized using electron backscattering technology, as shown in Figure 4. The retained austenite content in the joint increased to 12%. Compared to Examples 5-7, the joint elongation was significantly improved, fully demonstrating the significant improvement effect of this solution.

[0038] Compared to the first method of addition, the second method enables integrated welding. This involves adding carbon, an austenite-stabilizing element, into the QP1180 steel during the welding process, allowing residual austenite to be retained in the weld. This significantly reduces welding time and economic costs.

[0039] Example 3: Friction stir welding (TWIP) was performed on Fe-Mn-C series TWIP steel exhibiting the TWIP effect. Before welding, the mating surfaces of the workpieces were cleaned with acetone to remove oil stains. During the TWIP steel welding process, aluminum carbide particles were added at a rate of 1.0% of the weld volume. The stirring head rotation speed was 400 rpm, the welding speed was 200 mm / min, the gas pressure was 0.3 MPa, and the heating temperature was 400℃. No quenching or preheating treatment was performed. The mechanical properties of the joint were tested as follows:

[0040] Electron backscattering technology revealed that the content of annealed twins inside the joint was 25%. Annealed twins can refine the grains and significantly improve the joint strength without reducing the joint plasticity, which fully demonstrates the significant improvement effect of this solution.

[0041] Comparative Example 1: Same as Example 1, except that no austenitic stabilizing elements were added and no heat treatment was performed in Comparative Example 1. The results of the joint mechanical property test are as follows:

[0042] The distribution of austenite was characterized using electron backscattering technology, as shown in Figure 5. The content of residual austenite in the joint was increased to 0.1%.

[0043] Comparative Example 2: Same as Example 1, except that this comparative example adds austenitic stabilizing carbon but does not undergo heat treatment. The joint mechanical properties test results are as follows:

[0044] The residual austenite content in the central region of the welded joint is 0.3% (Figure 7), the joint strength is 1392 MPa, and the elongation is 13%.

[0045] Comparative Example 3: Same as Example 1, except that no austenitic stabilizing elements were added in Comparative Example 1, and quenching and partitioning heat treatment was performed. The joint mechanical properties test results are as follows:

[0046] The distribution of residual austenite is shown in Figure 6.

[0047] Comparative Example 5: Same as Example 2, except that no austenitic stabilizing elements were added in this comparative example, and no quenching and partitioning heat treatment was performed. The joint mechanical property test results are as follows:

[0048] Comparative Example 6: Same as Example 2, except that the carbon content was increased to 2.5%. The mechanical properties of the joint were tested as follows:

[0049] Compared with Example 2, increasing the amount of carbon added can effectively increase the content of retained austenite, but the tensile strength and elongation of the joint are reduced. This is mainly because the retained austenite in the joint is too stable and it is difficult to undergo phase transformation during plastic deformation. At the same time, a large amount of cementite is formed inside the joint, which deteriorates the joint performance.

[0050] Comparative Example 7: Same as Example 2, except that this example uses quenching heat treatment. The heat treatment process is as follows: heating to 800℃, holding for 300s; and rapidly cooling to room temperature. The joint mechanical property test results are as follows:

[0051] Comparative Example 8: Same as Example 3, except that no reinforcing particles were added and no heating was performed. The results of the joint mechanical property test are as follows:

[0052] The preferred embodiments described above in conjunction with the accompanying drawings are preferred but not intended to limit the invention. The various specific technical features described above can be combined in any suitable form without contradiction, and this invention will not elaborate on them one by one. Any simple modifications or alterations made by those skilled in the art, such as arbitrary combinations or equivalent substitutions, to the technical solutions without departing from the scope of the technical solutions do not affect the essence of the technical solutions and still fall within the protection scope of the technical solutions represented by the embodiments of this invention.

Claims

1. A welding method for metastable austenitic steel with TWIP effect, characterized in that, Welding was performed using a metastable austenitic steel friction stir welding device, specifically including: adding aluminum carbide reinforcing particles with a particle size of 1-2000 nm to the feed hopper (22) beforehand; performing friction stir welding on the welding surface of the workpiece by the stirring head (3); during the welding process, the aluminum carbide reinforcing particles entered the welding area, and the heating assembly heated the center area of ​​the weld; the heating temperature was 200-800℃; the rotation speed of the feed rod (21) was 1.0-100 r / min; the gas pressure range in the secondary feed chamber (12) was 0.4-0.8 MPa; the rotation speed of the stirring head (3) was 200-2000 rpm, and the forward speed was 10-600 rpm. mm / min; Metastable austenitic steel friction stir welding device setup: feeding chamber (1), feeding chamber (1) is connected to a primary feeding chamber (11) and a secondary feeding chamber (12) from top to bottom, a spiral feeding assembly (2) is installed in the primary feeding chamber (11) from the top; the lower end of the secondary feeding chamber (12) is connected to a stirring head (3), the stirring head (3) is embedded with a channel communicating with the secondary feeding chamber (12); a heating assembly (4) is installed outside the secondary feeding chamber (12).

2. The welding method for metastable austenitic steel with TWIP effect according to claim 1, characterized in that, The spiral conveying assembly (2) includes a conveying bin (22) and a conveying rod (21) connected from top to bottom; the conveying rod (21) has spiral blades (211) arranged circumferentially.

3. The welding method for metastable austenitic steel with TWIP effect according to claim 1 or 2, characterized in that, The stirring head (3) includes a shaft shoulder (31) and a stirring needle (32) connected by a shaft. A main channel (311) is provided in the shaft shoulder (31) along the axial direction and communicates with the main channel (311). A branch channel (321) is provided in the stirring needle (32).

4. The welding method for metastable austenitic steel with TWIP effect according to claim 3, characterized in that, There are multiple branch channels (321), and the branch channels are arranged in a centrifugal oblique direction.

5. The welding method for metastable austenitic steel with TWIP effect according to claim 3, characterized in that, The outer diameter of the stirring head (3) is 10-15 mm, the inner diameter of the main channel (311) is 3-5 mm, and the inner diameter of the branch channel (321) is 2-3 mm.

6. The welding method for metastable austenitic steel with TWIP effect according to claim 1 or 2, characterized in that, The heating component (4) is provided with a fixed outer shell (42), and an installation head (41) is provided at one end of the fixed outer shell (42). The heat insulation layer (421), heating tube (422) and array-type heat dissipation holes (423) are sequentially attached inside the fixed outer shell (42).

7. The welding method for metastable austenitic steel with TWIP effect according to claim 1 or 2, characterized in that, An air blowing assembly (5) is provided in communication with the secondary material conveying chamber (12). The air blowing assembly (5) includes an air pump (51) and an air pipe (52).

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