Friction stir welding method for ferrite-martensite double-phase high-strength steel

Abstract

The invention relates to the technical field of material connection, and discloses a friction stir welding method for ferrite-martensite double-phase high-strength steel, which comprises a stirring head, a fixing device and a welding device, and further comprises the following steps: step 1, plate processing: selecting according to the size and thickness of a material, and processing and cleaning the material; secondly, a fixing device and a base plate are machined, and the fixing device and the base plate are machined and cleaned; 3, designing and processing a stirring head: designing and processing the stirring head according to the size and thickness of the material; 4, parameter selection, wherein welding parameters are selected according to the properties of the materials; 5, welding and heat treatment are conducted, specifically, the machined fixing device, the base plate, the material and the welding device are fixed in sequence, and the position of a stirring head is installed and adjusted; the friction stir welding stability of the material can be improved, the defects of the material during welding are reduced, and the performance of the material is improved.

Description

Technical Field

[0001] This invention relates to the field of material joining technology, specifically to a friction stir welding method for ferrite-martensitic dual-phase high-strength steel. Background Technology

[0002] Friction stir welding is a "solid-state" welding process performed at temperatures below the material's melting point. A specially shaped, high-speed rotating stirring head is inserted into the joint of the workpiece and moves along the weld seam. The frictional heat and shear deformation generated between the stirring head and the workpiece soften the material in the contact area into a plastic state. Then, through the mechanical stirring and extrusion action of the stirring head, the materials on both sides are fully mixed and diffused, ultimately forming a dense solid-phase weld seam.

[0003] Due to its excellent high-temperature mechanical properties, low irradiation swelling rate, and good oxidation resistance, ODS steel has great application prospects in nuclear fusion reactors, advanced fission reactors, and high-temperature components in aerospace. However, its unique microstructure and flow viscosity make its joining technology a key bottleneck in engineering applications, facing a series of severe challenges. In order to achieve the joining of its structural components without significantly changing its submicron-level grain size and the microstructure of its uniformly distributed nano-oxidation particles, solid-state joining technologies such as diffusion welding and friction stir welding have become the optimal choices. In addition, considering the joining requirements of cladding structure components and the limitations of enclosed space, friction stir welding is a better choice for ODS steel under ideal conditions in the future.

[0004] Currently, based on nanoferritic alloys, the effects of welding parameters on the dispersion and grain size of nano-oxides, conventional mechanical properties, and residual stress in ODS steel have been studied. However, overall, there are still many problems with the friction stir welding technology for ODS steel, such as unstable performance, wear and contamination of the stirring head, wormholes, weak bonding, and grain coarsening in the welding area. These defects reduce the performance of the material and cannot meet the service requirements of future fusion reactor blankets. Summary of the Invention

[0005] This invention provides a friction stir welding method for ferritic-martensitic dual-phase high-strength steel. Through a buffer mechanism and welding device, the pressure between the fixture and the material can be adjusted in a timely manner. At the same time, the cooling range of the material can be adjusted according to the movement position of the stirring head. Combined with the yttrium oxide coating on the stirring head and the shoulder area and appropriate parameter selection, the problems of unstable performance, defects in the welded area and low material performance mentioned in the background art can be effectively avoided.

[0006] This invention provides the following technical solution:

[0007] A friction stir welding method for ferrite-martensitic dual-phase high-strength steel includes a stirring head, a fixing device, and a welding device, and further includes the following steps:

[0008] Step 1: Sheet material processing. Select materials based on their size and thickness, and then process and clean them.

[0009] Step 2: Processing of fixing devices and pads; Processing and cleaning of fixing devices and pads.

[0010] Step 3: Select the mixing head. Choose the mixing head according to the size and thickness of the material.

[0011] Step 4: Parameter selection. Choose welding parameters based on the properties of the material.

[0012] Step 5: Welding and heat treatment. After the processing is completed, fix the fixing device, backing plate, materials and welding device in sequence. After installing and adjusting the position of the stirring head, weld according to the selected parameters, and then carry out the annealing process.

[0013] As a preferred technical solution of the present invention, in step two, the pad material is CLF-1 steel with a thickness of 5mm-6mm, and the contact surface with the material is coated with an oxide raw material (e.g., yttrium oxide).

[0014] As a preferred technical solution of the present invention, in step three, the stirring head material is W-Re alloy, and the contact area between the stirring head and the sample is coated with a 100nm-200nm oxide raw material (e.g., yttrium oxide) coating.

[0015] As a preferred technical solution of the present invention, in steps two and three, the coating on the surface of the pad and the stirring head is one of PVD coating, ion sputtering coating, cold spray coating and electrochemical coating.

[0016] As a preferred embodiment of the present invention, in step four, the stirring head rotates at a speed of 500 rpm to 1200 rpm, travels at a speed of 30 mm / min to 100 mm / min, and presses in to a depth of 0.1 mm to 0.2 mm during welding.

[0017] As a preferred embodiment of the present invention, the fixing device includes a workbench and further includes: a pad fixing assembly for fixing the pad on the workbench, the pad fixing assembly being provided with a baffle; displacement hydraulic cylinders, symmetrically fixedly connected to the workbench, the sides of the displacement hydraulic cylinders that are close to each other being connected to a telescopic plate, a fixing hydraulic cylinder being fixedly connected to the telescopic plate, a clamp being fixedly connected to the bottom of the fixing hydraulic cylinder, wherein a buffer mechanism is fixedly connected to the top of the fixing hydraulic cylinder for adjusting the pressure between the clamp and the material; a bracket, disposed on the workbench, an adjusting member being slidably connected to the bracket, and the welding device 13 being disposed at the bottom of the adjusting member.

[0018] As a preferred embodiment of the present invention, the pad fixing assembly includes a mounting groove formed on the workbench. Fixing devices are symmetrically arranged on one side of the workbench near the mounting groove. Each fixing device includes a transverse fixing member and a longitudinal fixing member. A baffle is fixedly connected to one set of the longitudinal fixing members. The baffle is located above the pad and is used to limit one end of the material. Both the transverse and longitudinal fixing members are hydraulically driven. Displacement hydraulic cylinders are evenly distributed on both sides of the mounting groove. The telescopic plate is parallel to the material, and the fixing hydraulic cylinder is perpendicular to the material. Drive rails are symmetrically arranged on the side wall of the workbench, and the end of the bracket is slidably connected inside the drive rails.

[0019] As a preferred embodiment of the present invention, the buffer mechanism includes a buffer cylinder fixedly connected to a fixed hydraulic cylinder. The bottom of the buffer cylinder has a communicating hole that communicates with the fixed hydraulic cylinder. A piston rod is slidably connected inside the fixed hydraulic cylinder. A piston plate that fits tightly against the inner wall of the buffer cylinder is fixedly connected to the bottom end of the piston rod. A pressing block is fixedly connected to the top end of the piston rod. The pressing block is triangular in shape. A telescopic rod is fixedly connected between the piston plate and the top of the buffer cylinder. A U-shaped rod is slidably connected inside the buffer cylinder. A guide block is fixedly connected to the side of the U-shaped rod away from the buffer cylinder. A spring is fixedly connected between the end of the U-shaped rod away from the guide block and the inner wall of the buffer cylinder. A ratchet is fixedly connected to the side of the U-shaped rod near the piston rod. A ratchet groove that matches the ratchet is formed on the outer wall of the piston rod.

[0020] As a preferred embodiment of the present invention, the welding device includes a welding drive component fixedly connected to the bottom of the adjusting member. A telescopic shaft is provided inside the welding drive component. A stirring head is located at the bottom end of the telescopic shaft. The stirring head includes a shoulder and a stirring pin. The stirring pin is located at the bottom of the shoulder. A channel is formed on the side of the shoulder near the stirring pin. An exhaust pipe is connected to the side wall of the telescopic shaft near the stirring pin. The end of the exhaust pipe is connected to a jetting assembly for cooling the weld after welding. Guide rods and pressing rods are symmetrically fixedly connected to the side wall of the welding drive component. The guide rods match guide blocks, and the pressing rods match pressing blocks.

[0021] As a preferred embodiment of the present invention, the jet assembly includes a nozzle connected to an exhaust pipe. The nozzle has a spray hole at one end away from the exhaust pipe. A fixing frame is fixedly connected inside the nozzle. An adjusting rod is fixedly connected to the fixing frame. An adjusting head is fixedly connected to the side of the adjusting rod near the spray hole. The adjusting head has a central hole. The adjusting head is conical. The adjusting rod and the telescopic rod are connected by a pipe.

[0022] Compared with the prior art, the present invention provides a friction stir welding method for ferrite-martensitic dual-phase high-strength steel, which has the following beneficial effects:

[0023] 1. In the friction stir welding method for ferritic-martensitic dual-phase high-strength steel, a buffer mechanism can reduce the pressure between the clamp and the material when the stirring head passes through the clamp, preventing the material from being pressed into a depression by the clamp due to high temperature softening. After the material cools to a certain temperature, the clamp is driven again to press the material stably. This ensures the stability of the material during the welding process and also avoids the occurrence of local depressions in the material, thereby improving the stability of the material welding and the performance of the material.

[0024] 2. In the friction stir welding method for this ferritic-martensitic dual-phase high-strength steel, the spray range of the jet assembly can be adjusted by the buffer mechanism, so that the stirring passes through the high-temperature area of ​​the material, reducing the cooling effect on the fixture, avoiding the sudden temperature drop of the material due to double heat dissipation, thereby ensuring the thermal balance of the material during the welding process and further improving the stability of the material welding.

[0025] 3. In the friction stir welding method for this ferritic-martensitic dual-phase high-strength steel, the wear of the stirring head and the introduction of impurities during the welding process are reduced by the channel, which reduces the occurrence of large regional performance differences, end welding wormholes, and weak bonding during the welding process, thereby obtaining a better weld structure and performance.

[0026] The parts of this device not covered herein are the same as or can be implemented using existing technologies. This invention can improve the stability of friction stir welding of materials, reduce defects in materials during welding, and improve the performance of materials. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, the elements or parts are not necessarily drawn to actual scale.

[0028] Figure 1 This is a process flow diagram of the present invention;

[0029] Figure 2 This is a three-dimensional schematic diagram of the fixing device and welding device in this invention. Figure 1 ;

[0030] Figure 3 This is a three-dimensional schematic diagram of the fixing device and welding device in this invention. Figure 2 ;

[0031] Figure 4 This is a partial structural schematic diagram of the present invention;

[0032] Figure 5 This is a schematic diagram of the front cross-sectional structure of the buffer mechanism in this invention;

[0033] Figure 6 This is a top view cross-sectional structural diagram of the buffer mechanism in this invention;

[0034] Figure 7 This is a schematic diagram of the welding device in this invention;

[0035] Figure 8 This is a cross-sectional structural diagram of the nozzle in this invention.

[0036] In the diagram: 1. Workbench; 2. Mounting slot; 3. Fixed equipment; 4. Baffle; 5. Displacement hydraulic cylinder; 6. Telescopic plate; 7. Fixed hydraulic cylinder; 8. Clamp; 9. Buffer mechanism; 91. Buffer cylinder; 92. Connecting hole; 93. Piston rod; 94. Piston plate; 95. Pressing block; 96. U-shaped rod; 97. Guide block; 98. Ratchet; 99. Spring; 910. Telescopic rod; 10. Drive rail; 11. Bracket; 12. Adjustable distance component; 13. Welding device; 131. Welding drive component; 132. Telescopic shaft; 133. Shoulder; 134. Stirring needle; 135. Channel; 14. Guide rod; 15. Pressing rod; 16. Exhaust pipe; 17. Jet assembly; 171. Nozzle; 172. Spray hole; 173. Fixing frame; 174. Adjusting rod; 175. Adjusting head; 176. Center hole. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1:

[0039] Reference Figure 1 A method for friction stir welding of ferritic-martensitic dual-phase high-strength steel includes a stirring head, a fixing device, and a welding device 13, and further includes the following steps:

[0040] Step 1: Sheet material processing: Select materials according to their size and thickness, and process and clean them.

[0041] In step one, the welding material is 9Cr-ODS steel with a thickness of 2mm-2.5mm. After processing and cleaning, the material surface is free of cutting marks and oxide layer, and each plane has good flatness.

[0042] Step 2: Processing of fixing devices and pads: Processing and cleaning of fixing devices and pads;

[0043] In step two, the fixing device is made of H13 model steel, and the backing plate is made of CLF-1 steel, which has a similar composition to the welding material. The thickness of the backing plate is 5mm-6mm, and an oxide raw material coating is applied to the surface in contact with the welding material to reduce the deformation and displacement of the fixing device due to heat during the welding process, thereby ensuring the welding quality. In addition, a temperature test channel needs to be designed on the fixing device to facilitate welding.

[0044] Step 3: Selecting the mixing head: Choose the mixing head according to the size and thickness of the material;

[0045] In step three, the stirring head is made of W-Re alloy, the shoulder 133 is 12mm-15mm long, and the stirring pin 134 is 1.8mm-2.2mm long. A 100nm-200nm yttrium oxide layer is deposited on the contact area between the stirring head and the material to reduce wear and the introduction of impurities. Multiple argon gas inlet channels 135 are opened on the side of the shoulder 133 near the stirring pin 134 to reduce oxidation of the material surface during welding, control the cooling rate of the material after welding, and thus optimize the welding performance. The coating on the surface of the backing plate and the stirring head is achieved by PVD coating, ion sputtering coating, cold spray coating, or electrochemical coating to ensure the backing plate's resistance to high temperatures and deformation during welding.

[0046] Step 4: Parameter Selection: Select welding parameters based on the properties of the material;

[0047] In step four, during welding, the stirring head rotates at 500 rpm to 1200 rpm, travels at 30 mm / min to 100 mm / min, and is pressed into the ground at a depth of 0.1 mm to 0.2 mm. The stirring head remains in the ground for 5 to 8 seconds after initial pressing into the ground during the welding process.

[0048] Step 5: Welding and heat treatment: Fix the finished fixing device, pad, material and welding device 13 in sequence. After installing and adjusting the position of the stirring head, weld according to the selected parameters. Then perform annealing process to make the welded area obtain higher high temperature performance.

[0049] Example 2:

[0050] Reference Figures 2-8 Based on Embodiment 1, a fixing device and a welding device 13 are proposed. The fixing device includes a workbench 1 and further includes: a pad fixing assembly for fixing the pad onto the workbench 1, and a baffle 4 is provided on the pad fixing assembly; displacement hydraulic cylinders 5 are symmetrically fixedly connected to the workbench 1, and a telescopic plate 6 is connected to the side of the displacement hydraulic cylinders 5 that are close to each other. A fixing hydraulic cylinder 7 is fixedly connected to the telescopic plate 6, and a clamp 8 is fixedly connected to the bottom of the fixing hydraulic cylinder 7. A buffer mechanism 9 is fixedly connected to the top of the fixing hydraulic cylinder 7 for adjusting the pressure between the clamp 8 and the material; a bracket 11 is set on the workbench 1, and an adjusting member 12 is slidably connected to the bracket 11. The welding device 13 is set at the bottom of the adjusting member 12. The adjusting member 12 includes a sleeve sleeved on the bracket 11, a drive motor fixedly connected to the sleeve, and a guide wheel that fits against the bracket 11 is rotatably connected inside the sleeve. The output end of the drive motor is connected to the guide wheel through a pulley and a belt.

[0051] Reference Figures 2-3 The pad fixing assembly includes an installation groove 2 on the workbench 1. Fixing devices 3 are symmetrically arranged on one side of the workbench 1 near the installation groove 2. The fixing devices 3 include transverse fixing parts and longitudinal fixing parts. A baffle 4 is fixedly connected to one set of longitudinal fixing parts. The baffle 4 is located above the pad and is used to limit one end of the material. Both the transverse fixing parts and the longitudinal fixing parts are hydraulically driven. The displacement hydraulic cylinders 5 are evenly distributed on both sides of the installation groove 2. The telescopic plate 6 is parallel to the material. The fixing hydraulic cylinder 7 is perpendicular to the material. It also includes a longitudinal fixing part for fixing the side wall of the material, which is perpendicular to the weld of the material.

[0052] In this embodiment, it should be explained that fixing the pad by hydraulic drive is a conventional method in the prior art, so it will not be described in detail. The pad is fixed by squeezing the four sides of the pad through the horizontal and vertical fixing parts. The material is fixed on the pad by the vertical fixing part and the baffle 4. The length of the telescopic plate 6 can be adjusted by the displacement hydraulic cylinder 5, thereby adjusting the clamping position of the clamp 8 on the material, and also facilitating the picking and putting of welding materials.

[0053] Reference Figures 4-6 The buffer mechanism 9 includes a buffer cylinder 91 fixedly connected to a fixed hydraulic cylinder 7. The bottom of the buffer cylinder 91 has a communicating hole 92 that communicates with the fixed hydraulic cylinder 7. A piston rod 93 is slidably connected inside the fixed hydraulic cylinder 7. A piston plate 94, which fits tightly against the inner wall of the buffer cylinder 91, is fixedly connected to the bottom end of the piston rod 93. A pressing block 95, which is triangularly arranged, is fixedly connected to the top end of the piston rod 93. A telescopic rod 910 is fixedly connected between the piston plate 94 and the top of the buffer cylinder 91. The mechanism also includes a slidably connected component inside the buffer cylinder 91. A U-shaped rod 96 is fixedly connected to a guide block 97 on the side of the U-shaped rod 96 away from the buffer cylinder 91. A spring 99 is fixedly connected between the end of the U-shaped rod 96 away from the guide block 97 and the inner wall of the buffer cylinder 91. A ratchet 98 is fixedly connected to the side of the U-shaped rod 96 near the piston rod 93. A ratchet groove matching the ratchet 98 is opened on the outer wall of the piston rod 93. It also includes a guide rod 14 and a pressing rod 15 symmetrically fixedly connected to the side wall of the welding drive component 131. The guide rod 14 matches the guide block 97, and the pressing rod 15 matches the pressing block 95.

[0054] In this embodiment, the fixed hydraulic cylinder 7 drives the clamp 8 to fix the material. As the stirring head moves, when the stirring head moves close to the clamp 8, the temperature near the clamp 8 will rise sharply. The guide rod 14 and guide block 97 can drive the U-shaped rod 96 to move into the buffer cylinder 91. Then the ratchet 98 will disengage from the ratchet groove on the piston rod 93. The hydraulic oil in the fixed hydraulic cylinder 7 will flow into the buffer cylinder 91 through the connecting hole 92. At this time, the pressure between the clamp 8 and the material will be reduced, thereby preventing the material from softening at high temperature and being pressed into a depression by the clamp 8. When the stirring head moves away from the clamp 8, it will cool the weld seam and the surrounding area of ​​the material. At the same time, the U-shaped rod 96 will return to the initial position under the action of the spring 99. When the material cools down to a certain temperature, the piston rod 93 and piston plate 94 can be moved to the initial position by the pressing rod 15 and pressing block 95. The piston rod 93 is fixed by the ratchet 98, which ensures the stability of the pressure between the clamp 8 and the material and prevents the material from shifting during the welding process.

[0055] Reference Figures 2-3A drive rail 10 is provided at a symmetrical position on the side wall of the workbench 1, and the end of the bracket 11 is slidably connected to the inside of the drive rail 10.

[0056] In this embodiment, the drive rail 10 is used to drive the support 11 to move along the worktable 1, thereby moving the stirring head and thus the welding efficiency. By adjusting the moving speed of the support 11 through the drive rail 10, the welding speed of the material can be adjusted.

[0057] Reference Figure 2 , Figure 3 and Figure 7 The welding device 13 includes a welding drive 131 fixedly connected to the bottom of the adjusting member 12. The welding drive 131 has a telescopic shaft 132 inside. A stirring head is located at the bottom end of the telescopic shaft 132. The stirring head includes a shoulder 133 and a stirring needle 134. The stirring needle 134 is located at the bottom of the shoulder 133. A channel 135 is opened on the side of the shoulder 133 near the stirring needle 134. An exhaust pipe 16 is connected to the side wall of the telescopic shaft 132 near the stirring needle 134. The end of the exhaust pipe 16 is connected to a jet assembly 17 for cooling the weld after welding.

[0058] In this embodiment, the specific structure of the stirring needle 134 can be referred to the technical solutions in the prior art. Those skilled in the art will know that the channel 135 is used to introduce argon gas, which can not only reduce the wear between the shoulder 133 and the material, but also reduce the introduction of impurities. In addition, the welding drive component 131 includes a drive device for driving the telescopic shaft 132 to move up and down and a drive device for driving the shoulder 133 and the stirring needle 134 to rotate. This is a conventional method in the prior art, so it will not be described in detail. The exhaust pipe 16 can be made of a plastic material, which can adjust the angle and distance between the materials of the jet assembly 17, thereby completing the cooling of the weld and the surrounding materials and the formation of an atmosphere such as argon gas under welding conditions.

[0059] Reference Figures 7-8 The jet assembly 17 includes a nozzle 171 connected to the exhaust pipe 16. The nozzle 171 has a nozzle hole 172 at the end away from the exhaust pipe 16. A fixing bracket 173 is fixedly connected inside the nozzle 171. An adjusting rod 174 is fixedly connected to the fixing bracket 173. An adjusting head 175 is fixedly connected to the side of the adjusting rod 174 near the nozzle hole 172. A central hole 176 is opened on the adjusting head 175. The adjusting head 175 is conical. The adjusting rod 174 and the telescopic rod 910 are connected by a pipe.

[0060] In this embodiment, during the material welding process, gas is blown through the nozzle 172 and the center hole 176 onto the weld and surrounding material to cool them or provide a protective atmosphere. When the stirring head moves to one of the clamps 8, the telescopic rod 910 in the buffer cylinder 91 is compressed and delivers the gas to the adjusting rod 174. It should be explained that the adjusting rod 174 is a telescopic structure, including two sets of sealed cavities. The gas compressed by the telescopic rod 910 is delivered to the lower sealed cavity, which will cause the adjusting rod 174 to retract into the nozzle 171. At this time, the spray radius of the gas is reduced (because when the clamp 8 is in contact with the material, the clamp 8 becomes a natural and efficient heat dissipation channel, which will actively carry away the heat on the material. If the cooling at the clamp 8 is accelerated at this time, it will cause the local heat dissipation at the clamp 8 to be too fast, causing the temperature on the material to drop sharply and disrupting the thermal balance of the material). That is, the heat dissipation efficiency at the clamp 8 is reduced to ensure the stability of the material cooling.

[0061] In this invention, when welding materials, the processed pad is first placed in the mounting groove 2 and fixed by the fixing device 3. Then, the welding material is placed on the pad and pushed towards the baffle 4. The side wall of the material is then fixed to complete the fixing of the pad and the side of the material.

[0062] Then, the displacement hydraulic cylinder 5 drives the telescopic plate 6 to move the fixing hydraulic cylinder 7 to the designated position of the material. Finally, the fixing hydraulic cylinder 7 can drive the clamp 8 to fix the top of the material.

[0063] At the same time, the position of the stirring head is adjusted by the adjusting member 12 so that the stirring needle 134 is located at the connection of the material. Then, the stirring head is rotated by the welding drive member 131 and the telescopic shaft 132 is driven to move downward. Finally, the welding drive member 131 is driven to move along the connection of the material by the drive rail 10, so that the material can be welded.

[0064] During the welding process, when the stirring head moves to the clamp 8, the guide rod 14 and guide block 97 drive the U-shaped rod 96 to move into the buffer cylinder 91. Subsequently, the ratchet 98 disengages from the ratchet groove on the piston rod 93, and the hydraulic oil in the fixed hydraulic cylinder 7 flows into the buffer cylinder 91 through the connecting hole 92. At this time, the pressure between the clamp 8 and the material decreases, thus preventing the material from softening at high temperatures and being pressed into a depression by the clamp 8. Simultaneously, the telescopic rod 910 compresses gas and delivers it to the adjusting rod 174, causing the adjusting rod 174 to retract into the nozzle 171. At this time, the gas spray radius... The heat dissipation efficiency at clamp 8 is reduced to ensure the stability of material cooling. When the stirring head moves away from clamp 8, the U-shaped rod 96 will return to the initial position under the action of spring 99. When the material cools down to a certain temperature, the piston rod 93 and piston plate 94 can be moved to the initial position by pressing rod 15 and pressing block 95, and the piston rod 93 is fixed by ratchet 98, which ensures the stability of the pressure between clamp 8 and material and avoids material displacement during welding. At the same time, the adjusting head 175 moves to the initial position to ensure the stability of material cooling.

[0065] Example 3:

[0066] The process is basically the same as in Example 1, and the specific steps are as follows:

[0067] The 9Cr-ODS steel is processed into a rectangular plate with a length of 120mm, a width of 20mm, and a thickness of 2.2mm. The wire cutting marks and oxide layer on each surface of the material are removed by machine tools and grinding. Then, the stains and other marks on the surface of the material are cleaned with acetone and alcohol, so that the surface of the material is free of pollution, oxide layer, and embedded grinding particles after processing and cleaning, and its flatness is good.

[0068] Subsequently, the welding fixture, backing plate material, and stirring head are processed according to the pre-designed specifications, and their surfaces are polished and cleaned to ensure cleanliness and flatness.

[0069] The length and width of the fixing device in the experiment are both 300mm, and the material is 304 stainless steel. The material of the backing plate is CLF-1 steel, which is similar in composition to 9Cr-ODS steel. Its dimensions are 120mm long, 40mm wide, and 2mm thick. This is to reduce the thermal deformation of the device during the welding process and reduce the introduction of impurities in the welding area during the welding process.

[0070] Based on this, the stirring head, 9Cr-ODS steel welding material, backing plate, etc. are fixed in sequence, and the device is fixed on the welding table to ensure that the plate does not shift during the welding process. During the welding process, the stirring head speed is 200rpm-500rpm, the travel speed is 50mm / min, the pressing depth is 0.05mm, and the initial pressing time is 5s. As a result, the weld inside the initial section of the material welding area has defects such as incomplete penetration, weak bonding, and voids, resulting in insufficient mechanical properties. When the pressing depth is 0.1-0.15mm during the welding process, there are large-scale defects such as furrows on the material surface, and the heat of the welding process is insufficient.

[0071] Example 4:

[0072] The process is basically the same as in Example 1, and the specific steps are as follows:

[0073] The 9Cr-ODS steel is processed into a rectangular plate with a length of 120mm, a width of 20mm, and a thickness of 2.2mm. The wire cutting marks and oxide layer on each surface of the material are removed by machine tools and grinding. Then, the stains and other marks on the surface of the material are cleaned with acetone and alcohol, so that the surface of the material is free of pollution, oxide layer, and embedded grinding particles after processing and cleaning, and its flatness is good.

[0074] Subsequently, the welding fixture, backing plate material, and stirring head are processed according to the pre-designed specifications, and their surfaces are polished and cleaned to ensure cleanliness and flatness.

[0075] The length and width of the fixing device in the experiment are both 300mm, and the material is 304 stainless steel. The material of the backing plate is CLF-1 steel, which is similar in composition to 9Cr-ODS steel. Its dimensions are 120mm in length, 40mm in width, and 3mm in thickness. This is to reduce the thermal deformation of the device during the welding process and to reduce the introduction of impurities in the welding area during the welding process.

[0076] Based on this, fix the stirring head, 9Cr-ODS steel welding material, backing plate, etc. in sequence, and fix the device on the welding table to ensure that the plate does not shift during the welding process. During the welding process, the stirring head speed is 800rpm-1400rpm, the travel speed is 50mm / min, the pressing depth is 0.15mm-0.2mm, and the initial pressing time is 5s. At this time, the weld performance is unstable, and there are occasional defects such as incomplete penetration and porosity at the initial end.

[0077] Example 5:

[0078] The process is basically the same as in Example 1, and the specific steps are as follows:

[0079] The 9Cr-ODS steel is processed into a rectangular plate with a length of 120mm, a width of 20mm, and a thickness of 2.2mm. The wire cutting marks and oxide layer on each surface of the material are removed by machine tools and grinding. Then, the stains and other marks on the surface of the material are cleaned with acetone and alcohol, so that the surface of the material is free of pollution, oxide layer, and embedded grinding particles after processing and cleaning, and its flatness is good.

[0080] Subsequently, the welding fixture, backing plate material, and stirring head are processed according to the pre-designed specifications, and their surfaces are polished and cleaned to ensure cleanliness and flatness.

[0081] In the experiment, the length and width of the fixing device were both 300mm, and the material was H13 steel. The material of the pad was CLF-1 steel, which is similar in composition to 9Cr-ODS steel. Its dimensions were 120mm long, 40mm wide, and 7mm thick. This was to reduce the thermal deformation of the device during the welding process and to reduce the introduction of impurities in the welding area during the welding process.

[0082] Meanwhile, a 100nm-200nm yttrium oxide layer is deposited on the area where the backing plate and stirring head contact the material using PVD coating or other methods. Then, the stirring head, 9Cr-ODS steel welding material, backing plate, etc. are fixed in sequence, and the device is fixed on the welding table to ensure that the plate does not shift during the welding process. During the welding process, the stirring head rotates at 800rpm-1200rpm, the travel speed is 30-100mm / min, the indentation depth is 0.15mm-0.2mm, the initial indentation holding time is 5s-7s, the argon flow rate is 0.1-0.3MPa, and the flow rate is 25-30L / min. Finally, the annealing process at 600-700℃ for 1-3h is carried out to obtain 9Cr-ODS steel material with excellent welding area performance and a simple and controllable welding process.

[0083] Components not described in detail in this article are existing technologies.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for friction stir welding of ferrite-martensitic dual-phase high-strength steel, comprising a stirring head, a fixing device, and a welding device (13), characterized in that, It also includes the following steps: Step 1: Sheet material processing. Select materials based on their size and thickness, and then process and clean them. Step 2: Processing of fixing devices and pads; Processing and cleaning of fixing devices and pads. Step 3: Select the mixing head. Choose the mixing head according to the size and thickness of the material. Step 4: Parameter selection. Choose welding parameters based on the properties of the material. Step 5: Welding and heat treatment. Fix the finished fixing device, pad, material and welding device (13) in sequence. After installing and adjusting the position of the stirring head, weld according to the selected parameters, and then perform the annealing process.

2. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 1, characterized in that, In step two, the pad material is CLF-1 steel with a thickness of 5mm-6mm, and a nano-scale yttrium oxide coating is plated on the contact surface with the material.

3. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 2, characterized in that, In step three, the stirring head is made of W-Re alloy, and a 100nm-200nm nano-yttrium oxide layer is deposited on the contact area between the stirring head and the sample.

4. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 3, characterized in that, In steps two and three, the coating on the surface of the pad and the stirring head is one of PVD coating, ion sputtering coating, cold spray coating, and electrochemical coating.

5. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 1, characterized in that, In step four, the stirring head rotates at 500 rpm to 1200 rpm, travels at 30 mm / min to 100 mm / min, and presses in to a depth of 0.1 mm to 0.2 mm.

6. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 1, characterized in that, The fixing device includes a workbench (1), and further includes: A pad fixing assembly is used to fix the pad on the workbench (1), and a baffle (4) is provided on the pad fixing assembly; Displacement hydraulic cylinders (5) are symmetrically and fixedly connected to the worktable (1). A telescopic plate (6) is connected to one side of the displacement hydraulic cylinders (5) that are close to each other. A fixed hydraulic cylinder (7) is fixedly connected to the telescopic plate (6). A clamp (8) is fixedly connected to the bottom of the fixed hydraulic cylinder (7). The top of the fixed hydraulic cylinder (7) is fixedly connected to a buffer mechanism (9) for adjusting the pressure between the clamp (8) and the material; A support (11) is provided on the workbench (1), and an adjusting member (12) is slidably connected on the support (11). The welding device (13) is provided at the bottom of the adjusting member (12).

7. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 6, characterized in that, The pad fixing assembly includes a mounting groove (2) formed on the workbench (1). Fixing devices (3) are symmetrically arranged on one side of the workbench (1) near the mounting groove (2). The fixing devices (3) include transverse fixing members and longitudinal fixing members. A baffle (4) is fixedly connected to one set of the longitudinal fixing members. The baffle (4) is located above the pad and is used to limit one end of the material. The transverse and longitudinal fixing components are both hydraulically driven. The displacement hydraulic cylinders (5) are evenly distributed on both sides of the mounting groove (2). The telescopic plate (6) is parallel to the material. The fixing hydraulic cylinder (7) is perpendicular to the material. The drive rail (10) is symmetrically positioned on the side wall of the workbench (1). The end of the bracket (11) is slidably connected to the inside of the drive rail (10).

8. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 7, characterized in that, The buffer mechanism (9) includes a buffer cylinder (91) fixedly connected to a fixed hydraulic cylinder (7). The bottom of the buffer cylinder (91) has a communicating hole (92) that communicates with the fixed hydraulic cylinder (7). A piston rod (93) is slidably connected inside the fixed hydraulic cylinder (7). A piston plate (94) that is tightly fitted to the inner wall of the buffer cylinder (91) is fixedly connected to the bottom end of the piston rod (93). A pressing block (95) is fixedly connected to the top end of the piston rod (93). The pressing block (95) is triangularly arranged. The piston plate (94) and the buffer cylinder (91) are connected in a slidably connected manner. A telescopic rod (910) is fixedly connected between the top of the cylinder (91). A U-shaped rod (96) is slidably connected inside the buffer cylinder (91). A guide block (97) is fixedly connected to the side of the U-shaped rod (96) away from the buffer cylinder (91). A spring (99) is fixedly connected between the end of the U-shaped rod (96) away from the guide block (97) and the inner wall of the buffer cylinder (91). A ratchet (98) is fixedly connected to the side of the U-shaped rod (96) near the piston rod (93). A ratchet groove matching the ratchet (98) is opened on the outer wall of the piston rod (93).

9. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 8, characterized in that, The welding device (13) includes a welding drive (131) fixedly connected to the bottom of the adjusting member (12). A telescopic shaft (132) is provided inside the welding drive (131). The stirring head is located at the bottom end of the telescopic shaft (132). The stirring head includes a shoulder (133) and a stirring needle (134). The stirring needle (134) is located at the bottom of the shoulder (133). A channel (135) is provided on the side of the shoulder (133) near the stirring needle (134). Among them, the side wall of the telescopic shaft (132) near the stirring needle (134) is connected to an exhaust pipe (16), and the end of the exhaust pipe (16) is connected to an air jet assembly (17) for cooling the weld or providing an argon protective atmosphere. The side wall of the welding drive (131) is symmetrically fixed with a guide rod (14) and a pressing rod (15). The guide rod (14) matches the guide block (97), and the pressing rod (15) matches the pressing block (95).

10. The friction stir welding method for ferrite-martensitic dual-phase high-strength steel according to claim 9, characterized in that, The jet assembly (17) includes a nozzle (171) connected to an exhaust pipe (16). A nozzle (171) with a spray hole (172) is provided at the end of the nozzle (171) away from the exhaust pipe (16). A fixing bracket (173) is fixedly connected inside the nozzle (171). An adjusting rod (174) is fixedly connected to the fixing bracket (173). An adjusting head (175) is fixedly connected to the side of the adjusting rod (174) near the spray hole (172). A central hole (176) is provided on the adjusting head (175). The adjusting head (175) is conical, and the adjusting rod (174) and the telescopic rod (910) are connected by a pipe.

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