Friction stir welding process

Abstract

The invention belongs to the technical field of welding, and discloses a friction stir welding process which comprises the following steps: S1, laser coding; s2, cutting machining is carried out; s3, cleaning is conducted; s4, drying; s5, welding is conducted; s6, post-welding treatment is conducted; s7, assembling is conducted; s8, processing a finished product; and S9, packaging and warehousing. By the adoption of the process, the fit clearance and the unfitness of butt joint of a welding part can be stably controlled and can be 100% controlled within the required range, and finally the welding seam quality during welding is effectively guaranteed; compared with the prior art in which blank contours are adopted for welding, the process has the advantages that firstly, the product yield is increased in the production process of products obtained through the scheme and reaches up to 95%, and the problems of poor welding, welding tunnels and the like caused by the fact that two workpieces are not assembled in place are effectively avoided; the time for loading and unloading products on site is saved, the products can be assembled in place at a time, and the time for reassembling due to the fact that the two welding parts are not assembled in place can be saved.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a friction stir welding process. Background Art

[0002] Friction Stir Welding (FSW) is a welding technology that uses the friction between a high-speed rotating welding tool and a workpiece to generate heat, causing the welded material to partially melt and form a solid-phase weld. The main feature of this technology is that the stirring head rotates into the welding machine, rubbing against the welding material to generate heat, causing the material to become thermoplastic. When the stirring head moves, the thermoplastic material is transferred from the front to the back of the stirring head, forming a solid-phase connection under mechanical forging. This welding method does not require welding wire or protective gas. The welding process is pollution-free, smoke-free, and radiation-free. The joint has low residual stress, high welding efficiency, small deformation, low energy consumption, simple equipment, and a safe process. It is widely used in light metal structures such as aluminum alloys and magnesium alloys, as well as in the field of high melting point materials, such as aerospace, rail transportation, and ships.

[0003] During the actual processing process, the applicant found that the lap joint surface and the overlapped surface of the high-pressure die-cast aluminum alloy molded part had large variations in the blank molding dimensions and inconsistent grinding or pouring residues, resulting in an unstable fitting gap between the two welded parts. In addition, due to the large gap and misalignment, the quality of the weld finally formed during welding was poor. Also, because it was difficult to weld, the processing efficiency was low and it was difficult to control the production rhythm. Summary of the invention

[0004] In view of the problems raised by the above background technology, the purpose of the present invention is to provide a friction stir welding process.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

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

[0007] S1, laser coding;

[0008] Use a laser coder to engrave QR codes and plain codes on workpieces;

[0009] S2, chip processing;

[0010] S2.1. Use a fixture to position and clamp the workpiece;

[0011] S2.2, sending the fixture into the CNC equipment to cut the overlapping surface and the overlapped surface of the workpiece;

[0012] S2.3, after the chip processing is completed, the workpiece is processed into a process positioning hole and a process positioning surface;

[0013] S3, cleaning;

[0014] Remove burrs, oil stains and impurities from the workpiece;

[0015] S4, drying;

[0016] Use negative pressure to remove moisture from the workpiece;

[0017] S5, welding;

[0018] S5.1. Detect the fit clearance and misalignment between the two workpieces to be welded;

[0019] S5.2, fix the two workpieces on the special tooling of the friction stir welding equipment through the process positioning holes and the process positioning surfaces;

[0020] S5.3, start the friction stir welding equipment;

[0021] S6, post-weld treatment;

[0022] S6.1, after the welded workpiece is installed and positioned by the process positioning holes and process positioning surfaces processed in step S2.3, a chip is cut once, and new process positioning holes and process positioning surfaces are processed again;

[0023] S6.2, after installing and positioning the new process positioning holes and process positioning surfaces processed in step S6.1, perform secondary chip cutting;

[0024] S6.3, remove burrs, oil stains and impurities from the workpiece;

[0025] S6.4. Use negative pressure to remove moisture from the workpiece;

[0026] S6.5, random inspection;

[0027] S7, assembly;

[0028] S8, finished product processing;

[0029] S9, packaging and storage.

[0030] It is further defined that the method for positioning the workpiece in step S2.1, step S6.1 and step S6.2 is all a one-sided two-pin positioning method. The one-sided two-pin positioning method has a larger supporting surface, so the supporting stiffness is good, and it can withstand a larger processing force to ensure stability during the processing. This positioning method can achieve higher positioning accuracy by cooperating with the positioning holes on the workpiece through two positioning pins, ensuring that the size and shape of the processed parts meet the requirements. The one-sided two-pin positioning method is convenient for loading and unloading of the workpiece, improves production efficiency, and reduces labor intensity. The one-sided two-pin positioning is a complete positioning method, which can effectively limit the six degrees of freedom of the part and ensure stability and accuracy during the processing. The adjustable one-sided two-pin positioning device has position adjustability, can meet the positioning requirements of different workpieces and fixtures, and has strong compatibility and adaptability. The one-sided two-pin positioning has significant advantages in mechanical processing and is one of the commonly used positioning methods in the processing of shell and cover parts.

[0031] It is further defined that in step 2.2, the size range of the fitting clearance and the misalignment is 0.1 to 0.5 mm. In steps S2.3 and S6.1, the tolerance grade of the process positioning hole is H6 to H8, and the flatness error range of the process positioning surface is 0.1 to 0.5 mm. The control of the fitting clearance and the misalignment is conducive to controlling the accuracy during welding, thereby ensuring the quality of the weld. The control of the tolerance grade of the process positioning hole and the flatness error of the process positioning surface ensures the accuracy of the overall position after installation and positioning.

[0032] It is further defined that in step S3 and step S6.3, high-pressure cleaning is used as the cleaning method, and the cleaning pressure is 15 to 40 MPa. By utilizing the powerful impact force of the high-pressure water jet, high-pressure cleaning can complete the cleaning of a large area or complex surface in a short time with high cleaning efficiency. High-pressure cleaning uses water as the working medium and does not require the use of chemical cleaning agents, so no waste liquid or harmful gas is generated, and it is environmentally friendly. Although the initial investment in a high-pressure cleaning machine may be high, the long-term operating cost is low because it saves the cost of cleaning agents and has high cleaning efficiency and reduces labor costs. High-pressure cleaning utilizes the physical properties of water for cleaning and will not cause mechanical damage or chemical corrosion to the cleaning object. It is suitable for cleaning objects of various materials and shapes. High-pressure cleaning machines have a wide range of applications and can be used to clean various surfaces and objects, including buildings, pipes, equipment, etc. High-pressure cleaning has the advantages of high efficiency, environmental protection, low cost, no damage to the cleaning object and a wide range of applications.

[0033] It is further defined that in step S4 and step S6.4, the dryness and humidity range after drying is 50% to 80%. The performance of the workpiece material within this range is stable, avoiding problems such as material deformation and cracking caused by overdrying or overwetting, thereby improving product quality.

[0034] It is further defined that in step S8, the finished product processing includes air-tightness testing, helium water channel cavity testing, low-pressure cleaning, drying after cleaning and final inspection of the finished product to ensure the quality of the finished product.

[0035] The beneficial effects of the present invention are as follows:

[0036] By adopting the process of the present invention, the matching clearance and misalignment of the welded parts can be stably controlled and can be 100% controlled within the required range, thus effectively ensuring the quality of the weld during welding.

[0037] Compared with the prior art which uses the blank profile for welding, the process of the present invention has the following advantages: firstly, the product yield rate of the product obtained by the present solution is improved in the production, and the product yield rate is as high as 95%, which effectively avoids the problems of poor welding and welding tunnels caused by improper assembly between two workpieces; secondly, it saves the time of loading and unloading products on site, and the products can be assembled in place at one time, which can save the time of reassembly due to improper assembly of two welded parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention can be further illustrated by means of non-limiting examples given in the accompanying drawings;

[0039] Figure 1 A schematic flow chart of a friction stir welding process embodiment of the present invention; DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0041] Embodiment 1:

[0042] like Figure 1 As shown, a friction stir welding process of the present invention comprises the following steps:

[0043] S1, laser coding;

[0044] Use a laser coder to engrave QR codes and plain codes on workpieces;

[0045] S2, chip processing;

[0046] S2.1. Use a fixture to position and clamp the workpiece;

[0047] S2.2, sending the fixture into the CNC equipment to cut the overlapping surface and the overlapped surface of the workpiece;

[0048] S2.3, after the chip processing is completed, the workpiece is processed into a process positioning hole and a process positioning surface;

[0049] S3, cleaning;

[0050] Remove burrs, oil stains and impurities from the workpiece;

[0051] S4, drying;

[0052] Use negative pressure to remove moisture from the workpiece;

[0053] S5, welding;

[0054] S5.1. Detect the fit clearance and misalignment between the two workpieces to be welded;

[0055] S5.2, fix the two workpieces on the special tooling of the friction stir welding equipment through the process positioning holes and the process positioning surfaces;

[0056] S5.3, start the friction stir welding equipment;

[0057] S6, post-weld treatment;

[0058] S6.1, after the welded workpiece is installed and positioned by the process positioning holes and process positioning surfaces processed in step S2.3, a chip is cut once, and new process positioning holes and process positioning surfaces are processed again;

[0059] S6.2, after installing and positioning the new process positioning holes and process positioning surfaces processed in step S6.1, perform secondary chip cutting;

[0060] S6.3, remove burrs, oil stains and impurities from the workpiece;

[0061] S6.4. Use negative pressure to remove moisture from the workpiece;

[0062] S6.5, random inspection;

[0063] S7, assembly;

[0064] S8, finished product processing;

[0065] S9, packaging and storage.

[0066] In this implementation case, the two workpieces to be welded are first engraved with a QR code and a plain code using a laser coding machine. This operation is conducive to the traceability of the product in the later stage. Then the workpiece is placed in the fixture provided by the CNC equipment. The workpiece is clamped by the fixture and the CNC equipment is started to process the workpiece. The processing position is the overlapping surface and the overlapped surface of the workpiece. After the processing is completed, the process positioning hole and the process positioning surface are processed as the reference surface for subsequent welding and re-clamping.

[0067] After the chip processing is completed, the workpiece is cleaned to remove burrs, oil stains and impurities on the workpiece. After cleaning, the moisture on the workpiece is removed by negative pressure. It can be pointed out here that if the CNC used has the function of cleaning and drying, this action can be performed directly in the CNC equipment, eliminating the steps of unloading and installing it in the cleaning equipment and drying equipment, further improving the processing efficiency;

[0068] Check the dried workpiece to ensure that its matching clearance and misalignment are within the qualified range, and then install and fix it on the special tooling on the friction stir welding equipment through the process positioning holes and process positioning surfaces processed by the CNC equipment. It should be pointed out that the installation of the workpiece must ensure the cleanliness of the special tooling installation surface on the friction stir welding equipment, and then the friction stir welding equipment can be started to weld the workpiece. Because the overlapping surfaces and overlapped surfaces of the two welding equipment are both processed and cut, the docking accuracy is good and the joint is tightly closed, so the quality of the weld is high during welding;

[0069] After welding is completed, the workpiece is taken out from the stirring welding equipment, and then the workpiece is chipped again with the process positioning holes and process positioning surfaces on the workpiece. The chipping positions are the welding positions and process processing positions, and another set of process positioning holes and process positioning surfaces are cut out at the same time, thereby realizing the reference calibration between the two sets of process positioning holes and process positioning surfaces. After the workpiece is taken out, the newly chipped process positioning holes and process positioning surfaces can be used to accurately chip out a workpiece that meets the requirements;

[0070] The workpiece after two chip cuttings is cleaned by high pressure cleaning and then dried by negative pressure. It should be pointed out that the size of the workpiece can be inspected before each start of the automation equipment and before the workpiece is installed and fixed to ensure the quality of the finished product processing;

[0071] The qualified workpieces after welding are assembled, and the assembled products are quality inspected, and packaged and stored after passing the inspection.

[0072] Embodiment 2:

[0073] like Figure 1In this embodiment, the methods for positioning the workpiece in steps S2.1, S6.1 and S6.2 are all one-side two-pin positioning methods. The one-side two-pin positioning method has a larger supporting surface, so the supporting stiffness is good, it can withstand a larger processing force, and ensure the stability during the processing. This positioning method can achieve higher positioning accuracy by cooperating with the positioning holes on the workpiece through two positioning pins, ensuring that the size and shape of the processed parts meet the requirements. The one-side two-pin positioning method is convenient for loading and unloading workpieces, improving production efficiency and reducing labor intensity. The one-side two-pin positioning belongs to complete positioning, which can effectively limit the six degrees of freedom of the parts and ensure the stability and accuracy during the processing. The adjustable one-side two-pin positioning device has position adjustability, can meet the positioning requirements of different workpieces and fixtures, and has strong compatibility and adaptability. The one-side two-pin positioning has significant advantages in mechanical processing and is one of the commonly used positioning methods in the processing of shell and cover parts. In fact, there are many positioning methods. According to the performance of the equipment and the style of the workpiece, different positioning methods can be selected, such as three-claw clamping and pressing and fixing with a pressure plate.

[0074] Embodiment three:

[0075] like Figure 1 In this embodiment, in step S3 and step S6.3, high-pressure cleaning is used for cleaning, and the cleaning pressure is 15-40 MPa. By using the strong impact force of high-pressure water jet, high-pressure cleaning can complete the cleaning of large areas or complex surfaces in a short time, with high cleaning efficiency. High-pressure cleaning uses water as the working medium and does not require the use of chemical cleaning agents, so it does not produce waste liquid or harmful gases, and is environmentally friendly. Although the initial investment of a high-pressure cleaning machine may be high, the long-term operating cost is low because it saves the cost of cleaning agents, and at the same time has high cleaning efficiency and reduces labor costs. High-pressure cleaning uses the physical properties of water for cleaning, and will not cause mechanical damage or chemical corrosion to the cleaning object. It is suitable for cleaning objects of various materials and shapes. High-pressure cleaning machines have a wide range of applications and can be used to clean various surfaces and objects, including buildings, pipelines, equipment, etc. High-pressure cleaning has the advantages of high efficiency, environmental protection, low cost, no damage to the cleaning object and a wide range of applications. In fact, there are many ways to clean, which can be:

[0076] Solvent cleaning: Use organic solvents such as alcohol, acetone, trichloroethylene, etc. to remove oil and organic pollutants on the metal surface. This method has high cleaning efficiency, but attention should be paid to the volatility and toxicity of the solvent, and the operation should be carried out in a well-ventilated environment.

[0077] Pickling: Use pickling agents such as hydrochloric acid, sulfuric acid, and nitric acid to remove the oxide layer and rust on the metal surface. The pickling speed is fast, but the concentration, temperature, and cleaning time of the pickling solution must be strictly controlled to avoid excessive corrosion.

[0078] Ultrasonic cleaning: Use the cavitation effect of ultrasound in liquid to remove dirt and impurities from the metal surface. This method has high cleaning efficiency and is suitable for precision metal parts of various shapes and sizes.

[0079] Biological cleaning: Use enzymes or microorganisms to decompose oil stains on the metal surface and convert them into non-toxic water-soluble substances to achieve the purpose of environmental protection and energy saving.

[0080] Mechanical cleaning: including sandblasting, shot blasting and other methods, which remove rust, scales, etc. on the metal surface through physical impact. Suitable for cleaning large areas or heavy workpieces.

[0081] Each cleaning method has its own advantages and disadvantages. The specific selection needs to be considered comprehensively based on factors such as the material, shape, degree of contamination and subsequent processing requirements of the metal workpiece.

[0082] Embodiment 4:

[0083] like Figure 1 In this embodiment, in step S4 and step S6.4, the dryness and humidity range after drying is 50% to 80%. The performance of the workpiece material within this range is stable, avoiding problems such as material deformation and cracking caused by excessive drying or excessive humidity, thereby improving the quality of the product. In fact, the preferred dryness is 60%. Excessive drying or excessive humidity is not conducive to the storage of subsequent products, but the specific requirements depend on the dryness and humidity of the storage environment of the workpiece.

[0084] Embodiment five:

[0085] like Figure 1 In this embodiment, in step S8, the finished product processing includes air tightness detection, helium water channel cavity detection, low-pressure cleaning, drying after cleaning and final inspection to ensure the qualification of the finished product. In fact, the inspection of the finished product is a necessary process for the product to be a qualified product. The inspection method and key points are determined according to the frequency of occurrence of unqualified points in the current workpiece. The more likely it is that unqualified points will occur, the higher the inspection requirements will be, so as to ensure the qualified rate of the finished product.

[0086] Embodiment six:

[0087] like Figure 1In this embodiment, in step 2.2, the size range of the fitting clearance and the misalignment is 0.1-0.5 mm. In steps S2.3 and S6.1, the tolerance grade of the process positioning hole is H6-H8, and the flatness error range of the process positioning surface is 0.1-0.5 mm. The control of the fitting clearance and the misalignment is conducive to controlling the accuracy during welding, thereby ensuring the quality of the weld. The control of the tolerance grade of the process positioning hole and the flatness error of the process positioning surface ensures the accuracy of the overall position after installation and positioning. In fact, the size of the fitting clearance and the misalignment is preferably 0.2 mm. Too small a clearance size has too high a precision requirement, which is not easy to achieve, and will affect the processing rhythm to a certain extent, because the higher the precision, the lower the operating rhythm of the equipment. The tolerance grade of the process positioning hole can be H7, and the flatness error can be 0.3 mm. Of course, the higher the precision, the higher the quality of the finished product after welding. However, as long as the size is within the range, the finished product after welding can meet the qualified standards.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A friction stir welding process, characterized in that: The steps include: S1, laser coding; Use a laser coder to engrave QR codes and plain codes on workpieces; S2, chip processing; S2.

1. Use a fixture to position and clamp the workpiece; S2.2, sending the fixture into the CNC equipment to cut the overlapping surface and the overlapped surface of the workpiece; S2.3, after the chip processing is completed, the workpiece is processed into a process positioning hole and a process positioning surface; S3, cleaning; Remove burrs, oil stains and impurities from the workpiece; S4, drying; Use negative pressure to remove moisture from the workpiece; S5, welding; S5.

1. Detect the fit clearance and misalignment between the two workpieces to be welded; S5.2, fix the two workpieces on the special tooling of the friction stir welding equipment through the process positioning holes and the process positioning surfaces; S5.3, start the friction stir welding equipment; S6, post-weld treatment; S6.1, after the welded workpiece is installed and positioned by the process positioning holes and process positioning surfaces processed in step S2.3, a chip is cut once, and new process positioning holes and process positioning surfaces are processed again; S6.2, after installing and positioning the new process positioning holes and process positioning surfaces processed in step S6.1, perform secondary chip cutting; S6.3, remove burrs, oil stains and impurities from the workpiece; S6.

4. Use negative pressure to remove moisture from the workpiece; S6.5, random inspection; S7, assembly; S8, finished product processing; S9, packaging and storage.

2. A friction stir welding process according to claim 1, characterized in that: The methods for positioning the workpiece in step S2.1, step S6.1 and step S6.2 are all one-side two-pin positioning methods.

3. A friction stir welding process according to claim 1, characterized in that: In step 2.2, the size range of the fitting clearance and the misalignment is 0.1 to 0.5 mm. In steps S2.3 and S6.1, the tolerance grade of the process positioning hole is H6 to H8, and the flatness error range of the process positioning surface is 0.1 to 0.5 mm.

4. A friction stir welding process according to claim 1, characterized in that: In step S3 and step S6.3, high-pressure cleaning is used for cleaning, and the cleaning pressure is 15-40 MPa.

5. A friction stir welding process according to claim 1, characterized in that: In step S4 and step S6.4, the humidity after drying is in the range of 50% to 80%.

6. A friction stir welding process according to claim 1, characterized in that: In step S8, the finished product processing includes air tightness testing, helium water channel cavity testing, low-pressure cleaning, drying after cleaning and final inspection of the finished product.

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