Method for electron beam welding of high-entropy alloy and low-temperature steel based on tooth-shaped self-locking structure

Abstract

The invention provides a method for electron beam welding of a high-entropy alloy and low-temperature steel based on a tooth-shaped self-locking structure, belongs to the technical field of vacuum welding, and solves the problems that welding cracks are easily generated in the welding process of the high-entropy alloy and the low-temperature steel, and an existing method for regulating and controlling welding parameters is only suitable for specific metal types, complex in process and poor in practicability. Comprising the steps that firstly, a to-be-welded interface of the high-entropy alloy and the low-temperature steel metal plate is determined; step 2, assembling a workpiece; 3, vacuum welding is conducted; 4, welding is completed, heat preservation is conducted, and the welded workpiece is taken out; the tooth-shaped self-locking connector which is simple and easy to implement can be directly combined with an existing welding process, the connection strength and stability are improved in a mechanical mode, and compared with a traditional mode that a metallurgical regulation and control middle layer is added, the self-locking structure ensures that the connector still has certain connection strength and does not lose efficacy immediately after a welding seam cracks, the treatment time is reserved, and the service life of the connector is prolonged. And an early warning effect is achieved.

Description

Technical Field

[0001] The invention relates to a method for electron beam welding high entropy alloy and low-temperature steel based on a tooth-shaped self-locking structure, and belongs to the technical field of vacuum welding. Background Art

[0002] In the industrial field, welding is a common method of metal connection. With the continuous development of technology and industry, the combination of different types of metals has become more and more common in product design and manufacturing. The resulting dissimilar metal welded joints promote the application and combination of various materials and expand the freedom of design and manufacturing. The development of dissimilar metal welding is crucial to improving product quality, reducing costs, and improving industrial production efficiency. At the same time, dissimilar metal welding also provides the possibility of achieving sustainable development goals, such as the application potential in lightweighting, energy conservation and resource utilization, so the prospects for dissimilar metal welding are very broad.

[0003] High entropy alloys have excellent comprehensive properties. The nanotwins caused by deformation and work hardening make the alloy have excellent mechanical properties at room temperature and low temperature. It has high resistance to hydrogen embrittlement and fracture toughness, and has excellent application prospects in low-temperature resistant parts. However, the complex preparation process and high price of high entropy alloys limit their application. Low-temperature steel also has good low-temperature impact resistance and is widely used in low-temperature resistant parts such as cryogenic pressure vessels, cryogenic pipelines, and liquid ammonia fuel tanks. At the same time, its price is relatively low. Connecting high-entropy alloys with low-temperature steel has significant cost-effectiveness, which is conducive to the promotion and application of high-entropy alloys.

[0004] However, there are differences in the thermophysical properties of high entropy alloys and low-temperature steels, such as mismatches in linear expansion coefficient and specific heat capacity. When the electron beam welding method is used to weld the two, the expansion degree of the materials on both sides of the weld is different, and stress concentration is easily generated in the weld area, causing welding crack defects, reducing the performance and service reliability of the welded joint. In addition, the cooling rate of electron beam welding is extremely fast, and high entropy alloys are extremely sensitive to the welding cooling rate when welding with dissimilar materials. Therefore, slow cooling is required during welding, extending the high temperature residence time of the weld, suppressing welding stress, and reducing the tendency of welding cracks, which can generally be achieved by reducing the welding speed. Existing methods for regulating welding parameters, such as performing biased beam welding to improve the performance of dissimilar metal welded joints, are only applicable to specific metal types. In addition, the method of regulating the metallurgical compatibility of the weld by adding a metal layer requires a large amount of material and time to explore the process, and the process is complex and has poor practicality. The present invention adopts a method of designing the joint shape as a toothed self-locking structure to solve the problem of joint cracking. Summary of the invention

[0005] The present invention aims to solve the problem that welding cracks are easily generated during the welding process of high entropy alloy and low temperature steel. The existing method of adjusting welding parameters is only applicable to specific metal types and the process is complicated and has poor practicality. A method for electron beam welding high entropy alloy and low temperature steel based on a toothed self-locking structure is proposed, which specifically includes:

[0006] Step 1: prepare high entropy alloy and low temperature steel metal plates of the same size, and process the interfaces to be welded on the high entropy alloy and low temperature steel metal plates;

[0007] Step 2: Ultrasonic cleaning is performed on the processed high entropy alloy and low temperature steel metal plates, and the interface to be welded is polished with sandpaper. After polishing, the interface to be welded is wiped with petroleum ether, and then blown dry immediately after wiping;

[0008] Step 3: Butt the high entropy alloy and the low temperature steel metal plates along the toothed path, buckle them together along the thickness direction, place the assembled high entropy alloy and low temperature steel metal plates on a welding fixture, and place the welding fixture in the vacuum chamber of the electron beam welding machine;

[0009] Step 4: Turn on the vacuum system. When the vacuum degree in the vacuum chamber reaches the preset value, start the electron gun and the motion system, select the corresponding welding parameters, control the electron beam to weld the high entropy alloy and the low-temperature steel along the toothed butt surface, and keep warm after the welding is completed;

[0010] Step 5: After keeping warm, take out the workpiece and complete the welding of high entropy alloy and low temperature steel.

[0011] Optionally, in step 1, the interface to be welded is tooth-shaped, and the height and width of the teeth are greater than the width of the weld.

[0012] Optionally, in step 2, the ultrasonic frequency is 20 kHz, the ultrasonic cleaning time is 5 minutes, and the mesh number of the sandpaper is 1000-2000.

[0013] Optionally, in step 3, the docking interface is a tooth-shaped self-locking structure, the fillet radius of the tooth-shaped self-locking structure is 2.5 mm, the bevel angle is 80°, and the tooth width is 8 mm.

[0014] Optionally, the preset vacuum degree in the vacuum chamber in step 4 is 5×10 -2 Pa, the holding time is 10-20min, the acceleration voltage of the electron gun and the motion system is 60kV, the welding beam current is 20mA, and the welding speed is 10mm / s.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention is suitable for welding high-entropy alloys and low-temperature steels with a thickness of 2 to 5 mm. The welding energy distribution is regulated by electron beam welding, and the tooth-shaped weld is accurately tracked to achieve precise welding, thereby obtaining an electron beam welded joint with a self-locking structure.

[0017] (2) The present invention can be directly combined with the existing welding process through a simple and easy-to-use toothed self-locking joint, and the connection strength and stability can be increased by mechanical means. Compared with the traditional method of adding a metallurgical control intermediate layer, the self-locking structure ensures that the joint still has a certain connection strength after the weld cracks and will not fail immediately, which reserves processing time and has an early warning function.

[0018] (3) Compared with traditional straight welds, the direction of the serrated weld changes continuously, which changes the stress distribution of the joint and suppresses the stress concentration after welding. When local cracks occur in the weld, the straight weld is prone to cracking along the weld, while the direction of the serrated weld has a large angle deflection, which can effectively suppress the crack from extending along the straight line.

[0019] (4) Under the same workpiece size and welding speed, the serrated weld has a longer welding time, a longer high temperature residence time, and a slower cooling rate, which is beneficial to inhibiting the occurrence of welding cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a method for electron beam welding high entropy alloy and low temperature steel based on a toothed self-locking structure provided by the present invention;

[0021] Figure 2 It is a schematic diagram of the assembly process of the high entropy alloy and low temperature steel provided by the present invention;

[0022] Figure 3 The specific dimension diagram of the weld seam of the high entropy alloy and low temperature steel metal plate with the dimension of 200mm×50mm×2mm provided by the present invention;

[0023] Figure 4 The specific dimension diagram of the weld seam of the high entropy alloy and low temperature steel metal plate with the dimension of 260mm×50mm×3mm provided by the present invention;

[0024] Figure 5 The specific dimension diagram of the shaped weld of the high entropy alloy and low temperature steel metal plates with the dimensions of 280mm×60mm×4mm provided by the present invention. DETAILED DESCRIPTION

[0025] Specific implementation method 1: Combination Figure 1-3 To illustrate this embodiment, Figure 1 As shown, the method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure described in this embodiment includes the following steps:

[0026] S1: Determine the interface between high entropy alloy and low temperature steel metal plates to be welded;

[0027] In this embodiment, two pieces of high entropy alloy and low temperature steel materials with a size of 200 mm×50 mm×2 mm are prepared, such as Figure 3 As shown, teeth with a width of 6mm, a spacing of 6mm, and a radius of 2mm at the corners are processed on the interface to be welded, so that the interfaces of the two plates after processing are matched with each other and smooth and flat. For plates of different sizes, the tooth pitch and tooth width can be adjusted accordingly.

[0028] Compared with traditional straight welds, the direction of the serrated weld in this embodiment changes continuously, which changes the stress distribution of the joint and suppresses stress concentration after welding. When local cracks appear in the weld, the straight weld is prone to crack along the weld, while the direction of the serrated weld has a large angle deflection, which can effectively suppress the crack from extending along the straight line.

[0029] S2: Workpiece assembly;

[0030] S201: ultrasonically clean the processed high entropy alloy and low temperature steel metal plates at a frequency of 20 kHz for 5 minutes to remove pollutants such as oily water stains;

[0031] S202: Use 1000-2000# sandpaper to polish the interface to be welded to remove pollutants such as oxides and rust, then wipe the interface to be welded with petroleum ether and blow dry immediately after wiping;

[0032] S203: Figure 2 As shown, the metal plates are matched along the toothed path and snapped into each other in the thickness direction to ensure that the interfaces of the metal plates to be welded are aligned and overlapped.

[0033] S3: Vacuum welding;

[0034] S301: placing the assembled high entropy alloy and low temperature steel metal plates on a welding fixture and fixing them. After fixing, placing the fixture and the metal plates in a vacuum chamber of an electron beam welding machine and starting the vacuum system.

[0035] This embodiment can be directly combined with the existing welding process through a simple and easy toothed self-locking joint, and the connection strength and stability can be increased by mechanical means. Compared with the traditional method of adding a metallurgical control intermediate layer, the self-locking structure ensures that the joint still has a certain connection strength after the weld cracks and will not fail immediately, which reserves processing time and has an early warning function.

[0036] S302: The vacuum degree of the vacuum chamber reaches 5×10 -2 When Pa, the electron gun and the motion system are started, the focusing position is the upper surface of the metal plate, the appropriate welding parameters are selected, and the electron beam is controlled to weld the high entropy alloy and the low-temperature steel along the tooth-shaped weld.

[0037] S4: Finish welding and keep warm, then take out the welded workpiece;

[0038] After welding is completed, keep the workpiece in the vacuum chamber for 10 to 20 minutes and then take it out.

[0039] Specific implementation method 2: Combination Figure 1 , Figure 2 and Figure 4 To illustrate this embodiment, Figure 1 As shown, the method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure in this embodiment includes the following steps:

[0040] S1: Determine the interface between high entropy alloy and low temperature steel metal plates to be welded;

[0041] In this embodiment, two pieces of high entropy alloy and low temperature steel materials with a size of 260 mm×50 mm×3 mm are prepared, such as Figure 4 As shown, a tooth-shaped butt joint surface is machined on the long side, with a fillet radius of 2.5 mm, a bevel angle of 80°, and a tooth width of 8 mm.

[0042] S2: Workpiece assembly;

[0043] S201: ultrasonically clean the processed high entropy alloy and low temperature steel metal plates at a frequency of 20 kHz for 5 minutes to remove pollutants such as oily water stains;

[0044] S202: Use 1000-2000# sandpaper to polish the interface to be welded to remove pollutants such as oxides and rust, then wipe the interface to be welded with petroleum ether and blow dry immediately after wiping;

[0045] S203: Figure 2 As shown, the metal plates are matched along the toothed path and snapped into each other in the thickness direction to ensure that the interfaces of the metal plates to be welded are aligned and overlapped.

[0046] S3: Vacuum welding;

[0047] S301: placing the assembled high entropy alloy and low temperature steel metal plates on a welding fixture and fixing them. After fixing, placing the fixture and the metal plates in a vacuum chamber of an electron beam welding machine and starting the vacuum system.

[0048] S302: The vacuum degree of the vacuum chamber reaches 5×10 -2 Pa, start the electron gun and motion system, the acceleration voltage is 60kV, the focusing position is the upper surface of the metal plate, the welding beam current is 20mA, and the electron beam is controlled to weld the high entropy alloy and low-temperature steel along the toothed butt surface, and the welding speed is 10mm / s.

[0049] S4: Finish welding and keep warm, then take out the welded workpiece;

[0050] After welding is completed, keep the workpiece in the vacuum chamber for 10 to 20 minutes and then take it out.

[0051] Specific implementation method three: Combination Figure 1 , Figure 2 and Figure 5 To illustrate this embodiment, Figure 1 As shown, the method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure in this embodiment includes the following steps:

[0052] S1: Determine the interface between high entropy alloy and low temperature steel metal plates to be welded;

[0053] In this embodiment, two pieces of high entropy alloy and low temperature steel materials with a size of 280 mm×60 mm×4 mm are prepared, such as Figure 5 As shown, a tooth-shaped interface is machined on the long side, with a fillet radius of 3 mm, a bevel angle of 80°, and a tooth width of 10 mm.

[0054] S2: Workpiece assembly;

[0055] S201: ultrasonically clean the processed high entropy alloy and low temperature steel metal plates at a frequency of 20 kHz for 5 minutes to remove pollutants such as oily water stains;

[0056] S202: Use 1000-2000# sandpaper to polish the interface to be welded to remove pollutants such as oxides and rust, then wipe the interface to be welded with petroleum ether and blow dry immediately after wiping;

[0057] S203: Figure 2 As shown, the metal plates are matched along the toothed path and snapped into each other in the thickness direction to ensure that the interfaces of the metal plates to be welded are aligned and overlapped.

[0058] S3: Vacuum welding;

[0059] S301: placing the assembled high entropy alloy and low temperature steel metal plates on a welding fixture and fixing them. After fixing, placing the fixture and the metal plates in a vacuum chamber of an electron beam welding machine and starting the vacuum system.

[0060] S302: The vacuum degree of the vacuum chamber reaches 5×10 -2 Pa, start the electron gun and motion system, the acceleration voltage is 60kV, the focusing position is the upper surface of the metal plate, the welding beam current is 20mA, and the electron beam is controlled to weld the high entropy alloy and the low-temperature steel along the toothed interface, and the welding speed is 10mm / s.

[0061] S4: Finish welding and keep warm, then take out the welded workpiece;

[0062] After welding is completed, keep the workpiece in the vacuum chamber for 10 to 20 minutes and then take it out.

[0063] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for electron beam welding high entropy alloy and low temperature steel based on a toothed self-locking structure, characterized in that: The method for electron beam welding high entropy alloy and low temperature steel based on tooth-shaped self-locking structure comprises the following steps: Step 1: prepare high entropy alloy and low temperature steel metal plates of the same size, and process the interfaces to be welded on the high entropy alloy and low temperature steel metal plates; Step 2: Ultrasonic cleaning is performed on the processed high entropy alloy and low temperature steel metal plates, and the interface to be welded is polished with sandpaper. After polishing, the interface to be welded is wiped with petroleum ether, and then blown dry immediately after wiping; Step 3: Butt the high entropy alloy and the low temperature steel metal plates along the toothed path, buckle them together along the thickness direction, place the assembled high entropy alloy and low temperature steel metal plates on a welding fixture, and place the welding fixture in the vacuum chamber of the electron beam welding machine; Step 4: Turn on the vacuum system. When the vacuum degree in the vacuum chamber reaches the preset value, start the electron gun and the motion system, select the corresponding welding parameters, control the electron beam to weld the high entropy alloy and the low-temperature steel along the toothed butt surface, and keep warm after the welding is completed; Step 5: After keeping warm, take out the workpiece and complete the welding of high entropy alloy and low temperature steel.

2. The method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure according to claim 1, characterized in that: In step 1, the interface to be welded is tooth-shaped, and the height and width of the teeth are greater than the width of the weld.

3. The method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure according to claim 1, characterized in that: In step 2, the ultrasonic frequency is 20 kHz, the ultrasonic cleaning time is 5 minutes, and the mesh number of the sandpaper is 1000-2000.

4. The method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure according to claim 1, characterized in that: In step 3, the docking interface is a tooth-shaped self-locking structure, the fillet radius of the tooth-shaped self-locking structure is 2.5 mm, the bevel angle is 80°, and the tooth width is 8 mm.

5. The method for electron beam welding high entropy alloy and low temperature steel based on toothed self-locking structure according to claim 1, characterized in that: The preset vacuum degree in the vacuum chamber in step 4 is 5×10 -2 Pa, the holding time is 10-20min, the acceleration voltage of the electron gun and the motion system is 60kV, the welding beam current is 20mA, and the welding speed is 10mm / s.

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