Welding method of metal hafnium plate

Abstract

The invention relates to the technical field of nuclear materials. The invention discloses a welding method of a metal hafnium plate, which comprises the following steps of: pretreating a to-be-welded surface of the to-be-welded metal hafnium plate to obtain the treated to-be-welded metal hafnium plate; aligning the two treated metal hafnium plates to be welded in a first plane, and performing spot welding and fixing to obtain a test piece to be welded; and the to-be-welded test piece is fixed to a welding platform, and high-frequency oscillation scanning electron beam welding is conducted on the to-be-welded test piece in a vacuum electron beam welding machine. During vacuum electron beam welding, the electron beam high-frequency oscillation scanning process is added, stirring oscillation of a welding pool is achieved, effective overflow of internal gas is promoted, welding defects are reduced, a certain inhibiting effect on growth of crystal grains in a welding seam is achieved, and the mechanical property of the welding seam is improved.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear materials, and in particular to a welding method for a metal hafnium plate. Background Art

[0002] The neutron absorption cross section of hafnium metal is as high as 115b (1b = 1×10 -28 m 2 ), and its six isotopes all have high neutron absorption efficiency. When used under long-term irradiation conditions, its physical properties do not show a significant decrease trend. At the same time, it has excellent mechanical processing performance, good high-temperature corrosion resistance and oxidation resistance, and strong air absorption capacity. Therefore, metallic hafnium material is a very ideal neutron absorber material and is considered to be one of the best candidate materials for control rods for reactors at this stage.

[0003] Metal hafnium has a strong H, O, and N adsorption effect under high temperature conditions. During welding in an air environment, it is easy to cause the adsorption of more impurity elements such as H, O, and N in the weld and the formation of pore defects, which significantly reduces the weld performance. Therefore, choosing a suitable welding method is very important to ensure the performance of metal hafnium welds. The existing welding method is the traditional vacuum electron beam welding method, but due to the low content of alloy elements in metal hafnium materials, when the thickness of the welding base material is large, the welding heat input and post-weld cooling rate are large, and a large temperature gradient will be formed near the fusion line. The grains in the weld area grow significantly, which leads to a decrease in the mechanical properties of the welded joint. It is difficult to achieve high-quality connection of high-purity metal hafnium materials using traditional vacuum electron beam welding methods. Summary of the invention

[0004] In view of this, the present invention provides a welding method for a metal hafnium plate.

[0005] Specifically, the following technical solutions are included:

[0006] The present application provides a welding method for a metal hafnium plate, wherein a surface of the metal hafnium plate to be welded is pretreated to obtain the treated metal hafnium plate to be welded;

[0007] Aligning the two processed hafnium metal plates to be welded in a first plane, and fixing them by spot welding to obtain a test piece to be welded;

[0008] The test piece to be welded is fixed on a welding platform, and high-frequency oscillation scanning electron beam welding is performed on the test piece to be welded in a vacuum electron beam welding machine.

[0009] Preferably, the pre-treatment of the surface to be welded of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded comprises:

[0010] The surface to be welded is finely machined, and the roughness of the surface to be welded is less than or equal to 1.6 μm.

[0011] Preferably, the pre-treatment of the surface to be welded of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded comprises:

[0012] The surface to be welded is finely machined, and the straightness of the surface to be welded is less than or equal to 0.1 mm.

[0013] Preferably, the method of pre-treating the surface of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded further comprises:

[0014] The surface to be welded is ultrasonically degreased using a degreaser solution, and the degreasing time is greater than or equal to 30 minutes.

[0015] Preferably, the method of pre-treating the surface of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded further comprises:

[0016] The surface to be welded is ultrasonically cleaned and dried using deionized water.

[0017] Preferably, aligning and placing the two processed hafnium metal plates to be welded in a first plane and fixing them by spot welding to obtain a test piece to be welded comprises:

[0018] After the two treatments, the distortion amount of the metal hafnium plates to be welded in the thickness direction is less than or equal to 0.1 mm.

[0019] Preferably, the step of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welder comprises:

[0020] The acceleration voltage during vacuum electron beam welding is 50 kV to 60 kV, the current of the electron beam is 31 mA to 37 mA, the welding speed is 800 mm / min to 1200 mm / min, the distance from the surface to be welded to the electron gun is 200 mm to 400 mm, and the vacuum degree in the vacuum electron beam welding machine is less than or equal to 5×10 -2 Pa.

[0021] Preferably, the step of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welder further comprises:

[0022] The oscillation scanning frequency of the electron beam current is greater than or equal to 1000 Hz, and the oscillation scanning amplitude of the electron beam current is 0.3 mm to 0.7 mm.

[0023] Preferably, the step of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welder further comprises:

[0024] The test piece to be welded is fixed on a welding platform, and the first surface and the second surface of the test piece to be welded are welded in a vacuum electron beam welding machine.

[0025] Preferably, the thickness of the hafnium metal plate to be welded is 3-7 mm.

[0026] Preferably, the welding platform is located in a vacuum electron beam welding machine, and a tooling base, a clamping plate, and a clamping bolt are provided on the welding platform. The flatness of the tooling base is less than or equal to 0.1 mm, and an avoidance groove is provided on the tooling base;

[0027] The method of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welding machine also includes:

[0028] Placing the tooling base on the welding platform;

[0029] The test piece to be welded is placed on the tooling base, wherein the vertical plane where the weld seam of the test piece to be welded is located intersects with the plane where the bottom of the avoidance groove is located;

[0030] The clamping plate is placed on the specimen to be welded, and the clamping plate is clamped by the clamping bolts.

[0031] The beneficial effects of the technical solution provided by the present invention include at least:

[0032] The present application adds a high-frequency oscillation scanning electron beam process during vacuum electron beam welding to achieve a stirring effect on the welding molten pool, promote the escape of gas inside the molten pool, reduce the generation of welding defects, inhibit the growth of weld grains, and improve the mechanical properties of the welding weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 A schematic diagram of a welding method flow chart according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a pressing tool structure according to an embodiment of the present invention;

[0036] Figure 3 The figure is a schematic diagram of installing a test piece to be welded on a clamping fixture according to an embodiment of the present invention.

[0037] The above drawings have shown a clear embodiment of the present invention, which will be described in more detail below. These drawings and text descriptions are not intended to limit the scope of the present invention in any way, but to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Before further describing the embodiments of the present invention in detail, the directional nouns involved in the embodiments of the present invention, such as "upper part", "lower part", "side part", etc., are Figure 1 The directions shown in the figure are for reference only and do not limit the protection scope of the present invention.

[0040] To make the technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0041] As mentioned above, due to the low alloying element content of hafnium metal materials, the existing welding method has the technical problem that when the thickness of the welding base material is large, the welding heat input and the cooling rate after welding are large, a large temperature gradient will be formed near the fusion line, and the grains in the weld area will grow significantly, which will lead to the reduction of the mechanical properties of the welded joint. In order to solve the above technical problems, Figure 1 As shown, the present application provides a method for welding a metal hafnium plate, comprising:

[0042] S10: pre-treating the surface of the metal hafnium plate to be welded to obtain a treated metal hafnium plate to be welded.

[0043] S20: aligning and placing the two processed hafnium metal plates to be welded in a first plane, and fixing them by spot welding to obtain a test piece 4 to be welded.

[0044] S30: Fix the test piece 4 to be welded on a welding platform, and perform high-frequency oscillation scanning electron beam welding on the test piece 4 to be welded in a vacuum electron beam welding machine.

[0045] The present application adds an electron beam high-frequency oscillation scanning process during vacuum electron beam welding to achieve a stirring effect on the welding molten pool, achieve effective overflow of gas inside the molten pool and grain crushing, reduce the occurrence of welding defects, inhibit weld grain growth, and improve the mechanical properties of the welding weld.

[0046] Specifically, the step S10 of pre-treating the surface of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded includes:

[0047] S11: finishing the surface to be welded, wherein the roughness of the surface to be welded is less than or equal to 1.6 μm, and the straightness is less than or equal to 0.1 mm.

[0048] Specifically, the thickness of the metal hafnium plate to be welded by the welding method of the metal hafnium plate in this embodiment is 3-7 mm. Preferably, the thickness of the metal hafnium plate to be welded is 5 mm.

[0049] The surface to be welded is finely processed by a CNC machining center. The straightness of the surface to be welded is less than or equal to 0.1mm after processing. At the same time, attention should be paid to the matching of processing parameters and the processing cooling of the surface to be welded during the processing to avoid high temperature and surface oxidation during the processing of metal hafnium. The limitation of roughness ensures the welding quality of the weld. Too much roughness can easily cause the weld to penetrate deeply, uneven surface forming, and poor effect of high-frequency oscillation. The limitation of straightness ensures the stability of the focusing state during vacuum electron beam welding and improves the effect of high-frequency oscillation.

[0050] S12: ultrasonically degreasing the surface to be welded using a degreasing agent solution, and the degreasing time is greater than or equal to 30 minutes.

[0051] Specifically, during degreasing and cleaning, a degreasing agent solution is used to ultrasonically degrease the surface to be welded, and the ultrasonic degreasing time is ≥30 minutes to remove oil stains and residual coolant on the surface of the metal welding butt plate to be welded.

[0052] S13: using deionized water to ultrasonically clean and dry the surface to be welded.

[0053] Specifically, the surface to be welded is ultrasonically cleaned with hot deionized water to remove the degreasing agent solution on the surface to be welded.

[0054] Specifically, due to the high sensitivity of the welding process involving high-frequency oscillation, the surface cleanliness of the metal hafnium plate to be welded after pretreatment is required to be very high. If the cleanliness is not up to standard, welding defects are likely to occur. This embodiment can reduce foreign matter such as oil stains and residues remaining on the surface to be welded by ultrasonic degreasing, hot deionized water ultrasonic cleaning, and drying, which is conducive to reducing the defect rate of the weld and improving the mechanical properties of the welded joint.

[0055] Specifically, in step S20, the two processed hafnium metal plates to be welded are aligned and arranged in a first plane, and spot-welded to obtain a welded test piece 4, including:

[0056] S21: aligning the two processed hafnium metal plates to be welded in a first plane, wherein the misalignment amount of the two processed hafnium metal plates to be welded in a thickness direction is less than or equal to 0.1 mm.

[0057] Specifically, the first plane is a plane parallel to the welding platform, and in this embodiment, the first plane is a horizontal plane. The present application limits the straightness and distortion of the surface to be welded, which is a prerequisite for ensuring the stability of the focusing state during vacuum electron beam welding, and is also a guarantee for improving the high-frequency oscillation effect. When the surface straightness of the two hafnium metal plates to be welded is greater than 0.1 mm or the distortion is greater than 0.1 mm, it will cause the gap between the welds to be welded to be too large after assembly, and the surface focusing state near the welds to be welded will fluctuate, resulting in the focusing current being in a changing state during the welding process, which in turn leads to uneven penetration and surface forming of the entire weld.

[0058] S22: spot welding the two aligned and processed hafnium metal plates to be welded.

[0059] Specifically, after the two processed hafnium metal plates to be welded are precisely aligned, spot welding is performed on the butt weld in the alignment plane using a laser spot welding method with local argon protection to prevent local oxidation during the spot welding process.

[0060] Specifically, the step S30 of fixing the test piece 4 to be welded on the welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece 4 to be welded in a vacuum electron beam welding machine includes:

[0061] S31: Fix the test piece 4 to be welded on the welding platform.

[0062] Specifically, the welding platform is located in a vacuum electron beam welding machine, such as Figure 2 and Figure 3 As shown, the welding platform is provided with a tooling base 1, a clamping plate 2, and a clamping bolt 3, the flatness of the tooling base is less than or equal to 0.1 mm, and an avoidance groove is provided on the tooling base 1;

[0063] The steps of fixing the test piece 4 to be welded on the welding platform include:

[0064] Placing the tooling base 1 on the welding platform;

[0065] The test piece to be welded 4 is placed on the tooling base 1, wherein the vertical plane where the weld seam of the test piece to be welded 4 is located intersects with the plane where the bottom of the avoidance groove is located;

[0066] The clamping plate 2 is placed on the to-be-welded specimen 4, and the clamping plate 2 is clamped by the clamping bolts 3;

[0067] The tooling base 1 is fixed on the welding platform by the "convex" slot structure on the welding platform. The flatness of the tooling base 1 of the present application is to achieve good control of the welding deformation of the test piece 4 to be welded. The test piece 4 to be welded is in surface contact with the tooling base 1 and the clamping plate 2. The clamping bolt 3 is pressed down to the clamping plate 2 to achieve the clamping constraint of the test piece 4 to be welded, preventing the surface of the test piece 4 to be welded from being scratched. The use of this assembly method can ensure the surface quality of the test piece 4 to be welded, and at the same time, it can also achieve welding deformation control and prevent the occurrence of "V-shaped" bending deformation.

[0068] S32: performing high-frequency oscillation scanning electron beam welding on the test piece 4 to be welded in a vacuum electron beam welding machine.

[0069] Specifically, after the welded specimen 4 is placed in the welding vacuum chamber, the vacuum degree in the vacuum electron beam welding machine is less than or equal to 5×10 -2 Pa, the acceleration voltage during vacuum electron beam welding is 50kV~60kV, the current of the electron beam is 31mA~37mA, the welding speed is 800mm / min~1200mm / min, the distance from the surface to be welded to the electron gun is 200mm~400mm, and welding is performed after confirming the welding path through the cross cursor alignment.

[0070] Specifically, the oscillation scanning frequency of the electron beam is greater than or equal to 1000 Hz, and the oscillation scanning amplitude of the electron beam is 0.3 mm to 0.7 mm.

[0071] Specifically, in one embodiment, after the welded specimen 4 is placed in the welding vacuum chamber, the vacuum degree in the vacuum electron beam welding machine is evacuated to ≤5×10 -2 Pa, load the acceleration voltage of vacuum electron beam welding to 60kV, set the electron beam current to 35mA, welding speed to 1000mm / min, and the distance from the surface to be welded to the electron gun to 300mm. At the same time, the oscillation scanning frequency of the electron beam is 2000Hz, the oscillation scanning amplitude of the electron beam is 0.5mm, and the welding is carried out after confirming the welding path through the cross cursor alignment.

[0072] In this embodiment, by adding a high-frequency oscillation scanning process of an electron beam, a stirring and oscillating effect of the welding molten pool is achieved during the welding process, which promotes the effective overflow of tiny pore sources generated during the welding process, thereby effectively reducing the weld defect rate and optimizing the mechanical properties of the welded joint. At the same time, a double-sided welding forming process is adopted to achieve good connection of thick metal hafnium.

[0073] In this embodiment, in step S30, the test piece to be welded 4 is fixed on the welding platform, and high-frequency oscillation scanning electron beam welding is performed on the test piece to be welded 4 in a vacuum electron beam welder. The method also includes: fixing the test piece to be welded on the welding platform, and welding the first side and the second side of the test piece to be welded 4 in the vacuum electron beam welder.

[0074] Specifically, the method includes: fixing the test piece 4 to be welded on a welding platform, and performing high-frequency oscillation scanning electron beam welding on the first surface of the test piece 4 to be welded in a vacuum electron beam welding machine;

[0075] Remove the test piece 4 to be welded from the welding platform and turn it 180°;

[0076] The turned over test piece 4 to be welded is re-fixed on the welding platform, and high-frequency oscillation scanning electron beam welding is performed on the second surface of the test piece 4 to be welded in a vacuum electron beam welding machine.

[0077] The first surface and the second surface of the test piece 4 to be welded are arranged opposite to each other. In this embodiment, a double-sided welding process is adopted to achieve good connection between two thick hafnium metal plates.

[0078] The process flow of the application is simple, easy to implement, and has good feasibility and repeatability. It can be promoted and applied in the field of nuclear fuel, structural parts with metal hafnium as structural material, or other pure metal structural parts, and has good application prospects.

[0079] The welds using the welding method of this embodiment were inspected by ultrasonic, metallographic inspection and mechanical property testing. After testing, no defective ultrasonic echo signals were found, no defects were found in the metallographic inspection, and the tensile strength of the welded joint was ≥ 80% of the base material, indicating that the weld quality was good.

[0080] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The term "plurality" refers to two or more than two, unless otherwise clearly defined.

[0081] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The description and examples are to be considered exemplary only.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for welding a metal hafnium plate, characterized in that: Pre-treating the surface of the metal hafnium plate to be welded to obtain a treated metal hafnium plate to be welded; Aligning the two processed hafnium metal plates to be welded in a first plane, and fixing them by spot welding to obtain a test piece to be welded; The test piece to be welded is fixed on a welding platform, and high-frequency oscillation scanning electron beam welding is performed on the test piece to be welded in a vacuum electron beam welding machine.

2. A method for welding a metal hafnium plate according to claim 1, characterized in that: The method of pre-treating the surface of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded comprises: The surface to be welded is finely machined, and the roughness of the surface to be welded is less than or equal to 1.6 μm.

3. The method for welding a metal hafnium plate according to claim 1, characterized in that: The method of pre-treating the surface of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded comprises: The surface to be welded is finely machined, and the straightness of the surface to be welded is less than or equal to 0.1 mm.

4. The method for welding a metal hafnium plate according to claim 1, characterized in that: The method of pre-treating the surface of the metal hafnium plate to be welded to obtain the treated metal hafnium plate to be welded also includes: Ultrasonic degreasing is performed on the surface to be welded using a degreasing agent solution, and the degreasing time is greater than or equal to 30 minutes; The surface to be welded is ultrasonically cleaned and dried using deionized water.

5. The method for welding a metal hafnium plate according to claim 1, characterized in that: The method of aligning and placing two processed hafnium metal plates to be welded in a first plane and fixing them by spot welding to obtain a test piece to be welded comprises: After the two treatments, the distortion amount of the metal hafnium plates to be welded in the thickness direction is less than or equal to 0.1 mm.

6. The method for welding a metal hafnium plate according to claim 1, characterized in that: The step of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welding machine comprises: The acceleration voltage during vacuum electron beam welding is 50 kV to 60 kV, the current of the electron beam is 31 mA to 37 mA, the welding speed is 800 mm / min to 1200 mm / min, the distance from the surface to be welded to the electron gun is 200 mm to 400 mm, and the vacuum degree in the vacuum electron beam welder is less than or equal to 5×10 -2 Pa.

7. A method for welding a metal hafnium plate according to any one of claims 1 to 6, characterized in that: The method of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welding machine also includes: The oscillation scanning frequency of the electron beam is greater than or equal to 1000 Hz, and the oscillation scanning amplitude of the electron beam is 0.3 mm to 0.7 mm.

8. The method for welding a metal hafnium plate according to claim 1, characterized in that: The method of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welding machine also includes: The test piece to be welded is fixed on a welding platform, and the first surface and the second surface of the test piece to be welded are welded in a vacuum electron beam welding machine.

9. The method for welding a metal hafnium plate according to claim 1, characterized in that: The thickness of the hafnium metal plate to be welded is 3-7 mm.

10. The method for welding a metal hafnium plate according to claim 1, characterized in that: The welding platform is located in the vacuum electron beam welding machine, and is provided with a tooling base, a clamping plate, and a clamping bolt on the welding platform. The flatness of the tooling base is less than or equal to 0.1 mm, and an avoidance groove is provided on the tooling base; The method of fixing the test piece to be welded on a welding platform and performing high-frequency oscillation scanning electron beam welding on the test piece to be welded in a vacuum electron beam welding machine also includes: Placing the tooling base on the welding platform; The test piece to be welded is placed on the tooling base, wherein the vertical plane where the weld seam of the test piece to be welded is located intersects with the plane where the bottom of the avoidance groove is located; The clamping plate is placed on the specimen to be welded, and the clamping plate is clamped by the clamping bolts.

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