A method for electron beam welding of molybdenum joints using a c / re composite foil

Abstract

The application relates to a method for electron beam welding of molybdenum joints by using a C / Re composite foil, and belongs to the technical field of welding. The method is characterized in that a carbon film is plated on the section of molybdenum or / and molybdenum alloy by using a vacuum magnetron sputtering technology, Re foil is added in the electron beam welding process, and relevant processes are controlled, so that the purposes of rapid carburization and micro-zone alloying in the welding process are achieved; the C / Re composite film can also be prepared by using a method of magnetron sputtering of Re and C. The molybdenum joint prepared based on the above method has excellent performances such as high tensile strength and high hardness, the tensile strength can reach 496.85 MPa, the hardness of the welding seam area can reach 344 HV, and the method can be widely applied to the field of welding of refractory metals, and provides proper technical reference for the welding process development and engineering application of molybdenum alloy parts.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, and specifically relates to a method for adding carbon film and rhenium foil when electron beam welding molybdenum or / and molybdenum alloys. Background Technology

[0002] Molybdenum, a refractory metal, has a high melting point and high hardness. It also possesses high high-temperature strength, good electrical and thermal conductivity, a low coefficient of linear expansion, low high-temperature creep rate, and excellent wear resistance, making it widely used in defense, metallurgy, and nuclear industries. However, due to the hardness and brittleness of molybdenum and its alloys, welding is often affected by grain boundary impurities (especially oxygen) and recrystallization, resulting in poor weldability. This problem limits its widespread use in some demanding applications.

[0003] On the one hand, carburizing molybdenum alloy welded joints can significantly improve their mechanical properties. This is because the accumulation of carbon at grain boundaries can replace the enrichment of oxygen at grain boundaries, thereby reducing joint brittleness, increasing joint strength, and improving joint performance. However, traditional carburizing requires long-term (100-200 hours) carburizing treatment at high temperatures (not lower than 1200℃). This is not only inefficient, but the prolonged high-temperature aging also coarsens the grains of the base material, reducing its properties. On the other hand, utilizing the higher chemical activity of Re metal foil after high-temperature melting, it can be melt-alloyed with the powder metallurgy molybdenum matrix at the weld and mixed to form a solid solution. This solid solution refines the grains and hinders grain boundary migration, further improving performance through micro-area alloying.

[0004] This invention provides a method for improving welding performance by using composite foil in electron beam welding of molybdenum joints. It utilizes magnetron sputtering for rapid carburizing to improve welding efficiency, and further enhances welding performance through the combined action of Re and C. Summary of the Invention

[0005] The purpose of this invention is to provide a method for using C / Re composite foil for electron beam welding of molybdenum joints, which enables rapid and synchronous carburizing of the welding area during high-energy beam welding, greatly improving carburizing efficiency, and further enhancing the mechanical properties of the molybdenum alloy welded joint through the effect of Re micro-alloying.

[0006] The method for using C / Re composite foil for electron beam welding of molybdenum joints according to the present invention is implemented based on the following steps:

[0007] Step 1: Pre-treat the welding joint and Re foil material of the parts to be electron beam welded, wherein the material of the parts is molybdenum and / or molybdenum alloy;

[0008] Step 2: Sputter a carbon thin film onto the molybdenum or / and molybdenum alloy welding interface using magnetron sputtering technology, and then place a metallic Re foil at the weld seam to be welded; or prepare a C / Re composite thin film by co-sputtering Re and C using magnetron sputtering, and then perform electron beam welding;

[0009] Step 3: Control the relevant parameters and use electron beam welding to butt weld the molybdenum or / and molybdenum alloy sample prepared in Step 2. This allows for simultaneous carburizing and micro-alloying of the weld joint while electron beam welding of molybdenum or / and molybdenum.

[0010] Furthermore, the welded parts in step one can be thin plates, thin-walled tubes, or other complex components.

[0011] Furthermore, the specific pretreatment of the welding interface in step one is as follows: the welding interface of the parts to be welded is ground and polished, and then the polished parts are immersed in acetone solution for ultrasonic cleaning. The ultrasonic cleaning is performed at least three times, and the acetone solution is replaced after each ultrasonic cleaning. Each cleaning time is at least 10 minutes, and then the parts are dried. The specific pretreatment of the rhenium foil material is as follows: the rhenium foil is ground and then immersed in acetone solution for ultrasonic treatment, and the subsequent steps are the same.

[0012] Furthermore, in step two, the magnetron sputtering power is 200W, and the sputtering time is 0-4h. The thickness of the carbon film is generally not limited, and the sputtering time can be changed as needed. The thickness of the sputtered C film can be in the nanometer to micrometer range; the thickness of the Re foil is 0.1mm-0.5mm, and Re foil of different thicknesses can be added.

[0013] Furthermore, in step three, the electron beam welding is argon-protected vacuum electron beam welding. The welding process parameters can be selected as follows: accelerating voltage 55KV, focusing beam current 650mA-670mA, welding speed 700mm / min-900mm / min, and welding beam current 20mA-24mA.

[0014] The present invention has the following beneficial effects:

[0015] This invention discloses a method for using C / Re composite foil for electron beam welding of molybdenum joints. In specific operation, the interface of the molybdenum and / or molybdenum alloy joint and the rhenium foil are pretreated. Then, a carbon thin film is sputtered onto the molybdenum and / or molybdenum alloy welding interface using magnetron sputtering technology. Finally, Re foil material is added during the electron beam welding process, controlling relevant parameters. Alternatively, a C / Re composite thin film can be prepared using Re and C co-sputtering via magnetron sputtering for electron beam welding. At this time, molten pool stirring can be used to ensure that the sputtered carbon atoms are uniformly distributed within the weld pool, achieving simultaneous carburizing and micro-area alloying during electron beam welding, significantly improving the mechanical properties of the molybdenum and / or molybdenum alloy joint. The tensile strength of the joint welded using this method is improved by 240%–300%. Attached Figure Description

[0016] Figure 1 Schematic diagram of magnetron sputtering of carbon thin film at the interface of parts to be welded;

[0017] Figure 2 This is a schematic diagram of electron beam welding.

[0018] Figure 3 The hardness of the weld joints after welding pure molybdenum samples, samples with added Re foil, and C / Re composite foil films are given. Wherein, Mo is the Vickers hardness of the weld joint without any foil; Re = 0.1 is the Vickers hardness of the weld joint with a 0.1 mm thick Re foil; Re = 0.1C = 2h is the Vickers hardness of the weld joint after magnetron sputtering for 2 hours with the addition of a 0.1 mm thick Re foil; and Re = 0.1C = 4h is the Vickers hardness of the weld joint after magnetron sputtering for 4 hours with the addition of a 0.1 mm thick Re foil.

[0019] Figure 4 The tensile strength (1) and tensile strength numerical histogram (2) of the welded joints after welding pure molybdenum samples, samples with added Re foil, and C / Re composite foil are shown. Wherein, Mo is the tensile strength of the welded joint without any foil; Re = 0.1 is the tensile strength of the welded joint with 0.1 mm thick Re foil; Re = 0.1C = 2h is the tensile strength of the welded joint after magnetron sputtering for 2 hours with 0.1 mm thick Re foil; and Re = 0.1C = 4h is the tensile strength of the welded joint after magnetron sputtering for 4 hours with 0.1 mm thick Re foil.

[0020] Figure 5 The drawing shows the dimensions of the stretched part (1) and the cutting diagram of the stretched part (2). Detailed Implementation

[0021] The following is a further description through embodiments and in conjunction with figures, intended to better understand and illustrate the content of the present invention, but not limited to the following embodiments.

[0022] The method for using C / Re composite foil for electron beam welding of molybdenum joints according to the present invention includes the following steps:

[0023] Step 1: Pre-treat the welding interface and Re foil material of the electron beam welded parts, wherein the parts are made of molybdenum or molybdenum alloy;

[0024] Step 2: Sputter a carbon thin film onto the molybdenum or molybdenum alloy welding interface using magnetron sputtering technology; alternatively, a C / Re composite thin film can be prepared by Re and C co-sputtering using magnetron sputtering, followed by electron beam welding.

[0025] Step 3: Control the relevant parameters and use electron beam welding to weld the treated molybdenum or / and molybdenum alloy sample. This allows for rapid and simultaneous carburizing and micro-alloying of the weld joint while electron beam welding of molybdenum or / and molybdenum is being performed.

[0026] The welding parts in step 1) can be thin plates, thin-walled tubes or other complex components.

[0027] The specific pretreatment of the welding interface in step 1) is as follows: The welding interface of the parts to be welded is ground and polished. Then, the polished parts are immersed in an acetone solution for ultrasonic cleaning. The ultrasonic cleaning is performed at least three times, with the acetone solution replaced after each ultrasonic cleaning. Each cleaning session lasts at least 10 minutes. The parts are then dried. For Re foil material, the process involves grinding followed by ultrasonic treatment with acetone; the remaining steps are the same.

[0028] In step 2), the magnetron sputtering power is 200W, and the sputtering time is 0-4h. The Re foil thickness is 0.1mm-0.5mm.

[0029] In step 3), the electron beam welding is argon-protected vacuum electron beam welding, and its working parameters are: accelerating voltage 55KV, focusing beam current 668mA, welding speed 900mm / min, and welding beam current 22mA.

[0030] Example 1

[0031] Taking a commercial molybdenum thin plate electron beam welding joint as an example, with dimensions of 50*30*1.5mm and the welding interface in the width direction, the electron beam welding steps with C / Re composite foil are as follows:

[0032] Step 1: Grind the welding interface with 320#, 600#, 800#, and 1200# sandpaper in sequence. Grind the Re foil material with 1200# sandpaper. Then immerse the ground sample and Re foil in acetone solution and ultrasonically clean them at least three times. Replace the acetone solution after each cleaning. Each cleaning time should be no less than 10 minutes. Finally, blow the sample dry for later use.

[0033] Step 2: Add Re foil to the polished welding interface. The thickness of the Re foil should be 0.1mm.

[0034] Step 3: Electron beam welding is performed on molybdenum metal sheets with different thin films using the same process. The welding is butt welding, such as... Figure 2 As shown. Its operating parameters are: accelerating voltage 55KV, focused beam current 668mA, welding speed 900mm / min, and welding beam current 22mA; the properties measured after welding are: tensile strength 380.66MPa, and weld hardness 317.6HV.

[0035] Example 2

[0036] Taking a commercial molybdenum thin plate electron beam welding joint as an example, with dimensions of 50*30*1.5mm and the welding interface in the width direction, the electron beam welding steps with C / Re composite foil are as follows:

[0037] Step 1: Grind the welding interface with 320#, 600#, 800#, and 1200# sandpaper in sequence. Grind the Re foil material with 1200# sandpaper. Then immerse the ground sample and Re foil in acetone solution and ultrasonically clean them at least three times. Replace the acetone solution after each cleaning. Each cleaning time should be no less than 10 minutes. Finally, blow the sample dry for later use.

[0038] Step 2: Prepare a C-film on the polished weld interface using magnetron sputtering equipment. The magnetron sputtering power is 200W, and the sputtering time is 2 hours (C-film thickness is 290.3nm). Figure 1 As shown. Furthermore, a Re foil with a thickness of 0.1 mm is added at the welding interface.

[0039] Step 3: Electron beam welding is performed on molybdenum metal sheets with different thin films using the same process. The welding is butt welding, such as... Figure 2 As shown. Its operating parameters are: accelerating voltage 55KV, focused beam current 668mA, welding speed 900mm / min, and welding beam current 22mA; the properties measured after welding are: tensile strength 444.13MPa, and weld hardness 326.3HV.

[0040] Example 3

[0041] Taking a commercial molybdenum thin plate electron beam welding joint as an example, with dimensions of 50*30*1.5mm and the welding interface in the width direction, the electron beam welding steps with C / Re composite foil are as follows:

[0042] Step 1: Grind the welding interface with 320#, 600#, 800#, and 1200# sandpaper in sequence. Grind the Re foil material with 1200# sandpaper. Then immerse the ground sample and Re foil in acetone solution and ultrasonically clean them at least three times. Replace the acetone solution after each cleaning. Each cleaning time should be no less than 10 minutes. Finally, blow the sample dry for later use.

[0043] Step 2: Prepare a C film on the cross section of the polished welding interface using a magnetron sputtering device. The magnetron sputtering power is 200W and the sputtering time is 4h (C film thickness is 587.6nm). Add a Re foil at the welding interface with a thickness of 0.1mm.

[0044] Step 3: Electron beam welding is performed on molybdenum metal sheets with different thin films using the same process. The welding is butt welding, such as... Figure 2 As shown. Its operating parameters are: accelerating voltage 55KV, focused beam current 668mA, welding speed 900mm / min, and welding beam current 22mA; the properties measured after welding are: tensile strength 496.85MPa, and weld hardness 344HV.

[0045] Table 1 lists the different process parameters for specific embodiments.

[0046]

[0047] The hardness of samples welded after different sputtering times was measured using a Vickers hardness tester, where BM represents the base metal region, HAZ represents the heat-affected zone, and FZ represents the molten pool region. The hardness results are as follows: Figure 3 As shown, the hardness of the weld pool center significantly increased after electron beam welding with C / Re composite foil, reaching 350 HV, far exceeding the hardness of pure molybdenum butt welds, while the hardness of the heat-affected zone and the base material remained essentially unchanged. Tensile tests were further conducted on samples welded with different foil materials (see dimension diagram). Figure 5 The stretching results are as follows: Figure 4 As shown, the tensile strength of the weld after adding only 0.1 mm thick Re foil is 380.66 MPa; the tensile strength of the weld after magnetron sputtering C film for 2 h and 4 h with the addition of 0.1 mm Re foil is 444.13 MPa and 496.85 MPa, respectively; the strength of the original electron beam weld without any treatment is 110.27 MPa. The tensile strength of the composite C / Re foil is 240% to 350% higher than that of the original electron beam weld.

[0048] In summary, this invention enables C / Re composite foil to significantly enhance the hardness and tensile strength of molybdenum and molybdenum alloy joints during electron beam welding.

Claims

1. A method for electron beam welding of molybdenum joints using a C / Re composite foil, characterized in that, The method comprises the following steps: Step 1: Preprocessing the welding interface of the electron beam welding part and the Re foil material, wherein the part material is molybdenum or / and molybdenum alloy; Step 2: Sputtering a carbon film on the molybdenum or / and molybdenum alloy welding interface by using a magnetron sputtering technology, and then placing a metal Re foil on the molybdenum or / and molybdenum welding seam; or using a magnetron sputtering method to prepare a C / Re composite film by co-sputtering Re and C, and then performing electron beam welding; Step 3: Controlling relevant parameters, and using electron beam welding to butt weld the molybdenum or / and molybdenum alloy sample treated in step 2, so as to achieve the purpose of synchronous carburizing and micro-alloying of the welding joint while electron beam welding the molybdenum or / and molybdenum; The thickness of the Re foil is 0.1 mm; The magnetron sputtering power in step 2 is 200 W, and the sputtering time is 2-4 h.

2. The method of claim 1, wherein, The welding part in step 1 is in the form of a sheet or a thin-walled tube.

3. The method of claim 1, wherein, The specific operation of preprocessing the welding interface in step 1 is as follows: polishing the welding interface of the part to be welded, then soaking the polished part in an acetone solution for ultrasonic cleaning, wherein the number of ultrasonic cleaning is greater than or equal to 3, and the acetone solution is replaced after each ultrasonic cleaning, and the cleaning time is greater than or equal to 10 min each time, and then the part is dried; the specific operation of preprocessing the Re foil material is as follows: polishing the Re foil and then soaking it in an acetone solution for ultrasonic treatment, and the subsequent steps are the same.

4. The method of claim 1, wherein, The sputtering time can be changed as needed, and the thickness of the sputtered C film is in the nanometer to micrometer range.

5. The method of claim 1, wherein, In step 3, the electron beam welding is argon-protected vacuum electron beam welding; the welding process parameters are selected as follows: acceleration voltage 55 KV, focused beam current 650 mA-670 mA, welding speed 700 mm / min-900 mm / min, and welding beam current 20 mA-24 mA.

6. A welded body prepared according to the method of any one of claims 1-5.

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