Ti35 / austenitic stainless steel dissimilar joint for nuclear spent fuel reprocessing equipment and method for manufacturing the same

Abstract

The application discloses a Ti35 / austenitic stainless steel heterogeneous connecting piece for nuclear spent fuel reprocessing equipment, which is obtained by inserting an austenitic stainless steel rod into a Ti35 pipe or inserting a Ti35 rod into an austenitic stainless steel pipe, then performing explosion composite welding, and finally performing machining, and a specific method is also disclosed, in which the Ti35 pipe and the austenitic stainless steel rod or the Ti35 rod and the austenitic stainless steel pipe are assembled after polishing, explosion composite welding is performed, and then machining is performed. The Ti35 / austenitic stainless steel heterogeneous connecting piece has a combination area of more than 99%, and a minimum shear strength of not less than 240 MPa, and has the high strength of Ti35 titanium alloy, the corrosion resistance to high-concentration boiling nitric acid, the intergranular corrosion resistance, the plasticity and the welding performance of the austenitic stainless steel, and solves the problems of low shear strength of single stainless steel pipe and self-corrosion caused by direct contact with corrosive medium.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar metal composite preparation technology for component connection structures of spent nuclear fuel reprocessing equipment, specifically relating to a Ti35 / austenitic stainless steel dissimilar connector for spent nuclear fuel reprocessing equipment and its preparation method. Background Technology

[0002] Explosive welding is a novel metal welding process and technology that integrates pressure welding, fusion welding, and diffusion welding, all powered by explosives. During the instantaneous explosion, the chemical energy of the explosive is largely converted into the kinetic energy of the composite material through multiple and repeated energy transfers, absorptions, conversions, and distributions (extremely brief, measured in microseconds). This causes the composite material to collide at high speed with the substrate, achieving a metallurgical bond between the substrate and the composite material, resulting in a corrugated interface. This technology fully utilizes the excellent properties of both the substrate and composite materials, such as corrosion resistance, acid and alkali resistance, and resistance to high and low temperatures, to rapidly achieve strong metallurgical bonding of any metal, especially dissimilar metals. It has been widely applied in chemical, petroleum, shipbuilding, military, nuclear, and aerospace industries.

[0003] Nuclear energy, as a new type of alternative energy source, is increasingly widely used, and the research and development of processing equipment after nuclear fuel shortages are receiving increasing attention. Components such as dissolvers, evaporators of highly radioactive waste acid, and nitric acid recoverers, which operate in high-concentration nitric acid equipment for extended periods, face particularly harsh service environments, making them a research challenge in recent years. The earliest used high-purity austenitic stainless steel is prone to intergranular passivation and intergranular corrosion in boiling nitric acid, and is far from meeting the technical requirements of the equipment. Therefore, developing alternative materials has become a major trend. Titanium-stainless steel composite materials are layered metal composite materials with pure titanium or titanium alloys and stainless steel components as the base and cladding materials, respectively. This type of material combines the advantages of titanium and titanium alloys with stainless steel while overcoming the shortcomings of single-material functions. It possesses excellent corrosion resistance, making it the best alternative. Currently, it is widely used in petroleum, chemical, medical, light industry, environmental protection, and aerospace fields, and is an indispensable structural material in modern chemical industry and pressure vessels.

[0004] However, current process parameters for preparing titanium-stainless steel composite pipes using explosive welding technology largely reference the welding process for titanium-steel explosive composite plates. To avoid the formation of intermetallic compounds such as TiC, FeTi, and Fe2Ti at the composite interface, which result in low interfacial bonding strength, an intermediate layer metal (such as niobium, molybdenum, nickel, silver, copper, vanadium, etc.) is generally added to prevent atomic diffusion between titanium and steel. The intermediate layer metal must not only effectively block the diffusion of Ti, Fe, and C atoms, but also must not react with titanium and steel to form intermetallic compounds, or the formed intermetallic compounds should cause minimal damage to the interface. While the addition of an intermediate layer metal can prevent the formation of TiC, FeTi, or Fe2Ti at the titanium / steel interface, it also introduces new problems. It not only increases raw material and production costs but also promotes relative sliding at the titanium-steel interface, which is detrimental to shape control. Furthermore, the addition of an intermediate layer metal can introduce new brittle phases or pores at the interface, making the interface situation more complex.

[0005] Therefore, there is an urgent need to develop or improve existing explosive composite welding technology to produce high-strength, corrosion-resistant titanium-stainless steel composite pipes in order to solve or mitigate the above problems. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a Ti35 / austenitic stainless steel dissimilar connector for nuclear spent fuel reprocessing equipment. This Ti35 / austenitic stainless steel dissimilar connector has a bonding area of ​​over 99%, a minimum shear strength of not less than 240 MPa, and combines the high strength and corrosion resistance to high-concentration boiling nitric acid of Ti35 titanium alloy with the intergranular corrosion resistance, plasticity, and weldability of austenitic stainless steel. This solves the problems of low shear strength and self-corrosion due to direct contact with corrosive media inherent in single stainless steel pipes.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a Ti35 / austenitic stainless steel heterogeneous connector for nuclear spent fuel reprocessing equipment, characterized in that the heterogeneous connector is obtained by explosive composite welding of Ti35 tube with austenitic stainless steel rod inserted in it or austenitic stainless steel tube with Ti35 rod inserted in it, followed by machining.

[0008] The Ti35 / austenitic stainless steel heterogeneous connector provided by this invention, wherein the Ti35 titanium alloy is an α-type corrosion-resistant titanium alloy, which can work for a long time in a boiling state of high-concentration oxidizing acidic solution (containing cations), but its cost is high. Austenitic stainless steel, as an important structural material, is widely used in the nuclear power industry. It can work in high-concentration acidic solutions, but it is not resistant to cation corrosion. Compared with Ti35 titanium alloy, it has a lower cost. The connector pipe using the composite of the two materials combines the characteristics of the base material and the composite material, meets the process requirements of the process equipment system, and reduces the cost of the system. It can be used to manufacture connection structures for equipment components such as pressure vessels, towers, kettles, tanks, and transition joints in petrochemical and nuclear chemical industries. Under the premise of no special requirements, the structure with austenitic stainless steel on the outside and Ti35 titanium alloy on the inside should be selected as much as possible, because the pipe diameter is larger when it is on the outside, and stainless steel is cheaper, thus reducing costs.

[0009] The aforementioned Ti35 / austenitic stainless steel dissimilar connector for spent nuclear fuel reprocessing equipment is characterized in that the Ti35 tubes and Ti35 bars, by mass percentage, satisfy the following: Ta 5.5%~6.5%, Fe≤0.15%, C≤0.08%, N≤0.03%, H≤0.01%, O≤0.15%, with the balance being titanium and unavoidable impurity elements; the austenitic stainless steel bars or tubes are of grade S30403 or S32168. Compared to traditional pure titanium materials, this invention, by adding 5.5%~6.5% by mass of tantalum (Ta), further reduces corrosion resistance costs. Ta can form an infinite solid solution with Ti, greatly enhancing the corrosion resistance of titanium alloys in reducing and oxidizing media while improving the strength of the titanium alloys. By using S30403 or S32168 austenitic stainless steel, it has the advantages of low carbon content, resistance to acid corrosion, and resistance to intergranular corrosion.

[0010] The aforementioned Ti35 / austenitic stainless steel dissimilar connector for spent nuclear fuel reprocessing equipment is characterized in that the wall thickness of the Ti35 tube and the austenitic stainless steel tube is greater than 2 mm, and the diameter of the Ti35 bar and the austenitic stainless steel bar is greater than 6 mm. This invention ensures the effectiveness of explosive composite welding by controlling the wall thickness of the Ti35 tube and the austenitic stainless steel tube, preventing defects such as cracking that occur during explosive composite welding due to insufficient wall thickness. It also ensures the effectiveness of explosive composite welding by controlling the diameter of the Ti35 bar and the austenitic stainless steel bar, preventing the problem that if the diameter is too small, the explosive shock wave will not easily bond them together, and the smaller the bar diameter, the more explosive material is required, resulting in a higher risk factor.

[0011] In addition, the present invention provides a method for preparing Ti35 / austenitic stainless steel dissimilar connectors for nuclear spent fuel reprocessing equipment, characterized in that the method includes the following steps: Step 1: Weigh out sponge titanium, tantalum powder, and titanium powder, and mix them to obtain the raw materials; Step 2: The raw materials obtained in Step 1 are melted in a vacuum consumable arc furnace to obtain Ti35 ingots. Then, the Ti35 ingots are subjected to rough forging, fine forging, extrusion and rolling in sequence to obtain Ti35 pipes or Ti35 bars. Step 3: Select austenitic stainless steel bars or austenitic stainless steel tubes; Step 4: Polish the surface of the Ti35 tube obtained in Step 2 and the austenitic stainless steel bar selected in Step 3, or the Ti35 bar obtained in Step 2 and the austenitic stainless steel tube selected in Step 3. Step 5: Assemble the polished Ti35 pipe and austenitic stainless steel bar from Step 4, or the polished austenitic stainless steel pipe and Ti35 bar from Step 4, and then place them inside the blast-resistant container. Next, evenly apply grease to the outer surface of the Ti35 pipe or austenitic stainless steel pipe. Then, place explosives in the gap between the Ti35 pipe or austenitic stainless steel pipe and the blast-resistant container, and then perform explosive composite welding. Finally, perform machining to obtain the Ti35 / austenitic stainless steel dissimilar connector.

[0012] In this invention, Ti35 pipes or Ti35 bars are first prepared, and austenitic stainless steel bars or austenitic stainless steel pipes are selected. Then, the Ti35 pipes and austenitic stainless steel bars are assembled and explosively composite welded. Finally, they are machined to obtain a Ti35 pipe / austenitic stainless steel bar heterogeneous connector with Ti35 on the outside and austenitic stainless steel on the inside. Alternatively, Ti35 bars and austenitic stainless steel pipes are assembled and explosively composite welded, and finally machined to obtain an austenitic stainless steel pipe / Ti35 bar heterogeneous connector with austenitic stainless steel on the outside and Ti35 on the inside.

[0013] In this invention, the machining process involves opening a hole in the center of the product obtained after explosive composite welding, so that the Ti35 / austenitic stainless steel dissimilar connector is formed by Ti35 pipe wrapping austenitic stainless steel pipe or austenitic stainless steel pipe wrapping Ti35 pipe, and the upper part of the outer layer material is removed, and the inner layer material in the opposite direction is removed, to obtain a Ti35 / austenitic stainless steel dissimilar connector in the form of a pipe joint.

[0014] The above method is characterized in that the sponge titanium in step one is grade 0, with a grade of MHT-100 and a size of 0.83mm~12.7mm; the tantalum powder is FTa-01 metallurgical grade, with a size no larger than -325 mesh; and the titanium powder is grade TP200-1, with a size no larger than -200 mesh and a Mg content no larger than 0.1%. This invention ensures the quality of Ti35 / austenitic stainless steel dissimilar connectors by controlling the grade and size of the raw materials.

[0015] The method described above is characterized in that the melting process in step two is repeated at least three times. This invention ensures the uniformity of the Ti35 ingot through multiple melting processes.

[0016] The method described above is characterized in that the polishing in step four is polishing until the surface roughness is no greater than Ra1.6μm. This invention, by controlling the surface roughness, enables Ti35 tubing and austenitic stainless steel bars, or Ti35 bars and austenitic stainless steel tubing, to have better surface roughness, resulting in a higher area bonding law and improving product qualification rate.

[0017] The above method is characterized in that, in step five, there is a gap of 2mm to 6mm between the assembled Ti35 pipe and the austenitic stainless steel bar, or between the austenitic stainless steel pipe and the Ti35 bar, and a steel cap is installed on the top of the assembled Ti35 pipe and the austenitic stainless steel bar, or between the austenitic stainless steel pipe and the Ti35 bar. This invention limits the gap between the pipe and the bar, ensuring a tight fit between them and effectively preventing deformation after explosive bonding. By completely covering the Ti35 pipe or the austenitic stainless steel pipe with a steel cap, explosives are prevented from entering the bonding surface, thus ensuring the effectiveness of the explosive bonding weld.

[0018] The method described above is characterized in that a pad is provided at the bottom of the explosion-proof container in step five. The pad serves as an isolation layer, facilitating the removal of the prepared Ti35 / austenitic stainless steel dissimilar connector.

[0019] The above method is characterized in that, in step five, the detonator is placed at the top of the blast-resistant container during the explosive composite welding, and the explosive is TNT with a detonation velocity of 2300 m / s to 2500 m / s. This invention uses TNT to replace the rock emulsion explosive commonly used in titanium-steel composite plates. TNT has a high detonation velocity and high energy, enabling strong metallurgical bonding of the base and composite materials in a very short time or almost instantaneously, ensuring the quality of the Ti35 / austenitic stainless steel dissimilar connector.

[0020] Compared with the prior art, the present invention has the following advantages: 1. The Ti35 / austenitic stainless steel heterogeneous connector of the present invention has a bonding area of ​​over 99% and a minimum shear strength of not less than 240MPa. It combines the high strength and corrosion resistance to high-concentration boiling nitric acid of Ti35 titanium alloy with the intergranular corrosion resistance, plasticity, and weldability of austenitic stainless steel. It solves the problems of low shear strength and self-corrosion caused by direct contact with corrosive media in single stainless steel pipes. It greatly reduces the cost of using titanium alone to manufacture pressure vessel connecting structures in nuclear spent fuel reprocessing. With the continuous progress of equipment manufacturing technology in my country, the application fields of Ti35 / austenitic stainless steel composite materials will continue to expand, making practical engineering applications more economical.

[0021] 2. Compared to traditional pure titanium materials, this invention adds 5.5%~6.5% by mass of tantalum (Ta), further reducing corrosion resistance costs. Ta can form an infinite solid solution with Ti, greatly enhancing the corrosion resistance of the titanium alloy in both reducing and oxidizing media while improving its strength. By using S30403 or S32168 austenitic stainless steel, it possesses advantages such as low carbon content, resistance to acid corrosion, and resistance to intergranular corrosion, exhibiting high strength, corrosion resistance, and good thermal stability.

[0022] 3. Compared with conventional explosive composite welding methods that add an intermediate metal layer, the present invention can prepare Ti35 / austenitic stainless steel heterogeneous connectors without adding any intermediate metal layer. This can effectively reduce material and cost input, reduce unnecessary intermetallic compound formation, ensure the strength of the composite interface, and avoid the occurrence of self-corrosion of the bonding surface metal. Compared with titanium alloy / stainless steel composite pipe joints prepared by traditional rolling and friction welding methods, the composite pipe prepared by the explosive composite welding method has advantages such as large bonding area, high bonding strength, and high production efficiency.

[0023] 4. This invention limits the gap between the assembled Ti35 tube and the austenitic stainless steel bar, or between the austenitic stainless steel tube and the Ti35 bar, so that the bar and the tube fit tightly together, effectively avoiding deformation after explosive bonding.

[0024] 5. In explosive composite welding, this invention uses TNT explosives to replace the rock emulsion explosives commonly used in titanium-steel composite plates. TNT explosives have high detonation velocity and high energy, which can complete the strong metallurgical bond between the matrix and composite materials in a very short time or almost instantaneously. Moreover, the interface between the matrix and composite materials does not produce intermediate phases or intermetallic compounds. This not only avoids the increase in materials and costs, but also results in materials with high interfacial bonding strength and excellent corrosion resistance in extreme corrosive environments, avoiding the occurrence of internal metal corrosion, and exhibiting excellent comprehensive performance.

[0025] 6. This invention improves the surface properties of Ti35 / austenitic stainless steel dissimilar connectors by applying butter to prevent surface overheating.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the austenitic stainless steel tube and Ti35 bar assembled in Embodiment 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the Ti35 / austenitic stainless steel heterogeneous connector prepared in Example 1 of the present invention.

[0029] Figure 3 This is a SEM image of the connection between Ti35 and austenitic stainless steel in the Ti35 / austenitic stainless steel heterojunction prepared in Example 1 of the present invention.

[0030] Figure 4 This is a schematic diagram of the structure of Ti35 tube and austenitic stainless steel bar assembled in Embodiment 2 of the present invention.

[0031] Figure 5 This is a schematic diagram of the structure of the Ti35 / austenitic stainless steel heterogeneous connector prepared in Embodiment 2 of the present invention. Detailed Implementation

[0032] Example 1 This embodiment includes the following steps: Step 1: Weigh out sponge titanium, tantalum powder, and titanium powder, and mix them to obtain raw materials; the sponge titanium is grade 0, brand name MHT-100, and has a size of 0.83mm~12.7mm; the tantalum powder is FTa-01 metallurgical grade, with a size no larger than -325 mesh; the titanium powder is brand name TP200-1, with a size no larger than -200 mesh, and a Mg content no larger than 0.1% by mass. Step 2: The raw materials obtained in Step 1 are smelted three times in a vacuum consumable arc furnace to obtain Ti35 ingots. Then, the Ti35 ingots are subjected to rough forging, fine forging, and rolling in sequence to obtain Ti35 bars with a diameter of 30mm. The composition of the Ti35 bars, by mass percentage, is as follows: Ta 5.5%, Fe 0.15%, C 0.08%, N 0.03%, H 0.01%, O 0.12%, with the balance being titanium and unavoidable impurity elements. Step 3: Select austenitic stainless steel pipe with a wall thickness of 6mm and a grade of S30403 (022Cr19Ni10). Step 4: Polish the surfaces of the Ti35 bar obtained in Step 2 and the austenitic stainless steel tube selected in Step 3 until the surface roughness is no greater than Ra1.6μm; Step 5: Assemble the polished austenitic stainless steel tube and Ti35 bar from Step 4. There should be a 6mm gap between the assembled austenitic stainless steel tube and Ti35 bar. Then, place them into an blast-resistant container with a pad at the bottom. Next, evenly apply grease to the outer surface of the austenitic stainless steel tube. Then, place TNT explosives in the gap between the austenitic stainless steel tube and the blast-resistant container. Add a steel cover to the top and then perform explosive composite welding at a detonation velocity of 2300m / s. Finally, level, trim, and machine to shape the austenitic stainless steel outer Ti35-clad Ti35 heterogeneous connector.

[0033] Figure 1 This is a schematic diagram of the structure of the austenitic stainless steel tube and Ti35 bar assembled in this embodiment. Figure 1 As can be seen, Ti35 bars are inserted into austenitic stainless steel tubes, with a gap between them.

[0034] Figure 2 This is a schematic diagram of the structure of the Ti35 / austenitic stainless steel heterogeneous connector prepared in this embodiment. Figure 2 As can be seen from the above, the Ti35 / austenitic stainless steel heterogeneous connector prepared in this embodiment has a Ti35 titanium alloy tube with a size of 26.7mm×2.87mm (diameter×height) and an austenitic stainless steel tube with a size of 32.5mm×2.87mm (diameter×height), and the Ti35 titanium alloy extends beyond the austenitic stainless steel.

[0035] Figure 3 This is a SEM image of the Ti35 / austenitic stainless steel dissimilar connector prepared in this embodiment, showing the connection between Ti35 and austenitic stainless steel. Figure 3 As can be seen, there are usually periodic ripples on the bonding surface after explosive bonding. The wavy bonding ensures the bonding strength of the interface. There are also vortices at the wavy bonding. During the explosive bonding process, the material in the vortex is in a molten state, and an intermediate compound formed by Fe and Ti elements is formed here.

[0036] Example 2 This embodiment includes the following steps: Step 1: Weigh out sponge titanium, tantalum powder, and titanium powder, and mix them to obtain raw materials; the sponge titanium is grade 0, brand name MHT-100, and has a size of 0.83mm~12.7mm; the tantalum powder is FTa-01 metallurgical grade, with a size no larger than -325 mesh; the titanium powder is brand name TP200-1, with a size no larger than -200 mesh, and a Mg content no larger than 0.1% by mass. Step 2: The raw materials obtained in Step 1 are smelted three times in a vacuum consumable arc furnace to obtain Ti35 ingots. Then, the Ti35 ingots are subjected to rough forging, fine forging, extrusion, and rolling in sequence to obtain Ti35 pipes with a wall thickness of 8mm. The composition of the Ti35 pipes, by mass percentage, meets the following requirements: Ta 6%, Fe 0.09%, C 0.05%, N 0.03%, H 0.005%, O 0.10%, with the balance being titanium and unavoidable impurity elements. Step 3: Select austenitic stainless steel bar with a diameter of 76mm and a grade of S32168 (06Cr18Ni11Ti). Step 4: Polish the Ti35 tube obtained in Step 2 and the austenitic stainless steel bar selected in Step 3 until the surface roughness is no greater than Ra1.6μm; Step 5: Assemble the polished Ti35 tube and austenitic stainless steel bar from Step 4. There is a 3mm gap between the assembled Ti35 tube and austenitic stainless steel bar. Then, place them into an blast-resistant container with a pad at the bottom. Next, evenly apply grease to the outer surface of the Ti35 tube. Then, place TNT explosives in the gap between the Ti35 tube and the blast-resistant container. Add a steel cover to the top and then perform explosive composite welding at a detonation velocity of 2400m / s. Finally, level, trim, and machine to shape the Ti35 / austenitic stainless steel heterogeneous connector.

[0037] Figure 4 This is a schematic diagram of the structure of the Ti35 tube and austenitic stainless steel bar assembled in this embodiment. Figure 4 As can be seen, austenitic stainless steel bars are inserted into Ti35 tubes.

[0038] Figure 5 This is a schematic diagram of the structure of the Ti35 / austenitic stainless steel heterogeneous connector prepared in this embodiment. Figure 5 As can be seen from the above, the Ti35 / austenitic stainless steel heterogeneous connector prepared in this embodiment has a Ti35 titanium alloy tube with a specification of 73mm×5.16mm (diameter×height) and an austenitic stainless steel tube with a size of 83.4mm×5.16mm (diameter×height), and the austenitic stainless steel extends beyond the Ti35 titanium alloy.

[0039] Example 3 This embodiment includes the following steps: Step 1: Weigh out sponge titanium, tantalum powder, and titanium powder, and mix them to obtain raw materials; the sponge titanium is grade 0, brand name MHT-100, and has a size of 0.83mm~12.7mm; the tantalum powder is FTa-01 metallurgical grade, with a size no larger than -325 mesh; the titanium powder is brand name TP200-1, with a size no larger than -200 mesh, and a Mg content no larger than 0.1% by mass. Step 2: The raw materials obtained in Step 1 are smelted three times in a vacuum consumable arc furnace to obtain Ti35 ingots. Then, the Ti35 ingots are subjected to rough forging, fine forging, and rolling in sequence to obtain Ti35 bars with a diameter of 170 mm. The composition of the Ti35 bars, by mass percentage, is as follows: Ta 6.5%, Fe 0.15%, C 0.08%, N 0.03%, H 0.004%, O 0.08%, with the balance being titanium and unavoidable impurity elements. Step 3: Select austenitic stainless steel pipe with a wall thickness of 10mm and a grade of S30403 (022Cr19Ni10). Step 4: Polish the surfaces of the Ti35 bar obtained in Step 2 and the austenitic stainless steel tube selected in Step 3 until the surface roughness is no greater than Ra1.6μm; Step 5: Assemble the polished austenitic stainless steel tube and Ti35 bar from Step 4. There should be a 2mm gap between the assembled austenitic stainless steel tube and Ti35 bar. Then, place them into an blast-resistant container with a pad at the bottom. Next, evenly apply grease to the outer surface of the austenitic stainless steel tube. Then, place TNT explosives in the gap between the austenitic stainless steel tube and the blast-resistant container. Add a steel cover to the top and then perform explosive composite welding at a detonation velocity of 2500m / s. Finally, level, trim, and machine to shape the austenitic stainless steel outer Ti35-clad Ti35 heterogeneous connector.

[0040] Upon testing, the Ti35 titanium alloy tube in the Ti35 / austenitic stainless steel heterogeneous connector prepared in this embodiment has a size of 168.3mm × 7.11 (diameter × height), and the austenitic stainless steel tube has a size of 182.5mm × 7.11 (diameter × height), with the Ti35 titanium alloy extending beyond the austenitic stainless steel.

[0041] The Ti35 / austenitic stainless steel heterojunctions prepared in Examples 1-3 were tested for hardness using an HVS-50 Vickers hardness tester with a load of 1 kg. The average value was taken after 5 points were marked. The test results are shown in Table 1.

[0042] The Ti35 / austenitic stainless steel dissimilar connectors prepared in Examples 1-3 were subjected to tensile tests using an electronic universal testing machine. The nominal section size of the samples was 1-2×5×30mm. The average values ​​of tensile strength, yield strength and elongation of three samples with the same treatment were taken. The test results are shown in Table 1.

[0043] The corrosion current of the Ti35 / austenitic stainless steel dissimilar connectors prepared in Examples 1-3 was measured using a P4000 electrochemical workstation. The test conditions were as follows: the corrosion surface area was 1 cm². 2 Using the Ti35 / austenitic stainless steel dissimilar connectors prepared in Examples 1-3 as working electrodes, a saturated calomel electrode as a reference electrode, and a platinum sheet as an auxiliary electrode, the electrolyte containing 0.8 mol / L nitric acid was heated to boiling in a water bath, and hydrogen gas was introduced into the electrolyte at a flow rate of 20 mL / min. Linear potential scans were performed on the samples at a scan rate of 2 mV / s. The average value was taken after measuring three samples, and the experimental results are shown in Table 1.

[0044] The interfacial shear strength of the Ti35 / austenitic stainless steel heterojunctions prepared in Examples 1-3 was tested. The average value was taken after measuring 3 samples. The test results are shown in Table 1.

[0045] Table 1

[0046] As shown in Table 1, the Ti35 / austenitic stainless steel dissimilar connectors prepared by this invention possess high hardness and strength, as well as excellent corrosion resistance. Specifically, the highest hardness reaches 301 HV, the highest tensile strength reaches 417 MPa, the highest yield strength reaches 310 MPa, the maximum elongation is 41%, and the minimum corrosion current is 0.69 μA / cm. 2 Its highest shear strength is 412.8 MPa.

[0047] The Ti35 / austenitic stainless steel dissimilar connectors prepared in Examples 1-3 were subjected to ultrasonic testing. The testing results showed that the bonding rate of the Ti35 / austenitic stainless steel dissimilar connectors prepared in Examples 1-3 was greater than 99.8%. According to GJB3797-2015, the tensile shear strength of the interface was tested, and the tensile shear strength of the interface was greater than 350.0 MPa.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing Ti35 / austenitic stainless steel dissimilar connectors for nuclear spent fuel reprocessing equipment, characterized in that, The method includes the following steps: Step 1: Weigh out sponge titanium, tantalum powder, and titanium powder, and mix them to obtain the raw materials; Step 2: The raw materials obtained in Step 1 are melted in a vacuum consumable arc furnace to obtain Ti35 ingots. Then, the Ti35 ingots are subjected to rough forging, fine forging, extrusion and rolling in sequence to obtain Ti35 pipes or Ti35 bars. Step 3: Select austenitic stainless steel bars or austenitic stainless steel tubes; Step 4: Polish the surface of the Ti35 tube obtained in Step 2 and the austenitic stainless steel bar selected in Step 3, or the Ti35 bar obtained in Step 2 and the austenitic stainless steel tube selected in Step 3. Step 5: Assemble the polished Ti35 tubing and austenitic stainless steel bar from Step 4, or the polished austenitic stainless steel tubing and Ti35 bar from Step 4, and place them inside an explosion-proof container. Then, evenly apply grease to the outer surface of the Ti35 tubing or austenitic stainless steel tubing. Next, place explosives in the gap between the Ti35 tubing or austenitic stainless steel tubing and the explosion-proof container, and then perform explosive composite welding. Finally, machine to obtain a Ti35 / austenitic stainless steel dissimilar connector. A gap of 2mm to 6mm exists between the assembled Ti35 tubing and austenitic stainless steel bar, or the austenitic stainless steel tubing and Ti35 bar. A steel cap is installed on the top of the assembled Ti35 tubing and austenitic stainless steel bar, or the austenitic stainless steel tubing and Ti35 bar. In the explosive composite welding, the detonator is placed at the top of the explosion-proof container, and the explosive is TNT with a detonation velocity of 2300m / s to 2500m / s.

2. The method for preparing Ti35 / austenitic stainless steel dissimilar connectors for nuclear spent fuel reprocessing equipment according to claim 1, characterized in that, The sponge titanium mentioned in step one is grade 0, brand name MHT-100, and has a size of 0.83mm~12.7mm; the tantalum powder is FTa-01 metallurgical grade, with a size no larger than -325 mesh; the titanium powder is brand name TP200-1, with a size no larger than -200 mesh, and a Mg content no larger than 0.1%.

3. The method for preparing Ti35 / austenitic stainless steel dissimilar connectors for nuclear spent fuel reprocessing equipment according to claim 1, characterized in that, The smelting process described in step two is repeated at least three times.

4. The method for preparing Ti35 / austenitic stainless steel dissimilar connectors for nuclear spent fuel reprocessing equipment according to claim 1, characterized in that, The polishing described in step four refers to polishing until the surface roughness is no greater than Ra1.6μm.

5. The method for preparing Ti35 / austenitic stainless steel dissimilar connectors for nuclear spent fuel reprocessing equipment according to claim 1, characterized in that, A pad is installed at the bottom of the explosion-proof container described in step five.

6. A Ti35 / austenitic stainless steel dissimilar connector for a spent nuclear fuel reprocessing facility prepared according to claim 1, characterized in that, The heterogeneous connector is obtained by explosive composite welding of Ti35 tubes with austenitic stainless steel bars inserted or austenitic stainless steel tubes with Ti35 bars inserted, followed by machining.

7. The Ti35 / austenitic stainless steel dissimilar connector for nuclear spent fuel reprocessing equipment according to claim 6, characterized in that, The composition of the Ti35 tubes and Ti35 bars, by mass percentage, meets the following requirements: Ta 5.5%~6.5%, Fe≤0.15%, C≤0.08%, N≤0.03%, H≤0.01%, O≤0.15%, with the balance being titanium and unavoidable impurity elements; the grade of the austenitic stainless steel bars or tubes is S30403 or S32168.

8. The Ti35 / austenitic stainless steel dissimilar connector for nuclear spent fuel reprocessing equipment according to claim 6, characterized in that, The wall thickness of the Ti35 tube and the austenitic stainless steel tube is greater than 2 mm, and the diameter of the Ti35 bar and the austenitic stainless steel bar is greater than 6 mm.

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