Mechanical meshing auxiliary diffusion bonding rod-shaped tungsten alloy / steel composite part and preparation method thereof

Abstract

The invention relates to a mechanical meshing auxiliary diffusion bonding rod-shaped tungsten alloy / steel composite part and a preparation method thereof. The tungsten alloy-steel composite part is divided into two parts, namely a tungsten alloy inner core and a steel shell, and a composite interface of the tungsten alloy-steel composite part is metallurgical bonding assisted by mechanical meshing. The preparation process comprises the steps of determining the sizes of the tungsten alloy inner core and the steel outer sleeve, prefabricating a mechanical meshing structure and cleaning the surface, depositing metal on the middle layer of the surface to be welded and performing secondary cleaning, and performing mechanical meshing and hot isostatic pressure diffusion bonding on raw materials. And the preparation of the mechanical meshing auxiliary diffusion bonding rod-shaped tungsten alloy-steel composite part is completed. The material is reasonable in structure, the preparation method is simple, integrated preparation of the rod-shaped tungsten alloy / steel composite part with the high interface bonding strength under the low surface requirement is achieved, the problems of stress concentration and unstable co-sintering interface strength of existing threaded connection are solved, and the service life of the rod-shaped tungsten alloy / steel composite part is prolonged. The material and the preparation method designed by the invention are convenient for industrial production and application.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of tungsten alloy and steel composite components, and in particular relates to a preparation method for diffusion connection of a rod-shaped tungsten alloy / steel composite component assisted by mechanical engagement. Background Art

[0002] With the development of modern kinetic weapons, traditional steel kinetic weapons are difficult to meet the needs of attacking deep hidden targets due to their low surface density. Nowadays, one solution is to combine the high-density tungsten alloy core with the high-strength steel shell to prepare a composite warhead with higher surface density while reducing the sacrifice of charge as much as possible. This poses a challenge to the connection between tungsten alloy and steel. The main connection methods between these two metals are mechanical connection, diffusion connection, brazing connection and co-sintering.

[0003] Mechanical connection is the simplest connection method, and the two materials can be treated to the best performance state by heat treatment and other methods before connection. The components can be connected directly with threads, or with rivets, bolts and other connecting parts, but threaded connection will cause micro cracks inside the components, which will become the source of crack initiation during service and limit the maximum speed of the warhead; using connecting parts for connection requires prefabricated connection structures, which increases the useless volume of components and is difficult to avoid stress concentration (stress concentration caused by rivet holes, threaded holes, etc.). In addition, mechanical connection can only achieve partial directional force transmission, and it is difficult to fully exert the performance of the two materials at the same time.

[0004] Diffusion bonding is a method of metallurgically bonding tungsten alloy and steel under certain pressure and temperature. The literature "Wang, Y., et al., Interfacial structure and formation mechanism of tungsten / steel HIP diffusion bonding joints using Ni interlayer. Journal of Manufacturing Processes, 2020.52: p.235-246" uses diffusion bonding to connect tungsten alloy and steel with different surface roughness, proving that the joint strength of diffusion bonding is extremely sensitive to surface quality, and only a very low surface roughness can obtain ideal interface bonding strength; in addition, for complex rod-type or inner hole structures, it is difficult to process the surface, resulting in difficulty in obtaining laboratory-level interface bonding strength in actual industrial production.

[0005] Co-sintering is to combine tungsten alloy and steel green body, and then use HIP and other methods under the same temperature and pressure system to achieve one-time molding of the composite structure, which can achieve better metallurgical bonding of tungsten alloy / steel interface, and can also prepare more complex parts. Document CN113953512B discloses a preparation method for tungsten alloy / steel composite shell materials with large aspect ratio, but due to the different shrinkage degrees of different powders, the scrap rate is high and the dynamic balance of the sample is difficult. So far, it has not been possible to stably control the process to achieve mass production.

[0006] Brazing uses the melting and wetting of brazing filler metal to achieve the connection between tungsten alloy and steel. The literature "Kalin, BA, et al., Development of brazing foils to join monocrystalline tungsten alloys with ODS-EUROFER steel. 2007. 367: p. 1218-1222" and "Basuki, WW and J. Aktaa, Diffusion bonding between W and EUROFER97 using V interlayer. Journal of Nuclear Materials, 2012. 429 (1-3): p. 335-340" respectively use Ni-based, Ti-based and Fe-based brazing filler metals to achieve the welding of tungsten and steel. However, the brazing temperature (1150°C) is too high, which will cause the grain coarsening of the steel to be obvious, seriously affecting the performance of the components.

[0007] Therefore, there is an urgent need in the art for a method for preparing a rod-type tungsten alloy / steel composite component with high efficiency, low cost and high reliability. Summary of the invention

[0008] In order to solve the shortcomings of the existing rod-shaped tungsten alloy / steel composite component connection technology, the present invention combines the two methods of mechanical connection and diffusion connection to invent a preparation method for diffusion connection of rod-shaped tungsten alloy-steel composite components assisted by mechanical engagement, which is completely different from the preparation method of the prior art. The preparation method effectively improves the interface bonding strength of the rod-shaped tungsten alloy / steel composite components, reduces surface processing requirements, and improves the success rate of component preparation. The preparation process is simple and can be industrialized for mass production.

[0009] The present invention further improves the interface tensile strength of the product by optimizing the structural dimensions of the bonding surface and matching appropriate bonding materials and process parameters.

[0010] The present invention discloses a mechanically meshed assisted diffusion-bonded tungsten alloy / steel rod-shaped composite component, which comprises a steel outer shell, an intermediate layer, and a tungsten alloy inner core; the intermediate layer is located between the steel outer shell and the tungsten alloy inner core and the intermediate layer is in direct contact with the steel outer shell and the tungsten alloy inner core; before diffusion bonding, the inner cavity of the steel outer shell is provided with threads, and the outer surface of the tungsten alloy inner core is provided with threads matching the threads of the inner cavity of the steel outer shell; the threads are one of rectangular threads, trapezoidal threads, and triangular threads, the thread length is less than or equal to the sample length, the area of ​​the thread zone is less than or equal to the outer surface of the tungsten alloy inner core, the thread depth is 0.2-1.5 mm, preferably 0.35-1 mm, and the pitch is 0.2-1.5 mm, preferably 0.25-1 mm.

[0011] The tungsten content of the tungsten alloy is between 50% and 99% by mass, the impact energy is not less than 20J, and the elongation after fracture is not less than 10%. When used, the tungsten alloy can be a commercial tungsten alloy, such as tungsten-nickel-iron, tungsten-nickel-copper and other derivative systems.

[0012] The present invention discloses a mechanical meshing assisted diffusion connection tungsten alloy / steel rod-shaped composite component, wherein the steel shell has a tensile strength greater than 1.2 GPa, an impact energy not less than 65 J, a surface hardness HRC not less than 45, and a density not less than 7.7 g / cm 3 When applied, the steel casing may be commercially available high-strength steel or ultra-high-strength steel.

[0013] The invention discloses a mechanically meshed assisted diffusion-bonded tungsten alloy / steel rod-shaped composite component. A soft intermediate layer metal is deposited on the surface of the tungsten alloy by a physical or chemical method before diffusion bonding. The intermediate layer metal is one or two of the simple substances of Cu, Ni, Nb, Ti, Sn or their alloys.

[0014] The present invention discloses a mechanically meshed assisted diffusion-connected tungsten alloy / steel rod-shaped composite component. When the tungsten alloy inner core has a cone head, the inner cavity of the steel outer shell also has a portion matching the cone head of the tungsten alloy inner core; and the surface roughness Ra of the two is 1.6-3.2 μm. At the same time, no thread is required on the cone head.

[0015] The present invention provides a mechanical meshing assisted diffusion connection of a tungsten alloy / steel rod-shaped composite component. The mechanical meshing structure can be prefabricated on the welding contact surface using one or more of a subtractive manufacturing method such as turning and milling or an additive manufacturing mechanical processing method such as welding.

[0016] The present invention provides a method for preparing a mechanically meshed assisted diffusion-bonded tungsten alloy / steel rod-shaped composite component, which uses tungsten alloy as the inner core material and steel as the outer shell material, firstly processes threads of the same specification on the outer surface of the tungsten alloy and the inner cavity of the steel outer shell, then deposits a certain thickness of soft intermediate layer metal on the surface of the tungsten alloy, fully cleans the stains on the contact surfaces of the two, tightens the two to fit, and then uses a hot isostatic pressing method to perform diffusion bonding to obtain a product. When applied in industry, the target component can be obtained after the welded components are subjected to necessary mechanical processing.

[0017] The present invention provides a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion bonding, comprising the following steps:

[0018] Step 1: Determine the size of the tungsten alloy core and steel jacket, prefabricate the mechanical meshing structure and clean the surface

[0019] The tungsten alloy inner core and steel outer jacket with suitable size are machined into external and internal threads respectively, and a certain matching gap is reserved for the deposition of soft intermediate metal. After completion, they are fully cleaned and placed in a drying oven for full drying to obtain clean tungsten alloy inner core and steel outer jacket with prefabricated mechanical meshing structure. The tungsten alloy inner core can be processed into a tapered front section structure or only a flat head screw according to requirements. Except for the tapered part and without special requirements, other contact parts need to be processed into threads of the same size. The tapered part needs to maintain a relatively rough surface, Ra3.2-Ra1.6μm to achieve micro-scale mechanical meshing.

[0020] Step 2: Deposition of soft intermediate metal on the surface to be welded and secondary cleaning

[0021] Use physical or chemical methods to deposit an intermediate layer of metal on the surface of the tungsten alloy. After completion, fully clean it and put it into a drying oven to fully dry it, and then obtain a tungsten alloy core and a steel jacket with an intermediate layer of metal deposited and a prefabricated mechanical meshing structure.

[0022] Step 3: Mechanical meshing and hot isostatic pressing diffusion bonding of raw materials

[0023] The tungsten alloy inner core, which has been deposited with a soft intermediate layer and prefabricated with a mechanical meshing structure, is screwed together with the steel outer sleeve, and then the mating parts are placed in a suitable hot isostatic pressing sleeve for a "short-time welding + long-time low-temperature insulation and stress relief" hot isostatic pressing welding process. After the welding is completed, the blank is obtained.

[0024] When used in industry, the shape of the blank needs to be trimmed, that is, the blank is machined according to the technical requirements to obtain a composite component of tungsten alloy and steel bonded by mechanical meshing assisted diffusion bonding.

[0025] The present invention discloses a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion bonding. The material used for the tungsten alloy inner core in step 1 is a commercial tungsten alloy, tungsten-nickel-iron, tungsten-nickel-copper and other derivative systems. The mass percentage of tungsten content is between 50% and 99%, the impact energy is not less than 20J, and the elongation after fracture is not less than 10%. The steel shell is a commercial ultra-high strength steel with a tensile strength greater than 1.2GPa, an impact energy of not less than 65J, a surface hardness HRC of not less than 45, and a density of not less than 7.7g / cm 3 .

[0026] The present invention provides a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion bonding, wherein the mechanical processing method in step 1 includes one or more of a subtractive manufacturing method such as turning, milling, or an additive manufacturing mechanical processing method such as welding.

[0027] The present invention discloses a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion bonding, wherein the internal and external threads in step 1 are one of rectangular threads, trapezoidal threads, triangular threads or their variants. The fitting clearance is between 10-200 μm, the thread length is full thread or partial thread, the thread depth is 0.2-1.5 mm, and the pitch is 0.2-1.5 mm. The tapered part does not need to be threaded, but only needs to be processed to a roughness between Ra3.2 and Ra1.6. Too deep a thread will significantly affect the strength of the matrix, and too large a pitch will result in too small an effective contact area, making it difficult to play a role in mechanical meshing. The curved surface part uses a lower roughness to achieve microscopic-scale mechanical meshing and improve the bonding strength of the curved surface part.

[0028] The present invention provides a method for preparing a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component. The cleaning method in step 1 is one or more of organic solvent cleaning, acid cleaning, alkali cleaning and steam cleaning. The drying oven is one of a common drying oven or a vacuum drying oven. The drying temperature is 60-120°C and the drying time is 20-120 minutes.

[0029] The present invention discloses a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion connection. In step 2, the physical or chemical method of the intermediate layer is one or two of PVD, CVD, and electrodeposition. The intermediate layer metal is one or two of Cu, Ni, Nb, Ti, Sn simple substance or alloy thereof, which is deposited on the surface of the tungsten alloy with a deposition thickness of 10-100 μm. On the one hand, the soft intermediate layer can release residual stress after welding. On the other hand, for complex surfaces that cannot be processed with mechanical meshing structures, it can cooperate with a relatively rough surface and embed into the rough surface during welding to achieve mechanical meshing on a microscopic scale, thereby improving the bonding strength of the complex surface. Due to the low diffusion temperature, although steel can fill the gap between the steel and the intermediate layer by deformation, the tungsten alloy will not be significantly deformed during diffusion. With the help of the soft intermediate layer deposited on the surface of the tungsten alloy, the steel and the tungsten alloy form an early bond, thereby reducing the diffusion difficulty of the tungsten alloy / intermediate layer, reducing the diffusion process requirements, and improving the bonding strength.

[0030] The present invention provides a method for preparing a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component. The cleaning method in step 2 is one or more of organic solvent cleaning, acid cleaning, alkali cleaning and steam cleaning. The drying oven is one of a common drying oven or a vacuum drying oven. The drying temperature is 60-120°C and the drying time is 20-120 minutes.

[0031] The present invention provides a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion bonding. The tightening operation in step 3 should ensure sufficient contact. The fit can be a clearance fit, an interference fit or a transition fit. If the clearance is too small, it is difficult to install and may damage the coating. If the clearance is too large, it may cause too much deformation during diffusion, affecting the welding quality and the dimensional stability of the sample after welding.

[0032] The present invention discloses a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion bonding. In step 3, the wall thickness of the hot isostatic pressing sleeve is between 2 mm and 15 mm, and the assembly margin between the sleeve and the component is between 0.5 and 3 mm. If the sleeve wall thickness is too thin, it is easy to break. If it is too thick, the pressure loss will be too large due to the strong shielding effect of the sleeve wall, thereby reducing the actual welding pressure on the welding surface. If the assembly margin between the sleeve and the component is too small, it is difficult to install. If the margin is too large, the sleeve will shrink too much and easily crack, thereby reducing the welding success rate.

[0033] The invention discloses a method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical meshing assisted diffusion connection. The hot isostatic pressing welding process of "short-time high-temperature diffusion + long-time low-temperature insulation to relieve stress" described in step 3 comprises the following specific processes: firstly, the temperature is rapidly increased to 800°C-1050°C at a heating rate of 5-10°C / min, and the pressure is increased to 80MPa-200MPa with the furnace, and the insulation and pressure holding time is 40minσ90min, and then the temperature is slowly decreased to 400°C-600°C at a cooling rate of 2-5°C / min, and the pressure is reduced with the furnace, and the insulation and pressure holding time at 400°C-600°C is 30min-60min, and then the furnace is cooled to room temperature. A higher heating rate, a shorter high-temperature holding time, and a lower welding temperature can avoid excessive growth of steel grains and the massive generation of brittle intermetallic compounds at the joints; a higher welding pressure can make up for the insufficient welding temperature to ensure sufficient metallurgical bonding at the interface. In addition, a higher welding pressure can also bridge the cracks introduced during the prefabrication of mechanical structures; the holding stage at low temperature (400℃-600℃) can further release the residual stress of the joint and improve the strength of the weld. As a further preferred solution, the hot isostatic pressing welding process of "short-time diffusion + long-time low-temperature insulation to relieve stress" described in step 3 has the following specific process: first, the temperature is rapidly increased to 800°C-950°C at a heating rate of 5-10°C / min, and the pressure is increased to 100MPa-200MPa with the furnace, and the insulation and pressure holding time is 40min-90min, and then the temperature is slowly decreased to 550°C at a cooling rate of 2-5°C / min, and the pressure is reduced with the furnace. At 550°C, the insulation and pressure holding time is 30min-60min, and then the furnace is cooled to room temperature.

[0034] The present invention provides a method for preparing a mechanically meshed diffusion-assisted tungsten alloy / steel rod-shaped composite component. The method for mechanically processing the blank according to technical requirements includes one or more of subtractive manufacturing methods such as turning and milling and additive manufacturing methods such as welding.

[0035] In the present invention, when the tungsten alloy inner core material is 93W-4.9Ni-2.1Fe, the steel outer shell is 30CrMnSiNi2A, and the middle layer is Ni, the interface bonding strength (tensile strength) of the obtained product is 450-600MPa.

[0036] Principles and advantages

[0037] The present invention discloses a mechanical meshing assisted diffusion bonding tungsten alloy / steel rod-shaped composite component, the difficulty of which lies in the design of the mechanical meshing structure and the closure of the prefabricated cracks. The present invention proposes and optimizes the preparation method of "thread meshing + rough cone surface bonding + deposition of soft intermediate layer metal + hot isostatic pressing diffusion welding", and prepares a tungsten alloy / steel rod-shaped composite component with high interface bonding strength through macroscopic thread meshing and microscopic rough cone surface bonding combined with hot isostatic pressing diffusion bonding.

[0038] The specific principle is: first, a suitable mechanical meshing structure is selected, and the design criteria are: the mechanical meshing structure itself needs to have a certain strength, the processing method is simple, it can be applied to the surface of a simple rotating body, and it can achieve the matching of cylindrical samples. The rough conical surface is mainly used under the condition that it is difficult to process threads on the curved surface. By controlling the surface roughness of the contact surface and coordinating the deformation of the soft intermediate layer under high pressure, the micro-scale meshing of the rough curved surface is achieved, so that the interface bonding strength of the curved surface is not too low; then a suitable, soft intermediate layer metal is selected for welding, which deforms under the combined action of temperature and pressure to fill the pores to form a metallurgical bond, and releases the interface welding stress after welding, while preventing the large-scale generation of brittle intermetallic compounds to ensure the interface matching after welding; finally, the hot isostatic pressing diffusion welding process is used to achieve the establishment of metallurgical bonding at the interface and the closure of microcracks at the welding interface. The literature "Zhu Yuan, Zhang Hao, Cheng Xiaotong, et al. Effect of nickel foil intermediate layer thickness on the quality of solid phase diffusion welding of GH4099 alloy [J]. Journal of Welding, 2018, 39 (4): 93-98." shows that when the thickness of the soft intermediate layer is greater than the surface roughness Ra value during welding, the joint can be guaranteed to have a certain bonding strength. At this time, the soft intermediate layer will fill the rough surface during welding to improve the metallurgical quality. The feasibility of electroplating of the thread has been measured by the corresponding test block, see Figure 5 As shown, the threads are of three types: pitch 0.5mm, depth 0.5mm; pitch 1mm, depth 1mm, and a smooth cylindrical surface for comparison. The Ni plating thickness is 40-50μm. The surface plating of each sample is uniform, and the electroplating does not affect the subsequent coordination with the steel jacket.

[0039] Then, a preparation method for a mechanically meshed assisted diffusion-bonded tungsten alloy / steel rod-shaped composite component was designed. In order to achieve mechanical meshing of the tungsten alloy inner core and the steel outer shell and provide basic bonding strength for the joint, the present invention first designed a thread as a mechanical meshing method, and achieved mechanical meshing of the tungsten alloy inner core and the steel outer shell by selecting a suitable processing method, providing initial strength for the composite component, and processing the required welding curved surface into a relatively rough surface to facilitate subsequent meshing; then, an electroplating process was used to attach nickel as a soft intermediate layer to the surface of the tungsten alloy, which was used to deform under the combined action of temperature and pressure during welding to fill the pores to form a metallurgical bond, and to release the interface residual stress after welding. Finally, a hot isostatic pressing welding process of "high temperature welding + low temperature insulation stress relief" was designed. The specific process is: first, the temperature is increased to 800-1050℃ at a heating rate of 5-10℃ / min, and the pressure is increased to 80-200MPa with the furnace, and the insulation and pressure holding time is 40-90min. This process ensures that the components are fully diffused to form sufficient metallurgical bonding strength, and closes the microcracks caused by thread processing to reduce the potential risk of stress concentration; then the temperature is reduced to 400℃-600℃ at a cooling rate of 2-5℃ / min, and the pressure is reduced with the furnace. The insulation and pressure holding time at 400℃-600℃ is 30-60min, and then the furnace is cooled to room temperature. This process realizes the slow release of the sample welding stress.

[0040] Compared with the existing method, the advantages of the present invention are:

[0041] 1) The present invention sets a mechanical meshing structure (thread + rough surface structure) on the welding surface and deposits a matching design of soft intermediate layer metal, so that the welding surface does not need fine polishing, thereby realizing the composite of rod-shaped tungsten alloy and steel under low surface processing quality conditions. At the same time, the hot isostatic pressing densification technology is used to solve the potential stress concentration problem of traditional mechanical connection, and obtain high-performance rod-shaped tungsten alloy / steel composite components.

[0042] 2) The mechanical meshing assisted diffusion bonding of the tungsten alloy / steel rod-shaped composite components of the present invention solves the problems of unstable strength of traditional diffusion bonding joints, stress concentration at the crack tip of pure mechanical bonding, and only being able to withstand unidirectional loading and being easy to loosen, providing a new idea for the development of new tungsten alloy / steel projectiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of mechanical meshing assisted diffusion bonding of tungsten alloy / steel rod-shaped composite components, (a) is a schematic diagram of the rough surface fit at the conical position of the component head, and (b) is a schematic diagram of the thread fit at the middle straight tube (b);

[0044] Figure 2 It is a close-up of the test block used to test the feasibility of electroplating and the assembly diagram after electroplating;

[0045] Figure 3 A close-up of the double-layer structure at the end of an actual sample of a tungsten alloy / steel rod-shaped composite component that was mechanically meshed and diffusion-assisted.

[0046] Figure 4 The SEM photos of the interface macroscopic photos and microscopic morphology obtained after the fine threads are machined on the outer side of the tungsten alloy in Example 1 and then assembled and HIP diffusion welded;

[0047] Figure 5 This is a SEM photograph of the interface microstructure obtained after machining a coarse thread on the outside of the tungsten alloy and assembling and HIP diffusion welding in Example 2.

[0048] Figure 6 The schematic diagram (a), the actual picture (b) and the interface morphology picture (c) of HIP welding of the tungsten alloy core after centerless grinding and adding Ti and Cu intermediate layers in comparative example 1;

[0049] Figure 7 The diagram of comparative example 2, the actual image of the tungsten core after nickel electroplating, and the interface morphology after welding; wherein (a) is a schematic diagram, (b) is a actual image of the tungsten core after nickel electroplating, and (c) is a interface morphology after welding;

[0050] Figure 8 The diagram of comparative example 3, the actual picture of the tungsten core after nickel electroplating, and the interface morphology after welding; wherein (a) is a schematic diagram, (b) is a actual picture of the tungsten core after nickel electroplating, and (c) is a picture of the interface morphology after welding;

[0051] Fig. 9 The welding physical image, the interface morphology image after welding and the energy spectrum image of the relevant position of comparative example 4; wherein (a) is the welding physical image, (b) is the interface morphology image after welding, and (c) is the energy spectrum image of the relevant position;

[0052] from Figure 1 It can be seen that the thread is only processed on the cylindrical surface, and the oval surface at the tip is not threaded, only the processed surface is retained.

[0053] from Figure 2 It can be seen that the thread surfaces of the test blocks with different thread sizes are all covered with a uniform and continuous coating without any cracking, and they can also be screwed into the corresponding steel sleeves after electroplating.

[0054] from Figure 3 It can be seen that there is no significant crack on the interface of the threaded projectile sample after welding, the combination is good, and the double-layer structure is clear.

[0055] from Figure 4 It can be seen that there are basically no pores on the joint surface of the fine thread specimen.

[0056] from Figure 5It can be seen that there are still tiny pores on the joint surface of the coarse thread specimen.

[0057] from Figure 6 It can be seen that the manually added double-layer middle layer has no pores at the macro level after welding, but there are some unwelded holes between copper and steel at the micro level.

[0058] from Figure 7 It can be seen that the bonding interface has almost no pores and is very flat.

[0059] from Figure 8 It can be seen that the bonding interface has almost no pores and is very flat, and the thickness of the Ni layer is much smaller than that of the Cu layer.

[0060] from Fig. 9 It can be seen that the bonding interface has almost no pores and is very flat, but there is a thick metal compound layer. DETAILED DESCRIPTION

[0061] The following examples are intended to further illustrate the present invention, but are not intended to limit the present invention.

[0062] Example 1

[0063] Step 1: Determine the size of the tungsten alloy core and steel jacket, prefabricate the mechanical meshing structure and clean the surface

[0064] As mentioned above, the raw materials with determined sizes are prefabricated and cleaned. The prefabricated structure of the straight part uses a 60° triangular thread with a pitch of 0.5mm and a depth of 0.5mm. It is processed using a CNC lathe, and the processing tool is a 60° triangular thread cutter; the curved part is directly processed using a lathe, Ra3.2μm. The tungsten alloy core material is 93W-4.9Ni-2.1Fe, with a diameter of 30mm and a total length of 200mm. The steel jacket material is 30CrMnSiNi2A, with an inner diameter of 30mm and an outer diameter of 50mm and a total length of 300mm; the matching clearance is 60μm. After processing, the 93W-4.9Ni-2.1Fe core and the 30CrMnSiNi2A jacket are ultrasonically cleaned twice with alcohol as a cleaning agent, each time for 30 minutes; then they are dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0065] Step 2: Deposition of intermediate metal layer on the surface to be welded and secondary cleaning

[0066] As described above, the 93W-4.9Ni-2.1Fe inner core processed in step 1 is surface electroplated and cleaned, the electroplated metal is pure Ni, and the thickness of the electroplated layer is 50-60μm; after the electroplating is completed, it is ultrasonically cleaned twice with deionized water and alcohol, each time for 30 minutes; then it is dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0067] Step 3: Mechanical meshing and hot isostatic pressing diffusion bonding of raw materials

[0068] The 30CrMnSiNi2A outer jacket obtained in step 1 and the 93W-4.9Ni-2.1Fe inner core electroplated with pure Ni obtained in step 2 are screwed together and then subjected to the "short-time welding + long-time low-temperature insulation stress relief" hot isostatic pressing welding process. The jacket wall thickness is 3mm, the material is 20 steel, and the assembly margin is 0.5mm; after welding, the blank is obtained. The specific process is: first, the temperature is quickly increased to 950℃ at a heating rate of 5℃ / min, and the pressure is increased to 100MPa with the furnace, and the heat preservation and pressure holding time is 60min, then the temperature is slowly reduced to 550℃ at a cooling rate of 5℃ / min, and the pressure is reduced with the furnace. At 550℃, the heat preservation and pressure holding time is 60min, and then the furnace is cooled to room temperature.

[0069] Step 4: Finishing the blank

[0070] After the blank in step 3 is subjected to necessary mechanical processing such as removing the sheath and trimming the shape, a mechanically meshed diffusion-assisted tungsten alloy / steel rod-shaped composite component is obtained. After testing, the maximum interface bonding tensile strength is 598 MPa.

[0071] Example 2

[0072] Step 1: Determine the size of the tungsten alloy core and steel jacket, prefabricate the mechanical meshing structure and clean the surface

[0073] As mentioned above, the raw materials with determined sizes are prefabricated and cleaned. The prefabricated structure of the straight part uses a 60° triangular thread with a pitch of 1mm and a depth of 1mm, and is processed using a CNC lathe. The processing tool is a 60° triangular thread cutter; the curved surface is directly processed using a lathe, Ra3.2μm. The tungsten alloy inner core uses 93W-4.9Ni-2.1Fe, with a diameter of 30mm and a total length of 200mm. The steel outer jacket uses 30CrMnSiNi2A steel, with an inner diameter of 30mm and an outer diameter of 50mm and a total length of 300mm; the matching clearance is 60μm. After processing, the 93W-4.9Ni-2.1Fe inner core and the 30CrMnSiNi2A outer jacket are ultrasonically cleaned twice using alcohol as a cleaning agent, each time for 30 minutes; then they are dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0074] Step 2: Deposition of intermediate metal layer on the surface to be welded and secondary cleaning

[0075] As described above, the 93W-4.9Ni-2.1Fe inner core processed in step 1 is surface electroplated and cleaned, the electroplated metal is pure Ni, and the thickness of the electroplated layer is 50-60μm; after the electroplating is completed, it is ultrasonically cleaned twice with deionized water and alcohol, each time for 30 minutes; then it is dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0076] Step 3: Mechanical meshing and hot isostatic pressing diffusion bonding of raw materials

[0077] The 30CrMnSiNi2A outer jacket obtained in step 1 and the 93W-4.9Ni-2.1Fe inner core electroplated with pure Ni obtained in step 2 are screwed together and then subjected to the "short-term high-temperature welding + long-term low-temperature insulation stress relief" hot isostatic pressing welding process. The jacket wall thickness is 3mm, the material is 20 steel, and the assembly margin is 0.5mm; after welding, the blank is obtained. The specific process is: first, the temperature is quickly increased to 950℃ at a heating rate of 6℃ / min, and the pressure is increased to 100MPa with the furnace, and the heat preservation and pressure holding time is 60min, then the temperature is slowly reduced to 450℃ at a cooling rate of 5℃ / min, and the pressure is reduced with the furnace. At 450℃, the heat preservation and pressure holding time is 60min, and then the furnace is cooled to room temperature.

[0078] Step 4: Finishing the blank

[0079] After the blank in step 3 is subjected to necessary mechanical processing such as removing the sheath and trimming the shape, a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component is obtained. After testing, the maximum interface bonding tensile strength is 454MPa.

[0080] Comparative Example 1

[0081] Earlier work of the research group (Liu W, Pang X, Cai Q, et al. Fabrication of W / steel joining hot isostatic pressing with Ti / Cu / Ti liquid forming interlayer[J]. FUSION ENGINEERING AND DESIGN, 2018, 135: 59-64.)

[0082] Step 1: Determine the size of the tungsten alloy core and steel jacket and clean the surface

[0083] As mentioned above, the raw materials with determined sizes are prefabricated and cleaned. The comparative example does not undergo prefabrication, but the outer cylindrical surface of the tungsten alloy inner core is ground by a centerless grinder, and the inner hole of the steel sleeve is manually polished, with roughness better than Ra1.2μm; the tungsten alloy inner core is made of industrial pure tungsten (99.95wt.%), with dimensions of 30mm inner diameter, 40mm outer diameter and 75mm total length; the steel outer sleeve is made of high chromium steel (Fe-17Cr-0.1C), with dimensions of 41mm inner diameter, 50mm outer diameter and 75mm total length; after processing, the pure tungsten inner core and the high chromium steel outer sleeve are ultrasonically cleaned twice using alcohol as a cleaning agent, each time for 30 minutes; and then dried in a vacuum drying oven for use, the drying temperature is 80°C, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0084] Step 2: Cleaning of the intermediate metal layer

[0085] As described above, the surface of the pure tungsten inner core processed in step 1 is electroplated and cleaned. The intermediate metal is 20μm titanium and 400μm copper, both of which are foils. The foil is ultrasonically cleaned twice with deionized water and alcohol, each time for 30 minutes; then it is dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0086] Step 3: Mechanical meshing and hot isostatic pressing diffusion bonding of raw materials

[0087] The high chromium steel jacket and pure tungsten inner core obtained in step 1 are inserted with the titanium foil and copper foil obtained in step 2, and then the "short-time high-temperature welding" hot isostatic pressing welding process is carried out. The jacket wall thickness is 2mm, the material is 304 stainless steel, and the assembly margin is 0.5mm; after the welding is completed, the blank is obtained. The specific process is: firstly, the temperature is rapidly increased to 1050℃ at a heating rate of 5℃ / min, and the pressure is increased to 100MPa with the furnace, and the heat and pressure holding time is 60min, and then the furnace is cooled and the pressure is reduced with the furnace.

[0088] Step 4: Finishing the blank

[0089] After the blank in step 3 is subjected to necessary mechanical processing such as removing the sheath and trimming the shape, a mechanically meshed diffusion-assisted tungsten alloy / steel rod-shaped composite component is obtained. After testing, the maximum interface bonding shear strength is 248MPa.

[0090] Comparative Example 2, sleeve welding, no intermediate layer and no thread, previous literature (Liu W, Sheng Q, Ma Y, et al. Interfacial microstructures, residual stress and mechanical analysis of hotisostatic pressing diffusion bonded joint of 93W–4.9Ni–2.1Fe alloyand30CrMnSiNi2A steel[J]. Fusion Engineering and Design, 2020, 156:111602.)

[0091] Step 1: Determine the size of the tungsten alloy core and steel jacket and clean the surface

[0092] As mentioned above, the raw materials with determined sizes are prefabricated and cleaned. This control ratio does not prefabricate and does not deposit soft intermediate layer metal. The outer cylindrical surface of the tungsten alloy inner core is ground by centerless grinding, and the inner hole of the steel sleeve is polished by hand, and the surface roughness is better than Ra1.2μm; the tungsten alloy inner core is made of 93W-4.9Ni-2.1Fe, with the size of inner diameter 30mm, outer diameter 40 and total length 50mm, and the steel outer sleeve is made of 30CrMnSiNi2A steel, with the size of inner diameter 40mm, outer diameter 50mm and total length 500mm; the matching clearance is 60μm, and after processing, the 93W-4.9Ni-2.1Fe inner core and 30CrMnSiNi2A outer sleeve are ultrasonically cleaned twice with alcohol as a cleaning agent, each time for 30 minutes; then they are dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30min, and the drying oven pressure is maintained at -0.1MPa.

[0093] Step 2: Raw material assembly and hot isostatic pressing diffusion bonding

[0094] The 30CrMnSiNi2A outer jacket obtained in step 1 is inserted into the 93W-4.9Ni-2.1Fe inner core and then subjected to hot isostatic pressing welding process. The jacket wall thickness is 3mm, the material is 20 steel, and the assembly margin is 0.5mm. After welding, the blank is obtained. The specific process is: first, the temperature is quickly increased to 1050℃ at a heating rate of 10℃ / min, and the pressure is increased to 100MPa with the furnace, and the heat and pressure holding time is 60min, and then the temperature is slowly reduced to 400℃ at a cooling rate of 5℃ / min, and the pressure is reduced with the furnace, and then the furnace is cooled to room temperature.

[0095] Step 3: Finishing the blank

[0096] After the blank in step 2 is subjected to necessary mechanical processing such as removing the sheath and trimming the shape, the mechanical meshing assisted diffusion bonding tungsten alloy / steel rod-shaped composite component is obtained. After testing, the maximum interface bonding tensile strength is 310.5MPa

[0097] Comparative Example 3, rod welding, using nickel plating and copper as the intermediate layer, with unknown thickness and no thread, is based on the previous literature (Ma Yunzhu, Wang Jianning, Liu Wensheng, et al. Characteristics of electroplating-assisted hot isostatic pressing diffusion bonded tungsten / steel joints (English) [J]. Rare Metal Materials and Engineering, 2022, 51(07): 2393-2399.)

[0098] Step 1: Determine the size of the tungsten core and steel jacket and clean the surface

[0099] As mentioned above, the raw materials with determined sizes are prefabricated and cleaned. This control ratio does not perform prefabrication, but the outer cylindrical surface of the tungsten inner core is ground by a centerless grinder, and the inner hole of the steel sleeve is manually polished with a roughness Ra of 1.2μm; the inner core is made of pure tungsten, with a diameter of 30mm and a total length of 50mm, and the steel outer sleeve is made of high chromium steel (Fe-17Cr-0.1C), with a size of an inner diameter of 31mm, an outer diameter of 50mm and a total length of 50mm. After processing, the tungsten inner core and the high chromium steel outer sleeve are ultrasonically cleaned twice using alcohol as a cleaning agent, and the Cu foil to be used is cleaned at the same time, with a thickness of 0.5mm and a cleaning time of 30min each time; then it is dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30min, and the drying oven pressure is maintained at -0.1MPa.

[0100] Step 2: Deposition of intermediate metal layer on the surface to be welded and secondary cleaning

[0101] As described above, the pure tungsten inner core processed in step 1 is surface electroplated and cleaned, the electroplated metal is pure Ni, and the thickness of the electroplated layer is 10μm; after the electroplating is completed, it is ultrasonically cleaned twice with deionized water and alcohol, each time for 30 minutes; then it is dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0102] Step 3: Mechanical meshing and hot isostatic pressing diffusion bonding of raw materials

[0103] The high chromium steel jacket and copper foil obtained in step 1 are inserted into the pure tungsten inner core electroplated with pure Ni obtained in step 2 and then subjected to hot isostatic pressing welding process. The method is to first wrap the copper foil around the tungsten core and then insert it into the steel jacket. The jacket wall thickness is 3mm, the material is 20 steel, and the assembly margin is 0.5mm. After welding, the blank is obtained. The specific process is: first, the temperature is rapidly increased to 900℃ at a heating rate of 5℃ / min, and the pressure is increased to 100MPa with the furnace. The heat preservation and pressure holding time is 60min, and then the temperature is slowly reduced to 400℃ at a cooling rate of 5℃ / min, and the pressure is reduced with the furnace, and then the furnace is cooled to room temperature.

[0104] Step 4: Finishing the blank

[0105] After the blank in step 3 is subjected to necessary mechanical processing such as removing the sheath and trimming the shape, a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component is obtained. After testing, the maximum interface bonding tensile strength is 312MPa.

[0106] Comparative Example 4, rod welding, other literature (Lu C, Wang Y, Lei X, et al. Influence of Fe-Wintermetallic compound on fracture behavior of Steel / Tungsten HIP diffusion bonding joint: Experimental investigation and first-principles calculation [J]. Journal of Manufacturing Processes, 2020, 55: 131-142.)

[0107] Step 1: Determine the size of the tungsten alloy core and steel jacket and clean the surface

[0108] As mentioned above, the raw materials with determined sizes are prefabricated and cleaned. The control ratio does not prefabricate and does not deposit soft intermediate layer metal. The tungsten alloy inner core and the inner hole of the steel sleeve are finely polished using a curved polishing machine, and the surface roughness is better than Ra0.5μm; the tungsten alloy inner core is made of 90W-7Ni-3Fe, with a diameter of 36 and a total length of 50mm, and the steel outer sleeve is made of Q390 steel, with an inner diameter of 37mm, an outer diameter of 57mm and a total length of 50mm; after processing, the 93W-4.9Ni-2.1Fe inner core and the 30CrMnSiNi2A outer sleeve are ultrasonically cleaned twice using alcohol as a cleaning agent, each time for 30 minutes; then they are dried in a vacuum drying oven for use, the drying temperature is 80℃, the drying time is 30 minutes, and the drying oven pressure is maintained at -0.1MPa.

[0109] Step 2: Raw material assembly and hot isostatic pressing diffusion bonding

[0110] The 30CrMnSiNi2A outer jacket obtained in step 1 is inserted into the 93W-4.9Ni-2.1Fe inner core and then subjected to hot isostatic pressing welding process. The jacket wall thickness is 3mm, the material is 20 steel, and the assembly margin is 0.5mm. After welding, the blank is obtained. The specific process is: firstly, the temperature is rapidly increased to 1050℃ at a heating rate of 10℃ / min, and the pressure is increased to 120MPa with the furnace, and the heat and pressure holding time is 120min, and then the furnace is cooled to room temperature and the pressure is reduced with the furnace.

[0111] Step 3: Finishing the blank

[0112] After the blank in step 2 is subjected to necessary mechanical processing such as removing the sheath and trimming the shape, a mechanically meshed diffusion-assisted tungsten alloy / steel rod-shaped composite component is obtained. After testing, the maximum interface bonding tensile strength is 95 MPa.

Claims

1. A mechanically meshed assisted diffusion bonding of tungsten alloy / steel rod-shaped composite components, Features: It comprises a steel shell, an intermediate layer and a tungsten alloy inner core; the intermediate layer is located between the steel shell and the tungsten alloy inner core and the intermediate layer is in direct contact with the steel shell and the tungsten alloy inner core; before diffusion bonding, the inner cavity of the steel shell has threads, and the outer surface of the tungsten alloy inner core has threads matching the threads of the inner cavity of the steel shell; the threads are one of rectangular threads, trapezoidal threads and triangular threads, the thread length is less than or equal to the sample length, the area of ​​the thread zone is less than or equal to the outer surface of the tungsten alloy inner core, the thread depth is 0.2-1.5mm, preferably 0.35-1mm, and the pitch is 0.2-1.5mm, preferably 0.25-1mm; The intermediate layer is one or two of Cu, Ni, Nb, Ti, Sn or their alloys.

2. A mechanical engagement assisted diffusion bonding tungsten alloy / steel rod-shaped composite component according to claim 1, Features: The tungsten alloy has a tungsten content of 50% to 99% by mass, an impact energy of not less than 20J, and an elongation after fracture of not less than 10%; The tensile strength of the steel shell is greater than 1.2GPa, the impact energy is not less than 65J, the surface hardness HRC is not less than 45, and the density is not less than 7.7g / cm 3 .

3. A mechanical engagement assisted diffusion bonding tungsten alloy / steel rod-shaped composite component according to claim 1, Features: When the tungsten alloy inner core has a cone head, the inner cavity of the steel shell also has a portion that matches the cone head of the tungsten alloy inner core; and the surface roughness Ra of the two is 1.6~3.2μm; at the same time, there is no need to set a thread on the cone head.

4. A method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical engagement assisted diffusion bonding as claimed in any one of claims 1 to 3, Features: Tungsten alloy is used as the inner core material and steel is used as the outer shell material. First, threads of the same specification are processed on the outer surface of the tungsten alloy and the inner cavity of the steel shell. Then, a soft intermediate layer metal of a certain thickness is deposited on the surface of the tungsten alloy. After the stains on the contact surfaces of the two are fully cleaned, the two are tightened to fit together, and then hot isostatic pressing is used for diffusion connection to obtain the product.

5. The method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical engagement assisted diffusion bonding according to claim 4, It is characterized in that The steps include: Step 1: Determine the size of the tungsten alloy core and steel jacket, prefabricate the mechanical meshing structure and clean the surface The tungsten alloy inner core and steel outer sleeve of suitable size are machined into external and internal threads respectively, and a certain matching gap is reserved for the deposition of soft intermediate layer metal. After completion, they are fully cleaned and placed in a drying oven for full drying to obtain a clean tungsten alloy inner core and steel outer sleeve with prefabricated mechanical meshing structure. The tungsten alloy inner core can be processed into a screw with a tapered front section structure or only a flat head according to the needs. If there is a taper, the Ra of the tapered surface and the inner surface of the tapered cavity needs to be controlled to be 1.6~3.2μm; other contact parts need to be processed with threads of the same size; Step 2: Deposition of soft intermediate metal on the surface to be welded and secondary cleaning Use physical or chemical methods to deposit an intermediate layer of metal on the surface of the tungsten alloy. After completion, fully clean it and put it into a drying oven to fully dry it, so as to obtain a tungsten alloy core and a steel jacket with an intermediate layer of metal deposited and a prefabricated mechanical meshing structure; Step 3: Mechanical meshing and hot isostatic pressing diffusion bonding of raw materials The tungsten alloy inner core with a soft intermediate layer and a prefabricated mechanical meshing structure is screwed together with the steel outer sleeve, and then the mating parts are placed in a suitable hot isostatic pressing sleeve for a "short-time welding + long-time low-temperature insulation and stress relief" hot isostatic pressing welding process. After the welding is completed, the blank is obtained.

6. The method for preparing a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component according to claim 5, Features: The machining method in step 1 includes one or more of a subtractive manufacturing method such as turning, milling, or an additive manufacturing machining method such as welding; The cleaning method in step 1 is one or more of organic solvent cleaning, acid cleaning, alkali cleaning and steam cleaning, the drying oven is one of a common drying oven or a vacuum drying oven, the drying temperature is 60-120° C., and the drying time is 20-120 min.

7. The method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical engagement assisted diffusion bonding according to claim 5, Features: The internal and external threads in step 1 are one of rectangular threads, trapezoidal threads, triangular threads or their variants; and the fitting clearance is between 10-200 μm.

8. The method for preparing a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component according to claim 5, Features: In step 2, the physical or chemical method for depositing the intermediate layer is one or more of PVD, CVD, and electrodeposition, and the intermediate layer metal is one or more of Cu, Ni, Nb, Ti, Sn or their alloys, which are deposited on the surface of the tungsten alloy with a deposition thickness of 10-100 μm; The cleaning method in step 2 is one or more of organic solvent cleaning, acid cleaning, alkali cleaning and steam cleaning, the drying temperature is 60-120° C., and the drying time is 20-120 min.

9. The method for preparing a mechanically meshed assisted diffusion bonded tungsten alloy / steel rod-shaped composite component according to claim 5, Features: The wall thickness of the hot isostatic pressing package in step 3 is between 2 mm and 15 mm, and the assembly margin between the package and the component is between 0.5 and 3 mm.

10. The method for preparing a tungsten alloy / steel rod-shaped composite component by mechanical engagement assisted diffusion bonding according to claim 5, Features: The specific process of the hot isostatic pressing welding process of "short-time diffusion + long-time low-temperature insulation to relieve stress" described in step 3 is as follows: first, the temperature is quickly increased to 800℃-1050℃ at a heating rate of 5-10℃ / min, and the pressure is increased to 80MPa-200 MPa with the furnace, and the insulation and pressure holding time is 40min-90min, and then the temperature is slowly reduced to 400℃-600℃ at a cooling rate of 2-5℃ / min, and the pressure is reduced with the furnace. At 400℃-600℃, the insulation and pressure holding time is 30min-60min, and then the furnace is cooled to room temperature.

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