A method for joining a porous metallic material to a dense metallic connector

Abstract

The application discloses a heterogeneous material connecting method of a porous metal material and a dense metal connecting piece, and relates to the technical field of powder metallurgy.The method comprises the following steps: preparing a dense metal connecting piece made of stainless steel; the cylindrical structure of the dense metal connecting piece comprises a first part and a second part; the outer periphery of the second part is an annular inclined surface; a plurality of through grooves are formed in the outer periphery of the second part in the axial direction; the annular inclined surface is provided with a convex step in the radial direction of the annular inclined surface; interface transition metal powder is uniformly applied on the annular inclined surface of the dense metal connecting piece; the first part is located at the end of a filter tube mold; the dense metal connecting piece is sleeved into the filter tube mold; Fe3Al alloy powder is loaded into the filter tube mold; after cold isostatic pressing and forming, the filter tube mold is demoulded to obtain an integrally-formed pipe embryo; the integrally-formed pipe embryo is subjected to high-temperature constrained sintering; and after cooling, the heterogeneous material connecting piece is obtained. The application solves the problems of the existing heterogeneous material connecting scheme, such as great welding difficulty, poor mechanical performance of the weld after welding, and unsuitable batch production.

Description

Technical Field

[0001] This invention relates to the technical field of powder metallurgy, and more particularly to a method for joining heterogeneous materials, namely porous metal materials and dense metal connectors. Background Technology

[0002] Fe3Al alloy porous metal materials are functional materials with controllable pore structures prepared using powder metallurgy technology with Fe3Al intermetallic compounds as the matrix. They possess not only the excellent high-temperature resistance and corrosion resistance of ceramics but also the good thermal shock resistance, high strength, and ease of processing of metals, making them widely applicable in filtration, separation, purification, and flow control. For example, in the application of Fe3Al alloy porous metal materials in high-temperature and high-pressure dust removal in coal gasification, the core internal component of the high-temperature and high-pressure fly ash filters in most Shell coal gasification plants is currently the Fe3Al alloy filter tube. This filter tube is either an integral structure or a two-section welded structure with a flange diameter reduction and a tube bottom. Among them, the integral filter tube not only has a large filtration area, but also higher mechanical strength, which is more conducive to safe, stable and efficient production in industry. A very small number of working conditions have tried to use the welded structure. However, due to the weld seam between the two filter tubes, the weld seam is a sensitive part of the entire filter element. During long-term use, the filter element works under pulse pressure conditions. In the entire filtration system, it is often subjected to the instantaneous impact of fluid at irregular intervals and online back-blowing vibration with the filter tube as the axis. The welding stress concentration in the weld fusion line area and the fatigue stress of the filter tube under the working conditions have a superimposed effect. The heat-affected zone of the weld seam is very prone to cracks. The cracks propagate until the filter tube breaks from the weld seam, resulting in filtration failure.

[0003] With the continuous expansion of high-temperature and corrosion-resistant applications, industrial processes typically improve production efficiency by increasing the filtration area of ​​filter tubes and reducing system operating pressure differentials. Therefore, the length of Fe3Al porous metal materials is increasingly required (e.g., greater than 3m). However, if seamless, integral filter tubes are chosen for manufacturing, the reinvestment in ultra-large production equipment will significantly increase production costs, hindering mass production and engineering applications. To address these practical engineering challenges, there is an urgent need to develop heterogeneous joining methods for high-strength Fe3Al porous materials suitable for mass production.

[0004] Current experimental results indicate that Fe-Al intermetallic compounds have poor weldability, which is one of the main problems restricting their application as engineering materials. In Fe3Al porous metal materials, due to the high reactivity of Al and the numerous pores inherent in the porous material, improper protection can easily lead to the formation of high-melting-point Al2O3, causing localized non-melting or difficulty in forming a continuous and stable molten pool during welding. This makes it difficult to guarantee weld quality and unsuitable for mass production. Furthermore, the physical properties of Fe3Al porous metal materials differ significantly from those of stainless steel dense metal connectors, resulting in a complex weld composition during heterogeneous welding (including the stainless steel dense metal connector, filler material, and Fe3Al porous metal material). The different diffusion coefficients of alloying elements during welding lead to irregular distribution, and the interface reaction products are complex. Experiments show that cold and hot cracks are easily generated after welding, the welding process has narrow adaptability, and post-weld tensile strength tests reveal poor mechanical properties at the weld joint. This further indicates that the weld joint is a weak point in the filter tube connection.

[0005] Therefore, existing heterogeneous material connection schemes for Fe3Al porous metal materials and stainless steel dense metal connectors have problems such as high welding difficulty, poor mechanical properties of welds after welding, and unsuitability for mass production. Summary of the Invention

[0006] This invention provides a method for joining porous metal materials and dense metal connectors in heterogeneous materials, which solves the problems of high welding difficulty, poor mechanical properties of welds after welding, and unsuitability for mass production in existing heterogeneous material joining schemes.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for connecting a porous metal material and a dense metal connector in heterogeneous materials. The method includes: preparing a dense metal connector made of stainless steel; the dense metal connector is a cylindrical structure, the cylindrical structure including an integrally connected first part and a second part, the outer periphery of the second part being an annular inclined surface, and multiple through grooves being axially formed on the outer periphery of the second part; the annular inclined surface is provided with raised steps along its radial direction, and the surface of the raised steps is roughened. Interfacial transition metal powder is uniformly applied to the annular inclined surface of the dense metal connector. Then, the first part is positioned at the end of the filter tube mold. The dense metal connector is then fitted into the filter tube mold, and Fe3Al alloy powder is loaded into the filter tube mold. After cold isostatic pressing and molding, the mold is demolded to obtain an integrally formed tube blank. The thickness of the integrally formed tube blank is the same as the thickness of the first part. The integrally formed tube blank is subjected to high-temperature constrained sintering, and after cooling, a heterogeneous material connector is obtained.

[0008] In one possible implementation, the interface transition metal powder is FeNiCrAlVB. 0.5 P 0.5 alloy.

[0009] In one possible implementation, the particle size range of the interfacial transition metal powder is 15~53μm.

[0010] In one possible implementation, each of the through slots is an elongated through slot, and the end of the elongated through slot away from the end of the cylindrical structure is provided with an arc-shaped transition structure.

[0011] In one possible implementation, the plurality of through slots comprises 4 to 12 slots uniformly axially formed on the outer periphery of the second portion.

[0012] In one possible implementation, before uniformly applying interfacial transition metal powder to the annular bevel of the dense metal connector, the method further includes: Use a cleaning agent to clean the surface of the dense metal connector.

[0013] In one possible implementation, prior to cold isostatic pressing, the method further includes: compacting the Fe3Al alloy powder contained in the filter tube mold using a compaction platform, and then sealing the filter tube mold.

[0014] In one possible implementation, the pressure of the cold isostatic pressing is 100~200MPa, and the holding time is 1~3min.

[0015] In one possible implementation, the integrally formed tube blank is subjected to high-temperature constrained sintering, and after cooling, a heterogeneous material connector is obtained, specifically including: The integrally formed tube blank is loaded into a sintering boat and fitted with suitable filler. In a vacuum or protective atmosphere, the temperature is slowly increased and held in stages to constrain sintering to 1200℃~1300℃ for 2~4 hours to obtain the sintered connector. The sintered connector is cooled to room temperature in the furnace and discharged to obtain a connector made of heterogeneous materials.

[0016] In one possible implementation, the heterogeneous material connector includes a dense metal connector and a porous metal material tube formed by sintering the Fe3Al alloy powder. The porous metal tube has a diameter of 20-120 mm, a length of 50-3000 mm, a thickness of 2-10 mm, and a pore size of 0.3-100 μm.

[0017] The method for joining porous metal materials and dense metal connectors provided in this invention, during the fabrication of filter tubes, effectively increases the bonding area between the dense metal connector and the Fe3Al porous metal material through the design of the annular inclined surface, the design of the raised steps on the annular inclined surface, and the surface roughening treatment of the raised steps. Through the design of multiple through-grooves in the second part of the dense metal connector: ① the porous metal powder is pressed and embedded into the through-grooves of the connector, effectively preventing the dense metal connector from detaching from the porous metal material tube blank, ensuring the connection strength between the porous metal material tube blank and the dense metal connector; ② it effectively avoids the risk of sintering stress concentration and cooling cracking caused by the difference in thermal expansion coefficients between the two heterogeneous materials, Fe3Al porous metal material and dense metal connector, during high-temperature sintering; through the annular inclined surface and the Fe3Al porous metal material... By adding interfacial transition metal powder at the interface of the two dissimilar materials, an intermediate metal layer is added to the dissimilar bonding area to wet the bonding surface. This solves the problem that dissimilar materials with large differences in melting points are difficult to form a metallurgical bond at the bonding surface, resulting in a stable molten solidification structure. The method of this invention enables the dissimilar material connection between Fe3Al porous metal material and dense metal connector, forming a metallurgical bond at the interface of the two dissimilar materials. This allows the two dissimilar materials to be connected into a single unit with high strength, and the bonding area has a uniform transition, higher surface consistency, and no defects. This effectively solves the problems of high welding difficulty and poor mechanical properties of welds in existing dissimilar material connection schemes. Furthermore, the dissimilar material connector prepared by this invention has higher overall strength and can operate for a long period of time in harsh filtration environments (such as highly corrosive fluids and strong mechanical impacts), making it more suitable for mass production. Attached Figure Description

[0018] Figure 1 A flowchart illustrating the steps of a method for connecting a porous metal material and a dense metal connector in accordance with an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the heterogeneous material connector in a heterogeneous material connection method between a porous metal material and a dense metal connector provided in an embodiment of the present invention; Figure 3 This is a process flow diagram of a method for joining heterogeneous materials, namely porous metal material and dense metal connector, provided in an embodiment of the present invention.

[0019] Figure labels and descriptions: 1. Dense metal connector; 11. First part; 12. Second part; 13. Ring bevel; 14. Long strip through groove; 15. Arc-shaped transition structure; 16. Raised step; 2. Porous metal material tube. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, the use of "based on" or "according to" implies openness and inclusiveness, because processes, steps, calculations, or other actions "based on" or "according to" one or more of the stated conditions or values ​​may in practice be based on additional conditions or beyond the stated values.

[0022] In existing technologies, researchers have proposed a welding method for microporous Fe-Al intermetallic compound materials and the resulting welded components for heterogeneous joining of Fe-Al based metal compounds. This method addresses the poor weldability of Fe-Al microporous materials to dense stainless steel by employing fusion welding. The welding of Fe-Al intermetallic compound microporous materials to dense stainless steel is achieved through the use of welding wire and multi-channel welding gas protection in the joint area during welding. By optimizing process parameters and using welding wire material as filler, the two heterogeneous materials, Fe3Al porous metal material and dense stainless steel, can be combined. The welded filter tubes prepared using this method show full and uniform welds, free from defects such as undercut, surface cracks, missing material, and obvious weld beads. Furthermore, the method mentions that tensile and bending mechanical tests on the welded joints show that fracture occurred in the heat-affected zone of the weld. The welded joint comprises three parts: the weld, the fusion zone, and the heat-affected zone.

[0023] However, using welding to join dissimilar materials to prepare ultra-long Fe3Al porous metal materials still faces significant risks and limitations in engineering applications. Specifically, filter tubes welded using existing technology can only meet the requirements of a certain width, smoothness, and visual defects on the outer surface of the weld. In harsh filtration environments such as those with highly corrosive fluids and strong mechanical impacts, the weld, as a sensitive part of the filter tube, cannot guarantee the overall performance and service life of the entire filter tube due to insufficient bonding strength.

[0024] Therefore, using existing welding methods to join Fe3Al porous metal materials with dense metal connectors, or to prepare ultra-long porous metal materials, presents problems such as high welding difficulty, poor mechanical properties of the weld after welding, and unsuitability for mass production.

[0025] To address the problems of high welding difficulty, poor mechanical properties of welds, and unsuitability for mass production in existing heterogeneous material joining schemes, this invention provides a method for joining porous metal materials and dense metal connectors.

[0026] like Figure 1 , Figure 2 As shown, the method for connecting porous metal materials and dense metal connectors 1 in a heterogeneous material manner according to an embodiment of the present invention specifically includes the following steps: Step 101: Prepare a dense metal connector made of stainless steel.

[0027] Among them, the dense metal connector 1 is a cylindrical structure, which includes an integrally connected first part 11 and second part 12. The outer periphery of the second part 12 is an annular inclined surface 13, and multiple through grooves are axially opened on the outer periphery of the second part 12.

[0028] The annular inclined surface 13 has raised steps 16 along its radial direction, and the surface of the raised steps 16 is roughened.

[0029] Specifically, the dense metal connector 1 can be a stainless steel pipe made of materials such as S30408, S31603, or S31008. For example... Figure 2 As shown, the first part 11 refers to the upper half of the dense metal connector 1, and the second part 12 refers to the lower half of the dense metal connector 1. The upper half is a cylindrical structure; the lower half is a variable diameter tubular structure, and the outer surface of the lower half is an annular inclined surface 13. In order to increase the contact area between the annular inclined surface 13 and the Fe3Al porous metal material, the surface of the annular inclined surface 13 is provided with multiple raised steps 16 in the radial direction for mechanical engagement with the Fe3Al porous metal material. In order to increase the friction between the annular inclined surface 13 and the Fe3Al porous metal material, the surface of the raised steps 16 is roughened. In order to avoid stress concentration and cooling cracking risks caused by the difference in thermal expansion coefficients of heterogeneous materials during subsequent high-temperature confinement sintering, multiple through grooves are vertically opened in the lower half.

[0030] Step 102: Apply interface transition metal powder evenly to the annular inclined surface 13 of the dense metal connector 1, then position the first part 11 at the end of the filter tube mold, insert the dense metal connector 1 into the filter tube mold, and fill the filter tube mold with Fe3Al alloy powder. After cold isostatic pressing and molding, demold to obtain an integrally formed tube blank.

[0031] The thickness of the integrally formed tube blank is the same as the thickness of the first part 11.

[0032] Specifically, a layer of interface transition metal powder is applied to the surface of the annular inclined surface 13 of the dense metal connector 1. The dense metal connector 1 is placed at the end of the filter tube mold, with the end of the first part 11 of the dense metal connector 1 facing the end of the filter tube mold. Then, Fe3Al alloy powder is uniformly loaded into the filter tube mold. After that, it is pressed and formed using a cold isostatic pressing device. After demolding, an integrally formed tube blank is obtained.

[0033] The ends of the filter tube mold can be the upper end, the lower end, or both ends.

[0034] The interface transition metal powder is a metallic material used to wet the porous metal material and the dense metal connector 1, serving as an intermediate metal between the porous metal material and the dense metal connector 1 to achieve a metallurgical bonding effect.

[0035] Step 103: High-temperature constrained sintering of the integrally formed tube blank, followed by cooling to obtain a heterogeneous material connector.

[0036] After high-temperature confinement sintering, the heterogeneous materials form a metallurgical bond at the bonding surface, which enables the porous metal material and the dense metal connector 1 to be connected together with high strength at the bonding surface. Moreover, the heterogeneous material bonding area has a uniform transition, high surface consistency, and no visible defects.

[0037] Furthermore, the interface transition metal powder is FeNiCrAlVB. 0.5 P 0.5 alloy.

[0038] FeNiCrAlVB 0.5 P 0.5 This alloy is a high-entropy alloy, a multi-principal-element alloy with iron (Fe), nickel (Ni), chromium (Cr), and aluminum (Al) as the main elements, and vanadium (V), boron (B), and phosphorus (P) added. Through a unique multi-component synergistic effect, this alloy can significantly reduce the sintering temperature while ensuring material properties. Furthermore, the addition of small amounts of boron and phosphorus promotes the formation of low-melting-point phosphides or borides, and the presence of a low-melting-point liquid phase further accelerates the sintering process of the heterogeneous materials, greatly improving the composite strength of the heterogeneous material interface.

[0039] In this embodiment, FeNiCrAlVB 0.5 P 0.5 The chemical element mass fraction of the alloy is Fe (20%~25%), Ni (18%~22%), Cr (15%~20%), Al (10%~15%), V (17%~22%), B (0.5%~1.0%), and P (0.5%~1.0%).

[0040] Furthermore, the particle size range of the interfacial transition metal powder is 15~53μm.

[0041] In this embodiment, in FeNiCrAlVB 0.5 P 0.5 When alloy powder is used as an interfacial transition metal powder, the sintering activity is strongest when the particle size is selected from 15 to 53 μm.

[0042] Furthermore, such as Figure 2 As shown, each through groove is a long strip through groove 14, and the end of the long strip through groove 14 away from the end of the cylindrical structure is provided with an arc-shaped transition structure 15.

[0043] Furthermore, the multiple through slots include 4 to 12 slots uniformly axially formed around the outer periphery of the second part 12.

[0044] With this through-slot structure and quantity design, the connection strength of the dense metal connector 1 will not be reduced, and stress concentration can be effectively avoided.

[0045] Furthermore, before uniformly applying the interface transition metal powder to the annular bevel 13 of the dense metal connector 1, the method further includes: Use a cleaning agent to clean the surface stains of the dense metal connector 1.

[0046] The cleaning agents used can be alkaline or acidic specialized cleaning agents, or organic cleaning agents such as acetone.

[0047] Furthermore, before cold isostatic pressing, the method also includes: compacting the Fe3Al alloy powder inside the filter tube mold using a compaction platform, and then sealing the filter tube mold.

[0048] Specifically, the vibration platform uses mechanical vibration to rearrange the loose Fe3Al alloy powder in the filter tube mold, achieving a denser and more uniform packing state. This improves and stabilizes the powder packing density, thereby reducing the pressing pressure of the preform, improving the uniformity of the preform density, and increasing the preform strength. Consequently, it enhances the density, mechanical properties, and physical properties of the heterogeneous material connectors after high-temperature confined sintering, improves the dimensional accuracy and consistency of the product, and avoids problems such as sintering deformation, cracks, and uneven pore distribution caused by uneven powder packing.

[0049] Furthermore, the pressure for cold isostatic pressing is 100~200MPa, and the holding time is 1~3min.

[0050] Specifically, a pressure range of 100~200MPa and a holding time range of 1~3min can achieve the best comprehensive balance between equipment investment, mold cost, operating efficiency and process reliability while ensuring high uniformity and high performance of the pressed blank.

[0051] Furthermore, the integrally formed tube blank is subjected to high-temperature constrained sintering, and after cooling, a heterogeneous material connector is obtained, specifically including: The integrally formed tube blank is vertically inserted into the center of the sintering boat, and suitable fillers are installed around it to constrain it and prevent longitudinal bending and deformation. In a vacuum environment or protective atmosphere, the temperature is slowly increased and the temperature is held in stages to constrain sintering to 1200℃~1300℃ and held for 2~4 hours to obtain the sintered connector.

[0052] After sintering, the connector is cooled to room temperature with the furnace and discharged to obtain a connector made of heterogeneous materials.

[0053] Suitable packing materials must meet the following key requirements: Chemical inertness means that the filler does not react harmfully with the tube blank material under sintering temperature and atmosphere; Thermal stability, meaning the filler does not melt, decompose, or volatilize; With moderate particle size, the filler is usually fine powder (a few micrometers to tens of micrometers), ensuring that it can tightly fill the gaps and facilitate subsequent cleaning; Matching the coefficient of thermal expansion, that is, the coefficient of thermal expansion of the filler should be as close as possible to that of the tube blank material to reduce thermal stress; Easy to remove, meaning that the filler can be easily peeled off and cleaned from the surface or interior of the tube blank after sintering.

[0054] Furthermore, the heterogeneous material connector includes a dense metal connector 1 and a porous metal material tube 2 formed by sintering Fe3Al alloy powder.

[0055] The porous metal tube 2 has a diameter of 20~120mm, a length of 50~3000mm, a thickness of 2~10mm, and a filter pore diameter of 0.3~100μm.

[0056] The heterogeneous material connection method between porous metal material and dense metal connector 1 provided in this embodiment of the invention effectively increases the bonding area between the dense metal connector 1 and the Fe3Al porous metal material by designing the annular inclined surface 13, the raised step 16 of the annular inclined surface 13, and the surface roughening treatment of the raised step 16 during the preparation of the filter tube. The design of multiple through grooves in the second part 12 of the dense metal connector 1 achieves two objectives: ① the porous metal powder is pressed into the through grooves of the connector by external force, effectively preventing the dense metal connector from detaching from the porous metal tube blank. This ensures the connection strength between the porous metal tube blank and the dense metal connector; ② During the high-temperature sintering process, it effectively avoids the risk of sintering stress concentration and cooling cracking caused by the difference in thermal expansion coefficients between the two dissimilar materials, Fe3Al porous metal material and dense metal connector, during the high-temperature sintering process; By adding interface transition metal powder at the interface between the annular inclined surface 13 and the Fe3Al porous metal material, that is, adding an intermediate layer of metal in the dissimilar bonding area of ​​the two dissimilar materials, wetting the bonding surface, the problem of the dissimilar materials having large differences in melting points and being difficult to form a metallurgical bond at the bonding surface is solved, and a stable molten solidification structure is formed.

[0057] The method of this invention enables the connection of porous metal materials and dense metal connectors 1, forming a metallurgical bond at the interface of the two dissimilar materials. This allows the two dissimilar materials to be connected into a single unit with high strength, and the transition in the interface is uniform, with higher surface consistency and no defects. This effectively solves the problems of high welding difficulty and poor mechanical properties of welds in existing dissimilar material connection schemes. Furthermore, the dissimilar material connectors prepared by this invention have higher overall strength and can operate for a long period of time in harsh filtration environments (such as highly corrosive fluids and strong mechanical impacts), making them more suitable for mass production.

[0058] like Figure 3 As shown, the method for connecting the porous metal material and the dense metal connector 1, which are dissimilar materials according to an embodiment of the present invention, specifically includes: S1, Preparation as follows Figure 2 The stainless steel dense metal connector 1 is shown. The lower half of the dense metal connector 1 has an annular bevel 13 on its outer side, and 4 to 12 strip-shaped through grooves are evenly distributed axially on the outer periphery of the lower half. The top of the strip-shaped through grooves has an arc-shaped transition structure 15. The annular bevel 13 has a raised step 16 along its radial direction, and the surface of the raised step 16 is roughened.

[0059] S2. Use a cleaning agent such as acetone to wipe the stains off the surface of the dense metal connector 1.

[0060] S3. A layer of FeNiCrAlVB is deposited on the surface of the annular inclined surface 13 of the dense metal connector 1. 0.5 P0.5 Alloy powder is used as the interface transition metal powder. It is then inserted into the steel mold and mandrel of the filter tube mold to assemble the filter tube mold. The dense metal connector 1 is located at the end of the filter tube mold, and the end of the dense metal connector 1 away from the annular inclined surface 13 is in contact with the end of the filter tube mold. Then, 40 / 150 mesh Fe3Al alloy powder is uniformly loaded into the filter tube mold. After compaction on a vibration platform, the mold is sealed. The sealed mold is placed in a cold isostatic pressing equipment, and the pressing pressure is 100-200MPa. The holding time is 1-3min. After pressing and molding, the integrally formed tube blank is obtained.

[0061] S4. The integrally formed tube blank is placed into the sintering boat, and filler is filled inside and outside the integrally formed tube blank. Under vacuum or protective atmosphere, the temperature is slowly increased and held in stages, constrained to 1200℃~1300℃, and held for 2~4 hours to obtain the sintered connector. The specific sintering process is as follows:

[0062] S5. After sintering, the connector is cooled to room temperature with the furnace and discharged to obtain a heterogeneous material connector. The dense metal connector 1 of this heterogeneous material connector is integrated with the Fe3Al porous material with high strength, and the bonding area between the dense metal connector 1 and the Fe3Al porous material is uniformly transitioned, resulting in higher consistency of the overall surface quality of the heterogeneous material connector.

[0063] The filter tube prepared by the heterogeneous material connection method of porous metal material and dense metal connector 1 according to the embodiments of the present invention includes a porous metal material tube 2 and a dense metal connector 1 disposed at the open end of the porous metal material tube 2. The dense metal connector 1 is a cylindrical structure, the inner and outer diameters of its top are the same as the inner and outer diameters of the porous metal material tube 2; its bottom is a variable diameter tubular structure, that is, the inner diameter of the bottom of the porous metal material tube 2 is the same as the inner diameter of the porous metal material tube 2, and the outer side of the bottom of the porous metal material tube 2 is an annular inclined surface 13. The annular inclined surface 13 is provided with a raised step 16 in its radial direction, and the surface of the raised step 16 is roughened. 4 to 12 strip-shaped through grooves are uniformly opened axially on the outer periphery of the bottom of the dense metal connector 1, and the top of the strip-shaped through grooves is provided with an arc-shaped transition structure 15.

[0064] A layer of interface transition metal powder is coated between the contact surfaces of the porous metal material tube 2 and the dense metal connector 1. Specifically, an interface transition metal powder is applied to the surface of the annular inclined surface 13. After the dense metal connector 1 and the porous metal material are integrally formed and mechanically engaged, they are sintered into a strong, integrated connection structure under high temperature constraint in a vacuum or protective atmosphere environment. This greatly improves the connection strength between the dense metal connector 1 and the porous metal material. The special structure of this dense metal connector 1 can effectively expand the contact area at the connection between the dense metal connector 1 and the porous metal material tube 2 without affecting the overall filter tube filtration area.

[0065] The heterogeneous integrated filter tube prepared by the method of this invention and the filter tube with traditional welded joint were used to design and prepare tensile specimens. Tensile tests were conducted according to GB / T 228.1-2021, with 3 specimens in each group. The tensile strength and fracture location are shown in Table 1. Table 1. Tensile strength and fracture location of the heterogeneous joint area of ​​the present invention compared with those of a conventional welded joint.

[0066] As can be seen from the above, compared with traditional welded joints, the filter tube prepared by the method of the present invention has greater tensile strength. Furthermore, the tensile fracture point of the traditional welded joint is at the weld seam, while the tensile fracture point of the filter tube prepared by the method of the present invention is at the location of the Fe3Al porous metal material. Obviously, the filter tube prepared by the method of the present invention has higher connection strength at the joint surface between the heterogeneous materials.

[0067] The method for connecting the porous metal material and the dense metal connector 1 of the present invention is fundamentally different from the welding method of the prior art. The present invention can effectively avoid the existence of weak areas at the connection between the two materials.

[0068] Furthermore, existing technologies, such as a method for preparing a dense metal flange porous metal tube and a high-strength, fracture-resistant powder sintered filter tube, mention that dense metal and porous metal materials can be prepared by integral pressing and high-temperature constrained sintering. However, these existing technologies target the same material for both dense and porous metals, which is not applicable to the connection of dissimilar materials in this invention. Since Fe3Al porous metal and dense stainless steel have significant differences in physical (melting point, coefficient of thermal expansion, etc.) and chemical properties, and powder metallurgy porous metal sintering is generally solid-state sintering with a sintering temperature of approximately (0.7-0.8) Tm, simply using existing calculations for dissimilar material sintering and composite bonding would lead to delamination within or outside the bonding zone, or cracks appearing in the bonding zone, preventing the formation of an effective bonding interface.

[0069] In practical applications, the method for connecting the porous metal material and the dense metal connector 1 of the present invention specifically includes: applying an interface transition metal powder to the surface of the pre-prepared annular inclined surface 13 of the dense metal connector 1; integrally forming the dense metal connector 1 and the Fe3Al alloy powder in a filter tube mold using a cold isostatic pressing device; and then subjecting the integrally formed tube blank to high-temperature constrained sintering. This method enables the dissimilar materials to form a metallurgical bond at the bonding surface through high-temperature constrained sintering, resulting in a high-strength connection between the dissimilar materials at the bonding surface. The bonding area exhibits a uniform transition, higher surface consistency, and no defects, ensuring higher strength of the prepared dissimilar material connector and providing the advantage of long-term operation under harsh filtration environments.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for joining dissimilar materials, namely a porous metal material and a dense metal connector, characterized in that, include: A dense metal connector made of stainless steel is prepared. The dense metal connector is a cylindrical structure, which includes an integrally connected first part and a second part. The outer periphery of the second part is an annular inclined surface, and multiple through grooves are axially formed on the outer periphery of the second part. The annular inclined surface is provided with raised steps in its radial direction, and the surface of the raised steps is roughened. Interfacial transition metal powder is uniformly applied to the annular inclined surface of the dense metal connector. Then, the first part is positioned at the end of the filter tube mold. The dense metal connector is then fitted into the filter tube mold, and Fe3Al alloy powder is loaded into the filter tube mold. After cold isostatic pressing and molding, the mold is demolded to obtain an integrally formed tube blank. The thickness of the integrally formed tube blank is the same as the thickness of the first part. The integrally formed tube blank is subjected to high-temperature constrained sintering, and after cooling, a heterogeneous material connector is obtained.

2. The method for connecting porous metal materials and dense metal connectors according to claim 1, characterized in that, The interface transition metal powder is FeNiCrAlVB. 0.5 P 0.5 alloy.

3. The method for connecting porous metal materials and dense metal connectors in heterogeneous materials according to claim 2, characterized in that, The particle size range of the interfacial transition metal powder is 15~53μm.

4. The method for connecting porous metal materials and dense metal connectors according to claim 1, characterized in that, Each of the aforementioned through slots is a long, narrow through slot, and the end of the long, narrow through slot away from the end of the cylindrical structure is provided with an arc-shaped transition structure.

5. The method for connecting porous metal materials and dense metal connectors according to claim 4, characterized in that, The plurality of through slots includes 4 to 12 slots uniformly axially formed on the outer periphery of the second portion.

6. The method for connecting porous metal materials and dense metal connectors according to claim 1, characterized in that, Before uniformly applying interface transition metal powder to the annular bevel of the dense metal connector, the method further includes: Use a cleaning agent to clean the surface of the dense metal connector.

7. The method for connecting porous metal materials and dense metal connectors according to claim 1, characterized in that, Before cold isostatic pressing, the method further includes: compacting the Fe3Al alloy powder inside the filter tube mold using a compaction platform, and then sealing the filter tube mold.

8. The method for connecting porous metal materials and dense metal connectors in heterogeneous materials according to claim 7, characterized in that, The pressure for cold isostatic pressing is 100~200MPa, and the holding time is 1~3min.

9. The method for connecting porous metal materials and dense metal connectors according to claim 1, characterized in that, The integrally formed tube blank is subjected to high-temperature constrained sintering, and after cooling, a heterogeneous material connector is obtained, specifically including: The integrally formed tube blank is loaded into a sintering boat and fitted with suitable filler. In a vacuum or protective atmosphere, the temperature is slowly increased and held in stages to constrain sintering to 1200℃~1300℃ for 2~4 hours to obtain the sintered connector. The sintered connector is cooled to room temperature in the furnace and discharged to obtain a connector made of heterogeneous materials.

10. The method for connecting porous metal materials and dense metal connectors in heterogeneous materials according to claim 9, characterized in that, The heterogeneous material connector includes a dense metal connector and a porous metal material tube formed by sintering the Fe3Al alloy powder. The porous metal tube has a diameter of 20-120 mm, a length of 50-3000 mm, a thickness of 2-10 mm, and a pore size of 0.3-100 μm.

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