A method for preparing an in-situ filled aluminum foam metal tube

Abstract

A method for preparing an in-situ filled metal tube with aluminum foam belongs to the field of porous metal materials technology. This invention involves treating a foaming agent under a protective atmosphere, preparing an alloy, adding the foaming agent, casting a foamed preform, surface treatment, induction heating for foaming, and cooling to prepare the aluminum foam-filled metal tube component. During the preparation process, the foaming agent, titanium hydride, is treated at a high temperature above 600°C under a protective atmosphere. Then, an aluminum alloy is used to prepare the melt, which is melted using molten salt brazing flux before reaching the melting temperature of the preform, removing the oxide film from the preform and the inner wall of the thin-walled tube. Finally, induction heating is used to rapidly raise the temperature of the preform to the melting and foaming temperature, ensuring a tight bond between the preform and the thin-walled tube and preventing further oxidation. The method provided by this invention has a simple preparation process, produces uniformly porous aluminum foam, and enables a tight bond between the aluminum foam and the metal tube.

Description

Technical Field

[0001] This invention belongs to the field of porous metal materials technology, specifically relating to a method for preparing an in-situ filled aluminum foam metal tube. Background Technology

[0002] Aluminum foam is a lightweight, high-strength, high-energy-absorbing, and heat-insulating / noise-reducing structural-functional material, currently a hot topic for use as a lightweight, impact-resistant, and energy-absorbing material in lightweight vehicle body components. When used as an energy-absorbing material, it is often used as a core material to fill thin-walled metal tubes, enhancing energy absorption while facilitating connection with other components. Compared to thin-walled metal tubes, aluminum foam-filled tube components exhibit more stable compressive loads, and the interaction between the aluminum foam and the metal tube further enhances energy absorption capacity, making it an excellent buffer energy-absorbing element.

[0003] Existing methods for preparing aluminum foam-filled metal tube components mostly involve cutting pre-prepared aluminum foam into specific shapes and sizes, and then externally filling it into thin-walled hollow metal tubes. Currently, the conventional approach for the aluminum foam filling involves obtaining the required size and shape of the foam metal from a large piece of foam metal using wire cutting or other machining methods. This process is not only inefficient and wasteful of materials, but also costly. Furthermore, due to the external filling method, gaps exist between the aluminum foam and the tube wall, resulting in a lack of tight bonding and affecting the strength and energy absorption performance of the filled tube. Therefore, there is an urgent need to develop a new, short-process technology that can achieve in-situ filling and tight interfacial bonding. Summary of the Invention

[0004] The purpose of this invention is to propose a method for preparing an in-situ filled metal tube with aluminum foam. This method has a simple preparation process, uniform pore size of aluminum foam, and can achieve a tight bond with the metal tube.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing an in-situ filled aluminum foam metal tube includes the following steps:

[0007] Step 1: Protective atmosphere treatment of foaming agent

[0008] The foaming agent is heated to 600-620℃ in a protective atmosphere and held at that temperature for 20-60 minutes, then cooled to room temperature in a protective gas atmosphere. A thin oxide film is formed on the surface of the foaming agent.

[0009] Step 2: Prepare the alloy

[0010] Aluminum alloy is melted, the melt temperature is adjusted, metallic calcium is added to the aluminum alloy while stirring, and the temperature is lowered and then held at that temperature to obtain aluminum alloy melt.

[0011] Step 3: Add foaming agent

[0012] The foaming agent after heat treatment in step 1 is added to the aluminum alloy melt during stirring; wherein, the temperature of adding the foaming agent is 600-625℃, the stirring speed is 800-1200rpm, and the stirring time is 1-4min.

[0013] Step 4: Casting the foamed preform

[0014] After step 3 is completed, the melt is poured into a preheated mold to cast the preform. After the mold cools down, the preform is removed.

[0015] Step 5: Surface Treatment

[0016] Remove the oxide layer from the inner wall of the metal tube and the surface of the preform, apply brazing flux, and dry and store to obtain the preform to be filled and the metal tube; wherein the metal tube is an aluminum tube or a steel tube.

[0017] Step 6: Induction heating foaming

[0018] Place the preform to be filled inside the metal tube, aligning one end, ensuring a tight fit between the preform and the metal tube. If the metal tube is aluminum, a steel mold must be fitted over it, sealing one aligned end. If the metal tube is steel, seal one end of the steel tube, then place the preform at the bottom of the sealed end. Use an induction coil to heat from the aligned end. Once the preform begins to foam, move the coil to the other side at a speed ±10% of the speed at the non-aligned end of the preform.

[0019] Step 7: Cooling: After cooling, the foamed material forms a component of aluminum foam-filled metal tube.

[0020] In step 1, the foaming agent is titanium hydride;

[0021] In step 1, the protective gas is either argon or nitrogen.

[0022] In step 2, the preferred composition of the aluminum alloy in the alloy is AlSi10-12 or AlSi6Cu4 (Mg content less than 0.03%).

[0023] In step 2, after adjusting the temperature to 700-760℃, metallic calcium is added, and the amount added accounts for 2-3% of the total mass of the melt.

[0024] In step 2, metallic calcium is added while stirring at a speed of 800-1200 rpm for 5-10 minutes.

[0025] In step 3, titanium hydride treated with a protective atmosphere in step 1 is added, and the amount added is 1 to 1.5 wt% of the aluminum alloy mass.

[0026] In step 4, the mold preheating temperature is 300-500℃, and the shape and size of the mold cavity match the shape and size of the metal tube cavity.

[0027] In step 5, the inner wall of the metal tube is ground with an angle grinder wheel to remove the oxide layer on the surface of the preform.

[0028] In step 5, the brazing flux is potassium fluoroaluminate, which is prepared into a viscous liquid and applied to the surface of the preform and the inner wall of the metal tube, and then placed in a drying oven to dry and store.

[0029] In step 6, the induction coil is heated to 630-660°C for foaming, and the diameter of the induction coil is 10-20mm larger than the maximum diameter of the mold and the steel pipe.

[0030] At the induction coil, the flux melts first and quickly removes the oxide film on the surface of the preform, and then the aluminum foam expands and comes into contact with the metal tube.

[0031] In step 6, as the coil moves horizontally, the preform gradually foams and comes into contact with the metal tube, eventually resulting in a tightly bonded aluminum foam-filled tube.

[0032] In step 7, the portion heated by the coil is cooled by a forced-air cooling method.

[0033] The key point of this invention is:

[0034] (1) In step 1, the foaming agent titanium hydride is subjected to high temperature treatment above 600°C in a protective atmosphere, which can cause partial decomposition of titanium hydride and the formation of a dense oxide film on the surface. The initial decomposition temperature and the temperature corresponding to the decomposition peak of the treated titanium hydride are significantly increased, which can effectively delay the release of hydrogen. In addition, the protective gas can prevent the titanium hydride powder from burning and agglomerating, reducing the impact on subsequent processes.

[0035] (2) The preferred aluminum alloys are AlSi10-12 or AlSi6Cu4, which have low melting points and good fluidity. This can reduce the temperature at which the foaming agent is added. The titanium hydride treated in step 1 decomposes very little during the stirring process and the melt maintains good fluidity, thus achieving gravity casting of rod-shaped dense preforms with circular or rectangular cross sections.

[0036] (3) The use of molten salt brazing flux can melt before the melting temperature of the preform and remove the oxide film on the preform and the inner wall of the metal tube, so that the aluminum liquid and the inner wall of the tube are fully wetted, which is beneficial to forming a tightly bonded interface.

[0037] (4) The horizontal moving heating method using induction coils improves heating efficiency during the moving process. This allows the brazing flux to melt and remove the oxide layer while the temperature of the preform rapidly rises to the melting and foaming temperatures. The preform then begins to gradually foam, and it adheres tightly to the metal tube, preventing further oxidation. Rapid cooling afterward reduces adverse effects on the microstructure and mechanical properties of the metal tube. Attached Figure Description

[0038] Figure 1 This is a cross-sectional CT slice image of the cylindrical aluminum tube filled with aluminum foam in situ as prepared by the present invention.

[0039] Figure 2 This is a cross-sectional view of the in-situ filled rectangular steel pipe with aluminum foam obtained by the present invention.

[0040] Figure 3 This is a schematic diagram of the induction heating preform of aluminum tube filled with aluminum foam obtained by the present invention.

[0041] Figure 4 This is a schematic diagram of the induction heating preform of the aluminum foam in-situ filled steel pipe obtained by the present invention. Detailed Implementation

[0042] Example 1

[0043] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0044] First, the foaming agent titanium hydride is treated at high temperature in a protective atmosphere of argon: the titanium hydride is heated to 600℃ and held for 60 minutes, then cooled for later use.

[0045] Using AlSi10 alloy as the foam matrix, it was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 760℃, and 2% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 800 rpm for 10 minutes. The temperature was then lowered to 625℃, and 1 wt% of treated titanium hydride was added to the 625℃ aluminum alloy melt. The mixture was stirred at 800 rpm for 4 minutes. After stirring, the melt was quickly poured into a preheated cylindrical mold at 500℃. After cooling, a dense preform was obtained.

[0046] Using an angle grinder wheel, the inner wall of the aluminum tube is ground to remove the oxide layer on the surface of the preform. Potassium fluoroaluminate is prepared into a viscous liquid as a brazing flux and applied to the surface of the preform and the inner wall of the aluminum tube. The tube is then placed in a drying oven to dry and store, resulting in the preform and aluminum tube to be filled.

[0047] Align the preform with one end of the aluminum tube and insert it into a tubular mold that is sealed at one end, as shown in the attached figure. Figure 3As shown, an induction heating coil with a diameter 10mm larger than the mold diameter is used to heat the material from the sealed end to 630℃. After the preform begins to foam, the coil is moved to the other side at a speed ±10% of the speed of the misaligned end of the preform. The portion heated by the coil is then cooled by forced air. After cooling, the foamed material forms a foamed aluminum-filled aluminum tube component, as shown in the attached diagram. Figure 1 As shown in the figure, the aluminum foam and aluminum tube are tightly bonded with a uniform pore structure, resulting in a tightly bonded aluminum foam-filled tube.

[0048] Example 2

[0049] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0050] First, the foaming agent titanium hydride is treated at high temperature in a protective atmosphere of argon: the titanium hydride is heated to 620℃ and held for 20 minutes, then cooled for later use.

[0051] Using AlSi10 alloy as the foam matrix, it was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 730°C, and 2.5% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 900 rpm for 8 minutes. The temperature was then lowered to 600°C, and 1.2 wt% of treated titanium hydride was added to the 600°C semi-solid aluminum melt. The mixture was stirred at 900 rpm for 3 minutes. After stirring, the melt was quickly poured into a preheated rectangular mold at 500°C. After cooling, a dense preform was obtained.

[0052] Using an angle grinder wheel, the inner wall of the steel pipe is ground to remove the oxide layer on the surface of the precast body. Potassium fluoroaluminate brazing flux is prepared into a viscous liquid, applied to the surface of the precast body and the inner wall of the steel pipe, and then placed in a drying oven to dry and store, thus obtaining the precast body and steel pipe to be filled.

[0053] Align the precast structure with one end of the steel pipe and seal it, as shown in the attached document. Figure 4 As shown, an induction heating coil with a diameter 10mm larger than the steel pipe diameter is used to heat the precast material from the sealed end to 630℃. After the precast material begins to foam, the coil is moved to the other side. The coil's moving speed is ±10% of the speed of the misaligned end of the precast material. The portion heated by the coil is then cooled by forced air. After cooling, the foamed material forms a foamed aluminum filled steel pipe component, as shown in the attached diagram. Figure 2 As shown in the figure, the aluminum foam and steel pipe are tightly bonded with a uniform pore structure, resulting in a tightly bonded aluminum foam-filled pipe.

[0054] Example 3

[0055] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0056] First, the foaming agent titanium hydride is treated at high temperature in a nitrogen protective atmosphere: the titanium hydride is heated to 600℃ and held for 60 minutes, then cooled for later use.

[0057] Using AlSi12 alloy as the foam matrix, it was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 760°C, and 3% (by weight) of metallic calcium (by mass of the aluminum alloy) was added to the melt. The mixture was stirred at 1200 rpm for 5 minutes. The temperature was then lowered to 625°C, and 1.5 wt% of treated titanium hydride was added to the 625°C aluminum alloy melt. The mixture was stirred at 1200 rpm for 1 minute. After stirring, the melt was quickly poured into a preheated cylindrical mold at 500°C. After cooling, a dense preform was obtained.

[0058] Using an angle grinder wheel, the inner wall of the aluminum tube is ground to remove the oxide layer on the surface of the preform. Potassium fluoroaluminate is prepared into a viscous liquid as a brazing flux and applied to the surface of the preform and the inner wall of the aluminum tube. The tube is then placed in a drying oven to dry and store, resulting in the preform and aluminum tube to be filled.

[0059] Align the preform with one end of the aluminum tube and place it into a tubular mold sealed at one end. Use an induction heating coil with a diameter 10mm larger than that of the steel tube to start heating from the sealed end. Heat to 640℃ and the preform begins to foam. Then move the coil to the other side. The speed of the coil is ±10% of the speed of the non-aligned end of the preform. Cool the part that has passed through the coil heating with a blower. After cooling, the foamed body forms a filled aluminum tube component with aluminum foam tightly bonded to the aluminum tube.

[0060] Example 4

[0061] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0062] First, the foaming agent titanium hydride is treated at high temperature in a nitrogen protective atmosphere: the titanium hydride is heated to 620℃ and held for 20 minutes, then cooled for later use.

[0063] Using AlSi12 alloy as the foam matrix, it was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 700℃, and 2% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 800 rpm for 10 minutes. The temperature was then lowered to 625℃, and 1 wt% of treated titanium hydride was added to the 625℃ semi-solid aluminum melt. The mixture was stirred at 800 rpm for 4 minutes. After stirring, the melt was quickly poured into a preheated rectangular mold at 300℃. After cooling, a dense preform was obtained.

[0064] Using an angle grinder wheel, the inner wall of the steel pipe is ground to remove the oxide layer on the surface of the precast body. Potassium fluoroaluminate brazing flux is prepared into a viscous liquid, applied to the surface of the precast body and the inner wall of the steel pipe, and then placed in a drying oven to dry and store, thus obtaining the precast body and steel pipe to be filled.

[0065] Align and seal one end of the precast body with the steel pipe. Use an induction heating coil with a diameter 10mm larger than the diameter of the steel pipe to start heating from the sealed end. Heat to 640℃ and after the precast body starts to foam, move the coil to the other side. The speed of the coil is ±10% of the speed of the non-aligned end of the precast body. Cool the part that has passed through the coil heating with a blower. After cooling, the foamed body forms a filled steel pipe component in which aluminum foam and metal pipe are tightly bonded.

[0066] Example 5

[0067] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0068] First, the foaming agent titanium hydride is treated at high temperature in a nitrogen protective atmosphere: the titanium hydride is heated to 600℃ and held for 40 minutes, then cooled for later use.

[0069] Using AlSi6Cu4 alloy (Mg content less than 0.03%) as the foam matrix, the aluminum alloy melt was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 730℃, and 3% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 1200 rpm for 5 minutes. The temperature was then lowered to 625℃, and 1.5 wt% of treated titanium hydride was added to the 625℃ semi-solid aluminum melt. The mixture was stirred at 1200 rpm for 1 minute. After stirring, the melt was quickly poured into a preheated cylindrical mold at 400℃. After cooling, a dense preform was obtained.

[0070] Using an angle grinder wheel, the inner wall of the aluminum tube is ground to remove the oxide layer on the surface of the preform. Potassium fluoroaluminate is prepared into a viscous liquid as a brazing flux and applied to the surface of the preform and the inner wall of the aluminum tube. The tube is then placed in a drying oven to dry and store, resulting in the preform and aluminum tube to be filled.

[0071] Align the preform with one end of the aluminum tube and place it into a tubular mold sealed at one end. Use an induction heating coil with a diameter 20mm larger than that of the steel tube to start heating from the sealed end. Heat to 650℃ and the preform begins to foam. Then move the coil to the other side. The coil moving speed is ±10% of the speed of the non-aligned end of the preform. Cool the part that has passed through the coil heating with a blower. After cooling, the foamed body forms a filled aluminum tube component with aluminum foam tightly bonded to the aluminum tube.

[0072] Example 6

[0073] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0074] First, the foaming agent titanium hydride is treated at high temperature in a nitrogen protective atmosphere: the titanium hydride is heated to 600℃ and held for 40 minutes, then cooled for later use.

[0075] Using AlSi6Cu4 alloy (Mg content less than 0.03%) as the foam matrix, the aluminum alloy melt was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 750℃, and 2.5% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 900 rpm for 5 minutes. The temperature was then lowered to 620℃, and 1.2 wt% of treated titanium hydride was added to the 620℃ semi-solid aluminum melt. The mixture was stirred at 900 rpm for 4 minutes. After stirring, the melt was quickly poured into a preheated rectangular mold at 400℃. After cooling, a dense preform was obtained.

[0076] Using an angle grinder wheel, the inner wall of the steel pipe is ground to remove the oxide layer on the surface of the precast body. Potassium fluoroaluminate brazing flux is prepared into a viscous liquid, applied to the surface of the precast body and the inner wall of the steel pipe, and then placed in a drying oven to dry and store, thus obtaining the precast body and steel pipe to be filled.

[0077] Align and seal one end of the precast body with the steel pipe. Use an induction heating coil with a diameter 20mm larger than the diameter of the steel pipe to start heating from the sealed end. Heat to 650℃ and after the precast body begins to foam, move the coil to the other side. The speed of the coil is ±10% of the speed of the non-aligned end of the precast body. Cool the part that has passed through the coil heating with a blower. After cooling, the foamed body forms a filled steel pipe component in which aluminum foam and metal pipe are tightly bonded.

[0078] Example 7

[0079] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0080] First, the foaming agent titanium hydride is treated at high temperature in a protective atmosphere of argon: the titanium hydride is heated to 620℃ and held for 50 minutes, then cooled for later use.

[0081] Using AlSi12 alloy as the foam matrix, it was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 730°C, and 2.5% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 900 rpm for 8 minutes. The temperature was then lowered to 600°C, and 1.2 wt% of treated titanium hydride was added to the 600°C semi-solid aluminum melt. The mixture was stirred at 900 rpm for 3 minutes. After stirring, the melt was quickly poured into a preheated cylindrical mold at 300°C. After cooling, a dense preform was obtained.

[0082] Using an angle grinder wheel, the inner wall of the aluminum tube is ground to remove the oxide layer on the surface of the preform. Potassium fluoroaluminate is prepared into a viscous liquid as a brazing flux and applied to the surface of the preform and the inner wall of the aluminum tube. The tube is then placed in a drying oven to dry and store, resulting in the preform and aluminum tube to be filled.

[0083] Align the preform with one end of the aluminum tube and place it into a tubular mold sealed at one end. Use an induction heating coil with a diameter 20mm larger than that of the steel tube to start heating from the sealed end. Heat to 660℃ and the preform begins to foam. Then move the coil to the other side. The speed of the coil is ±10% of the speed of the non-aligned end of the preform. Cool the part that has passed through the coil heating with a blower. After cooling, the foamed body forms a filled aluminum tube component with aluminum foam tightly bonded to the aluminum tube.

[0084] Example 8

[0085] A method for preparing an in-situ filled aluminum foam metal tube comprises the following steps:

[0086] First, the foaming agent titanium hydride is treated at high temperature in a nitrogen protective atmosphere: the titanium hydride is heated to 620℃ and held for 50 minutes, then cooled for later use.

[0087] Using AlSi10 alloy as the foam matrix, it was melted in a crucible to obtain an aluminum alloy melt. The temperature was then adjusted to 760℃, and 3% (by weight of the aluminum alloy) of calcium was added to the melt. The mixture was stirred at 1200 rpm for 5 minutes. The temperature was then lowered to 625℃, and 1.5 wt% of treated titanium hydride was added to the 625℃ semi-solid aluminum melt. The mixture was stirred at 1200 rpm for 1 minute. After stirring, the melt was quickly poured into a preheated cylindrical mold at 300℃. After cooling, a dense preform was obtained.

[0088] Using an angle grinder wheel, the aluminum tube is ground to remove the oxide layer on the surface of the preform. Potassium fluoroaluminate is prepared into a viscous liquid as a brazing flux and applied to the surface of the preform and the inner wall of the aluminum tube. The tube is then placed in a drying oven to dry and store, resulting in the preform and aluminum tube to be filled.

[0089] Align the preform with one end of the aluminum tube and place it into a tubular mold sealed at one end. Use an induction heating coil with a diameter 20mm larger than that of the steel tube to start heating from the sealed end. Heat to 660℃ and the preform begins to foam. Then move the coil to the other side. The speed of the coil is ±10% of the speed of the non-aligned end of the preform. Cool the part that has passed through the coil heating with a blower. After cooling, the foamed body forms a filled aluminum tube component with aluminum foam tightly bonded to the aluminum tube.

Claims

1. A method for preparing an in-situ filled aluminum foam metal tube, characterized in that, Includes the following steps: Step 1: Protective atmosphere treatment of foaming agent: Heat the foaming agent to 600-620℃ in a protective atmosphere and keep it at that temperature for 20-60 minutes. Then cool it to room temperature in a protective gas atmosphere. An oxide film will be formed on the surface of the foaming agent. Step 2: Alloy preparation: Melt the aluminum alloy, adjust the melt temperature, stir and add metallic calcium into the aluminum alloy, and then keep it at a certain temperature after cooling to obtain the aluminum alloy melt; Step 3: Add foaming agent: Add the foaming agent obtained from the heat treatment in Step 1 to the aluminum alloy melt while stirring; wherein, the temperature at which the foaming agent is added is 600-625℃; Step 4: Casting the foamed preform: After step 3, pour the melt into a preheated mold to cast the preform. After the mold cools down, remove the preform. Step 5: Surface treatment: Remove the oxide layer from the inner wall of the metal tube and the surface of the preform, apply brazing flux, and dry and store to obtain the preform to be filled and the metal tube; wherein the metal tube is an aluminum tube or a steel tube; Step 6: Induction heating foaming: Place the preform to be filled inside the metal tube, aligning one end, ensuring the preform is tightly fitted to the metal tube; use an induction coil to start heating from the aligned end, and after the preform begins to foam, move the coil to the other side, with the coil moving speed being ±10% of the moving speed of the non-aligned end of the preform; Step 7: Cooling: After cooling, the foamed material forms a component of aluminum foam-filled metal tube.

2. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 1, the foaming agent is titanium hydride, and the protective gas is either argon or nitrogen.

3. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 2, the aluminum alloy composition in the alloy is either AlSi10-12 or AlSi6Cu4, wherein the Mg content in AlSi6Cu4 is less than 0.03%. After adjusting the temperature to 700-760℃, add metallic calcium, which accounts for 2-3% of the total mass of the melt. Add metallic calcium while stirring at 800-1200 rpm for 5-10 minutes.

4. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 3, titanium hydride treated with a protective atmosphere in step 1 is added, and the amount added is 1 to 1.5 wt% of the aluminum alloy mass; the stirring speed is 800 to 1200 rpm, and the stirring time is 1 to 4 min.

5. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 4, the mold preheating temperature is 300~500℃, and the shape and size of the mold cavity match the shape and size of the metal tube cavity.

6. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 5, the inner wall of the metal tube is ground with an angle grinder wheel to remove the oxide layer on the surface of the preform. The brazing flux is potassium fluoroaluminate, which is prepared into a viscous liquid and applied to the surface of the preform and the inner wall of the metal tube, and then placed in a drying oven to dry and store.

7. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 6, if the metal tube is an aluminum tube, a steel mold needs to be fitted over the metal tube and one end of the mold needs to be aligned and sealed; if the metal tube is a steel tube, one end of the steel tube is sealed and then the preform is installed at the bottom of the sealed end. The induction coil is heated to 630~660℃ for foaming. The diameter of the induction coil is 10-20mm larger than the maximum diameter of the mold and steel pipe. At the induction coil, the brazing flux melts first and quickly removes the oxide film on the surface of the preform. Then the aluminum foam expands and comes into contact with the metal pipe. As the coil moves horizontally, the preform gradually foams and comes into contact with the metal pipe, finally resulting in a tightly bonded aluminum foam-filled pipe.

8. The method for preparing an in-situ filled aluminum foam metal tube according to claim 1, characterized in that, In step 7, the portion heated by the coil is cooled by a forced-air cooling method.

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