Preparation method and preparation device of spherical regularly-distributed porous metal

Abstract

The invention provides a preparation method and a preparation device of spherical regularly-distributed porous metal, and particularly relates to the technical field of foamed aluminum materials, the preparation method comprises the following steps: an aluminum ingot is put into an aluminum melting furnace to be melted into molten aluminum for later use; preparing sodium sulfate, sodium chloride, phosphate, kaolin, hexamethylenetetramine and modified starch, mixing, and placing in a ball mill for spheroidizing to form a porous preform; placing the porous prefabricated body in a mold, uniformly filling the mold with the porous prefabricated body, and preheating the mold; after preheating, the mold is placed on a vibrator, and molten aluminum is injected into the mold; and electrifying the two sides of the mold, and carrying out electric pulse treatment. According to the preparation method and the preparation device of the spherical regularly-distributed porous metal, the porous prefabricated body is fully and thoroughly demoulded from the metal material, the sodium chloride is modified, so that the material and the process of the porous prefabricated body are optimized, and the adhesion phenomenon is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of foam aluminum materials, and in particular relates to a preparation method and a preparation device for spherical regularly distributed porous metal. Background Art

[0002] Porous aluminum foam is a material with integrated structure and function, with high specific strength, specific stiffness, good energy absorption, damping and sound absorption properties, and therefore has a wide range of uses in transportation, aerospace, machinery, packaging and other industries. So far, from the foaming form of aluminum foam studied by various countries, aluminum foam materials are generally divided into two types of bubbles, one is that the bubbles exist independently, called independent bubble type, also called closed-cell type, and the other is that the bubbles are continuous, called continuous bubble type, also called open-cell type.

[0003] Porous aluminum foam is divided into spherical, regular polyhedral and polygonal holes according to the shape of the holes. At present, regular polyhedral and polygonal holes are usually irregular, with very complex internal structures, and poor performance repeatability and reproducibility. Therefore, the development of spherical through-hole aluminum foam and corresponding preparation technology is very necessary for practical applications, and the main process of spherical porous aluminum foam is the infiltration method, which is as follows: first prepare spherical particles, then prepare the spherical particles into a porous preform, apply a certain pressure to the molten metal to make it infiltrate into the porous preform, remove the particles after solidification, and obtain a foam metal with three-dimensional through holes. Among them, the preparation of spherical particle porous preform is one of its key processes.

[0004] There are many methods for preparing spherical particle preforms. For example, polygonal sodium chloride particles are used as raw materials, the polygonal sodium chloride particles are spheroidized, and then made into porous preforms; or salt powder is first crushed and sieved with a ball mill, and then the sodium chloride particles are placed on a rough plate for further polishing to obtain spherical sodium chloride particles.

[0005] However, due to the limitations of the material, there is a big problem in the current production process of spherical porous foam aluminum, that is, the porous preform is not fully and thoroughly demolded from the metal material, and there is a phenomenon of adhesion; therefore, this scheme proposes a preparation method and preparation device for spherical regularly distributed porous metal to solve the above-mentioned technical problems. Summary of the invention

[0006] The purpose of the present invention is to provide a method and a device for preparing spherical regularly distributed porous metal, which solves the technical problem of fully and thoroughly demolding a porous preform from a metal material. By modifying sodium chloride, the material and process of the porous preform are optimized, adhesion is avoided, and the demolding and cleaning process of foam aluminum is greatly facilitated.

[0007] A method for preparing spherical regularly distributed porous metal comprises the following steps: Step S1: placing the aluminum ingot into an aluminum melting furnace to melt it into aluminum liquid for standby use; Step S2: preparing sodium sulfate, sodium chloride, phosphate, kaolin, hexamethylenetetramine, and modified starch, mixing them in a mass ratio of (2.0-3.0): (5.0-7.0): (0.5-1.5): (1.0-3.0): (1.0-2.0): (0.5-1.0), and placing them in a ball mill for spheroidization treatment to form a porous preform; Step S3: placing the porous preform in a mold and filling the mold evenly, and preheating the mold; Step S4: After preheating, the mold is taken out, and then the aluminum liquid is injected into the mold. During the injection process, the bottom of the mold is vacuumed. After the injection is completed, the air pressure is increased inside the top of the mold; Step S5: After cooling is completed, the relevant devices and molds are disassembled, the metal parts are taken out, and the non-bonded spherical aluminum foam material is obtained after cleaning.

[0008] Preferably, in step S2, graphene is also mixed, and the mass ratio of sodium sulfate to graphene is: sodium sulfate / graphene=(2.0-3.0):(1.0-2.0).

[0009] Preferably, in step S2, the mass ratio of the phosphate+hexamethylenetetramine to the modified starch is (2.0-2.5):(0.6-0.8).

[0010] Preferably, both sides of the mold are electrified and subjected to electric pulse treatment, so that the aluminum liquid and the porous preform are placed in the electric field of the electric pulse as a whole.

[0011] A device for preparing spherical regularly distributed porous metal includes a mold, a vibrator arranged at the bottom of the mold, a ventilation component connected to the top of the mold, an air suction component connected to the bottom of the mold, and an electric pulse component connected to the outside of the mold, wherein the ventilation component, the air suction component and the electric pulse component are all connected to a fixed frame.

[0012] Preferably, the mold comprises a horizontally arranged bottom plate, first side plates respectively positioned at both sides of the bottom plate, second side plates respectively positioned at both ends of the bottom plate, and a closing plate movably arranged at the top ends of the first side plate and the second side plate, and the upper end surfaces of the bottom plate are respectively provided with long grooves, the bottom ends of the first side plates are embedded in the long grooves, and the ends of the first side plates are clamped on the second side plates; Two ends of the bottom plate are respectively vertically provided with vertical screw rods, the vertical screw rods pass through the second side plate, and the top end of the vertical screw rods is provided with a nut 1; The outer sides of the two second side panels are respectively provided with protruding blocks, on which transverse screw rods are passed, and two nuts are respectively provided at both ends of the transverse screw rods to form a pulling state, and fastening bolts are passed through the outer sides of the transverse screw rods, and the small heads of the fastening bolts are against the first side panels.

[0013] Preferably, the ventilation assembly includes an air pipe 1 whose one end is connected to the closing plate and an air compressor connected to the other end of the air pipe 1, and the air compressor is fixed on the fixing frame.

[0014] Preferably, the suction component includes an air pipe 2 connected to the base plate at one end and a vacuum pump connected to the other end of the air pipe 2. A perforation is provided on the base plate, and multiple layers of filter plates are provided in the perforations. A threaded barrel is provided at the bottom end of the perforations, and one end of the air pipe 2 is threadedly connected to the threaded barrel.

[0015] Preferably, the electric pulse component includes a pulse power supply and two wires connected to the pulse power supply, and one end of the two wires are respectively connected to the two first side plates.

[0016] Preferably, a rotating rod is rotatably provided on the fixing frame, one end of the rotating rod is rotatably connected to the fixing frame, and a pressure column is vertically passed through the other end, the outer side of the pressure column is threadedly connected to the rotating rod and the bottom end is pressed against the upper end surface of the closing plate.

[0017] The beneficial effects of the present invention are as follows: (1) The porous preform in this scheme contains sodium sulfate. Since sodium sulfate is neutral and has weak oxidizing and reducing properties, it does not react with aluminum. Therefore, sodium sulfate will not adhere to aluminum at high temperatures, which facilitates the subsequent demolding of the porous preform and the foamed aluminum. (2) Phosphates inhibit the pitting resistance of aluminum foam to a certain extent, making it easy to corrode, while a small amount of phosphates helps the surface of aluminum foam to bond with foreign objects; The porous preform in this scheme contains kaolin, which is a soil with a high aluminum content. The main component, aluminum oxide, has good bonding properties, helps spheroidization, and has a certain strength; Hexamethylenetetramine is not only a foaming agent, but also used as a metal cleaning agent. Therefore, it not only helps to form aluminum foam, but also helps in the subsequent washing process of aluminum foam. (3) Adding modified starch to the porous preform can, on the one hand, increase the overall stability and viscosity of the preform and reduce the surface tension; on the other hand, the modified starch reacts with phosphate to produce phosphate starch, which can improve the smoothness of the porous preform and enhance the finish of the pores of the foamed aluminum. In addition, the modified starch also has good tensile strength, disintegration and anti-hygroscopicity, and is not affected by air humidity; (4) Graphene and aluminum matrix have non-wetting properties, resulting in weak interfacial bonding strength and low interfacial load transfer efficiency, which is the bottleneck of graphene-reinforced aluminum-based composites. However, this scheme uses the opposite approach to achieve efficient separation of porous preforms and foamed aluminum. (5) Electric pulse treatment of the molten metal helps to refine the coarse dendritic primary crystals in the alloy solidification structure into a spherical structure. The dendrites are broken and crushed, and the grains are significantly refined. The spherical grains in the alloy structure and the spherical porous preform are in point contact with each other and have weak connectivity. Therefore, the separation of the two is also easier. In this scheme, grain refinement is introduced into the preparation of porous metals.

[0018] (6) The final experimental results also prove that the porous preform formula and corresponding treatment process provided in this scheme, after the modification of sodium chloride, make the demoulding of the porous preform from the foamed aluminum more complete and thorough, avoiding adhesion, and the bubble pores are uniform in size and regularly distributed, with good effects, reducing costs and increasing the market competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the porous metal preparation device in the present invention.

[0020] Figure 2 It is a structural schematic diagram of the mold in the present invention.

[0021] Figure 3 It is a schematic diagram of the position structure of the ventilation component, the suction component and the electric pulse component in the present invention.

[0022] Figure 4 It is a schematic diagram of the connection structure between the bottom plate and the first side plate in the present invention.

[0023] Among them, the figure markings are: 1, vibrator; 2, bottom plate; 3, support column; 4, first side plate; 5, horizontal screw; 51, fastening bolt; 6, nut one; 7, second side plate; 8, nut two; 9, closing plate; 10, pressure column; 11, rotating rod; 12, air pipe one; 13, air compressor; 14, pulse power supply; 15, wire; 16, vacuum pump; 17, air pipe two; 21, long groove; 22, filter. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the technical features of this solution, this solution is described below through specific implementation methods.

[0025] Embodiment 1:

[0026] Sodium sulfate, sodium chloride, phosphate, kaolin, hexamethylenetetramine, and modified starch are prepared, mixed in a mass ratio of (2.0-3.0): (5.0-7.0): (0.5-1.5): (1.0-3.0): (1.0-2.0): (0.5-1.0), and placed in a ball mill for spheroidization to form a porous preform; Table 1 shows the mass ratio of each component in Example 1, in kg.

[0027] Table 1 Mass ratio of each component in Example 1 Case Ingredients Example 1 (Group 1) Example 1 (Group 2) Comparative Example Sodium sulfate 2.0 3.0 Sodium chloride 5.0 7.0 100% Phosphate 0.5 1.5 Kaolin 1.0 3.0 Hexamethylenetetramine 1.0 2.0 Modified starch 0.5 1.0 When the porous preform contains only sodium chloride, the interface impurities are very obvious, not cleaned, uneven in size, and extremely irregular in distribution. By comparing the foaming conditions in Example 1 (Group 1) and Example 1 (Group 2), it can be seen that after the sodium chloride is modified in this scheme, the porous preform is fully and thoroughly demolded from the metal material, avoiding adhesion, and the size is uniform and the distribution is regular.

[0028] It should be noted that in this Example 1, when the mass ratio of phosphate + hexamethylenetetramine to modified starch is (2.0-2.5): (0.6-0.8), experimental results similar to those in the following Example 2 can be obtained, which will not be described in detail here.

[0029] Embodiment 2:

[0030] Based on the above-mentioned Example 1, Example 2 was designed. Table 2 shows the mass ratios of the various components in Example 2, in kg.

[0031] Table 2 Mass ratio of each component in Example 2 Case Ingredients Example 2 (Group 1) Example 2 (Group 2) Comparative Example Sodium sulfate 2.0 3.0 Sodium chloride 5.0 7.0 100% Phosphate 0.5 1.5 Kaolin 1.0 3.0 Hexamethylenetetramine 1.0 2.0 Modified starch 0.5 1.0 Graphene 1.0 2.0 By comparing the foaming conditions in Example 2 (Group 1) and Example 2 (Group 2), it can be seen that after the sodium chloride is modified in this scheme and graphene is added, the porous preform is fully and thoroughly demolded from the metal material to avoid adhesion. At the same time, compared with Example 2, it can be seen that the entire interface is brighter and smoother. It can be seen that the addition of graphene improves the overall foaming quality, and the size is uniform and the distribution is regular.

[0032] Embodiment 3:

[0033] On the basis of the above-mentioned embodiment 2, embodiment 3 is designed to add electric pulse treatment. The entire interface is brighter and smoother than embodiment 2, the treatment effect is better, and the size is uniform and the distribution is regular. Therefore, the quality of aluminum foam treated by graphene superimposed with electric pulses is proved to be an effective decontamination method.

[0034] See also Figure 1-Figure 4 A preparation device for spherical regularly distributed porous metal includes a mold, a ventilation component connected to the top of the mold, an air suction component connected to the bottom of the mold, and an electric pulse component connected to the outside of the mold. The ventilation component, the air suction component and the electric pulse component are all connected to a fixed frame.

[0035] The mold includes a horizontally arranged bottom plate 2, first side plates 4 respectively positioned at both sides of the bottom plate 2, second side plates 7 respectively positioned at both ends of the bottom plate 2, and a closing plate 9 movably arranged at the top ends of the first side plate 4 and the second side plate 7. Long grooves 21 are respectively arranged on the upper end surfaces of the bottom plate 2, the bottom ends of the first side plates 4 are embedded in the long grooves 21, and the ends of the first side plates 4 are clamped on the second side plates 7. Vertical screws are vertically arranged at both ends of the bottom plate 2, respectively. The vertical screws pass through the second side plate 7, and a nut 6 is arranged at the top of the vertical screws. The outer sides of the two second side plates 7 are respectively provided with protruding blocks, on which transverse screw rods 5 are passed, and two nuts 8 are respectively provided at both ends of the transverse screw rods 5 to form a pulling state, and fastening bolts 51 are passed through the outer sides of the transverse screw rods 5, and the small heads of the fastening bolts 51 are against the first side plate 4.

[0036] More preferably, a vibrator 1 is arranged at the bottom end of the mold, and micro-vibration is achieved under the action of the vibrator 1.

[0037] The bottom surface of the bottom plate 2 is positioned on the vibrator 1 through the support column 3 .

[0038] The ventilation assembly includes an air pipe 12 whose one end is connected to the closing plate 9 and an air compressor 13 connected to the other end of the air pipe 12. The air compressor 13 is fixed on a fixed frame.

[0039] The suction component includes an air pipe 17 connected to the base plate 2 at one end and a vacuum pump 16 connected to the other end of the air pipe 17. The base plate 2 is provided with a perforation, and a multi-layer filter sheet 22 is arranged in the perforation. A threaded barrel is arranged at the bottom end of the perforation, and one end of the air pipe 17 is threadedly connected to the threaded barrel.

[0040] The multi-layer filter 22 designed here has no connection relationship between the upper and lower adjacent layers, but only a contact relationship. When the top layer of the filter comes into contact with the molten metal, this layer of the filter can further block the aluminum liquid from falling, and it is also convenient to separate the layers of the filter when removing the foam aluminum later.

[0041] The electric pulse component includes a pulse power supply 14 and two wires 15 connected to the pulse power supply 14 . One end of the two wires 15 is connected to the two first side plates 4 respectively.

[0042] A rotating rod 11 is rotatably arranged on the fixed frame, one end of the rotating rod 11 is rotatably connected to the fixed frame, and a pressure column 10 is vertically penetrated at the other end. The outer side of the pressure column 10 is threadedly connected to the rotating rod 11, and the bottom end is pressed on the upper end surface of the closing plate 9 to achieve the closure of the mold cavity.

[0043] Working principle of a preparation device for spherical regularly distributed porous metal: The bottom plate 2, the first side plate 4 and the second side plate 7 are installed, and a long groove 21 is provided on the upper end surface of the bottom plate 2, the bottom end of the first side plate 4 is embedded in the long groove 21, and a protruding structure is provided on the inner surface of the second side plate 7, and the outer end of the first side plate 4 is clamped on the outer side of the protruding structure. Under the pulling of the vertical screw and the horizontal screw 5, and under the pressing of the first side plate 4 by the fastening bolts, the overall fastening and sealing of the outer side of the mold is achieved; the closing plate 9 is horizontally slidably set on the top ends of the first side plate 4 and the second side plate 7, and under the action of the rotating rod 11 and the pressure column 10, the threaded pre-tightening force of the pressure column 10 makes the closing plate 9 tightly fit the top ends of the first side plate 4 and the second side plate 7 to achieve sealing.

[0044] When the mold preparation is completed, the closing plate 9 is removed, the spherical porous preform is placed in the mold, the closing plate 9 is covered, and the mold is placed in a heating furnace for preheating treatment; After preheating, the mold is taken out and connected to the vibrator 1, the air pipe 1 12 and the air pipe 2 17 are connected to the top and bottom of the mold respectively, and the two wires 15 are connected to the two first side plates 4 respectively, and the pulse power supply 14 is started; the closing plate 9 is opened, and then the aluminum liquid is injected into the mold. During the injection process, the bottom of the mold is vacuumed. After the injection is completed, the closing plate 9 is moved to seal the top of the mold, and the air compressor 13 is turned on to increase the air pressure inside the top of the mold to increase the speed of the aluminum liquid flowing from top to bottom. At the same time, the vibrator 1 is turned on, which not only speeds up the flow of the aluminum liquid, but also helps to discharge bubbles; At the same time, power is supplied to both sides of the mold for electric pulse treatment, so that the aluminum liquid and the porous preform are placed in the electric field of the electric pulse as a whole; after cooling is completed, the relevant devices and molds are disassembled, the metal parts are taken out, and after cleaning, a non-bonded spherical aluminum foam material is obtained.

[0045] Technical features not described in the present invention can be achieved through or by adopting existing technologies and will not be described in detail here. Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for preparing spherical regularly distributed porous metal, characterized in that: The specific steps include: Step S1: placing the aluminum ingot into an aluminum melting furnace to melt it into aluminum liquid for standby use; Step S2: preparing sodium sulfate, sodium chloride, phosphate, kaolin, hexamethylenetetramine, and modified starch, mixing them in a mass ratio of (2.0-3.0): (5.0-7.0): (0.5-1.5): (1.0-3.0): (1.0-2.0): (0.5-1.0), and placing them in a ball mill for spheroidization treatment to form a porous preform; Step S3: placing the porous preform in a mold and filling the mold evenly, and preheating the mold; Step S4: After preheating, the mold is taken out, and then the aluminum liquid is injected into the mold. During the injection process, the bottom of the mold is vacuumed. After the injection is completed, the air pressure is increased inside the top of the mold; Step S5: After cooling is completed, the relevant devices and molds are disassembled, the metal parts are taken out, and the non-bonded spherical aluminum foam material is obtained after cleaning with a high-pressure spray gun.

2. The method for preparing a spherical regularly distributed porous metal according to claim 1, characterized in that: In the step S2, graphene is also mixed, and the mass ratio of sodium sulfate to graphene is: sodium sulfate / graphene=(2.0-3.0):(1.0-2.0).

3. The method for preparing a spherical regularly distributed porous metal according to claim 1, characterized in that: In the step S2, the mass ratio of the phosphate+hexamethylenetetramine to the modified starch is (2.0-2.5):(0.6-0.8).

4. The method for preparing a spherical regularly distributed porous metal according to claim 1, characterized in that: In the step S4, during pouring, both sides of the mold are energized to perform electric pulse treatment, so that the aluminum liquid and the porous preform are placed in the electric field of the electric pulse as a whole.

5. A device for preparing spherical regularly distributed porous metal, using a method for preparing spherical regularly distributed porous metal as claimed in any one of claims 1 to 4, characterized in that: The invention comprises a mold, a vibrator (1) arranged at the bottom end of the mold, a ventilation component connected to the top end of the mold, an air suction component connected to the bottom end of the mold, and an electric pulse component connected to the outer side of the mold, wherein the ventilation component, the air suction component and the electric pulse component are all connected to a fixing frame.

6. The device for preparing spherical regularly distributed porous metal according to claim 5, characterized in that: The mold comprises a horizontally arranged bottom plate (2), first side plates (4) respectively positioned on both sides of the bottom plate (2), second side plates (7) respectively positioned on both ends of the bottom plate (2), and a closing plate (9) movably arranged at the top ends of the first side plate (4) and the second side plate (7), the upper end surfaces of the bottom plate (2) are respectively provided with long grooves (21), the bottom ends of the first side plates (4) are embedded in the long grooves (21), and the ends of the first side plates (4) are clamped on the second side plates (7); Vertical screw rods are respectively arranged vertically at both ends of the bottom plate (2), the vertical screw rods pass through the second side plate (7), and a nut 1 (6) is arranged at the top end of the vertical screw rods; The outer sides of the two second side plates (7) are respectively provided with protruding blocks, and a transverse screw rod (5) is passed through the protruding blocks. Two nuts (8) are respectively provided at both ends of the transverse screw rod (5) to form a pulling state. A fastening bolt (51) is passed through the outer sides of the transverse screw rod (5), and the small head of the fastening bolt (51) abuts against the first side plate (4).

7. The device for preparing spherical regularly distributed porous metal according to claim 6, characterized in that: The ventilation assembly comprises an air pipe (12) having one end connected to the closing plate (9) and an air compressor (13) connected to the other end of the air pipe (12); the air compressor (13) is fixed on the fixing frame.

8. The device for preparing spherical regularly distributed porous metal according to claim 6, characterized in that: The air suction component comprises a second air pipe (17) whose one end is connected to the bottom plate (2), and a vacuum pump (16) connected to the other end of the second air pipe (17); the bottom plate (2) is provided with a perforation, a multi-layer filter sheet (22) is provided in the perforation, a threaded barrel is provided at the bottom end of the perforation, and one end of the second air pipe (17) is threadedly connected to the threaded barrel.

9. The device for preparing spherical regularly distributed porous metal according to claim 5, characterized in that: The electric pulse assembly comprises a pulse power supply (14), and two wires (15) connected to the pulse power supply (14), wherein one end of the two wires (15) is respectively connected to the two first side plates (4).

10. The device for preparing spherical regularly distributed porous metal according to claim 6, characterized in that: A rotating rod (11) is rotatably arranged on the fixing frame, one end of the rotating rod (11) is rotatably connected to the fixing frame, and a pressure column (10) is vertically passed through the other end, the outer side of the pressure column (10) is threadedly connected to the rotating rod (11) and the bottom end is pressed against the upper end surface of the closing plate (9).

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