CN110257660A - A kind of device and method producing small pore diameter foamed aluminium - Google Patents

Abstract

A device and method for producing small-diameter aluminum foam, the device includes a melt storage system, a circulation pipeline, a mixing system, a cooling chamber system and a rolling system; the shrinking and expanding tube of the mixing system is provided with a gas inlet, the The rear end is assembled with the powder feeding equipment; from front to back, the expansion tube is the inlet section of the expansion tube, the constriction section, the horizontal section of the throat, the expansion section and the outlet section of the expansion tube, and the gas inlet is located in the horizontal section of the throat; The method is as follows: introduce the aluminum melt into the storage room; adjust the pressure in the storage room; open the valve to make the aluminum melt flow to the shrinking and expanding tube; then enter the mixing tube to mix the aluminum melt and the tackifier and flow into the cooling room; The inert gas is injected into the tube; the aluminum melt containing bubbles is gradually formed on the top of the liquid surface, and the rolling rollers are started for rolling. The device integration method of the invention reduces the abrasion of the blowing pipe, reduces the secondary pollution to the aluminum liquid, simplifies the device, and realizes the industrialized rapid production of small-diameter closed-cell foamed aluminum.

Description

A device and method for producing small-pore foamed aluminum

technical field

The invention belongs to the technical field of porous metal foam materials, and in particular relates to a device and method for producing foamed aluminum with small pore diameters.

Background technique

As a porous medium, aluminum foam has a large specific surface area and good performance, such as good energy absorption performance, good electromagnetic shielding performance, and is widely used in the aviation industry and construction fields; common aluminum foam is divided into two types: open cell and closed cell , closed-cell aluminum foam is more widely used because of its good thermal insulation performance; the preparation methods of closed-cell aluminum foam are mainly air blowing foaming method, powder metallurgy method and melt foaming method; among them, the air blowing foaming method has simple process , low cost, continuous production and other advantages.

The size of the foamed aluminum cells directly affects the performance of the foamed aluminum material. The smaller the foamed aluminum pore size, the better the energy absorption performance of the foamed aluminum, the better the damping and shock absorption performance, and the higher the mechanical strength; prepared by the existing blowing process For aluminum foam, the pore diameter is generally greater than 5mm; however, as a structural material, the foam aluminum material with a pore diameter less than 5mm has the following advantages: 1. It has better mechanical properties; 2. The shape of the small-pore foam aluminum cavity will be closer to spherical, and the heat conduction More uniform; 3. During the cooling process, the collapse of small-pore aluminum foam cells will be improved, which is conducive to large-scale production; 4. After heat treatment, small-pore foam aluminum is easier to flow and deform, which is conducive to secondary processing; due to blowing The continuous production cost of the foaming method is low, so the preparation of small-pore foamed aluminum with excellent performance by the blowing method is an important direction for the production of foamed aluminum.

The pore size of foamed aluminum is directly related to the bubble size in the preparation process; in the existing foamed aluminum preparation process, a vibrating or rotating blowing pipe is often used to inject gas into the container to generate bubbles with a size of less than 5mm, but this preparation method also There are some disadvantages: 1. Dynamic injection of gas will cause wear and tear of the blowing pipe, which will shorten the service life of the blowing pipe accordingly; 2. The movement of the blowing pipe may cause secondary pollution of the aluminum liquid; 3. This method increases the blowing pipe. Motion control device, the equipment will be more complicated; 4. During the preparation process, the bubbles are blown in one by one, the bubble generation rate is relatively low, and the production efficiency of foamed aluminum is difficult to improve.

Contents of the invention

In view of the above problems, the present invention provides a device and method for producing foamed aluminum with small apertures. By adding a shrinking and expanding pipe to the horizontal section of the liquid aluminum flow pipeline, the high-speed flow of the fluid is sheared to break the airflow, and a large number of small-sized bubbles are generated in a short time. It is used for the cooling and forming of aluminum foam, avoiding the wear and tear of blowing equipment or devices, and at the same time speeding up the generation rate of bubbles, reducing the secondary pollution of molten aluminum, improving the production efficiency of aluminum foam, and realizing the rapid and continuous production of small-diameter aluminum foam materials Production.

The device for producing foamed aluminum with small apertures of the present invention comprises a melt storage system, a circulation pipeline, a mixing system, a cooling chamber system and a rolling system; the top plate of the storage chamber of the melt storage system is provided with an air intake pipe with a There is an outlet pipe with a valve and a pressure gauge. The side wall of the storage room is provided with a heating and heat preservation device, and a feed pipe is provided on the side wall. The feed pipe is provided with a feed valve and a check valve; the flow pipe is equipped with a pipe The valve, the front end of the circulation pipe is connected with the bottom of the storage chamber, and the back end is connected with the mixing system; the mixing system is composed of shrinking and expanding tubes and powder feeding equipment, in which there are more than one gas inlets on the shrinking and expanding tubes, and the rear end of the shrinking and expanding tubes Assembled together with the powder feeding equipment; the shrinking and expanding pipes from front to back are the shrinking and expanding pipe inlet section, the shrinking section, the throat horizontal section, the expansion section and the shrinking and expanding pipe outlet section, and the rear of the shrinking and expanding pipe inlet section and the flow pipe The outlet section of the shrinking and expanding tube is connected with the front end of the mixing pipe of the powder feeding equipment; the gas inlet connects the horizontal section of the throat with the gas source through a pipeline with a valve. When there are more than one gas inlet, each gas inlet Evenly distributed on the same vertical section of the horizontal section of the throat; the powder feeding equipment includes a mixing pipe and a viscosifier feeding pipe connected to it. There is a check valve, a stirring paddle is installed inside the mixing pipe, and the rear end of the mixing pipe is connected with the feed port of the cooling chamber of the cooling system; the cooling chamber of the cooling system is a box, and the bottom is provided with a valve The liquid discharge pipe has a discharge port on the upper side wall, and the outside of the discharge port is connected with the rolling channel of the rolling system. A baffle is provided between the discharge port and the rolling channel, and the top of the discharge port is located at the cooling At the top of the chamber, the height of the discharge port matches the height of the rolling channel; the rolling system is composed of two sets of rolling rollers, the space between the two sets of rolling rollers is the rolling channel.

In the above-mentioned shrinking and expanding tubes, the internal space of the constricting section is a side-mounted circular frustum, the diameter of the top surface of the circular frustum is D1, the diameter of the bottom surface is D2, and the length L1 in the horizontal direction; the internal space of the horizontal section of the throat is a circle Tubular shape with a diameter of D1 and a length of L2 in the horizontal direction; the inner space of the expansion section is in the shape of a truncated cone placed sideways, the diameter of the top surface of the truncated cone is D1, the diameter of the bottom surface is D2, and the length in the horizontal direction is L3; where D2 :D1=1.5～2.5, L1:L3=0.35～0.8, L1:L2=0.4～0.9.

The above-mentioned circulation pipeline includes a horizontal section, and the rear end of the horizontal section communicates with the mixing system.

In the above device, the bottom of the storage chamber is higher than the top of the cooling chamber.

In the above device, the feeding port of the cooling chamber is located at the lower part of the cooling chamber.

In the above device, an asbestos lining is laid on the inner wall of the storage chamber and/or the cooling chamber to protect the aluminum melt.

In the above device, the number of gas inlets is 1-10, and the aperture is 1-2mm.

The method for producing small-aperture aluminum foam of the present invention is to adopt the above-mentioned device, and carries out according to the following steps:

1. Heat aluminum or aluminum alloy to 850-900°C to form aluminum melt; introduce the aluminum melt into the storage room through the feed port, and maintain the temperature of the aluminum melt in the storage room at 850-900°C through the heating and heat preservation device;

2. Open the outlet pipe, pass the inert gas into the storage room through the inlet pipe to discharge the air, then close the outlet pipe, and control the pressure of the inert gas in the storage room at 0-2MPa;

3. Open the pipeline valve on the circulation pipeline so that the aluminum melt flows through the circulation pipeline to the shrinking and expanding tube, and control the flow rate of the aluminum melt at the inlet section of the shrinking and expanding tube to 2-15m/s;

4. Open the feeding valve on the feeding pipe, add the tackifier to the tackifier feeding pipe, the tackifier enters the mixing pipe through the check valve, and open the stirring paddle to mix the tackifier with the aluminum melt to form a mixture The material flows into the cooling chamber;

5. When the liquid level of the mixed material in the cooling chamber is higher than the feed port of the cooling chamber, it is judged that the aluminum melt has filled the circulation pipe; open the gas inlet, and pass the inert gas into the expansion tube through the gas source, and the inert gas is in the Bubbles are formed in the mixed material and enter the cooling chamber together with the mixed material;

6. When the liquid level of the mixed material in the cooling chamber is at the bottom of the discharge port, keep the liquid level at the bottom of the discharge port by opening and closing the valve on the discharge pipe;

7. The mixed material containing bubbles is gradually formed on the top of the liquid surface, and the formed aluminum foam intermediate is accumulated above the liquid surface;

8. When the foamed aluminum intermediate is filled above the liquid level, open the baffle and start two sets of rolling rollers. The foamed aluminum enters the rolling channel from the cooling chamber and is rolled into foamed aluminum material.

In the above step 5, the liquid level of the mixed material is higher than the feeding port of the cooling chamber, keeping at least 10s, and then opening the gas inlet.

In the above step 4, the tackifier is SiC ceramic particles with a particle size of 1-10 μm; the amount of the tackifier entering the mixing tube according to the mass ratio of the tackifier to the aluminum melt per unit time is 0.015 ~0.03.

In the above step 2, the inert gas is nitrogen.

In the above-mentioned step 5, the inert gas is nitrogen; the feed rate of the inert gas enters the volume ratio of the inert gas and the aluminum melt in the contraction and expansion tube per unit time to be 0.003～0.2, and the flow velocity of the inert gas in the gas inlet is 2～6m/s.

In the above method, the temperature fluctuation range of the aluminum melt in the storage chamber is controlled by the heating and heat preservation device to be less than or equal to 20°C.

In the above step 3, while the aluminum melt is discharged, the inert gas is introduced into the storage chamber through the inlet pipe, so that the pressure in the storage chamber fluctuates to ≤0.03 MPa.

In the above method, the flow rate of the aluminum melt at the inlet of the shrinking and expanding tube is coordinated and controlled by the height difference and pressure difference of the materials in the storage chamber and the cooling chamber.

The diameter of the pores in the aluminum foam material is 0.5-5mm, and the porosity is 65-90%.

In the above method, put pure aluminum or aluminum alloy into the mold, heat the mold to melt the pure aluminum or aluminum alloy to obtain aluminum melt, and then introduce it into the storage room through the feeding port,

The working principle of the present invention is as follows: pure aluminum or aluminum alloy is stored in the melt storage room after being melted, and flows downward through the circulation pipe. Multiple air holes in the upper horizontal section lead into the shrinking and expanding tube; the pressure of the aluminum melt decreases at the shrinking point, and the flow rate increases, the gas is directly broken into small-pore bubbles, and a two-phase fluid mixed with small bubbles flows out of the shrinking and expanding tube together. Enter the powder feeding equipment; when the powder feeding equipment is fed with a viscosifier, the viscosity of the two-phase fluid increases, making the foam more stable; the bubbles are further broken by stirring, and the size and distribution of the bubbles are more uniform, and finally cooled in the cooling chamber gradually Forming, and finally obtain a small-pore foam aluminum product with excellent performance.

Compared with the existing invention, the present invention proposes a new method for producing aluminum foam with small pore size, and for the first time in the preparation of aluminum foam by blowing method, the method of contraction and expansion is used to generate small-sized bubbles; Compared with that, the wear of the air blowing pipe is reduced, the secondary pollution to the aluminum liquid is reduced, and the device is simplified; in the production process of the existing air blowing method for preparing small-pore foamed aluminum, single bubbles are injected sequentially, and the present invention utilizes a strong flow field The crushing air flow can generate a large number of small bubbles at the same time, which speeds up the bubble generation rate and realizes the industrialized rapid production of small-pore closed-cell aluminum foam; a powder feeding device is installed at the outlet of the shrinking and expanding tube, the gas-liquid mixture flows through the powder feeding device, and the agitator stirs At the same time as the thickener, the bubbles are further broken, so that the size of the bubbles is reduced, the error of the pore size of the bubbles is reduced, and it is also conducive to the uniform distribution of the bubbles in the aluminum liquid.

Description of drawings

Fig. 1 is the device structural representation of the production small-pore-diameter aluminum foam in the embodiment of the present invention;

Fig. 2 is the schematic diagram of the cross-sectional structure of the shrinking and expanding pipe in Fig. 1;

Among the figure, 1-1, storage chamber, 1-2, intake pipe with valve (adjacent is the outlet pipe with valve), 1-3, pressure gauge, 1-4, heating and insulating device, 1- 5. Feed pipe, 2-1, pipeline valve, 2-2, flow pipe, 3-1, shrinking and expanding pipe, 3-1-1, shrinking and expanding pipe inlet section, 3-1-2, shrinking section, 3 -1-3. Throat horizontal section, 3-1-4. Expansion section, 3-1-5. Shrinking and expanding pipe outlet section, 3-2. Gas inlet, 3-3. Powder feeding equipment, 4-1 , Cooling chamber, 4-2, drain pipe, 5-1, baffle plate, 5-2, rolling roller.

Detailed ways

The aluminum alloy used in the embodiment of the present invention is A357 aluminum alloy, and its liquidus temperature is 615°.

D1 in the embodiment of the present invention=80-100mm.

L1 in the embodiment of the present invention=80-100mm.

In the embodiment of the present invention, the temperature fluctuation range of the aluminum melt in the storage chamber is controlled by the heating and heat preservation device to be ≤20°C.

In the embodiment of the present invention, while the aluminum melt is being discharged, an inert gas is introduced into the storage chamber through the inlet pipe, so that the pressure in the storage chamber fluctuates by ≤0.03 MPa.

In the embodiment of the present invention, the flow rate of the aluminum melt at the inlet of the shrinking and expanding tube is controlled by the height difference and pressure difference between the storage chamber and the cooling chamber.

In the embodiment of the present invention, pure aluminum or aluminum alloy is put into the mold, and the mold is heated to melt the pure aluminum or aluminum alloy to obtain aluminum melt, which is then introduced into the storage chamber through the feeding port,

The diameter of the pores in the aluminum foam material in the embodiment of the present invention is 0.5-5mm, and the porosity is 65-90%.

In the embodiment of the present invention, the stirring paddle is driven by a motor outside the mixing tube.

In the embodiment of the present invention, the stirring speed is 80-2500 rpm.

Example 1

The device structure for producing small-diameter aluminum foam is shown in Figure 1, including a melt storage system, a circulation pipeline 2-2, a mixing system, a cooling chamber system and a rolling system;

The top plate of the storage room 1-1 of the melt storage system is provided with an air inlet pipe 1-2 with a valve, an air outlet pipe with a valve and a pressure gauge 1-3, and the side wall of the storage room 1-1 is provided with a heating insulation A device 1-4, and a feed pipe 1-5 is provided on the side wall, and a feed valve and a check valve are provided on the feed pipe 1-5;

The circulation pipeline 2-2 is equipped with a pipeline valve 2-1, the front end of the circulation pipeline 2-2 communicates with the bottom of the storage chamber 1-2, and the rear end communicates with the mixing system;

The mixing system is composed of shrinking and expanding pipe 3-1 and powder feeding equipment 3-3. There is more than one gas inlet 3-2 on the shrinking and expanding pipe 3-1, and the rear end of shrinking and expanding pipe 3-1 is connected with the powder feeding equipment. 3-3 assembled together;

The structure of the shrinking and expanding tube is shown in Figure 2. From front to back, it is the inlet section of the shrinking and expanding tube 3-1-1, the contraction section 3-1-2, the horizontal section of the throat 3-1-3, and the expansion section 3-1- 4 and the shrinking and expanding tube outlet section 3-1-5, the shrinking and expanding tube inlet section 3-1-1 communicates with the rear end of the circulation pipeline 2-2, the shrinking and expanding tube outlet section 3-1-5 is connected to the powder feeding equipment 3- The front end of the mixing pipe of 3 is communicated; each gas inlet 3-2 connects the throat horizontal section 3-1-3 with the gas source through a pipeline with a valve, and the number of gas inlets 3-2 is 5, and the aperture 1.5mm, each gas inlet 3-2 is evenly distributed on the same vertical section of the throat horizontal section 3-1-3;

The powder feeding equipment 3-3 includes a mixing pipe and a tackifier feeding pipe connected thereto. The tackifier feeding pipe is provided with a feeding valve, and a check valve is arranged between the feeding valve and the mixing pipe. There is a stirring paddle, and the rear end of the mixing pipe communicates with the feed port of the cooling chamber 4-1 of the cooling system;

The cooling chamber 4-1 of the cooling system is a box, the bottom of which is provided with a drain pipe 4-2 with a valve, and the upper side wall is provided with a discharge port, and the outside of the discharge port is connected with the rolling channel of the rolling system Connected, a baffle 5-1 is provided between the discharge port and the rolling channel, and the top of the discharge port is located at the top of the cooling chamber 4-1, and the height of the discharge port matches the height of the rolling channel;

The rolling system is composed of upper and lower two sets of rolling rollers 5-2, and the space between the two sets of rolling rollers 5-2 is the rolling channel;

The inner space of the constriction section 3-1-2 is a side-mounted circular frustum, the diameter of the top surface of the circular frustum is D1, the diameter of the bottom surface is D2, and the length in the horizontal direction is L1; the interior of the throat horizontal section 3-1-3 The space is cylindrical, with a diameter of D1 and a length of L2 in the horizontal direction; the internal space of the expansion section 3-1-4 is in the shape of a truncated cone placed sideways, the diameter of the top surface of the truncated cone is D1, the diameter of the bottom surface is D2, and the horizontal The length of the direction is L3; where D2:D1=1.5, L1:L3=0.35, L1:L2=0.4;

The circulation pipeline 2-2 includes a horizontal section, and the rear end of the horizontal section communicates with the mixing system;

The bottom of the storage chamber is higher than the top of the cooling chamber;

The feed port of the cooling chamber is located at the lower part of the cooling chamber;

Asbestos lining is laid on the inner wall of the storage room and cooling room to protect the aluminum melt;

The method proceeds as follows:

Heat aluminum or aluminum alloy to 850°C to form an aluminum melt; introduce the aluminum melt into the storage room through the feed port, and maintain the temperature of the aluminum melt in the storage room at 850°C through the heating and heat preservation device;

Open the outlet pipe, pass nitrogen into the storage chamber through the inlet pipe to discharge the air, then close the outlet pipe, and control the pressure of nitrogen in the storage chamber to 0-2 MPa relative to the atmospheric pressure;

Open the pipeline valve on the circulation pipeline, so that the aluminum melt flows through the circulation pipeline to the expansion tube, and control the flow rate of the aluminum melt at the inlet section of the expansion tube to 2m/s;

Open the feeding valve on the feeding pipe, add tackifier to the tackifier feeding pipe, the tackifier enters the mixing pipe through the check valve, open the stirring paddle to mix the tackifier with the aluminum melt, and the formed mixture flows into the Cooling chamber; the viscosifier is SiC ceramic particles with a particle size of 1-10 μm; the mass ratio of the viscosifier to the aluminum melt entering the mixing tube per unit time is 0.015;

When the liquid level of the mixed material in the cooling chamber is higher than the inlet of the cooling chamber, it is judged that the aluminum melt has filled the flow pipe; after holding for 10s, open the gas inlet, and pass inert gas into the shrinking and expanding tube through the gas source, inert The gas forms bubbles in the mixed material, and enters the cooling chamber together with the mixed material; the inert gas is nitrogen; the volume ratio of the inert gas entering the shrinking and expanding tube per unit time to the aluminum melt is 0.1, and the inert gas The flow velocity of the gas in the gas inlet is 2m/s;

When the liquid level of the mixed material in the cooling chamber is at the bottom of the discharge port, the liquid level is maintained at the bottom of the discharge port by opening and closing the valve on the discharge pipe;

The aluminum melt containing bubbles is gradually formed on the top of the liquid surface, forming foamed aluminum intermediates that accumulate above the liquid surface;

When the foamed aluminum intermediate is filled above the liquid level, the baffle is opened, and two sets of rolling rollers are started, and the foamed aluminum enters the rolling channel from the cooling chamber, and is rolled into foamed aluminum material.

Example 2

Device is the same as embodiment 1, and difference is:

(1) The number of gas inlets 3-2 is 10, and the aperture is 1 mm;

(2) D2:D1=2, L1:L3=0.5, L1:L2=0.6;

Method is with embodiment 1, and difference is:

(1) The temperature of the aluminum melt is maintained at 860°C;

(2) The flow velocity of the aluminum melt at the inlet section of the shrinking and expanding tube is 5m/s;

(3) The mass ratio of the tackifier and the aluminum melt entering the mixing tube per unit time is 0.02;

(4) The volume ratio of the inert gas and the aluminum melt entering the shrinking tube per unit time is 0.003, and the flow velocity of the inert gas in the gas inlet is 3m/s.

Example 3

Device is the same as embodiment 1, and difference is:

(1) The number of gas inlet 3-2 is 1, and the aperture is 2mm;

(2) D2:D1=2, L1:L3=0.6, L1:L2=0.8;

Method is with embodiment 1, and difference is:

(1) The temperature of the aluminum melt is maintained at 880°C;

(2) The flow velocity of the aluminum melt at the inlet section of the shrinking and expanding tube is 10m/s;

(3) The mass ratio of the tackifier and the aluminum melt entering the inside of the mixing tube per unit time is 0.025;

(4) The volume ratio of the inert gas and the aluminum melt entering the shrinking tube per unit time is 0.05, and the flow velocity of the inert gas in the gas inlet is 4m/s.

Example 4

Device is the same as embodiment 1, and difference is:

(1) The number of gas inlets 3-2 is 8, and the aperture is 1.5mm;

(2) D2:D1=2.5, L1:L3=0.8, L1:L2=0.9;

Method is with embodiment 1, and difference is:

(1) The temperature of the aluminum melt is maintained at 900°C;

(2) The flow velocity of the aluminum melt at the inlet section of the shrinking and expanding tube is 15m/s;

(3) The mass ratio of the tackifier and the aluminum melt entering the mixing tube per unit time is 0.03;

(4) The volume ratio of the inert gas and aluminum melt entering the shrinking tube per unit time is 0.2, and the flow velocity of the inert gas in the gas inlet is 6m/s.

Although the specific implementation of the present invention has been described above, those skilled in the art should understand that the above implementation can be modified in many ways without departing from the principle and essence of the present invention, and the protection scope of the present invention is only limited by the claims.

Claims (10)

1. A device for producing foamed aluminum with small apertures, characterized in that it includes a melt storage system, a circulation pipeline, a mixing system, a cooling chamber system and a rolling system; the top plate of the storage chamber of the melt storage system is provided with a valve The inlet pipe, outlet pipe with valve and pressure gauge, the side wall of the storage room is equipped with a heating and heat preservation device, and the side wall is provided with a feed pipe, and the feed pipe is provided with a feed valve and a check valve; the circulation The pipeline is equipped with pipeline valves, the front end of the circulation pipeline is connected with the bottom of the storage chamber, and the rear end is connected with the mixing system; the mixing system is composed of shrinking and expanding pipes and powder feeding equipment, wherein the shrinking and expanding pipes are provided with more than one gas inlet. The rear end of the shrinking and expanding tube is assembled with the powder feeding equipment; the shrinking and expanding tube is sequentially divided into the inlet section of the shrinking and expanding tube, the constriction section, the horizontal section of the throat, the expansion section and the outlet section of the shrinking and expanding tube, and the inlet section of the shrinking and expanding tube It communicates with the back end of the circulation pipe, and the outlet section of the shrinkage and expansion pipe communicates with the front end of the mixing pipe of the powder feeding equipment; the gas inlet connects the horizontal section of the throat with the gas source through a pipeline with a valve. When there are more than one gas inlet , the gas inlets are evenly distributed on the same vertical section of the horizontal section of the throat; the powder feeding equipment includes a mixing pipe and a viscosifier feeding pipe connected to it. There is a check valve between the mixing pipes, a stirring paddle is arranged inside the mixing pipe, and the rear end of the mixing pipe communicates with the feeding port of the cooling chamber of the cooling system; the cooling chamber of the cooling system is a box, and the bottom of the mixing pipe is set There is a discharge pipe with a valve, and the upper side wall is provided with a discharge port, the outside of the discharge port is connected with the rolling channel of the rolling system, and a baffle is provided between the discharge port and the rolling channel, and the discharge port The top of the feed port is located at the top of the cooling chamber, and the height of the discharge port matches the height of the rolling channel; the rolling system consists of two sets of rolling rollers, the space between the two sets of rolling rolls is the rolling channel. 2. A device for producing small-diameter foamed aluminum according to claim 1, characterized in that in the shrinking-expanding tube, the inner space of the shrinking section is a truncated circular shape placed sideways, and the diameter of the top surface of the truncated circular shape is D1, the diameter of the bottom surface is D2, the length in the horizontal direction is L1; the internal space of the horizontal section of the throat is cylindrical, the diameter is D1, and the length in the horizontal direction is L2; The diameter of the top surface of the shape is D1, the diameter of the bottom surface is D2, and the length in the horizontal direction is L3; where D2:D1=1.5～2.5, L1:L3=0.35～0.8, L1:L2=0.4～0.9. 3. A device for producing foamed aluminum with small pore diameters according to claim 1, characterized in that the number of said gas inlets is 1-10, and the pore diameter is 1-2mm. 4. A method for producing small-aperture aluminum foam, characterized in that the device according to claim 1 is used to carry out in the following steps: (1) Heating aluminum or aluminum alloy to 850-900°C to form aluminum melt; introducing the aluminum melt into the storage room through the feed port, and maintaining the temperature of the aluminum melt in the storage room at 850-900°C through the heating and heat preservation device; (2) Open the outlet pipe, pass inert gas into the storage chamber through the inlet pipe to discharge the air, then close the outlet pipe, and control the pressure of the inert gas in the storage chamber at 0-2 MPa; (3) Open the pipeline valve on the circulation pipeline, so that the aluminum melt flows to the shrinkage expansion tube through the circulation pipeline, and control the flow velocity of the aluminum melt at the inlet section of the shrinkage expansion tube to be 2 to 15m/s; (4) Open the feeding valve on the feed pipe, add tackifier to the tackifier feeding pipe, the tackifier enters the mixing pipe through the check valve, and open the stirring paddle to mix the tackifier with the aluminum melt to form a The mixed material flows into the cooling chamber; (5) When the liquid level of the mixed material in the cooling chamber is higher than the feed inlet of the cooling chamber, it is judged that the aluminum melt has filled the flow pipe; open the gas inlet, and pass the inert gas into the shrinking and expanding pipe through the gas source, and the inert gas Bubbles are formed in the mixed material and enter the cooling chamber together with the mixed material; (6) When the liquid level of the mixed material in the cooling chamber is at the bottom of the discharge port, the liquid level is maintained at the bottom of the discharge port by opening and closing the valve on the discharge pipe; (7) The mixed material containing bubbles is gradually formed on the top of the liquid surface, and the formed aluminum foam intermediate is accumulated above the liquid surface; (8) When the foamed aluminum intermediate is filled above the liquid level, open the baffle and start two sets of rolling rollers, and the foamed aluminum enters the rolling channel from the cooling chamber and is rolled into foamed aluminum material. 5. A method for producing small-pore aluminum foam according to claim 4, characterized in that in step (4), the tackifier is SiC ceramic particles with a particle diameter of 1 to 10 μm; the amount of the tackifier The mass ratio of the tackifier to the aluminum melt entering the mixing tube per unit time is 0.015-0.03. 6. A kind of method of producing small-pore aluminum foam according to claim 4, it is characterized in that in step (5), inert gas is nitrogen; The feed rate of inert gas enters the inert gas of contraction and expansion pipe in unit time The volume ratio of the aluminum melt to the aluminum melt is 0.003-0.2, and the flow velocity of the inert gas in the gas inlet is 2-6 m/s. 7. A method for producing small-pore foamed aluminum according to claim 4, characterized in that in step (3), the flow rate of the aluminum melt at the inlet of the shrinking and expanding tube passes through the height difference between the storage chamber and the cooling chamber material and differential pressure control. 8. A method for producing small-diameter foamed aluminum according to claim 4, characterized in that the diameter of the holes in the foamed aluminum material is 0.5-5mm, and the porosity is 65-90%. 9. A method of producing small-pore aluminum foam according to claim 4, characterized in that in step (5), the liquid level of the mixed material is higher than the feed port of the cooling chamber, keeps at least 10s, and then opens the gas vent Entrance. 10. A method of producing small-pore aluminum foam according to claim 4, characterized in that in step (2), the inert gas is nitrogen.