Stirrer for preparing metal matrix composite material by liquid stirring casting method

Abstract

The invention discloses a stirrer for preparing a metal-based composite material by a liquid stirring casting method, and relates to the field of metal-based composite material preparation. The invention aims to solve the problem that particles with the particle size of less than 10 microns are not easy to enter and disperse in a metal melt. The device is composed of a motor, a flange, a cylinder, a pore plate, fixing rods and an auger screw shaft, the flange is fixed to a motor shell, the pore plate is fixed to one end of the cylinder, the cylinder and the flange on the motor are fixedly connected together through the three fixing rods, the upper end of the auger screw shaft is fixedly connected with a rotating shaft of the motor, and the lower end of the auger screw shaft is located in a center hole of the pore plate. The upper portion of an auger spiral blade on the auger spiral shaft is located outside the cylinder, the lower portion of the auger spiral blade on the auger spiral shaft is located in the cylinder, the outer edge of the auger spiral blade located in the cylinder is attached to the inner wall of the cylinder, and the auger spiral shaft on the stirrer is driven by the motor to rotate. According to the method, the problem that particles with the particle size smaller than 10 micrometers and metal melt are poor in wettability and difficult to add is solved, and the particles can be distributed in a matrix more evenly.

Description

Technical Field

[0001] The invention belongs to the field of preparation of metal-based composite materials, and in particular relates to a liquid metal stirring casting method for metal-based composite materials. Background Art

[0002] Aluminum-based composites have attracted widespread attention due to their high specific strength, specific stiffness, and specific elastic modulus, as well as their excellent wear and high-temperature resistance. Commonly used technologies for preparing particle-reinforced aluminum-based composites include powder metallurgy and casting. Mechanical stirring casting offers simplicity, ease of operation, and the ability to produce large volumes of composite materials. It requires minimal equipment investment, offers low production costs, and offers high efficiency, making it suitable for large-scale production and amenable to industrial applications.

[0003] The performance of particle-reinforced aluminum-based composites is closely related to the size of the reinforcing particles. Currently, the most widely used particles are between 1 and 30 μm. Research has shown that the smaller and more dispersed the reinforcing particles are, the less they reduce the plasticity of the matrix. This is because small particles not only have fewer structural defects themselves, but also have a higher thermal mismatch density around them. Therefore, fine particles exhibit a better strengthening effect on the metal matrix. However, when fine particles agglomerate, the performance of the composite material is greatly reduced and unstable.

[0004] As the size of the particles decreases, their surface energy increases. For example, nanoparticles are more likely to agglomerate than micron particles. Fine particles below 10 μm have poor wettability with the metal melt, making it difficult to enter and evenly disperse in the metal melt, and are prone to agglomeration. This factor makes it difficult to produce metal-based composites with fine particles uniformly distributed in the matrix using the mechanical stirring casting method, restricting its widespread industrial application. The vortex method uses high-speed rotating blades to stir the liquid metal melt, causing it to flow strongly and form a vortex with the stirrer's axis as the center of symmetry. Particles are added to the vortex and the negative pressure suction effect of the vortex is used to draw the particles into the melt. This method has the problem that the vortex stirring easily causes the particles to adhere to the side walls and bottom of the crucible under the action of the vortex centrifugal force. Therefore, it is difficult to add all the fine particles to the melt. It is mainly used to produce metal-based composites containing coarse particles (diameter 50 μm to 100 μm).

[0005] The existing document of the patent application publication number CN114029483A discloses a particle dispersion device consisting of a conveyor, a gas ejector and a dispersion-type breathable brick. The device uses gas powder feeding to add particles to the aluminum alloy melt, and uses breathable bricks for dispersion, so that particles of 100nm to 10μm are evenly dispersed in the aluminum alloy melt. However, the composition of the particle dispersion device is relatively complex, the production cost is high, the operation is relatively complicated, and when gas is introduced into the melt, the particles in the aluminum alloy melt are easily refined out of the melt.

[0006] The existing literature of the patent application publication number CN1676237 discloses a vacuum mechanical double-stirring casting method for preparing particle-reinforced aluminum-based composite materials. The micron particles are evenly distributed in the melt through internal and external double stirrers. The distance between the internal and external stirrers is large, and the shearing effect on the melt may be small. When the shearing effect on the melt is insufficient, particles below 10μm are difficult to disperse.

[0007] Therefore, how to solve the problem that particles smaller than 10 μm are difficult to enter and disperse in the metal melt is one of the key issues in the development of metal matrix composite materials. In view of the above technical problems, this application is specially proposed. Summary of the Invention

[0008] In order to solve the problem that particles below 10 μm are difficult to enter and disperse in a metal melt, the present invention provides a stirrer for preparing a metal matrix composite material by a liquid stirring casting method, thereby improving the performance of the metal composite material.

[0009] The implementation of the present invention can be achieved like this:

[0010] The present invention provides an agitator for a liquid metal stirring casting method, which consists of a motor, a flange, a cylinder, a orifice plate, a fixing rod and an auger screw shaft. The flange is fixed to the motor housing, the orifice plate is fixed to one end of the cylinder, and three fixing rods fix the cylinder and the flange on the motor together. The upper end of the auger screw shaft is fixedly connected to the rotating shaft of the motor, and the lower end is located in the center hole of the orifice plate; the upper part of the auger spiral blade on the auger screw shaft is located outside the cylinder, and the lower part is located inside the cylinder, and the outer edge of the auger spiral blade located in the cylinder is in contact with the inner wall of the cylinder; the auger screw shaft on the agitator can rotate under the drive of the motor, and the flange, fixing rod, cylinder and orifice plate are stationary.

[0011] Preferably, the helix angle of the auger spiral blade is 0.1-10°. The smaller the helix angle, the higher the metal melt filling coefficient and the less air entrainment. The rotational speed of the auger spiral shaft is 300-1200 r / min. The smaller the helix angle, the more conducive to increasing the rotational speed of the auger spiral shaft. Small through holes are evenly distributed on the orifice plate. The center distance between each two small through holes is 4-7 mm. The aperture of the small through holes is 1-2 mm. The smaller the aperture of the small holes or the fewer the number, the greater the shearing effect of the agitator on the melt. The thickness of the orifice plate is 5-10 mm.

[0012] Instructions for Use: This stirrer is designed to operate with the auger shaft, cylinder, and orifice plate placed in a molten metal. The molten metal is placed in a crucible in a furnace, and the motor is located outside the furnace. The motor drives the auger shaft, propelling the molten metal downward from the liquid surface. Because the lower portion of the auger shaft is enclosed by a cylinder, the molten metal rapidly flows out through the small holes in the orifice plate. After reaching the bottom of the crucible, the molten metal then flows upward along the outer wall of the cylinder, forming a flow cycle. The fixed rod is rigid and can be of sufficient length. The auger shaft, cylinder, and orifice plate can be sized to suit production batches, making them suitable for large-scale production of metal-matrix composites. All surfaces of the stirrer that come into contact with the molten metal are coated with an inorganic non-metallic high-temperature-resistant coating, or all components that come into contact with the molten metal are made of inorganic non-metallic high-temperature-resistant materials. Particles are added to the melt while the stirrer is stirring. The particles must be preheated to the same temperature as the melt to prevent solidification.

[0013] The principle of the present invention for solving the problem of completely adding particles below 10 μm into the metal melt is as follows: an auger spiral shaft is used, which has a small centrifugal force on the melt, and can prevent the particles from adhering to the side walls and bottom of the crucible under the action of centrifugal force. At the same time, the stirring range of the auger spiral shaft is wide enough, and the particles will be dispersed into the melt after passing through the orifice plate. The dispersed particles are difficult to escape from the melt, thereby achieving the goal of completely adding the particles to the metal melt.

[0014] The present invention solves the problem of dispersing particles smaller than 10 μm by the following principle: a motor drives the auger's spiral shaft to rotate, propelling the molten metal downward from the liquid surface. Because the lower portion of the auger's spiral shaft is enclosed by a cylinder, the molten metal then rapidly flows out of the small holes in the orifice plate. The melt rapidly passes through the orifice plate's small holes, creating turbulent flow within the small holes. According to the volume flow formula Q = Av and the Reynolds number calculation formula Re = ρvd / μ, the melt flow rate Q1 through the orifice plate per unit time is equal to the reduced flow rate Q2 in the cylinder. The sum of the cross-sectional areas A1 of all the orifice plates' holes is smaller than the cross-sectional area A2 of the cylinder's inner wall. Therefore, the melt flow velocity v1 through the orifices is greater than the flow velocity v2 within the cylinder. d is the equivalent diameter of all the orifice plates' holes, ρ is the density of the molten metal, and μ is the viscosity of the molten metal. Turbulent flow occurs when the Reynolds number Re exceeds 4000. This invention transforms the aluminum alloy melt from laminar flow to numerous tiny turbulent flows, enhancing mixing and achieving more uniform particle distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a schematic structural diagram of a stirrer used in a liquid metal stirring casting method;

[0016] Figure 2 It is a structural diagram of the auger spiral shaft;

[0017] Figure 3Schematic diagram of the cylinder and orifice plate assembly, with the orifice plate fixed to the bottom end of the cylinder;

[0018] Figure 4 A three-dimensional model of a blender;

[0019] Figure 5 10μm SiC prepared using the stirrer of the present invention p Optical metallographic photos of A356 aluminum matrix composites

[0020] Figure 6 40nmAl2O prepared by using the stirrer of the present invention 3p / Al aluminum matrix composite material SEM image.

[0021] Icon: 1-motor; 2-flange; 3-fixing rod; 4-auger screw shaft; 5-cylinder; 6-orifice plate. DETAILED DESCRIPTION

[0022] Example 1

[0023] The present invention provides a stirrer for liquid metal stirring casting, which is composed of a motor, a flange, a cylinder, a perforated plate, a fixing rod and an auger screw shaft. The flange is fixed to the motor housing, the perforated plate is fixed to one end of the cylinder, and the three fixing rods fix the cylinder and the flange on the motor together. The fixing rod and the cylinder are connected by a clamp, and the fixing rod and the flange are fixed by a nut. The upper end of the auger screw shaft is fixedly connected to the rotating shaft of the motor, and the lower end is located in the center hole of the perforated plate; the upper part of the auger spiral blade on the auger screw shaft is located in the cylinder. The outer edge of the auger blades is located outside the cylinder, while the lower portion is located inside the cylinder. The outer edge of the auger blades inside the cylinder is in contact with the inner wall of the cylinder. The auger shaft on the agitator rotates driven by the motor, while the flange, fixed rod, cylinder, and orifice plate remain stationary. The outer edge of the auger shaft is 39mm, the helix angle of the auger blades is 10°, the cylinder is 40mm, and the auger shaft rotates at 300 rpm. The orifice plate has small holes evenly distributed on it, a thickness of 5mm, and the center-to-center spacing between each small hole is 4mm. The aperture of each small hole is 1.5mm. The auger shaft and fixed rod are made of steel and sprayed with a high-temperature resistant inorganic non-metallic coating. The cylinder and orifice plate are made of high-purity graphite.

[0024] First, 1000 g of industrial pure aluminum was melted in a crucible and heated to 720 ° C. The auger screw shaft, cylinder and orifice plate on the stirrer were preheated to 720 ° C. The 10 μm SiC particle powder was preheated to 720 ° C. Then the auger screw shaft, cylinder and orifice plate on the stirrer were inserted into the A356 aluminum alloy melt. Then the stirrer was started and 211 g of 10 μm SiC particle powder was slowly added. After it was completely added, stirring was continued for 5 minutes. Finally, the stirrer was removed to obtain 10 μm SiC p / A356 aluminum matrix composite material. Prepared 10μmSiC p Optical metallographic photos of A356 aluminum matrix composite materials Figure 5 shown.

[0025] Example 2

[0026] The present invention provides a stirrer for liquid metal stirring casting, which is composed of a motor, a flange, a cylinder, a perforated plate, a fixing rod and an auger screw shaft. The flange is fixed to the motor housing, the perforated plate is fixed to one end of the cylinder, and the three fixing rods fix the cylinder and the flange on the motor together. The fixing rod and the cylinder are connected by a clamp, and the fixing rod and the flange are fixed by a nut. The upper end of the auger screw shaft is fixedly connected to the rotating shaft of the motor, and the lower end is located in the center hole of the perforated plate; the upper part of the auger spiral blade on the auger screw shaft is located in the cylinder. The outer edge of the auger blades is located outside the cylinder, while the lower portion is located inside the cylinder. The outer edge of the auger blades is aligned with the inner wall of the cylinder. The auger shaft on the agitator rotates under the drive of the motor, while the flange, fixed rod, cylinder, and orifice plate remain stationary. The outer edge of the auger shaft is 39mm, the helix angle of the auger blades is 5°, the cylinder is 40mm, and the auger shaft rotates at 600 rpm. The orifice plate has evenly distributed small through-holes, a thickness of 5mm, and a center-to-center spacing of 3mm between each small through-hole. The aperture of each small through-hole is 1.5mm. The auger shaft, fixed rod, cylinder, and orifice plate are made of high-temperature resistant inorganic non-metallic materials.

[0027] First, 1000 g of pure aluminum was melted in a crucible and heated to 720 ° C. The auger screw shaft, cylinder and orifice plate on the stirrer were preheated to 720 ° C. The 40 nm Al2O3 particle powder was preheated to 720 ° C. Then the auger screw shaft, cylinder and orifice plate on the stirrer were inserted into the pure aluminum melt. Then the stirrer was started and the 40 nm Al2O3 particle powder was slowly added. After it was completely added, stirring was continued for 5 minutes. Finally, the stirrer was removed to obtain 40 nm Al2O3 particle powder. 3p / Al aluminum-based composite materials. Prepared 40nmAl2O 3p Optical metallographic photos of / Al aluminum-based composite materials Figure 6 shown.

Claims

1. A stirrer for preparing metal matrix composite materials by liquid stirring casting method, characterized in that: The agitator consists of a motor, a flange, a cylinder, a orifice plate, a fixing rod and an auger screw shaft. The flange is fixed to the motor housing, the orifice plate is fixed to one end of the cylinder, and three fixing rods fix the cylinder and the flange on the motor together. The upper end of the auger screw shaft is fixedly connected to the rotating shaft of the motor, and the lower end is located in the center hole of the orifice plate; the upper part of the auger spiral blade on the auger screw shaft is located outside the cylinder, and the lower part is located inside the cylinder. The outer edge of the auger spiral blade located in the cylinder is in contact with the inner wall of the cylinder; the auger screw shaft on the agitator rotates driven by the motor, and the flange, fixing rod, cylinder and orifice plate are stationary.

2. A stirrer for preparing metal matrix composite materials by liquid stirring casting according to claim 1, characterized in that: The spiral angle of the auger spiral blade is 0.1~10°, the speed of the auger spiral shaft is 300~1200r / min, small through holes are evenly distributed on the orifice plate, the center distance between each two small through holes is 3~7mm, the aperture of the small through hole is 1~2mm, and the thickness of the orifice plate is 5~10mm.

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