Powder dropping device for metal composite material, binder jet printing process and metal composite material

Abstract

The present invention provides a powder dropping device for metal composite materials, a binder jet printing process and a metal composite material, comprising a movable powder cylinder, a powder hopper and a plane moving device; at least one powder hopper is installed inside the powder cylinder, and the powder hopper is used to mix metal powders of two different materials; the feeding speed of the powder hopper is controlled to achieve gradient mixing of the metal powders of two different materials; a plane moving device is installed on the powder hopper to make the powder outlet of the powder mixing device move in the plane; the movement of the powder bed is controlled and the position of the powder outlet of the powder mixing device is changed by the plane moving device, so as to achieve the gradient change of the mixed metal powder in space. The present invention can realize the manufacture of component gradient and structural gradient metal composite parts for binder jet printing.

Description

Technical Field

[0001] The present invention relates to the technical field of metal powder bed 3D printing, and in particular to a powder dropping device for metal composite materials, a binder jetting printing process and a metal composite material. Background Art

[0002] Binder jetting uses an inkjet printhead to spray a binder onto powder, allowing a layer of powder to be bonded together in a specified area. Each layer of powder is combined with the previous layer of powder, and is formed into a whole through the penetration of the binder, stacked layer by layer, to create an object with a three-dimensional structure. This technology is suitable for the manufacture of polymer materials, metals and ceramic materials. In the manufacture of metal and ceramic materials, the prototype is sintered at high temperature to remove the binder, thereby obtaining a finished product with the required density and strength.

[0003] However, existing technologies cannot achieve the laying of heterogeneous powder beds, which limits the binder jet printing of heterogeneous materials and composite materials.

[0004] The prior art discloses a multi-material, adjustable-format powder feeding device and powder feeding method suitable for binder jet additive manufacturing, but it has the following problems: the powder cylinder is divided by a baffle, and the material composition change in the X direction cannot be achieved, and only multi-layer heterogeneous metal composite materials can be prepared; there is no composition gradient in the printing direction (Z), that is, there is no composition gradient between layers; the powder falls from the powder storage bin into the powder receiving shaft, and the powder in the powder receiving shaft falls into the powder spreading shaft again, and the powder in the powder spreading shaft falls into the forming cylinder again. The powder is transported three times, and the heterogeneous powders are mixed to form mixed powders during the three transport processes, and the determined composition of the printed part at the specified position cannot be accurately controlled. It is not operable and practical. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a powder dropping device for metal composite materials, a binder jet printing process and a metal composite material. The position of the powder hopper is controlled by a plane moving device to achieve powder scattering at a specified position on the printing forming surface. The mixing function of the powder hopper achieves gradient mixing of heterogeneous powders, thereby realizing the manufacturing of metal composite material parts with composition gradient and structure gradient.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A powder dropping device for metal composite materials, comprising a movable powder cylinder, a powder hopper, an ultrasonic vibration device and a plane moving device;

[0008] A screen is installed at the powder outlet of the powder cylinder, and at least one powder hopper is installed inside the powder cylinder, and the powder hopper is used to mix metal powders of two different materials; the gradient mixing of the metal powders of two different materials is achieved by controlling the feeding speed of the powder hopper; the powder outlet of the powder hopper extends to the screen and is in close contact with the screen; a plane moving device is installed on the powder hopper, which is used to move the powder outlet of the powder mixing device in a plane; the ultrasonic vibration device is in contact with the screen, and the powder in the powder cylinder and the powder hopper is evenly scattered in the forming cylinder to form a metal composite material powder bed by vibrating the screen; by controlling the movement of the powder bed and changing the position of the powder outlet of the powder hopper through the plane moving device, the composition and structural gradient changes of the mixed metal powder in space can be achieved.

[0009] Furthermore, the powder hopper includes a powder mixer, a powder conveying pipe and a powder feeding pipe; the powder feeders of two different metal powders are connected to the powder mixer inlet through the powder feeding pipes respectively, and the powder mixer is used to mix the metal powders; the powder conveying pipe is installed at the outlet of the powder mixer, and one end of the powder conveying pipe is in close contact with the screen.

[0010] Furthermore, by controlling the conveying speeds of the powder feeders of the two different metal powders respectively, the amounts of the two different metal powders entering the powder mixer are controlled, thereby controlling the composition gradient of the metal powders of the two different materials; the range of the composition gradient is 10%-90%.

[0011] Furthermore, the mesh size of the sieve is 200-1000 meshes; and the ultrasonic vibration frequency of the ultrasonic vibration device is 80-2000 Hz.

[0012] A binder jet printing process using a powder dropping device of a metal composite material comprises the following steps:

[0013] Printing of the current layer: moving the powder hopper to a set position by means of a plane moving device, mixing powders of different metal materials and dropping the powders to the set position; placing base powder in the powder cylinder; laying a powder bed, compacting the powder bed and printing the current layer;

[0014] Printing the next layer: changing at least one of the set position, the powder mixing gradient of different metal materials, and the base powder material, and forming a changed powder bed, compacting the powder bed and printing the next layer;

[0015] Change the height of the powder bed and repeat the printing of the next layer.

[0016] Furthermore, in the printing of the next layer, the set position and the powder mixing gradient of different metal materials are changed, so that the spatial position gradient of the different metal materials after molding in the matrix changes, and the composition gradient of the different metal materials changes.

[0017] A metal composite material with a composition gradient and a structure gradient is printed by a binder jet printing process.

[0018] Furthermore, each layer of the metal composite material includes a matrix region and a reinforcement region, and there is at least one reinforcement region in the matrix region, and the reinforcement region is formed by mixed powders of different metal materials; the positions and / or material compositions of the reinforcement regions in adjacent layers of the metal composite material are different.

[0019] Furthermore, the materials of the matrix regions in adjacent layers of the metal composite material are changed alternately.

[0020] The beneficial effects of the present invention are:

[0021] 1. In the powder dropping device for the metal composite material described in the present invention, the powder outlet of the powder hopper extends to the screen and is in close contact with the screen, so that the metal powder in the powder conveying pipe will not be mixed with the matrix powder, and the close contact with the screen can prevent powder leakage from the side. The metal powder falls directly onto the powder bed of the forming cylinder, the process path is simple, there is no powder transfer process, and it is ensured that different powders will not mix with each other and there is no cross contamination between different powders.

[0022] 2. The powder dropping device for the metal composite material described in the present invention controls the powder dropping amount of the screen by an ultrasonic vibration device, and controls the position of the powder hopper by a plane moving device to achieve powder scattering at a specified position on the surface.

[0023] 3. The binder jet printing process described in the present invention realizes the gradient mixing of heterogeneous powders through the powder mixing function of the powder hopper, and can realize the manufacture of metal composite parts with composition gradient and structural gradient. The powder hopper can be moved in plane and the powder bed can be moved, so that the heterogeneous alloy powders can be freely moved in the three directions of X, Y, and Z, that is, the printing of heterogeneous materials at the specified position is realized. By changing the set position in the printing layer, the powder mixing gradient of different metal materials, and the matrix powder material, a composite material with a gradient change in the spatial position of different metal materials in the matrix and a gradient change in the composition of different metal materials can be formed.

[0024] 4. The metal composite material with composition gradient and structure gradient described in the present invention can solve the structural changes and composition changes in three-dimensional directions, and can prepare composite materials with reinforcing ribs of heterogeneous materials, lattice structure composite parts with composition and structure gradients, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a schematic diagram of a powder dropping device for manufacturing composition gradient and structure gradient metal composite materials by binder injection molding according to the present invention.

[0027] Figure 2 Schematic diagram of powder laying in a single-layer powder bed of the present invention.

[0028] Figure 3 The printed part is a 316L stainless steel-based composite material with H13 die steel / 420 stainless steel as reinforcing ribs.

[0029] Figure 4 This is a multi-material lattice structure print with composition gradient and structure gradient according to the present invention.

[0030] In the figure:

[0031] 1-first powder hopper; 1-1-powder mixer; 1-2-powder conveying pipe; 1-3-powder feeding pipe; 2-second powder mixing device; 3-plane moving device; 4-screen; 5-powder cylinder; 6-ultrasonic vibration device; 7-forming cylinder; 8-guide rail; 9-first powder feeder; 10-second powder feeder; 11-matrix area; 12-strengthening area. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0034] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] like Figure 1 As shown, the powder dropping device of the metal composite material of the present invention comprises a powder cylinder 5 movable along a guide rail 8, a powder hopper, an ultrasonic vibration device 6 and a plane moving device 3; the powder cylinder 5 is located 5-15 mm above the forming cylinder 7, and after the powder is dropped, the powder cylinder 5 can be moved out of the forming cylinder 7 along the guide rail 8. A screen 4 is installed at the powder outlet of the powder cylinder 5, and the powder cylinder 5 will be filled with composite material matrix powder M;

[0036] At least one powder hopper is installed inside the powder cylinder 5, and the powder hopper is used to mix metal powders of two different materials; the mixing speed of the powder hopper is controlled to control the gradient mixing of the metal powders of two different materials; the powder outlet of the powder hopper extends to the screen 4 and is in close contact with the screen 4, that is, the powder outlet of the powder hopper is inserted into the composite material matrix powder M and extends to the screen 4, so that the metal powder in the powder mixing device will not be mixed with the matrix powder M, and the close contact with the screen 4 can prevent powder leakage from the side. The screen 4 and the powder conveying pipe 1-2 are made of metal, which can ensure close contact and prevent the screen from deformation. The powder hopper is equipped with a plane moving device 3 for moving the powder outlet of the powder hopper in a plane; the ultrasonic vibration device 6 is installed on the outside of the powder outlet of the powder cylinder 5, and the ultrasonic vibration device 6 contacts the metal screen 4, and the powder is dropped by vibrating the screen 4. The powder output is controlled by controlling the vibration frequency and vibration time, and the powder is compacted by a roller to form a metal composite material powder bed in the forming cylinder 7; the position of the powder outlet of the powder hopper is changed by controlling the plane moving device 3 to achieve the spatial gradient change of the mixed metal powder on the single-layer printing format. By controlling the up and down movement of the powder bed and combining the plane movement of the powder hopper on the single-layer printing format, the continuous composition and structural gradient change of the metal powder in the three-dimensional space on the multi-layer printing format is controlled.

[0037] The powder hopper includes a powder mixer 1-1, a powder conveying pipe 1-2 and a powder feeding pipe 1-3; the two powder feeding pipes 1-3 are respectively connected to the inlet of the powder mixer 1-1, and the two powder feeding pipes 1-3 are respectively connected to powder feeders for placing different materials. A rotating track is provided in the powder mixer 1-1, and the mixed powder is driven to flow in the spiral track by the carrier gas of the powder so as to be fully mixed, which is used to evenly mix the metal powder; the powder conveying pipe 1-2 is installed at the outlet of the powder mixer 1-1, and one end of the powder conveying pipe 1-2 is in close contact with the screen 4, and the mixed powder is temporarily stored in the powder conveying pipe 1-2 according to the composition gradient state, and the screen 4 is vibrated and scattered above the powder bed. In the embodiment, the first powder feeder 9 containing metal powder A and the second powder feeder 10 containing metal powder B are respectively connected to the inlet of the powder mixer 1-1 through the powder feeding pipe 1-3, and a flow controller can be provided on the powder feeding pipe 1-3 to control the mass entering the powder mixer 1-1. By controlling the rotation speed of the first powder feeder 9 and the second powder feeder 10 respectively, the conveying speed of the metal powder A and the metal powder B is controlled, thereby controlling the composition gradient of the mixed powder. The composition gradient range of the metal powder A and the metal powder B is 10%-90%, and the gradient range is the mass percentage or molar ratio of the mixture. The mixed AB powder is located in the powder conveying pipe 1-2. The powder conveying pipe 1-2 can be replaced according to the shape and size requirements of the reinforcement ribs of the printed parts. The powder conveying pipe 1-2 is threadedly connected to the powder mixer 1-1. If the outlet shape of the powder conveying pipe 1-2 is circular, square or other irregular shapes, the powder outlet area of ​​the powder conveying pipe 1-2 is 0.25cm2 -2cm 2 The reinforcing ribs here are material forming structures composed of mixed powders of metal powder A and metal powder B.

[0038] The first powder feeder 9 and the second powder feeder 10 are both airborne powder feeders. The working principle of the airborne powder feeder is to store the powder in a storage tank and transport the powder in the form of a fluid through a carrier gas. During the transportation process, the air flow velocity is controlled to ensure that the powder reaches a suspended state in the pipeline. The bottom of the powder storage tank is provided with a scraper, and the function of the scraper is to scrape the powder from the storage tank to the powder feeding tube 1-3. During operation, the scraper is in close contact with the surface of the turntable. As the turntable rotates, the scraper continuously scrapes the powder off, and then the powder is sent to the powder mixer 1-1 through the powder feeding tube 1-3 under the action of the carrier gas. By adjusting the rotation speed of the turntable, the powder output speed of the storage tank can be controlled. The following specifically describes the calculation method of the molar ratio of the gradient range for mixing:

[0039] Calculate the powder discharge speed of each powder feeder according to the composition gradient of metal powder A and metal powder B, and set the powder discharge speed, powder discharge pressure and gas flow rate of each storage tank, so that metal powder A and metal powder B continuously enter the powder mixer 1-1 for powder mixing;

[0040] The composition gradient calculation satisfies the following formula:

[0041] Wherein: n1 is the amount of metal powder A; n2 is the amount of metal powder B; a is a correction parameter, with a value range of 0.8-1.2, ρ1 is the density of metal powder A; ρ2 is the density of metal powder B; P1 is the carrier gas pressure of the first powder feeder 9, and P2 is the carrier gas pressure of the second powder feeder 10; v 气1 v is the flow rate of the carrier gas of the first powder feeder 9; 气2 is the carrier gas flow rate of the second powder feeder 10; 转1 is the scraper speed in the first powder feeder 9; 转2 is the rotation speed of the scraper plate in the second powder feeder 10.

[0042] The plane moving device 3 is composed of two independent displacement devices, an X displacement device and a Y displacement device, which are respectively mounted on the powder cylinder 5, and can realize the movement of the powder mixing device relative to the powder cylinder 5. The X displacement device and the Y displacement device are both electric push rods. The displacement device is connected to the computer and is controlled to move by computer instructions. The interlayer displacement accuracy is 50 microns and the displacement range is less than 15 cm. The plane moving device 3 is controlled by a computer, and the final position is determined by controlling the electric push rods in the X and Y directions of the displacement device according to the position information shown by the slice of the three-dimensional entity of the printed parts.

[0043] The powder outlet of the powder cylinder 5 is in close contact with the screen 4, and its size is equivalent to the width of the forming cylinder 7, ensuring that the powder falling from the screen 4 can completely cover the entire width of the forming cylinder 7. The mesh size of the screen 4 is generally selected according to the powder particle size, which is between 10-75 microns, and the mesh size is generally 200-1000 mesh.

[0044] By controlling the frequency and amplitude of the ultrasonic vibration device 6, the powder falling amount and powder falling speed of the powder outlet of the powder cylinder 5 can be controlled. Generally, the purpose is to lay a single layer of powder with a thickness of 25-120 microns, and the ultrasonic vibration frequency is 80-2000Hz.

[0045] like Figure 1 In the embodiment of the present invention, two powder hoppers are installed inside the powder cylinder 5, namely, a first powder hopper 1 and a second powder hopper 2. The first powder hopper 1 mixes metal powder A and metal powder B; the second powder hopper 2 mixes metal powder C and metal powder D. The first powder hopper 1 and the second powder hopper 2 achieve the mixing of the four metal powders in pairs. Figure 2 The cross-sectional view of the powder outlet of the powder cylinder 5 is shown.

[0046] A binder jet printing process using a powder dropping device of a metal composite material comprises the following steps:

[0047] Printing steps of the current layer: move the powder hopper to the set position by the plane moving device 3, mix the powders of different metal materials and drop them to the set position; place the base powder in the powder cylinder 5; lay the powder bed, compact the powder bed and print the current layer; the set position here is determined according to the molding material;

[0048] The next layer of printing steps: lower the height of the powder bed, change at least one of the set position, the powder mixing gradient of different metal materials, and the base powder material, and form a changed powder bed, compact the powder bed and print the next layer; in the printing of the next layer, change the set position of the reinforcement rib and the powder mixing gradient of different metal materials, so that the spatial position gradient of the reinforcement rib after forming in the base changes, and the gradient of the metal material composition in the reinforcement ribs of different layers changes. In the printing of the next layer, change the base powder material to change the base powder of different printed layers after forming.

[0049] The powder bed in the forming cylinder 7 is moved downward by one printing thickness, and the printing steps for the next layer are repeated.

[0050] Example 1

[0051] like Figure 3 To strengthen the rib M-based composite material printed part, the binder jet printing process using the powder dropping device of the metal composite material of the present invention comprises the following steps:

[0052] One end of the powder conveying pipe 1-2 of the first powder hopper 1 is brought into close contact with the screen, and the powder conveying pipe 1-2 of the first powder hopper 1 is moved to a corresponding set position by the plane moving device 3. By controlling the conveying speed of the first powder feeder 9 and the second powder feeder 10, the metal powder A and the metal powder B are mixed in a required proportion and dropped into the bottom of the powder conveying pipe 1-2; similarly, one end of the powder conveying pipe 1-2 of the second powder hopper 2 is brought into close contact with the screen, and the powder conveying pipe 1-2 of the second powder hopper 2 is moved to a corresponding set position, and the metal powder C and the metal powder D are mixed in a required proportion and dropped into the bottom of the powder conveying pipe 1-2; the set position and the required proportion are determined according to the needs of the molding material.

[0053] The composite material matrix powder M is placed in the powder cylinder 5 outside the powder conveying pipe 1-2;

[0054] The powder cylinder 5 moves to the top of the forming cylinder 7 through the guide rail, and the amount of powder falling is controlled by the ultrasonic vibration screen, so that the powder is evenly scattered on the entire width of the forming cylinder 7, and the entire width forms a powder bed, which includes powder M, a mixed powder of powder A and powder B, and a mixed powder of powder C and powder D. Figure 2 shown.

[0055] After the powder falls onto the 7-width of the forming cylinder, a two-stage roller is used to compact the powder bed. The first-stage roller has a larger diameter and a faster rotation speed, which can roughly shape and roughly compact the powder bed. The secondary roller has a slightly smaller diameter and a slower rotation speed, and the roller surface has a smaller roughness, which can finely shape the powder bed width, making the powder bed more compacted and more flat.

[0056] The adhesive nozzle moves to the top of the forming cylinder 7, sprays the adhesive at the designated position, and the infrared lamp pre-dries the previous layer of adhesive, thus completing the printing of the current layer.

[0057] During the printing of the next layer, according to the needs of the molding material, the position of the powder conveying tube 1-2 in the powder cylinder 5 is changed by the plane moving device 3, and the mixing ratio of metal powder A and metal powder B in the powder conveying tube 1-2 can be changed at the same time, so as to complete the laying of the powder bed, compacting the powder bed and spraying the binder. In this way, during the printing process, the position of the powder conveying tube 1-2 in each layer can be changed in a gradient, and the mixed powder ratio therein can also be changed in a gradient, even if the spatial position of different metal materials in the matrix after molding changes in a gradient, and the composition of different metal materials changes in a gradient. The height of the powder bed needs to be moved during the printing process. In the embodiment, during the printing of the next layer, only the mixing ratio of metal powder A and metal powder B in the first powder hopper 1 can be changed, or only the mixing ratio of metal powder C and metal powder D in the second powder hopper 2 can be changed, or the mixing ratio of metal powder A and metal powder B and the mixing ratio of metal powder C and metal powder D can be changed at the same time.

[0058] Example 2

[0059] The printing process of the powder dropping device with composition gradient and structure gradient manufactured by binder jet molding of the present invention is used to manufacture the printed parts of H13 die steel / 420 stainless steel / 316L stainless steel-based composite materials, 316L stainless steel is used as the matrix material, H13 die steel and 420 stainless steel are used as reinforcing rib materials due to their higher strength, that is, the A alloy powder material is H13 die steel, and the B alloy powder material is 420 stainless steel, which specifically includes the following steps:

[0060] One end of the powder conveying pipe 1-2 of the first powder hopper 1 is brought into close contact with the screen, and the powder conveying pipe 1-2 of the first powder hopper 1 is moved to the set position by the plane moving device 3. By controlling the conveying speed of the first powder feeder 9 and the second powder feeder 10, the alloy powder H13 mold steel and 420 stainless steel are mixed in the required proportion, and the mass percentage of the H13 mold steel in the whole printing process is controlled to change gradually from 10% to 90%, and fall into the bottom of the powder conveying pipe 1-2.

[0061] The composite material matrix powder 316L stainless steel is placed in the powder cylinder 5 outside the powder conveying pipe 1-2;

[0062] The powder cylinder 5 moves to the top of the forming cylinder 7 through the guide rail, and the amount of powder falling is controlled by the ultrasonic vibration screen, so that the powder is evenly scattered on the entire width of the forming cylinder 7, and the entire width forms a powder bed, which includes powder 316L stainless steel, H13 mold steel and 420 stainless steel mixed powder;

[0063] After the powder falls onto the 7-width of the forming cylinder, a two-stage roller is used to compact the powder bed. The first-stage roller has a larger diameter and a faster rotation speed, which can roughly shape and roughly compact the powder bed. The secondary roller has a slightly smaller diameter and a slower rotation speed, and the roller surface has a smaller roughness, which can finely shape the powder bed width, making the powder bed more compacted and more flat.

[0064] The adhesive nozzle moves to the top of the forming cylinder 7, sprays the adhesive at the designated position, and the infrared lamp pre-dries the previous layer of adhesive, thus completing the printing of the current layer.

[0065] During the printing of the next layer, according to the needs of the molding material, the position of the powder conveying pipe 1-2 in the powder cylinder 5 is changed by the plane moving device 3, and the mixing ratio of H13 mold steel and 420 stainless steel in the powder conveying pipe 1-2 can be changed at the same time, so as to complete the laying of the powder bed, compacting the powder bed and spraying the binder. In this way, during the printing process, the position of the powder conveying pipe 1-2 in each layer can be changed gradually, and the mixed powder ratio therein also changes gradually. The height of the powder bed in the molding cylinder 7 is changed during the printing process.

[0066] Example 3

[0067] like Figure 4For a multi-material lattice structure print with composition gradient and structural gradient, on the basis of Example 1, there are 6 powder hoppers in the powder cylinder 5, the composite material matrix of the upper layer of the powder cylinder 5 is powder M, and the composite material matrix of the lower layer of the powder cylinder 5 is powder N, and the powder M and the powder N are alternately distributed in the printing direction.

[0068] The metal composite material with composition gradient and structure gradient described in the present invention is printed by the binder jet printing process. The metal composite material can be sliced ​​and layered according to the printing direction, and each layer includes a base region 11 and a reinforcement region 12. The base region 11 is formed by base powder, and there is at least one reinforcement region 12 in the base region 11. The reinforcement region 12 is formed by mixed powders of different metal materials; the positions and / or material compositions of the reinforcement regions 12 in adjacent layers of the metal composite material are different.

[0069] In the metal composite material printed by the process of Example 2, the material of the base region 11 is 316L stainless steel, and there is a strengthening region 12 mixed with H13 mold steel and 420 stainless steel in the base region 11. Generally, the strengthening regions 12 mixed with H13 mold steel and 420 stainless steel in adjacent layers at least partially overlap. However, in some special cases, the strengthening regions 12 mixed with H13 mold steel and 420 stainless steel in adjacent layers do not overlap.

[0070] In the metal composite material printed by the process of Example 3, the materials of the matrix regions 11 in adjacent layers of the metal composite material change alternately.

[0071] The additive process of the powder dropping device for manufacturing composition gradient and structure gradient metal composite materials using the binder injection molding described in the present invention can solve the structural changes and composition changes in three-dimensional directions, and can prepare composite materials with reinforcing ribs of heterogeneous materials, lattice structure composite parts with composition and structure gradients, etc.

[0072] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0073] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A powder dropping device for preparing a metal composite material, characterized in that: It comprises a movable powder cylinder (5), a powder hopper, an ultrasonic vibration device (6) and a plane moving device (3); The powder outlet of the powder cylinder (5) is installed with a screen (4), and at least one powder hopper is installed inside the powder cylinder (5), and the powder hopper is used to mix metal powders of two different materials; the feeding speed of the powder hopper is controlled so that the metal powders of two different materials are mixed in a gradient; the powder outlet of the powder hopper extends to the screen (4) and is in close contact with the screen (4); a plane moving device (3) is installed on the powder hopper, which is used to move the powder outlet of the powder mixing device in a plane; the ultrasonic vibration device (6) is in contact with the screen (4), and by vibrating the screen (4), the powder in the powder cylinder and the powder hopper is evenly scattered in the forming cylinder (7) to form a metal composite material powder bed; by controlling the movement of the powder bed and changing the position of the powder outlet of the powder hopper through the plane moving device (3), the composition and position gradient of the mixed metal powder in space are changed.

2. The powder dropping device for preparing a metal composite material according to claim 1, characterized in that: The powder hopper comprises a powder mixer (1-1), a powder conveying pipe (1-2) and a powder feeding pipe (1-3); powder feeders for two different metal powders are respectively connected to the inlet of the powder mixer (1-1) through the powder feeding pipe (1-3), and the powder mixer (1-1) is used to mix the metal powders; the powder conveying pipe (1-2) is installed at the outlet of the powder mixer (1-1), and one end of the powder conveying pipe (1-2) is in close contact with the screen (4).

3. The powder dropping device for preparing a metal composite material according to claim 2, characterized in that: By controlling the conveying speeds of the powder feeders of the two different metal powders respectively, the amounts of the two different metal powders entering the powder mixer (1-1) are controlled, thereby controlling the composition gradient of the metal powders of the two different materials; the composition gradient ranges from 10% to 90%, and the composition gradient is the mass percentage or molar ratio of the two different materials.

4. The powder dropping device for preparing a metal composite material according to claim 1, characterized in that: The mesh size of the screen (4) is 200-1000 meshes; the ultrasonic vibration frequency of the ultrasonic vibration device (6) is 80-2000 Hz.

5. A binder jet printing process using the powder dropping device for preparing a metal composite material according to any one of claims 1 to 4, characterized in that: The steps include: Printing the current layer: moving the powder hopper to a set position by means of a plane moving device (3), mixing powders of different metal materials and dropping the powders to the set position; placing base powder in the powder cylinder (5); laying a powder bed, compacting the powder bed and printing the current layer; Printing the next layer: changing at least one of the set position, the powder mixing gradient of different metal materials, and the base powder material, and forming a changed powder bed, compacting the powder bed and printing the next layer; Change the height of the powder bed and repeat the printing of the next layer.

6. The binder jet printing process according to claim 5, characterized in that: In the printing of the next layer, the set position and the powder mixing gradient of different metal materials are changed, so that the spatial position gradient of the different metal materials after molding in the matrix changes, and the composition gradient of the different metal materials changes.

7. A metal composite material, characterized in that: The metal composite material is prepared by printing using the binder jet printing process according to claim 5.

8. The metal composite material according to claim 7, characterized in that: Each layer of the metal composite material comprises a matrix region (11) and a reinforcement region (12), wherein the matrix region (11) has at least one reinforcement region (12), and the reinforcement region (12) is formed from mixed powders of different metal materials; and the positions and / or material compositions of the reinforcement regions (12) in adjacent layers of the metal composite material are different.

9. The metal composite material according to claim 8, characterized in that: The materials of the matrix regions (11) in adjacent layers of the metal composite material change alternately.

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