CN111761061A - 3D printing three-dimensional network structure graphite/metal composite material and atmospheric pressure casting infiltration preparation method thereof - Google Patents
3D printing three-dimensional network structure graphite/metal composite material and atmospheric pressure casting infiltration preparation method thereof Download PDFInfo
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- B22F1/0003—
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F3/26—Impregnating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention provides a 3D printing three-dimensional network structure graphite/metal composite material with good antifriction property, shock absorption property, thermal conductivity, electrical conductivity, strength and toughness and lower density and thermal expansibility and a normal pressure casting infiltration preparation method thereof. The composite material is a gradient/non-gradient metal matrix composite material which is formed by graphite and metal of an interconnected network structure communicated in a three-dimensional space, the thickness of a graphite layer is controllable, and the graphite network structure can be changed according to requirements. The preparation method comprises the following steps: (1) preparing mixed powder of flake graphite powder and metal powder; (2) 3D printing a graphite/metal composite material network structure prefabricated body by adopting a laser selective sintering method; (3) the graphite/metal composite material with the three-dimensional network structure is prepared by adopting a normal-pressure casting infiltration method. The invention can be used as materials with self-lubricating antifriction, vibration reduction/sound insulation, high-efficiency heat conduction, electric conduction and the like to be applied to the fields of machinery, metallurgy, environmental protection, aerospace, electronics and the like.
Description
Technical Field
The invention relates to the technical field of 3D printing (additive manufacturing), metal matrix composite materials and normal pressure casting, in particular to a 3D printing three-dimensional network structure graphite/metal composite material and a normal pressure casting infiltration preparation method thereof.
Background
Three-dimensional continuous Network structure Metal Matrix Composite (Three-dimensional Co-connecting Network Metal Matrix Composite, or interconnecting Network Metal Matrix Composite, or INMMC material for short) is a new type of Composite material research field that has been paid more and more attention to by material research workers at home and abroad in recent decades. The composite material has a completely different space topological structure type from the traditional composite material, namely, the metal matrix phase and the composite phase (or called modified phase) are continuous (communicated) in three-dimensional space and are in an interlaced network structure. The two phases are in a topological structure form of mutual entanglement and coiling, mutual penetration and infiltration in a three-dimensional space, and the composite material is a brand new composite modified structure form in the field of synthetic materials. The structural form enables the material to have more unique strength performance, antifriction/wear resistance, vibration damping performance, thermal performance and the like, has isotropy of performance, has good technical feasibility when being used as antifriction/wear resistance materials, high-damping vibration damping/sound insulation materials, heat conduction/low expansion materials, high-temperature resistant structural materials, electronic packaging materials and the like in the industries of mechanical equipment, environmental protection, aerospace, electronic communication and the like, and has extremely wide development prospect.
The graphite modified metal-based self-lubricating antifriction/heat conduction/low expansion composite material prepared by utilizing the high-temperature lubricating property of graphite is a new hotspot in the technical field of composite materials. The graphite/metal matrix composite material is prepared by adopting a conventional stirring and casting method for preparing the graphite particle or graphite fiber modified metal composite material, although the production cost is low, the distribution uniformity of the graphite is difficult to control, and the adding amount of the graphite is difficult to increase (the graphite is easy to float in molten metal to generate component segregation). The graphite/metal compact composite material is prepared by adopting a mixed powder laser selective melting method (SLM method) or sintering method (SLS method) of graphite and metal, the distribution uniformity of graphite can be improved, the graphite addition amount can be greatly increased (as shown in figure 1), and the production efficiency is low and the cost is high.
In the methods, graphite particles are basically distributed in a dispersion mode, the distribution mode of graphite is uncontrollable, and graphite phases are difficult to be communicated to form a continuous network structure, so that the characteristics of a network structure composite material with two uniformly interconnected phases are difficult to obtain, and the improvement of the performances of vibration reduction, friction reduction, heat conduction, electric conduction and the like is limited.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art, and provide a normal-pressure casting and infiltration preparation method of a 3D printing three-dimensional network structure graphite/metal composite material with high efficiency and low cost, and the three-dimensional network structure graphite/metal composite material which is prepared by the method and has good antifriction/wear resistance, vibration reduction/sound insulation, strength, hardness, toughness, electric/thermal conductivity, corrosion resistance and lower density and thermal expansibility.
The invention relates to a normal pressure casting infiltration preparation method of a 3D printing three-dimensional network structure graphite/metal composite material, which comprises the following steps:
(1) preparing mixed powder of flake graphite powder and metal powder;
(2) 3D printing a graphite/metal composite material network structure prefabricated body by adopting a laser selective sintering method;
(3) the graphite/metal composite material with the three-dimensional network structure is prepared by adopting a normal-pressure casting infiltration method.
The invention takes the crystalline flake graphite powder as the composite phase (modified phase) to modify the metal, and adopts the normal pressure casting and infiltration process to prepare the three-dimensional network structure graphite/metal composite material, the adopted crystalline flake graphite powder has excellent lubricity, thermal conductivity, electrical conductivity, corrosion resistance and low density and thermal expansibility, the 3D printing process is adopted to obtain small blocks of graphite/metal composite material network structure prefabricated bodies with different outline shapes, different porosities, different pore structures and different pore diameter distributions according to the requirements, the combination of the small blocks of different prefabricated bodies can prepare the gradient/non-gradient composite material products with large size, controllable graphite layer thickness and randomly changeable graphite network structure, the preparation efficiency can be obviously improved, the production cost is reduced, and the prepared three-dimensional network structure graphite/metal composite material has good strength performance, Antifriction/antiwear properties, vibration damping/sound insulation properties, hardness properties, toughness, electrical/thermal conductivity, corrosion resistance and low thermal expansion.
The method of the invention prepares the graphite/metal composite material network structure prefabricated body by the 3D printing process, avoids the adverse effect of inorganic binder brought in when the network structure graphite prefabricated body is prepared by adopting a plastic precursor impregnation method, does not need to carry out surface metallization treatment on the network structure prefabricated body before metal casting infiltration, simplifies the preparation process, and can randomly change the network structure type of the prefabricated body, thereby improving the mechanical property, the performances of friction reduction, vibration reduction and the like of the composite material.
Further, in the mixed powder prepared in the step (1), the volume ratio of the crystalline flake graphite powder to the metal powder is 1: 2-2: 1. When the metal powder is too little, metal bonding points among graphite particles are too little, the strength of the network prefabricated body is reduced, and the network prefabricated body is easy to collapse and disperse during casting and infiltration; when the metal powder is excessive, metal bonding points among graphite particles are excessive, the distribution continuity of the graphite particles is reduced, the interconnection degree of two phases of the composite material is reduced, and the comprehensive performance of the composite material is influenced.
Furthermore, in the step (1), the average particle diameter of the crystalline flake graphite powder is less than or equal to 53 microns, and the carbon content is more than or equal to 95 percent; the metal powder is alloy powder with the average particle diameter less than or equal to 25 mu m and the melting point higher than that of corresponding infiltration casting metal. Here, the metal powder serves as a binder for the particles of the scaly graphite powder, and it is preferable to use a metal powder having a finer particle size than the scaly graphite powder so as to preferentially fill the gaps between the graphite particles without excessively affecting the direct connection between the graphite particles. The high-purity crystalline flake graphite has better lubricity, thermal conductivity, electrical conductivity and corrosion resistance and low density and thermal expansibility, so that the performance of the prepared graphite/metal composite material with the three-dimensional network structure is better; the high-melting-point alloy powder is selected as the metal powder, so that the melting point of the 3D printing graphite/metal composite material network structure preform is improved, and the preform is prevented from melting, collapsing and collapsing during the subsequent casting and infiltration forming of the composite material. The scale graphite powder and the metal powder are preferably spherical or nearly spherical particles so as to reduce the powder spreading resistance and improve the powder spreading uniformity. The flake graphite powder and the metal powder must be fully and uniformly mixed to prevent component segregation, otherwise, the uneven distribution of graphite is easy to generate during printing. Specifically, the metal powder particles are alloy steel powder, alloy cast iron powder, titanium alloy powder, copper alloy powder, aluminum alloy powder, magnesium alloy powder and the like with the average diameter less than or equal to 25 mu m.
And (2) in the step (2), when the selective laser sintering is carried out, the layering thickness of the mixed powder is larger than the average diameter of the particles of the flake graphite powder each time, so that the powder paving scraper is prevented from scraping away too many coarse graphite powder particles.
Further, in the step (2), the laser power during selective laser sintering is not less than 50KW, and the oxygen content in the 3D printing forming chamber is not more than 200 ppm. The laser power needs to be changed according to the type of the metal powder, and the higher the melting point of the metal powder is, the higher the laser power needs to be. When the laser power is too small, the metal powder is difficult to sinter, the cohesive force between the graphite powder is small, and the strength of the composite powder network prefabricated body is low; however, when the laser power is too high, the metal powder melts and diffuses to coat the graphite particles, and although the bonding force between the graphite particles is increased, the direct connection degree between the graphite particles is reduced. The lower the oxygen content of the forming chamber during printing, the better to prevent oxidation of the metal powder and graphite powder.
Thirdly, the specific steps of the step (3) are as follows: combining a plurality of graphite/metal composite material network structure prefabricated bodies forming the product in advance according to the shape requirement of the product, fixing the combined prefabricated bodies in a casting sand mold cavity by using metal nails with the same type as the subsequent metal casting and infiltration, pouring molten metal into the graphite/metal composite material network structure prefabricated bodies under the atmospheric pressure by using static pressure and dynamic pressure of the molten metal under the action of natural gravity, and cooling, solidifying and forming to obtain the three-dimensional continuous network structure graphite/metal composite material. The production process is simple and the production cost is low.
The three-dimensional network structure graphite/metal composite material prepared by the method is composed of graphite and metal of an interconnected network structure communicated in a three-dimensional space, and the structural type and the size of the graphite network can be changed according to the performance requirements of products, wherein the volume of the graphite accounts for 6-35%.
According to the scheme, the 3D printing three-dimensional network structure graphite/metal composite material product prepared by the method has good lubricity, thermal conductivity, electrical conductivity, corrosion resistance and low density and thermal expansibility, and the mechanical, physical and chemical properties such as strength, hardness, density, friction coefficient, damping coefficient, thermal conductivity, electrical conductivity, thermal expansibility, corrosion resistance and the like of the network structure graphite/metal composite material can be controlled by changing the three-dimensional network structure type, the pore size and the framework size of the graphite metal composite powder 3D printing prefabricated body, so that the 3D printing three-dimensional network structure graphite/metal composite material product can be widely used for manufacturing structural/functional parts in the fields of machinery, electronics, chemical engineering, environmental protection, aerospace and the like.
Further, the casting infiltration metal liquid is cast steel, cast iron, cast titanium alloy, cast copper alloy, cast aluminum alloy, cast magnesium alloy or the like. Different kinds of cast-infiltration metals are selected, different composite material products can be prepared, and the requirements of different industries are met.
Drawings
FIG. 1 is an enlarged view (10 times) of a section of a graphite/stainless steel dense body composite material prepared by a Selective Laser Sintering (SLS) method by using mixed powder of graphite and stainless steel (the volume ratio of the graphite powder is 25%) in the prior art;
FIG. 2 is a macroscopic topography enlarged view (3 times) of a graphite/stainless steel composite material network structure preform 3D printed by adopting a laser selective sintering method (SLS method) in the invention;
FIG. 3 is an enlarged (3 times) sectional view of a three-dimensional network structure graphite/cast steel composite material obtained by the method of the present invention.
Detailed Description
The present invention will be described in more detail below.
The 3D printing three-dimensional network structure graphite/metal composite material is composed of graphite and metal of an interconnected network structure communicated in a three-dimensional space, and the structural type and the size of a graphite network can be changed according to the performance requirements of products, wherein the volume of the graphite accounts for 6-35%. In the present example, the volume ratio of graphite is specifically 10%. The graphite is flake graphite with excellent lubricating property, thermal conductivity, electric conductivity, corrosion resistance and low density and thermal expansibility. The metal is cast infiltration metal and can be cast steel, cast iron, cast titanium alloy, cast copper alloy, cast aluminum alloy or cast magnesium alloy and the like.
The normal pressure casting infiltration preparation method of the 3D printing three-dimensional network structure graphite/metal composite material comprises the following steps:
(1) preparing mixed powder of flake graphite powder and metal powder;
(2) 3D printing the graphite/metal composite material network structure prefabricated body by adopting a laser selective sintering method (SLS method);
(3) the graphite/metal composite material with the three-dimensional network structure is prepared by adopting a normal-pressure casting infiltration method.
In the step (1), the average particle diameter of the flake graphite powder is less than or equal to 53 microns, and the carbon content is more than or equal to 95%. The high-purity crystalline flake graphite has better lubricity, thermal conductivity, electrical conductivity and corrosion resistance and low density and thermal expansibility, so that the prepared graphite/metal composite material with the three-dimensional network structure has better performance. The metal powder plays a role in bonding the scaly graphite powder particles, the metal powder with the granularity smaller than that of the scaly graphite powder needs to be adopted, and the average diameter is preferably less than or equal to 25 mu m, so that gaps among the graphite particles can be filled preferentially, and meanwhile, direct connection among the graphite particles is not influenced excessively. The metal powder is preferably alloy powder with a melting point higher than that of corresponding infiltration casting metal, so that the melting point of the 3D printing graphite metal network prefabricated body is improved, and the network prefabricated body is prevented from melting, collapsing and collapsing during subsequent composite material infiltration casting. Specifically, the metal powder is alloy steel powder, alloy cast iron powder, titanium alloy powder, copper alloy powder, aluminum alloy powder, magnesium alloy powder and the like with the average particle diameter of less than or equal to 25 mu m. In this example, the metal powder is stainless steel powder having an average particle diameter of 25 μm or less. The scale graphite powder and the metal powder are preferably spherical or nearly spherical particles so as to reduce the powder spreading resistance and improve the powder spreading uniformity. The flake graphite powder and the metal powder must be fully and uniformly mixed to prevent component segregation, otherwise, the uneven distribution of graphite is easy to generate during printing.
In the prepared mixed powder, the volume ratio of the crystalline flake graphite powder to the metal powder is 1: 2-2: 1. When the metal powder is too little, metal bonding points among graphite particles are too few, the strength of the network prefabricated body is reduced, and the network prefabricated body is easy to collapse and collapse during casting and infiltration; when the metal powder is excessive, metal bonding points among graphite particles are excessive, the distribution continuity of the graphite particles is reduced, the interconnection degree of two phases of the composite material is reduced, and the comprehensive performance of the composite material is influenced. In this embodiment, the volume ratio of the flake graphite powder to the metal powder is specifically 1: 1.
In the step (2), a graphite/metal composite material network structure preform is 3D printed by adopting a Selective Laser Sintering (SLS) method. During 3D printing, the oxygen content in the 3D printing forming chamber needs to be less than or equal to 200ppm so as to prevent the metal powder and the graphite powder from being oxidized. In the embodiment, the oxygen content in the 3D printing forming chamber is less than or equal to 100 ppm. The laser power during printing needs to be more than or equal to 50KW, because the metal powder is difficult to sinter, the adhesive force between graphite powder is small and the strength of the composite powder network prefabricated body is low when the laser power is too small; when the laser power is too high, the metal powder can melt and diffuse to coat the graphite particles, so that the bonding force between the graphite particles can be increased, but the direct connection degree between the graphite particles is reduced. Therefore, the larger the proportion of graphite powder is, the larger the laser power needs to be. In this embodiment, when stainless steel powder is used as the metal powder, the laser power is preferably not less than 160 KW. When the selective laser sintering is carried out, the layering thickness of the mixed powder is larger than the average particle diameter of the flake graphite powder each time, so that the powder laying scraper is prevented from scraping away excessive and thick graphite powder each time. Taking the average particle diameter of the graphite powder as an example to be less than or equal to 38 mu m, the thickness of the layering is preferably more than or equal to 40 mu m.
The specific steps of the step (3) are as follows: combining a plurality of graphite/metal composite material network structure prefabricated bodies forming the product in advance according to the shape requirement of the product, fixing the combined prefabricated bodies in a casting sand mold cavity by using metal nails with the same type as the subsequent metal casting and infiltration, pouring molten metal into the graphite/metal composite material network structure prefabricated bodies under the atmospheric pressure by using static pressure and dynamic pressure of the molten metal under the action of natural gravity, and cooling, solidifying and forming to obtain the three-dimensional continuous network structure graphite/metal composite material. Specifically, the resin sand mold cavity is obtained by mixing the components shown in the following table according to mass percent, and then filling the mixture into a sand box for curing and molding.
The specific preparation process of the resin sand cavity comprises the following steps: a batch type sand mixer is adopted, silica sand and an organic sulfonic acid solution curing agent are mixed for 2 min, and then a resin binder is added into the mixture to be continuously mixed for 1 min, and then sand is immediately discharged. And filling the uniformly mixed resin self-hardening sand into a sand box, and demolding after curing and forming. In order to obtain a casting with a smooth surface and avoid casting defects such as sand washing, sand inclusion and the like, a layer of alcohol-based zircon powder coating or corundum powder coating is coated on the inner surface of the prepared cavity, and the alcohol-based zircon powder coating or corundum powder coating is ignited and combusted immediately to dry the coating.
When molten metal is poured, top pouring is adopted in the invention in order to increase the static pressure and dynamic pressure of the molten metal and ensure that the pouring position is beneficial to molten metal mold filling and casting feeding. The inner pouring channel and the whole sample cavity are completely arranged in the lower box, the straight pouring channel is positioned in the upper mould, and the heights of the upper mould and the pouring cup are increased as much as possible, so that the pouring system can fully play a feeding role during liquid shrinkage. A larger cross section area of an inner pouring gate is selected, pouring is performed as fast as possible, and a closed pouring system is adopted, namely Sigma F direct, Sigma F transverse and Sigma F internal. The head height should be as great as possible. In order to improve the filling capacity of molten metal and the wettability of the molten metal and the surface of the graphite/metal composite material network structure prefabricated body, the pouring temperature is required to be as high as possible. At a certain temperature, the surface energy of the liquid metal linearly decreases with the increase of the temperature, and the wetting angle of the metal and the graphite decreases with the increase of the temperature. Because the graphite/metal composite material network structure prefabricated body contains a certain amount of metal, the metal on the surface of the prefabricated body occupies a certain proportion of area, and the bare metal becomes a good joint surface of the cast-infiltration metal and the network structure prefabricated body, the graphite/metal composite material network structure prefabricated body does not need surface metallization before metal casting and infiltration, and the preparation process is simplified.
In the invention, the metal can be selected from cast steel, cast iron, cast copper alloy, cast aluminum alloy, cast magnesium alloy or cast titanium alloy according to the material performance requirement.
After the casting is completed, in order to reduce the thermal stress caused by uneven wall thickness in the cooling process, it is necessary to ensure that the casting can be opened after being sufficiently cooled. And preparing the graphite/metal composite material with the three-dimensional network structure.
The prepared graphite/metal composite material with the three-dimensional network structure is subjected to line cutting and section morphology observation, and the graphite skeleton is found to be uniformly distributed in a metal matrix, the graphite/metal interface is clear, no obvious reaction layer is seen, no obvious casting defects such as holes and air holes are seen, and the casting infiltration effect is ideal.
The invention takes the crystalline flake graphite powder as a composite phase (modified phase) to modify metal, and adopts a normal pressure casting and infiltration process to prepare the three-dimensional network structure graphite/metal composite material, the adopted crystalline flake graphite powder has excellent lubricity, thermal conductivity, electrical conductivity, corrosion resistance and low density and thermal expansibility, the mechanical, physical and chemical properties of the network structure graphite/metal composite material, such as strength, hardness, density, friction coefficient, damping coefficient, thermal conductivity, electrical conductivity, thermal expansibility, corrosion resistance and the like, can be controlled by changing the three-dimensional network structure type, the pore size and the framework size of the graphite metal composite powder 3D printing prefabricated body, and a plurality of graphite/metal composite material network structure prefabricated bodies with different outline shapes, different porosities, different pore structures, different pore diameter distributions are obtained by adopting the 3D printing process according to requirements, the combination of different small prefabricated bodies can prepare a gradient/non-gradient composite material product (as shown in figure 3) with large size, controllable graphite layer thickness and randomly changeable graphite network structure at one time, can obviously improve the preparation efficiency and reduce the production cost, and the prepared three-dimensional network structure graphite/metal composite material has good strength property, antifriction/wear resistance, vibration reduction/sound insulation property, hardness property, toughness, electric conduction/heat conduction property, corrosion resistance and lower thermal expansion.
Claims (9)
1. A normal-pressure casting infiltration preparation method for a graphite/metal composite material with a three-dimensional network structure through 3D printing is characterized by comprising the following steps:
(1) preparing mixed powder of flake graphite powder and metal powder;
(2) 3D printing a graphite/metal composite material network structure prefabricated body by adopting a laser selective sintering method;
(3) the graphite/metal composite material with the three-dimensional network structure is prepared by adopting a normal-pressure casting infiltration method.
2. The atmospheric pressure casting infiltration preparation method of the 3D printing three-dimensional network structure graphite/metal composite material according to claim 1 is characterized by comprising the following steps: in the step (1), the volume ratio of the crystalline flake graphite powder to the metal powder in the mixed powder is 1: 2-2: 1.
3. The atmospheric pressure casting infiltration preparation method of the 3D printing three-dimensional network structure graphite/metal composite material according to claim 1 is characterized by comprising the following steps: in the step (1), the average particle diameter of the crystalline flake graphite powder is less than or equal to 53 microns, and the carbon content is more than or equal to 95 percent; the metal powder is alloy powder with the average particle diameter less than or equal to 25 mu m and the melting point higher than that of corresponding infiltration casting metal.
4. The atmospheric pressure casting infiltration preparation method of the 3D printing three-dimensional network structure graphite/metal composite material according to claim 3 is characterized by comprising the following steps: the metal powder particles are alloy steel powder, alloy cast iron powder, titanium alloy powder, copper alloy powder, aluminum alloy powder or magnesium alloy powder with the average diameter less than or equal to 25 mu m.
5. The atmospheric pressure casting infiltration preparation method of 3D printing three-dimensional network structure graphite/metal composite material according to claim 1, characterized in that, in the step (2), when the selective laser sintering is carried out, the thickness of the layer of the mixed powder is larger than the average particle diameter of the crystalline flake graphite powder.
6. The atmospheric pressure casting infiltration preparation method of the 3D printing three-dimensional network structure graphite/metal composite material according to claim 1, characterized in that in the step (2), the laser power during selective laser sintering is not less than 50KW, and the oxygen content in a 3D printing forming chamber is not more than 200 ppm.
7. The atmospheric pressure casting infiltration preparation method of the 3D printing three-dimensional network structure graphite/metal composite material according to claim 1, characterized in that the specific steps of the step (3) are as follows: combining a plurality of graphite/metal composite material network structure prefabricated bodies forming the product in advance according to the shape requirement of the product, fixing the combined prefabricated bodies in a casting sand mold cavity by using metal nails with the same type as the subsequent metal casting and infiltration, pouring molten metal into the graphite/metal composite material network structure prefabricated bodies under the atmospheric pressure by using static pressure and dynamic pressure of the molten metal under the action of natural gravity, and cooling, solidifying and forming to obtain the three-dimensional continuous network structure graphite/metal composite material.
8. A graphite/metal composite material with a three-dimensional network structure prepared by the method of claim 1, wherein the composite material is composed of graphite and metal with an interconnected network structure communicated in a three-dimensional space, and the structural form and the dimension of the graphite network can be changed according to the performance requirement of a product, wherein the volume percentage of the graphite is 6-35%.
9. The three-dimensional network structure graphite/metal composite material according to claim 8, characterized in that: the metal is cast steel, cast iron, cast titanium alloy, cast copper alloy, cast aluminum alloy or cast magnesium alloy.
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