Preparation method and use method of graphite powder for 3D printing

Abstract

The invention discloses a preparation method of graphite powder for 3D printing. The preparation method comprises the following steps: uniformly mixing 60-90% of powder A and 1-40% of powder B; the powder A is graphite powder with the particle size of 5-130 microns; a preparation method of the powder B comprises the following steps: S110, performing vacuum sintering on graphite powder with the particle size of 5-130 microns, and cooling to room temperature; and S120, crushing the sintered material, and screening powder with the particle size of 40-100 [mu] m to obtain the powder B. According to the preparation method of the graphite powder for 3D printing, disclosed by the invention, the powder A and the powder B are mixed according to a specific proportion for preparation, so that the stacking density of the graphite powder is effectively improved, the fluidity is improved, and the phenomenon of'sample stacking 'in the printing process is solved; and the powder B is pyrolysis treatment powder, most organic matters are subjected to pyrolysis separation, and the separation A is matched, so that the dust raising phenomenon in the printing process can be prevented on the basis of improving the stacking density of the graphite powder, and the printing quality is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method for preparing and using graphite powder for 3D printing. Background Art

[0002] Graphite has the advantages of high temperature resistance, high thermal conductivity, excellent chemical stability and good plasticity, and is widely used in metallurgy, aerospace, nuclear energy and other fields. Traditional graphite product methods have defects such as low utilization rate during processing and difficulty in forming complex structures, which cannot meet the requirements of related fields for high-performance complex graphite products. The development of additive manufacturing technology provides corresponding solutions for graphite products. This technology is based on three-dimensional models and the principle of discrete stacking. It is a scientific and technological method for directly manufacturing parts driven by three-dimensional model data of parts.

[0003] Binder jet printing is an additive manufacturing method that selectively sprays liquid binder onto the surface of the powder bed and binds the powder to form the designed shape. This technology has the advantages of high design freedom, rapid generation of complex structural parts, isotropic structure of printed parts, high material utilization, short generation cycle, and product diversification; compared with fused deposition modeling (FDM), binder jet technology has the advantages of high molding accuracy and fast printing speed; compared with photo-curing molding technology, binder jet technology has the advantages of high compatibility with powdered materials and low binder requirements; compared with laser selective sintering technology, binder jet technology has the advantages of low equipment requirements and high molding accuracy.

[0004] Binder jetting technology is an important molding method for 3D printing graphite products. At present, there is a technical problem in the binder jet printing graphite material technology that the density of the green product is low, which leads to large changes in the density of the final graphite sintered parts, and the graphite products are prone to defects and low mechanical properties. Summary of the invention

[0005] Based on this, in order to solve the above technical problems, the present invention provides a method for preparing and using graphite powder for 3D printing.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing graphite powder for 3D printing, wherein the graphite powder for 3D printing comprises 60% to 90% of A powder and 1% to 40% of B powder by mass percentage; the graphite powder for 3D printing can be obtained by uniformly mixing 60% to 90% of A powder and 1% to 40% of B powder; the A powder is graphite powder with a particle size of 5 μm to 130 μm; the method for preparing the B powder comprises the following steps:

[0008] S110, sintering graphite powder with a particle size of 5 μm to 130 μm in vacuum and then cooling to room temperature;

[0009] S120, crushing the sintered material, and screening the powder with a particle size of 40 μm to 100 μm to obtain the B powder.

[0010] Furthermore, a mixer is used to mix the A powder and the B powder, and the mixing time is 0.5h to 2h.

[0011] Furthermore, in the step S110, the sintering temperature is 600° C. to 1200° C., and the sintering time is 2 h to 6 h.

[0012] Furthermore, the graphite powder includes one or more of petroleum coke, asphalt coke, coal tar pitch and carbon black.

[0013] In a second aspect, the present application further provides a method of use, which is applied to any of the above-mentioned graphite powders for 3D printing, and the method of use comprises the following steps:

[0014] S210, adding the graphite powder for 3D printing into a powder spreading device, and adding a binder into an inkjet device;

[0015] S220, the powder spreading device is started and performs a powder spreading operation to form a molding surface;

[0016] S230, the print head sprays the binder onto the molding surface according to the layered cross section of the part; the working box drops one printing layer thickness, and the powder spreading device spreads powder again;

[0017] S240, repeat step S230 until printing is completed.

[0018] Furthermore, the method of use also includes a curing step. After printing is completed, the working box is placed in an oven for curing; after curing, the powder is removed to obtain a green graphite product.

[0019] Furthermore, in the curing step, the curing temperature is 120° C. to 300° C., and the curing time is 2 h to 6 h.

[0020] Furthermore, the binder is one of phenolic resin, furan resin, epoxy resin, acrylic acid, polyurethane, polyvinyl alcohol, and asphalt.

[0021] Furthermore, the injection amount of the binder is 1% to 50% of the mass of the green body.

[0022] Furthermore, the printing layer thickness is 130 μm to 300 μm.

[0023] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0024] The invention discloses a method for preparing graphite powder for 3D printing. A powder and B powder are mixed in a specific ratio to prepare final graphite powder, which effectively improves the packing density of the graphite powder, improves fluidity, and solves the "piling" phenomenon in the printing process. B powder is a pyrolysis-treated powder, and most organic matter is cracked and separated. When combined with A powder, it can improve the packing density of the graphite powder and prevent dust from being raised during the printing process, thereby effectively improving the printing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] none DETAILED DESCRIPTION

[0026] For ease of understanding of the present invention, the present invention will be described more fully below with reference to relevant embodiments. Preferred embodiments of the present invention are provided in the embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0028] One of the purposes of the present invention is to disclose a method for preparing graphite powder for 3D printing, wherein the graphite powder for 3D printing comprises 60% to 90% of A powder and 1% to 40% of B powder by mass percentage. Among them, A powder is graphite powder with a particle size of 5μm to 130μm, which has a wide particle size distribution range, poor fluidity, large friction between powders, and is prone to dust during printing, affecting the flatness of the powder surface; however, A powder has a better post-processing effect on graphite printed products, which is beneficial to improving the mechanical properties of graphite products. B powder is a pyrolysis-treated powder, and its preparation method may include the following steps:

[0029] S110, putting graphite powder with a particle size of 5 μm to 130 μm into a vacuum furnace, heating it to 600° C. to 1200° C., and keeping it at that temperature for 2 h to 6 h for vacuum sintering;

[0030] S120, after cooling to room temperature, the vacuum sintered material is placed in a crusher and crushed into powder;

[0031] S130, using an ultrasonic vibration screening machine to screen the crushed powder, and the screened powder with a particle size of 40μm to 100μm is powder B.

[0032] B powder is a pyrolysis treated powder material. After high temperature treatment at 600℃~1200℃, most of the organic matter in the material is cracked and separated, which increases the density of the powder material. It is suitable for binder jet 3D printing, but the particle size distribution range of B powder is narrow, which is not conducive to powder filling. In addition, its fluidity is good but it is easy to cause the "pushing sample" phenomenon, that is, the printed sheet is easy to slide and warp, affecting the printing molding effect.

[0033] Experimental verification shows that direct printing of powders A and B alone cannot produce good binder jet-printed graphite products.

[0034] Combined with the characteristics of binder jet printing technology, the present invention designs a method for preparing high-density graphite powder for 3D printing, that is, 60% to 90% of A powder and 1% to 40% of B powder are evenly mixed, wherein the mixing time can be 0.5h to 2h. The preparation method is simple, and the obtained graphite powder can improve the density of graphite printing green body under the premise of satisfying fluidity, thereby reducing green body defects, and the density of graphite products after sintering changes little, effectively improving the mechanical properties and yield rate of graphite products.

[0035] The second object of the present invention is to provide a method of use, which is applied to any of the above-mentioned graphite powders for 3D printing. Specifically, the method of use may include the following steps:

[0036] S210, adding graphite powder for 3D printing into a powder spreading device, and adding a binder into an inkjet device; setting the printing layer thickness to 130 μm to 300 μm;

[0037] The binder may be one or more of phenolic resin, furan resin, epoxy resin, acrylic acid, polyurethane, polyvinyl alcohol, and asphalt; the amount of the binder used is 1% to 50% of the mass of the green body;

[0038] S220, the powder spreading device is started and performs a powder spreading operation to form a molding surface;

[0039] S230, the print head sprays the binder onto the molding surface according to the layered cross section of the part; the working box drops one printing layer thickness, and the powder spreading device spreads powder again;

[0040] S240, repeat step S230 until printing is completed;

[0041] S250, placing the working box in an oven for curing, the curing temperature is 120°C to 300°C, and the curing time is 2h to 6h;

[0042] S260, after the curing is completed, the excess powder is removed to obtain the green graphite product.

[0043] Embodiment 1

[0044] A method for preparing graphite powder for 3D printing, wherein 60% of A powder and 40% of B powder are put into a mixer and mixed evenly to obtain the graphite powder for 3D printing of this embodiment, wherein the mixing time is 2 hours.

[0045] Wherein, the A powder is graphite powder with a particle size of 5 μm to 130 μm; and the B powder is graphite powder after pyrolysis treatment with a particle size of 40 μm to 100 μm.

[0046] The preparation method of B powder may include the following steps:

[0047] S110, putting graphite powder with a particle size of 5 μm to 130 μm into a vacuum furnace, heating it to 850°C, and keeping it at this temperature for 3 hours for vacuum sintering;

[0048] S120, after cooling to room temperature, the vacuum sintered material is placed in a crusher and crushed into powder;

[0049] S130, using an ultrasonic vibration screening machine to screen the crushed powder, and the screened powder with a particle size of 40μm to 100μm is powder B.

[0050] Using the graphite powder for 3D printing of this embodiment for binder jet 3D printing may include the following steps:

[0051] S210, adding graphite powder for 3D printing into a powder spreading device, and adding a binder into an inkjet device; setting the printing layer thickness to 130 μm;

[0052] The binder is phenolic resin; the amount of the binder used is 8% of the green body mass;

[0053] S220, the powder spreading device is started and performs a powder spreading operation to form a molding surface;

[0054] S230, the print head sprays the binder onto the molding surface according to the layered cross section of the part; the working box drops one printing layer thickness, and the powder spreading device spreads powder again;

[0055] S240, repeat step S230 until printing is completed;

[0056] S250, put the working box into an oven for curing, the curing temperature is 120°C, and the curing time is 6h;

[0057] S260, after the curing is completed, the excess powder is removed to obtain the green graphite product.

[0058] The graphite product has small density change after sintering and excellent mechanical properties.

[0059] Embodiment 2

[0060] A method for preparing graphite powder for 3D printing, wherein 70% of A powder and 30% of B powder are put into a mixer and mixed evenly to obtain the graphite powder for 3D printing of this embodiment, wherein the mixing time is 1.5 hours.

[0061] Wherein, the A powder is graphite powder with a particle size of 5 μm to 130 μm; and the B powder is graphite powder after pyrolysis treatment with a particle size of 40 μm to 100 μm.

[0062] The preparation method of B powder may include the following steps:

[0063] S110, putting graphite powder with a particle size of 5 μm to 130 μm into a vacuum furnace, heating it to 600° C., and keeping it at this temperature for 6 hours for vacuum sintering;

[0064] S120, after cooling to room temperature, the vacuum sintered material is placed in a crusher and crushed into powder;

[0065] S130, using an ultrasonic vibration screening machine to screen the crushed powder, and the screened powder with a particle size of 40μm to 100μm is powder B.

[0066] Using the graphite powder for 3D printing of this embodiment for binder jet 3D printing may include the following steps:

[0067] S210, adding graphite powder for 3D printing into a powder spreading device, and adding a binder into an inkjet device; setting the printing layer thickness to 200 μm;

[0068] The binder is furan resin; the amount of the binder used is 10% of the green body mass;

[0069] S220, the powder spreading device is started and performs a powder spreading operation to form a molding surface;

[0070] S230, the print head sprays the binder onto the molding surface according to the layered cross section of the part; the working box drops one printing layer thickness, and the powder spreading device spreads powder again;

[0071] S240, repeat step S230 until printing is completed;

[0072] S250, put the working box into an oven for curing, the curing temperature is 200°C, and the curing time is 5h;

[0073] S260, after the curing is completed, the excess powder is removed to obtain the green graphite product.

[0074] The graphite product has small density change after sintering and excellent mechanical properties.

[0075] In order to facilitate understanding of the improvement effect of the present invention, the existing graphite powder is used as a comparative example, and various parameters of the graphite powder of the comparative example and each embodiment of the present invention are measured. The measurement results are shown in the following table:

[0076] Repose Angle Bulk density Green density Comparative Example 45° <![CDATA[0.66g / cm 3 ]]> <![CDATA[0.78g / cm 3 ]]> Example 1 38° <![CDATA[0.72g / cm 3 ]]> <![CDATA[0.91g / cm 3 ]]> Example 2 36° <![CDATA[0.70g / cm 3 ]]> <![CDATA[0.88g / cm 3 ]]>

[0077] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing graphite powder for 3D printing, characterized in that: The graphite powder for 3D printing comprises, by weight percentage, 60% to 90% of A powder and 1% to 40% of B powder; The graphite powder for 3D printing can be obtained by uniformly mixing 60% to 90% of A powder and 1% to 40% of B powder; The A powder is graphite powder with a particle size of 5 μm to 130 μm; The preparation method of the B powder comprises the following steps: S110, vacuum sintering graphite powder with a particle size of 5 μm to 130 μm and then cooling to room temperature; S120, crushing the sintered material, and screening the powder with a particle size of 40 μm to 100 μm to obtain the B powder.

2. The method for preparing graphite powder for 3D printing according to claim 1, characterized in that: The A powder and the B powder are mixed using a mixer for 0.5 h to 2 h.

3. The method for preparing graphite powder for 3D printing according to claim 1, characterized in that: In the step S110, the sintering temperature is 600° C. to 1200° C., and the sintering time is 2 h to 6 h.

4. The method for preparing graphite powder for 3D printing according to claim 1, characterized in that: The graphite powder includes one or more of petroleum coke, asphalt coke, coal tar pitch and carbon black.

5. A method of use, applied to the graphite powder for 3D printing as claimed in any one of claims 1 to 4, characterized in that: The steps include: S210, adding the graphite powder for 3D printing into a powder spreading device, and adding a binder into an inkjet device; S220, the powder spreading device is started and performs a powder spreading operation to form a molding surface; S230, the print head sprays the binder onto the molding surface according to the layered cross section of the part; the working box drops one printing layer thickness, and the powder spreading device spreads powder again; S240, repeat step S230 until printing is completed.

6. The method of use according to claim 5, characterized in that: Also includes a curing step; After printing is completed, the working box is placed in an oven for curing; after curing, the powder is removed to obtain a green graphite product.

7. The method of use according to claim 6, characterized in that: The curing temperature is 120°C to 300°C, and the curing time is 2h to 6h.

8. The method of use according to claim 6, characterized in that: The binder is one of phenolic resin, furan resin, epoxy resin, acrylic acid, polyurethane, polyvinyl alcohol and asphalt.

9. The method of use according to claim 8, characterized in that: The injection amount of the binder is 1% to 50% of the mass of the green body.

10. The method of use according to claim 5, characterized in that: The printing layer thickness is 130 μm to 300 μm.