CN118164760B - Preparation method of graphite material for electric spark machining - Google Patents
Preparation method of graphite material for electric spark machining Download PDFInfo
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- 239000007770 graphite material Substances 0.000 title claims abstract description 72
- 238000002360 preparation method Methods 0.000 title claims abstract description 33
- 238000010892 electric spark Methods 0.000 title claims abstract description 26
- 238000003754 machining Methods 0.000 title claims abstract description 24
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 126
- 239000000843 powder Substances 0.000 claims abstract description 67
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 63
- 239000010426 asphalt Substances 0.000 claims abstract description 34
- 238000004898 kneading Methods 0.000 claims abstract description 34
- 238000005245 sintering Methods 0.000 claims abstract description 32
- 239000000571 coke Substances 0.000 claims abstract description 31
- 238000002156 mixing Methods 0.000 claims abstract description 27
- 238000001816 cooling Methods 0.000 claims abstract description 26
- 239000004005 microsphere Substances 0.000 claims abstract description 25
- 238000000748 compression moulding Methods 0.000 claims abstract description 19
- 239000006229 carbon black Substances 0.000 claims abstract description 17
- 238000007873 sieving Methods 0.000 claims abstract description 13
- 238000000227 grinding Methods 0.000 claims abstract description 11
- 238000005096 rolling process Methods 0.000 claims abstract description 5
- 238000003825 pressing Methods 0.000 claims abstract description 4
- 239000003245 coal Substances 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 26
- 238000000462 isostatic pressing Methods 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 14
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 8
- 239000002006 petroleum coke Substances 0.000 claims description 8
- 239000002985 plastic film Substances 0.000 claims description 8
- 229920006255 plastic film Polymers 0.000 claims description 8
- 238000001291 vacuum drying Methods 0.000 claims description 8
- 238000009461 vacuum packaging Methods 0.000 claims description 8
- 229910002804 graphite Inorganic materials 0.000 claims description 7
- 239000010439 graphite Substances 0.000 claims description 7
- 238000005087 graphitization Methods 0.000 claims description 5
- 239000002931 mesocarbon microbead Substances 0.000 claims description 3
- 239000011294 coal tar pitch Substances 0.000 claims description 2
- 230000000630 rising effect Effects 0.000 claims description 2
- 239000011271 tar pitch Substances 0.000 claims description 2
- 239000006253 pitch coke Substances 0.000 claims 3
- 238000001354 calcination Methods 0.000 claims 1
- 238000010304 firing Methods 0.000 claims 1
- 238000000465 moulding Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 12
- 238000007580 dry-mixing Methods 0.000 abstract description 8
- 238000012545 processing Methods 0.000 abstract description 8
- 238000007598 dipping method Methods 0.000 abstract description 3
- 239000011148 porous material Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 12
- 239000002245 particle Substances 0.000 description 12
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 239000012071 phase Substances 0.000 description 9
- 239000011300 coal pitch Substances 0.000 description 7
- 235000019580 granularity Nutrition 0.000 description 7
- 238000005098 hot rolling Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 6
- 239000003575 carbonaceous material Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 238000003763 carbonization Methods 0.000 description 3
- 238000000280 densification Methods 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 241000872198 Serjania polyphylla Species 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 210000003739 neck Anatomy 0.000 description 2
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- 208000032170 Congenital Abnormalities Diseases 0.000 description 1
- 238000005411 Van der Waals force Methods 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
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- 239000003153 chemical reaction reagent Substances 0.000 description 1
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- 238000009826 distribution Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000016507 interphase Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 239000007790 solid phase Substances 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/522—Graphite
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Abstract
The invention discloses a preparation method of a graphite material for electric spark machining, which comprises the following steps: (1) Uniformly mixing raw coke powder, graphite powder, mesophase carbon microspheres and carbon black, and pressing and forming to obtain a blank; (2) Placing the green body into a pressure roasting furnace for sintering treatment, controlling the sintering temperature to be 450-550 ℃, the sintering pressure to be 1-5MPa, and grinding to obtain primary powder; (3) Dry-mixing the calcined asphalt coke aggregate and the primary powder, adding molten coal asphalt, kneading, rolling, cooling, crushing and sieving to obtain pressed powder; (4) And (3) carrying out compression molding, roasting and graphitizing treatment on the pressed powder to obtain the graphite material for electric spark machining. The preparation method of the invention does not need dipping and repeated roasting, has the advantages of short production period, low production cost, high mechanical strength, good conductivity and the like, and meets the performance requirement of the graphite material for electric spark processing, and the special carbon graphite material has an ultra-fine structure and isotropy.
Description
Technical Field
The invention belongs to the field of carbon materials, and particularly relates to a preparation method of a graphite material.
Background
The graphite is an inorganic nonmetallic material which consists of carbon atoms and has a layered structure, the carbon atoms are connected through sp 2 hybridized orbits to form a hexagonal graphite layer network structure, the graphite layers are connected through strong covalent bonds, and the graphite layers are connected through weak van der Waals forces. Therefore, the graphite material has the advantages of high lubricity, corrosion resistance, good electric conduction and heat conduction, heat resistance, thermal shock resistance, high mechanical strength at high temperature, good machining property and the like, and is widely applied to the fields of electric spark processing industry, photovoltaic industry, semiconductor industry, aerospace, nuclear industry and the like closely connected with the development of the current high technology.
The electric spark processing is also called as electric discharge processing or electric erosion processing, which is a special processing method for performing pulse discharge on a workpiece immersed in a liquid medium with certain insulation degree by utilizing a continuously moving electrode to generate an electric erosion effect so as to etch away conductive materials, and is one of important processes for processing metal parts with complex structures. The electrode material for electric spark machining is mainly graphite material at present, and is more and more widely applied to the precision die machining industry, the product performance requirement is high, the production process is complex, and higher technical difficulty exists. The preparation of graphite materials for electric spark processing by domestic enterprises is still in an exploration stage, and the prior art needs repeated dipping and repeated roasting in order to ensure that the prepared graphite materials reach ideal performance, and has long production period and high production cost.
Disclosure of Invention
The invention aims to solve the technical problems and overcome the defects and shortcomings in the background art, and provides a preparation method of a graphite material for electric spark machining, which has the advantages of short production period, higher volume density, higher mechanical strength and high practicability. In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Uniformly mixing raw coke powder, graphite powder, mesophase carbon microspheres and carbon black, and pressing and forming to obtain a blank;
(2) Placing the green body in the step (1) into a pressure roasting furnace for sintering treatment, controlling the sintering temperature to be 450-550 ℃ and the sintering pressure to be 1-5MPa during sintering treatment, cooling to room temperature after the sintering treatment is finished, and grinding to obtain first-stage powder;
(3) Mixing calcined asphalt coke aggregate with the one-stage powder obtained in the step (2), adding molten coal asphalt, kneading, rolling, cooling, crushing and sieving to obtain pressed powder;
(4) And (3) performing compression molding, roasting and graphitization treatment on the pressed powder obtained in the step (3) to obtain the graphite material for electric spark machining.
In the preparation method, preferably, the raw coke powder is raw asphalt coke powder with the D50 of 2-4 mu m, the graphite powder is artificial graphite powder, flake graphite powder or high-power graphite electrode powder with the D50 of 1-5 mu m, the D50 of the intermediate phase carbon microsphere is 2-6 mu m, the D50 of the calcined asphalt coke aggregate is 6-10 mu m, and the raw coke powder, the graphite powder, the intermediate phase carbon microsphere and the calcined asphalt coke aggregate firstly remove moisture in the surfaces and pores of each drier through a vacuum drying system at 110-150 ℃. By matching the powder with different granularities, the stacking density of the green body is higher.
In the preparation method, preferably, the mass ratio of raw coke powder, graphite powder, intermediate phase carbon microsphere powder and carbon black is controlled to be (10-15) when the raw coke powder, the graphite powder, the intermediate phase carbon microsphere powder and the carbon black are uniformly mixed: (5-8): (2-4): 1, after 1-5 hours in a mixing machine, the blank is obtained by compression molding under the pressure of 1-3 MPa. Through the powder mixing of the mass ratio, the active layer is formed on the surfaces of the graphite powder and the carbon black with weaker activity by the raw coke powder and the intermediate phase carbon microsphere powder, the requirement of the subsequent sintering process is met, and the performance of the final graphite material product is better.
In the preparation method, preferably, during sintering, the temperature rising rate of 10-30 ℃/h is increased to 450-550 ℃, the sintering pressure is kept at 1-5MPa, the temperature is kept for 6-10h, the temperature is reduced to room temperature at the temperature reducing rate of 30-50 ℃/h, and the D50 of the primary powder is controlled to be 2-6 mu m through grinding.
In the above preparation method, preferably, the mass ratio of the calcined asphalt coke aggregate to the primary powder is 1: (1-3), more preferably 1:2, the addition amount of the coal tar pitch is 55-65wt.% of the total mass of the calcined tar pitch and the primary powder.
In the preparation method, preferably, the dry-mixing treatment is carried out for 1-2 hours at 110-150 ℃, the kneading temperature is kept at 160-180 ℃ during the kneading treatment, the kneading rotating speed is 30-50rpm, and the kneading time is 0.5-2 hours.
In the preparation method, preferably, the pressed powder is obtained by rolling, cooling, crushing and sieving, wherein the pressed powder is obtained by hot rolling the sheet for 3-5 times at 160-180 ℃, and the pressed powder is obtained by crushing and sieving with a 160-325 mesh sieve after cooling to room temperature.
In the preparation method, preferably, when the pressed powder is pressed and molded, firstly, the pressed powder is placed for 10-20 hours, then the pressed powder is molded under 1-3MPa to obtain a green body, the green body is placed for 10-20 hours, the green body is placed in an aluminum plastic film for vacuum packaging, then, the green body is preheated in an oven at 80-100 ℃ for 4-8 hours, and then, the preheated green body in the oven is placed in a preheated isostatic pressing cylinder body for warm isostatic pressing under 150-200 MPa. The invention adopts the temperature isostatic pressing technology to promote the secondary migration of the binder, so that the binder forms more uniform spreading among aggregates, and the interfacial binding force among different aggregates is increased.
In the preparation method, the green body obtained by compression molding is preferably placed into a down-draft kiln or an atmosphere resistance furnace for landfill, and is heated to 1000-1050 ℃ at 5-10 ℃/h for heat preservation for 2-6h.
In the preparation method, preferably, the graphitization treatment is to put the baked carbon block obtained by the baking treatment into an Acheson furnace, landfill the sieved petroleum coke or metallurgical coke, heating to 2600-3000 ℃ at 2-10 ℃/h, and preserving the heat for 150-200 h.
Aiming at the problems of long production period, higher production cost, high porosity, low mechanical strength, poor electric conductivity and the like of a graphite material for electric spark machining in the traditional preparation method, raw coke powder, graphite powder and mesophase carbon microspheres are uniformly mixed with carbon black, pressed and formed into a blank body, and then the blank body is subjected to pressure roasting treatment, an activated layer matched with binder coal pitch is formed on the surfaces of the graphite powder and the carbon black with poor surface activity by utilizing active functional groups rich in the surfaces of the raw coke and the mesophase carbon microspheres with self-sintering characteristics (the intermediate phase carbon microspheres and the raw coke are generally used as solid phase densification in the prior art, the effect is completely different from that of the invention), the interface bonding problem of a carbonaceous aggregate and the binder is improved, the thermal adaptation of the aggregate and the binder in the carbonization process is enhanced, the formation of sintering necks is promoted, the formation of different carbon interphase synchronous shrinkage densification is realized in the subsequent roasting stage, the formation of a carbon network structure can be better formed, the congenital defects of the carbon graphite material are reduced, the microcracks in the carbon material are reduced, the comprehensive performances of the carbon graphite material are improved, and the like. Finally, the first-stage powder and the calcined asphalt coke aggregate are mixed and then subjected to subsequent treatment, and the obtained graphite material has excellent comprehensive performance.
In order to achieve the above effects, the process parameters in the sintering treatment of the invention need to be precisely controlled, especially the sintering temperature and pressure need to be controlled, the sintering pressure is too small to construct an active layer on the surface of the carbonaceous material, the requirement on equipment is extremely high due to the too high sintering pressure, and the maintenance cost and period of the equipment can be increased, so the invention controls the sintering pressure to be 1-5MPa. The sintering temperature is controlled to be 450-550 ℃, and in the temperature range, active substances can be carbonized into a carbon net on the surface of the carbonaceous material to construct an active layer. If the sintering temperature is too low and is lower than the carbonization temperature, an active layer cannot be formed, and if the sintering temperature is too high and exceeds the carbonization temperature, active groups of the carbonaceous material are carbonized and removed too much, and the carbonized active layer cannot be formed. In combination, the invention controls the sintering temperature and the sintering pressure within the above ranges.
In the whole, the preparation method disclosed by the invention does not need dipping and repeated roasting, and the special carbon graphite material with an ultra-fine structure and isotropy can be prepared, so that the graphite material has the advantages of short production period, low production cost, high mechanical strength, good conductivity and the like, meets the performance requirements of the graphite material for electric spark processing, and improves the productivity and profit of enterprises.
Compared with the prior art, the invention has the advantages that:
1. according to the preparation method of the graphite material for electric spark machining, raw coke powder, graphite powder, intermediate phase carbon microspheres and carbon black are uniformly mixed, a blank is obtained by compression molding, then the blank is subjected to pressure roasting treatment, the problem of interface combination of a carbonaceous material and a binder is improved by utilizing active functional groups rich in surfaces of the raw coke and the intermediate phase carbon microspheres with self-sintering characteristics, the formation of sintering necks is promoted, the synchronous shrinkage densification of different carbon phases is realized in the subsequent roasting stage, the formation of microcracks in the carbon graphite material is reduced, and the special carbon graphite material which does not need to be impregnated and roasted for multiple times and has an ultra-fine structure and isotropy is prepared, and the comprehensive performance of the carbon graphite material is improved.
2. The preparation method of the graphite material for electric spark machining can realize the preparation of the graphite material for electric spark machining through one-time roasting and one-time graphitization, reduces the process flow of repeated impregnation and roasting, and has short production period and low production cost.
3. According to the preparation method of the graphite material for electric spark machining, graphite and carbon black are used as secondary aggregates to be dispersed in the matrix, and the front-end pretreatment is carried out through pressure roasting, so that the manufacturability is improved, the heat uniformity of a heat treatment product is improved, and the thermal shock resistance of the graphite material is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is an SEM image of the graphite material obtained in example 1.
Fig. 2 is a polarization diagram of the graphite material obtained in example 1.
Fig. 3 is an SEM image of the graphite material obtained in comparative example 1.
Fig. 4 is a polarization chart of the graphite material obtained in comparative example 1.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments are shown, for the purpose of illustrating the invention, but the scope of the invention is not limited to the specific embodiments shown.
Unless defined otherwise, all technical and scientific terms used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
Example 1:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Preparing raw asphalt coke powder with the D50 of 2 mu m, calcined asphalt coke aggregate with the particle size D50 of 10 mu m, artificial graphite powder with the D50 of 5 mu m and mesophase carbon microspheres with the D50 of 2 mu m by adopting a Raymond mill and a high-energy airflow mill, and removing moisture on the surfaces and pores of each dry material by a vacuum drying system at the temperature of 110 ℃;
(2) And (2) mixing the raw asphalt coke powder, graphite powder, mesophase carbon microsphere powder and carbon black obtained in the step (1) according to a mass ratio of 10:5:3:1, adding the mixture into a mixing machine for mixing for 1h, and then performing compression molding at 3MPa to obtain a blank;
(3) Placing the blank obtained in the step (2) into a pressurized roasting furnace, replacing air in the roasting furnace with nitrogen or argon, heating to 550 ℃ with a program of 20 ℃/h, controlling the pressure to be 3MPa, preserving heat for 8h, cooling to room temperature with a program of 40 ℃/h, and preparing surface modified primary powder with the granularity D50 of 5 mu m by a Raymond mill and airflow grinding;
(4) The one-stage powder prepared in the step (3) and the calcined asphalt coke aggregate prepared in the step (1) are mixed according to the mass ratio of 1:2, putting into a kneading pot, dry-mixing for 1h at 120 ℃, removing water, continuously heating to 175 ℃, adding 55wt.% of molten coal pitch, keeping the kneading temperature at 175 ℃, kneading at 50rpm, kneading for 1h, hot-rolling the sheet at 175 ℃ for 3 times, cooling to room temperature, crushing, and sieving with a 200-mesh sieve to obtain pressed powder;
(5) Placing the pressed powder prepared in the step (4) for 12 hours, performing compression molding at 3MPa to obtain a green body, placing for 12 hours, placing the green body in an aluminum plastic film for vacuum packaging, and preheating for 4 hours in a 90 ℃ oven; placing the preheated blank in the oven into a preheated isostatic pressing cylinder, and performing warm isostatic pressing at 200MPa to prepare a carbon graphite material green body;
(6) Placing the carbon graphite material green body prepared in the step (5) into a down-draft kiln or an atmosphere resistor for landfill, heating to 1050 ℃ at 10 ℃/h, preserving heat for 4 hours, and cooling to room temperature to prepare a baked carbon block;
(7) And (3) placing the baked carbon block prepared in the step (6) into an Acheson furnace, and burying with sieved petroleum coke or metallurgical coke (80% of 5mm and 20% of 5-20 mm), and heating to 2900 ℃ at a speed of 10 ℃ per hour to obtain the graphite material of the embodiment.
And (3) referring to YB/T4379-2014 standard, testing the volume density, the open porosity, the resistivity, the flexural strength, the compressive strength, the Shore hardness and the like of the graphite material prepared in the step (7). The volume density was 1.82g/cm 3, the open porosity was 12%, the electrical resistivity was 12.5. Mu.OMEGA.m, the flexural strength was 51MPa, the compressive strength was 115MPa, and the Shore hardness was 65HSD, as shown in Table 1 below.
SEM images and polarization images of the graphite material obtained in this example are shown in fig. 1 and 2. As shown in FIG. 1, the sample pore structure is distributed uniformly, and the pore size is generally smaller, so that the sample is mostly single independent air holes. As shown in fig. 2, the pores of the sample are relatively uniform and small in size.
Example 2:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Preparing raw asphalt coke powder with the particle size D50 of 2 mu m, calcined asphalt coke aggregate with the particle size D50 of 10 mu m, artificial graphite powder with the particle size D50 of 5 mu m and mesophase carbon microspheres with the particle size D50 of 2 mu m by adopting a Raymond mill and a high-energy airflow mill, and removing moisture on the surfaces and pores of each dry material through a vacuum drying system at the temperature of 110 ℃;
(2) And (3) mixing the raw asphalt coke powder, graphite powder, mesophase carbon microsphere powder and carbon black obtained in the step (1) according to a mass ratio of 12:6:4:1, adding the mixture into a mixing machine for mixing for 1h, and then performing compression molding at 3MPa to obtain a blank;
(3) Placing the blank obtained in the step (2) into a pressurized roasting furnace, replacing air in the roasting furnace with nitrogen or argon, heating to 500 ℃ with a program of 20 ℃/h, controlling the pressure to be 2MPa, preserving heat for 8h, cooling to room temperature with a program of 40 ℃/h, and preparing surface modified primary powder with the granularity D50 of 5 mu m by a Raymond mill and airflow grinding;
(4) The one-stage powder prepared in the step (3) and the calcined asphalt coke aggregate prepared in the step 1) are mixed according to the mass ratio of 1:2, putting into a kneading pot, dry-mixing for 1h at 120 ℃, removing water, continuously heating to 175 ℃, adding 60wt.% of molten coal pitch, keeping the kneading temperature at 175 ℃, kneading at 50rpm, kneading for 1h, hot-rolling the sheet at 175 ℃ for 3 times, cooling to room temperature, crushing, and sieving with a 200-mesh sieve to obtain pressed powder;
(5) Placing the pressed powder prepared in the step (4) for 12 hours, performing compression molding at 3MPa to obtain a green body, placing for 12 hours, placing the green body in an aluminum plastic film for vacuum packaging, and preheating for 4 hours in a 90 ℃ oven; placing the preheated blank in the oven into a preheated isostatic pressing cylinder, and performing warm isostatic pressing at 200MPa to prepare a carbon graphite material green body;
6) Placing the carbon graphite material green body prepared in the step 5) into a down-draft kiln or an atmosphere resistor for landfill, heating to 1050 ℃ at 10 ℃/h, preserving heat for 4 hours, and cooling to room temperature to prepare a baked carbon block;
(7) And (3) placing the baked carbon block prepared in the step (6) into an Acheson furnace, and burying with sieved petroleum coke or metallurgical coke (80% of 5mm and 20% of 5-20 mm), and heating to 2900 ℃ at a speed of 10 ℃ per hour to obtain the graphite material of the embodiment.
And (3) referring to YB/T4379-2014 standard, testing the volume density, the open porosity, the resistivity, the flexural strength, the compressive strength, the Shore hardness and the like of the graphite material prepared in the step (7). The volume density was 1.80g/cm 3, the open porosity was 13%, the electrical resistivity was 13. Mu.OMEGA.m, the flexural strength was 47MPa, the compressive strength was 107MPa, and the Shore hardness was 52HSD, as shown in Table 1 below.
Example 3:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Preparing raw asphalt coke powder with the particle size D50 of 4 mu m and calcined asphalt coke aggregate with the particle size D50 of 8 mu m by adopting a Raymond mill and a high-energy airflow mill, wherein D50 is artificial graphite powder with the particle size D50 of 3 mu m, D50 is mesophase carbon microspheres with the particle size D50 of 2 mu m, and removing moisture on the surfaces and in pores of each dry material through a vacuum drying system at the temperature of 110 ℃;
(2) And (2) mixing the raw coke powder, the graphite powder, the mesocarbon microbead powder and the carbon black obtained in the step (1) according to a mass ratio of 14:7:2:1, adding the mixture into a mixing machine for mixing for 1h, and then performing compression molding at 3MPa to obtain a blank;
(3) Placing the blank obtained in the step (2) into a pressurized roasting furnace, replacing air in the roasting furnace with nitrogen or argon, heating to 450 ℃ with a program of 20 ℃/h, controlling the pressure to be 1MPa, preserving heat for 8h, cooling to room temperature with a program of 40 ℃/h, and preparing surface modified primary powder with the granularity D50 of 5 mu m by a Raymond mill and airflow grinding;
(4) The one-stage powder prepared in the step (3) and the calcined asphalt coke aggregate prepared in the step 1) are mixed according to the mass ratio of 1:2, putting into a kneading pot, dry-mixing for 1h at 120 ℃, removing water, continuously heating to 175 ℃, adding 60wt.% of molten coal pitch, keeping the kneading temperature at 175 ℃, kneading at 50rpm, kneading for 1h, hot-rolling the sheet at 175 ℃ for 3 times, cooling to room temperature, crushing, and sieving with a 200-mesh sieve to obtain pressed powder;
(5) Placing the pressed powder prepared in the step (4) for 12 hours, performing compression molding at 3MPa to obtain a green body, placing for 12 hours, placing the green body in an aluminum plastic film for vacuum packaging, and preheating for 4 hours in a 90 ℃ oven; placing the preheated blank in the oven into a preheated isostatic pressing cylinder, and performing warm isostatic pressing at 200MPa to prepare a carbon graphite material green body;
(6) Placing the carbon graphite material green body prepared in the step (5) into a down-draft kiln or an atmosphere resistor for landfill, heating to 1050 ℃ at 10 ℃/h, preserving heat for 4 hours, and cooling to room temperature to prepare a baked carbon block;
(7) And (3) placing the baked carbon block prepared in the step (6) into an Acheson furnace, and burying with sieved petroleum coke or metallurgical coke (80% of 5mm and 20% of 5-20 mm), and heating to 2900 ℃ at a speed of 10 ℃ per hour to obtain the graphite material of the embodiment.
And (3) referring to YB/T4379-2014 standard, testing the volume density, the open porosity, the resistivity, the flexural strength, the compressive strength, the Shore hardness and the like of the graphite material prepared in the step (7). The volume density was 1.78g/cm 3, the open porosity was 13.2%, the electrical resistivity was 13.1. Mu.OMEGA.m, the flexural strength was 45MPa, the compressive strength was 108MPa, and the Shore hardness was 50HSD, as shown in Table 1 below.
Comparative example 1:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Preparing raw asphalt coke powder with the D50 of 2 mu m, calcined asphalt coke aggregate with the particle size D50 of 10 mu m, artificial graphite powder with the D50 of 5 mu m and mesophase carbon microspheres with the D50 of 2 mu m by adopting a Raymond mill and a high-energy airflow mill, and removing moisture on the surfaces and pores of each dry material by a vacuum drying system at the temperature of 110 ℃;
(2) And (3) mixing the raw coke powder, the graphite powder, the mesocarbon microbead powder and the carbon black obtained in the step (1) according to a mass ratio of 10:5:3:1, adding the mixture into a mixing machine for mixing for 1h, and then performing compression molding at 3MPa to obtain a blank;
(3) Grinding the blank obtained in the step (2) by a Raymond mill and an air flow mill to obtain first-stage powder with the granularity D50 of 5 mu m;
(4) The one-stage powder prepared in the step (3) and the calcined asphalt coke aggregate prepared in the step (1) are mixed according to the mass ratio of 1:2, putting into a kneading pot, dry-mixing for 1h at 120 ℃, removing water, continuously heating to 175 ℃, adding molten coal pitch, keeping the kneading temperature at 175 ℃, kneading at 50rpm, kneading for 1h, hot-rolling the sheet at 175 ℃ for 3 times, cooling to room temperature, crushing, and sieving with a 200-mesh sieve to obtain pressed powder;
(5) Placing the pressed powder prepared in the step (4) for 12 hours, performing compression molding at 3MPa to obtain a green body, placing for 12 hours, placing the green body in an aluminum plastic film for vacuum packaging, and preheating for 4 hours in a 90 ℃ oven; placing the preheated blank in the oven into a preheated isostatic pressing cylinder, and performing warm isostatic pressing at 200MPa to prepare a carbon graphite material green body;
(6) Placing the carbon graphite material green body prepared in the step (5) into a down-draft kiln or an atmosphere resistor for landfill, heating to 1050 ℃ at 10 ℃/h, preserving heat for 4 hours, and cooling to room temperature to prepare a baked carbon block;
(7) And (3) placing the baked carbon block prepared in the step (6) into an Acheson furnace, and burying with sieved petroleum coke or metallurgical coke (80% of 5mm and 20% of 5-20 mm), and heating to 2900 ℃ at a speed of 10 ℃ per hour to obtain the graphite material of the embodiment.
And (3) referring to YB/T4379-2014 standard, testing the volume density, the open porosity, the resistivity, the flexural strength, the compressive strength, the Shore hardness and the like of the graphite material prepared in the step (7). The volume density was 1.73g/cm 3, the open porosity was 16%, the electrical resistivity was 15. Mu.OMEGA.m, the flexural strength was 41MPa, the compressive strength was 89MPa, and the Shore hardness was 40HSD, as shown in Table 1 below.
The SEM image and the polarized light image of the graphite material obtained in this comparative example are shown in fig. 3 and 4, and as shown in fig. 3, the sample pore structure has poor uniformity of distribution of the sample pore structure and a large pore diameter. As shown in fig. 4, the sample was heterogeneous in pores and had larger pores.
Comparative example 2:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Preparing raw asphalt coke powder with the D50 of 2 mu m, calcined asphalt coke aggregate with the particle size D50 of 10 mu m, artificial graphite powder with the D50 of 5 mu m and mesophase carbon microspheres with the D50 of 2 mu m by adopting a Raymond mill and a high-energy airflow mill, and removing moisture on the surfaces and pores of each dry material by a vacuum drying system at the temperature of 110 ℃;
(2) And (2) mixing the raw asphalt coke powder, graphite powder, mesophase carbon microsphere powder and carbon black obtained in the step (1) according to a mass ratio of 10:5:3:1, adding the mixture into a mixing machine for mixing for 1h, and then performing compression molding at 3MPa to obtain a blank;
(3) Placing the blank obtained in the step (2) into a pressurized roasting furnace, replacing air in the roasting furnace with nitrogen or argon, heating to 600 ℃ with a program of 20 ℃/h, controlling the pressure to be 3MPa, preserving heat for 8h, cooling to room temperature with a program of 40 ℃/h, and preparing surface modified primary powder with the granularity D50 of 5 mu m by a Raymond mill and airflow grinding;
(4) The one-stage powder prepared in the step (3) and the calcined asphalt coke aggregate prepared in the step (1) are mixed according to the mass ratio of 1:2, putting into a kneading pot, dry-mixing for 1h at 120 ℃, removing water, continuously heating to 175 ℃, adding 55wt.% of molten coal pitch, keeping the kneading temperature at 175 ℃, kneading at 50rpm, kneading for 1h, hot-rolling the sheet at 175 ℃ for 3 times, cooling to room temperature, crushing, and sieving with a 200-mesh sieve to obtain pressed powder;
(5) Placing the pressed powder prepared in the step (4) for 12 hours, performing compression molding at 3MPa to obtain a green body, placing for 12 hours, placing the green body in an aluminum plastic film for vacuum packaging, and preheating for 4 hours in a 90 ℃ oven; placing the preheated blank in the oven into a preheated isostatic pressing cylinder, and performing warm isostatic pressing at 200MPa to prepare a carbon graphite material green body;
(6) Placing the carbon graphite material green body prepared in the step (5) into a down-draft kiln or an atmosphere resistor for landfill, heating to 1050 ℃ at 10 ℃/h, preserving heat for 4 hours, and cooling to room temperature to prepare a baked carbon block;
(7) And (3) placing the baked carbon block prepared in the step (6) into an Acheson furnace, and burying with sieved petroleum coke or metallurgical coke (80% of 5mm and 20% of 5-20 mm), and heating to 2900 ℃ at a speed of 10 ℃ per hour to obtain the graphite material of the embodiment.
And (3) referring to YB/T4379-2014 standard, testing the volume density, the open porosity, the resistivity, the flexural strength, the compressive strength, the Shore hardness and the like of the graphite material prepared in the step (7). The volume density was 1.75g/cm 3, the open porosity was 13.8%, the electrical resistivity was 14.6. Mu.OMEGA.m, the flexural strength was 43MPa, the compressive strength was 95MPa, and the Shore hardness was 46HSD, as shown in Table 1 below.
Comparative example 3:
the preparation method of the graphite material for electric spark machining comprises the following steps:
(1) Preparing raw asphalt coke powder with the D50 of 2 mu m, calcined asphalt coke aggregate with the particle size D50 of 10 mu m, artificial graphite powder with the D50 of 5 mu m and mesophase carbon microspheres with the D50 of 2 mu m by adopting a Raymond mill and a high-energy airflow mill, and removing moisture on the surfaces and pores of each dry material by a vacuum drying system at the temperature of 110 ℃;
(2) And (2) mixing the raw asphalt coke powder, graphite powder, mesophase carbon microsphere powder and carbon black obtained in the step (1) according to a mass ratio of 10:5:3:1, adding the mixture into a mixing machine for mixing for 1h, and then performing compression molding at 3MPa to obtain a blank;
(3) Placing the blank obtained in the step (2) into a pressurized roasting furnace, replacing air in the roasting furnace with nitrogen or argon, heating to 550 ℃ with a program of 20 ℃/h, controlling the pressure to be 0MPa, preserving heat for 8h, cooling to room temperature with a program of 40 ℃/h, and preparing surface modified primary powder with the granularity D50 of 5 mu m by a Raymond mill and airflow grinding;
(4) The one-stage powder prepared in the step (3) and the calcined asphalt coke aggregate prepared in the step (1) are mixed according to the mass ratio of 1:2, putting into a kneading pot, dry-mixing for 1h at 120 ℃, removing water, continuously heating to 175 ℃, adding 55wt.% of molten coal pitch, keeping the kneading temperature at 175 ℃, kneading at 50rpm, kneading for 1h, hot-rolling the sheet at 175 ℃ for 3 times, cooling to room temperature, crushing, and sieving with a 200-mesh sieve to obtain pressed powder;
(5) Placing the pressed powder prepared in the step (4) for 12 hours, performing compression molding at 3MPa to obtain a green body, placing for 12 hours, placing the green body in an aluminum plastic film for vacuum packaging, and preheating for 4 hours in a 90 ℃ oven; placing the preheated blank in the oven into a preheated isostatic pressing cylinder, and performing warm isostatic pressing at 200MPa to prepare a carbon graphite material green body;
(6) Placing the carbon graphite material green body prepared in the step (5) into a down-draft kiln or an atmosphere resistor for landfill, heating to 1050 ℃ at 10 ℃/h, preserving heat for 4 hours, and cooling to room temperature to prepare a baked carbon block;
(7) And (3) placing the baked carbon block prepared in the step (6) into an Acheson furnace, and burying with sieved petroleum coke or metallurgical coke (80% of 5mm and 20% of 5-20 mm), and heating to 2900 ℃ at a speed of 10 ℃ per hour to obtain the graphite material of the embodiment.
And (3) referring to YB/T4379-2014 standard, testing the volume density, the open porosity, the resistivity, the flexural strength, the compressive strength, the Shore hardness and the like of the graphite material prepared in the step (7). The volume density was 1.74g/cm 3, the open porosity was 15.2%, the electrical resistivity was 14.8. Mu.OMEGA.m, the flexural strength was 42MPa, the compressive strength was 92MPa, and the Shore hardness was 43HSD, as shown in Table 1 below.
The performance data of the graphite materials prepared in examples 1 to 3 and comparative examples 1 to 3 are shown in Table 1 below.
Table 1: performance data of graphite materials prepared in examples 1 to 3 and comparative examples 1 to 3
| Bulk density of | Open porosity | Resistivity of | Flexural Strength | Compressive Strength | Shore hardness | |
| Example 1 | 1.82g/cm3 | 12％ | 12.5μΩm | 51MPa | 115MPa | 65HSD |
| Example 2 | 1.80g/cm3 | 13％ | 13μΩm | 47MPa | 107MPa | 52HSD |
| Example 3 | 1.78g/cm3 | 13.2％ | 13.1μΩm | 45MPa | 108MPa | 50HSD |
| Comparative example 1 | 1.73g/cm3 | 16％ | 15μΩm | 41MPa | 89MPa | 40HSD |
| Comparative example 2 | 1.75g/cm3 | 13.8％ | 14.6μΩm | 43MPa | 95MPa | 46HSD |
| Comparative example 3 | 1.74g/cm3 | 15.2％ | 14.8μΩm | 42MPa | 92MPa | 43HSD |
As can be seen from the above Table 1, the graphite materials prepared in examples 1 to 3 have significantly better overall properties than those of comparative examples 1 to 3, and meet the performance requirements of the graphite materials for electric discharge machining, and particularly, the overall properties are better by controlling the process parameters in example 1.
Claims (10)
1. The preparation method of the graphite material for electric spark machining is characterized by comprising the following steps of:
(1) Uniformly mixing raw coke powder, graphite powder, mesophase carbon microspheres and carbon black, and pressing and forming to obtain a blank;
(2) Placing the green body in the step (1) into a pressure roasting furnace for sintering treatment, controlling the sintering temperature to be 450-550 ℃ and the sintering pressure to be 1-5MPa during sintering treatment, cooling to room temperature after the sintering treatment is finished, and grinding to obtain first-stage powder;
(3) Mixing calcined asphalt coke aggregate with the one-stage powder obtained in the step (2), adding molten coal asphalt, kneading, rolling, cooling, crushing and sieving to obtain pressed powder;
(4) And (3) performing compression molding, roasting and graphitization treatment on the pressed powder obtained in the step (3) to obtain the graphite material for electric spark machining.
2. The preparation method according to claim 1, wherein the raw coke powder is raw pitch coke powder with a D50 of 2-4 μm, the graphite powder is artificial graphite powder, flake graphite powder or high-power graphite electrode powder with a D50 of 1-5 μm, the D50 of the mesophase carbon microsphere is 2-6 μm, the D50 of the calcined pitch coke aggregate is 6-10 μm, and the raw coke powder, the graphite powder, the mesophase carbon microsphere and the calcined pitch coke aggregate are first subjected to moisture removal at 110-150 ℃ by a vacuum drying system.
3. The preparation method according to claim 1, wherein the mass ratio of raw coke powder, graphite powder, mesocarbon microbeads and carbon black is controlled to be (10-15): (5-8): (2-4): 1, after 1-5 hours in a mixing machine, the blank is obtained by compression molding under the pressure of 1-3 MPa.
4. The method according to claim 1, wherein the sintering process is performed at a temperature rising rate of 10-30 ℃/h to 450-550 ℃, the sintering pressure is kept at 1-5MPa, the temperature is kept for 6-10h, the temperature is reduced to room temperature at a temperature reducing rate of 30-50 ℃/h, and the D50 of the primary powder is controlled to be 2-6 μm by grinding.
5. The preparation method according to any one of claims 1 to 4, wherein the mass ratio of the calcined asphalt coke aggregate to the one-stage powder is 1: (1-3), wherein the addition amount of the coal tar pitch is 55-65wt.% of the total mass of the calcined tar pitch and the primary powder.
6. The method according to any one of claims 1 to 4, wherein the dry-blending treatment is carried out at 110 to 150 ℃ for 1 to 2 hours, the kneading temperature is kept at 160 to 180 ℃ and the kneading rotation speed is 30 to 50rpm, and the kneading time is 0.5 to 2 hours.
7. The method according to any one of claims 1 to 4, wherein the rolling, cooling, crushing, sieving to obtain a pressed powder is hot rolled at 160 to 180 ℃ for 3 to 5 times, and after cooling to room temperature, crushing, sieving with a 160 to 325 mesh sieve to obtain a pressed powder.
8. The method according to any one of claims 1 to 4, wherein the powder is pressed and formed by first placing the powder for 10 to 20 hours, then pressing and forming the powder under 1 to 3MPa to obtain a green body, placing the green body for 10 to 20 hours, placing the green body in an aluminum plastic film for vacuum packaging, preheating the green body in an oven at 80 to 100 ℃ for 4 to 8 hours, placing the preheated green body in the oven in a preheated isostatic pressing cylinder, and performing warm isostatic pressing under 150 to 200 MPa.
9. The method according to any one of claims 1 to 4, wherein the firing is performed by placing the green compact obtained by press molding in a down-draft kiln or an atmosphere resistance furnace for landfill, and heating to 1000 to 1050 ℃ at 5 to 10 ℃/h, and preserving the heat for 2 to 6 hours.
10. The method according to any one of claims 1 to 4, wherein the graphitization treatment is to put the baked carbon block obtained by the calcination treatment into an acheson furnace, landfill the sieved petroleum coke or metallurgical coke, raise the temperature to 2600 to 3000 ℃ at2 to 10 ℃/h, and keep the temperature for 150 to 200 hours.
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| CN102530933A (en) * | 2011-12-30 | 2012-07-04 | 清华大学 | Artificial graphite product taking emulsified asphalt as binder and preparation method thereof |
| CN105098184A (en) * | 2015-09-25 | 2015-11-25 | 深圳市贝特瑞新能源材料股份有限公司 | Preparation method of composite graphite, composite graphite and lithium ion battery |
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| JP6021099B2 (en) * | 2012-04-02 | 2016-11-02 | 国立研究開発法人産業技術総合研究所 | Carbon-solid electrolyte composite and method for producing the same |
| CN109400162B (en) * | 2018-12-13 | 2021-08-03 | 湖南长宇科技发展有限公司 | Graphite for electric spark machining and preparation method thereof |
| CN115353391B (en) * | 2022-09-06 | 2023-06-27 | 湖南大学 | Method for preparing special graphite material by isostatic pressing of graphite waste in short process |
| CN115872744B (en) * | 2022-12-14 | 2023-08-08 | 湖南大学 | Method for preparing high-performance binder-free carbon graphite material by solid-phase densification |
| CN116692848A (en) * | 2023-05-26 | 2023-09-05 | 山西博翔汇良新材料有限公司 | Preparation method of high-density isostatic pressing graphite |
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| CN102530933A (en) * | 2011-12-30 | 2012-07-04 | 清华大学 | Artificial graphite product taking emulsified asphalt as binder and preparation method thereof |
| CN105098184A (en) * | 2015-09-25 | 2015-11-25 | 深圳市贝特瑞新能源材料股份有限公司 | Preparation method of composite graphite, composite graphite and lithium ion battery |
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