CN110981483A - Method for preparing graphite electrode joint material by utilizing isotropic coke - Google Patents
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- C04B35/528—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 obtained from carbonaceous particles with or without other non-organic components
- C04B35/532—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 obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder
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Abstract
The invention relates to the technical field of electrode material preparation, in particular to a method for preparing a graphite electrode joint material by utilizing isotropic coke, wherein the aggregate adopts equi-square coke, the adhesive adopts medium-temperature asphalt, and the impregnant adopts impregnating asphalt; the isotropic coke has the characteristics that the physical and chemical properties of the isotropic coke in all directions cannot be changed due to different directions, and has the characteristics of high isotropy, high density, high strength, low porosity and small pore. The prepared graphite electrode joint material has the characteristics of large volume density, low resistivity, high mechanical strength, low ash content, low thermal expansion coefficient and the like. The volume density is more than or equal to 1.75g/cm3The resistivity is less than or equal to 5.5 mu omega m, the elastic modulus is less than or equal to 16GPa, the breaking strength is more than or equal to 14MPa, and the thermal expansion coefficient is less than or equal to 2.2 x 10-6V, and ash content is less than or equal to 0.25 percent.
Description
Technical Field
The invention relates to the technical field of electrode material preparation, in particular to a method for preparing a graphite electrode joint material by utilizing isotropic coke.
Background
The graphite electrode is a conductor which releases electric energy in the form of electric arc in an electric arc furnace to heat and melt furnace burden, and can be divided into ordinary power, high power and ultrahigh power according to the low quality index.
The graphite electrode joint means that when the electrode is used on a smelting furnace, the upper and lower 2-3 graphite electrodes are connected by processing male threads and female threads with corresponding sizes to realize continuous use. In the arc steel making, as the discharge power and the diameter of the electrode are increased, the heat generated by the working current is rapidly increased, and the requirements on the joint connection are more strict. The ideal connection of the electrode is realized, the processing quality of the joint and the joint hole is improved, the joint material is improved, and the tightening torque is also properly required, so that the pretightening force is proper, and the phenomenon that the pretightening force is too large to cause the breakage of the joint part in the work or the pretightening force is too small to cause the falling of the electrode in the work is avoided.
When the graphite electrode joint is connected with a threaded hole, strict requirements are placed on the perpendicularity of the end face and the axis of the thread, the end face needs to be recessed by 0.05-0.1mm (determined according to the elastic modulus of an electrode material), and the ideal connection state of the electrode is that the end face generates elastic compression deformation by applying proper pretightening force, so that the recessed state is overcome, and the comprehensive fit is realized. Meanwhile, the pre-tightening force is controlled to be not too large and exceed the yield strength of the joint, so that failure fracture is generated; the screw thread is not too small, the pretightening force is small, and sufficient positive pressure and friction force between the screw threads cannot be provided, so that loosening is caused.
During the production of graphite electrode and joint, petroleum coke and needle coke are used as main material and coal pitch as binding agent, and the material is produced through calcining, compounding, kneading, pressing, roasting, graphitizing and machining.
The method is favorable for improving the product percent of pass, fully utilizes the characteristic of isotropic coke, and the medium-temperature coal pitch is easy to graphitize in the graphitization process, so that the physical and chemical indexes of the final product can be fully met.
In the preparation process of the graphite product, the formula has great influence on the performance parameters of the graphite product, particularly on the volume density, the porosity and the thermal expansion coefficient. Generally, the product obtained by adopting a fine particle formula is large in volume density, small in porosity and elegant and high in fracture resistance and compression strength, square cokes with high isotropy, high density, high strength, low porosity and small pores are selected during material selection, superfine grinding powder and small particle formula are adopted during material preparation, and the maximum material diameter of aggregate is less than 0.5 mm. In this particle size range, the distribution of particle sizes of the particles directly affects the manner of stacking of the particles, and the more densely the particles are stacked, the larger the volume density and the smaller the porosity of the graphite product, and in this particle size range, the average particle size doubles and the thermal expansion rate decreases by about 7% while the particle size is maintained.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for preparing a graphite electrode joint material by utilizing isotropic coke.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a method for preparing a graphite electrode joint material by utilizing isotropic coke comprises the following steps:
s1, grinding: the aggregate is placed in a ball mill for milling at the temperature of 140 ℃ to 160 ℃, the milling time is 6-24 hours, and the speed is 300 ℃ to 600 r/min;
s2, kneading: adding the adhesive into the aggregate for kneading twice, wherein the kneading temperature is 150-170 ℃;
s3, molding: pouring the paste kneaded in the S2 into a forming machine for extrusion forming, wherein the tamping pressure of the extrusion forming is 8MPa, the pre-pressing pressure is 20MPa, the pre-pressing time is 4min, the extrusion pressure is 5-7.5MPa, the extrusion speed length is 1800mm and 150S, the outlet temperature of the extrusion forming machine is 110-3；
S4, primary roasting: the molded green body in S3 is loaded into a roasting furnace to be roasted to obtain a first green body
S5, dipping: preheating the first blank in S4, dipping, vacuumizing the dipping tank, pressurizing to 1.5Mpa, maintaining the pressure at 1.35Mpa for 50-60 minutes, and dipping;
s6, secondary roasting: roasting the impregnated blank in S5 for 330 hours at the temperature of 650-800 ℃;
s7, graphitizing: graphitizing the green body after roasting in S6 for 500 hours at the temperature of 2850 and 3100 ℃;
and S8, electrifying the graphitized motor connector material in S7, heating to the temperature of 750 ℃ and 900 ℃ under the condition of air isolation, keeping the current intensity at 15A for 8-10 hours, and enhancing the conductivity to obtain the pure graphite electrode connector material.
Furthermore, the aggregate is made of equal square coke, and the true density is more than or equal to 2.13g/cm3Powder resistivity is less than or equal to 55 mu omega m, ash content is less than or equal to 0.25 percent, and pores are 25-5 percent5 nm; the binder adopts medium-temperature coal pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 48 percent, and the ash content is less than or equal to 0.3 percent; the impregnant adopts impregnating pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 48 percent, and the quinoline insoluble substance is less than or equal to 0.25 percent.
Further, the weight ratio of the iso-square coke to the medium-temperature coal pitch is 70:30-75: 25%.
Further, the particle size range and the content of the equiaxed coke are as follows:
the grain diameter is less than or equal to 0.500mm and is 15-20 wt% when the grain diameter is 0.335 mm;
the grain diameter is less than or equal to 0.075mm and is 20-25 wt% of grain diameter;
the grain diameter is less than or equal to 0.075mm and 15-20 wt% in the range of 0.010 mm;
0< particle size <0.075mm 45-50 wt%.
Further, in the kneading process of S2, the adhesive is added in two times, the weight of the adhesive added in the first time is 75-85% of the total weight of the adhesive, and the kneading time is 20-25 minutes; the weight of the adhesive added for the second time is 15-25% of the total weight of the adhesive, and the time of the wet mixing for the second time is 20-25 minutes.
Further, the roasting temperature-raising procedure in S4 is as follows: the heating rate is 1.2-1.6 ℃/h at the temperature of 150-; the heating rate is 0.8-1 ℃/h at the temperature of 350-550 ℃; the heating rate is 1.2-1.4 ℃/h at the temperature of 850 ℃ below 550-; the temperature rise rate is 2.2-2.9 ℃/h at 850-1150 ℃.
Further, before the S5 impregnation, the impregnant is subjected to moisture removal and impurity removal treatment, the impregnant is heated to 320 ℃ at 220 ℃, the temperature is kept for 1-2.5 hours, and then the impregnant is heated to 200 ℃ at 180 ℃.
Further, the preheating temperature of the first blank body during the S5 impregnation is 360-380 ℃, and the weight gain rate after the impregnation is 13-14%.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method for preparing a graphite electrode joint material by utilizing isotropic coke, wherein the aggregate adopts equal-square coke, the adhesive adopts medium-temperature asphalt, and the impregnant adopts impregnating asphalt; object isotropically pointing in all directions using an isotropic focusThe characteristics of physical and chemical properties which do not change with different directions, and the characteristics of high isotropy, high density, high strength, low porosity and small pore. The prepared graphite electrode joint material has the characteristics of large volume density, low resistivity, high mechanical strength, low ash content, low thermal expansion coefficient and the like. The volume density is more than or equal to 1.75g/cm3The resistivity is less than or equal to 5.5 mu omega m, the elastic modulus is less than or equal to 16GPa, the breaking strength is more than or equal to 14MPa, the thermal expansion coefficient is less than or equal to 2.2 x 10-6/DEG C, and the ash content is less than or equal to 0.25 percent.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A method for preparing a graphite electrode joint material by utilizing isotropic coke comprises the following steps:
s1, grinding: the aggregate is placed in a ball mill for milling at the temperature of 140 ℃ to 160 ℃, the milling time is 6-24 hours, and the speed is 300 ℃ to 600 r/min;
s2, kneading: adding the adhesive into the aggregate for kneading twice, wherein the kneading temperature is 150-170 ℃; the adhesive is added in twice, the weight of the adhesive added in the first time is 75-85% of the total weight of the adhesive, and the kneading time is 20-25 minutes; the weight of the adhesive added for the second time is 15-25% of the total weight of the adhesive, and the time of wet mixing for the second time is 20-25 minutes;
s3, molding: pouring the paste kneaded in the S2 into a forming machine for extrusion forming, wherein the tamping pressure of the extrusion forming is 8MPa, the pre-pressing pressure is 20MPa, the pre-pressing time is 4min, the extrusion pressure is 5-7.5MPa, the extrusion speed length is 1800mm and 150S, the outlet temperature of the extrusion forming machine is 110-≥1.78g/cm3；
S4, primary roasting: and (3) putting the molded green body in S3 into a roasting furnace for roasting to obtain a first green body, wherein the roasting temperature-raising program is as follows: the heating rate is 1.2-1.6 ℃/h at the temperature of 150-; the heating rate is 0.8-1 ℃/h at the temperature of 350-550 ℃; the heating rate is 1.2-1.4 ℃/h at the temperature of 850 ℃ below 550-; the heating rate is 2.2-2.9 ℃/h at 850-1150 ℃;
s5, dipping: preheating the primary blank in S4 to the temperature of 360-380 ℃, then dipping, vacuumizing the dipping tank, pressurizing to 1.5Mpa, maintaining the pressure at 1.35Mpa for 50-60 minutes, and dipping; before impregnation, the impregnant is subjected to moisture removal and impurity removal treatment, the impregnant is heated to 320 ℃ of 220-
S6, secondary roasting: roasting the impregnated blank in S5 for 330 hours at the temperature of 650-800 ℃;
s7, graphitizing: graphitizing the green body after roasting in S6 for 500 hours at the temperature of 2850 and 3100 ℃;
and S8, electrifying the graphitized motor connector material in S7, heating to 750-900 ℃ under the condition of air isolation, keeping the current intensity at 15A, and maintaining for 8-10 hours to obtain the graphite electrode connector material.
In the embodiment, the aggregate is made of equirectangular coke, and the true density is more than or equal to 2.13g/cm3The resistivity of the powder is less than or equal to 55 mu omega m, the ash content is less than or equal to 0.25 percent, and the pore space is 25-55 nm; the binder adopts medium-temperature coal pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 48 percent, and the ash content is less than or equal to 0.3 percent; the impregnant adopts impregnating pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 48 percent, and the quinoline insoluble substance is less than or equal to 0.25 percent.
In this embodiment, the weight ratio of the isosbane coke to the medium-temperature coal pitch is 70:30 to 75:25%, preferably 72 to 70:28 to 30%.
In this embodiment, the particle size range and content of the equiaxed coke are as follows:
the grain diameter is less than or equal to 0.500mm and is 15-20 wt% when the grain diameter is 0.335 mm;
the grain diameter is less than or equal to 0.075mm and is 20-25 wt% of grain diameter;
the grain diameter is less than or equal to 0.075mm and 15-20 wt% in the range of 0.010 mm;
0< particle size <0.075mm 45-50 wt%;
the particle size range and content of the isosbane coke are preferably as follows:
0.335mm < particle size less than or equal to 0.500mm 20 wt%;
0.075mm < particle size less than or equal to 0.335mm 25 wt%;
0.010mm < the particle size is less than or equal to 0.075mm and 15 wt%;
0< particle size <0.075mm 50 wt%.
The dosage of the binder is directly related to the surface area of the aggregate, the smaller the particle size of the aggregate is, the larger the surface area is, the more the binder is, but the too much binder is, the compaction is not easy to occur during the molding, so the volume density of the product is smaller, and the product is easy to deform after the demolding. The proportion of the binder and the aggregate is 70:75-30:25%, after the aggregate and the binder are kneaded, the obtained paste is basically not in the form of lumps, most of the paste is in the form of loose particles or a few small lumps are poured on a material airing table, and a molded product with high volume density is obtained after molding.
The smaller the particles of the aggregate, the larger the surface area, the more difficult it is to mix uniformly in wet mixing, the longer the wet mixing time, and the more energy consumption. In the wet mixing process, the binder is added into the dry-mixed aggregate for mixing and kneading twice, the binder accounting for 70-80% of the total binder is added for the first time to be bonded with the aggregate, the mixture has low viscosity due to small addition amount, and can be uniformly mixed and kneaded in a short time under the action of stirring force under the same condition, the particle size of the raw material particles is uniformly increased after the first wet mixing, the specific surface area of the raw material particles is reduced, and the rest binder is added, so that the aggregate and the binder can be uniformly mixed in a short time. The medium-temperature asphalt serving as the binder is added twice, so that the wet mixing time can be shortened, the energy consumption is reduced, the paste can be uniformly kneaded, the paste with good plasticity is obtained, and the yield and the physical property of the formed green body can be improved.
The purpose of roasting is to carbonize the binder pitch, form coke grids among the aggregate particles, and firmly bond the aggregates with different granularities into a whole. When the small particle formula is used for preparing the carbon material, the probability of cracks in the subsequent heat treatment process is high, and the yield is possibly low.
The primary roasting process is carried out under the condition of air isolation, the highest temperature reaches 850-; the polycondensation reaction in the roasted product is enhanced at the temperature of 350-550 ℃, coke is formed, the temperature is raised by 0.8-1 ℃ per hour, the coking rate of the binder is favorably improved, and the semi-coking is converted into coking; at the temperature of 550 ℃ and 850 ℃, the polycondensation reaction continues to occur, the product is further coked, and the temperature is raised by 1.2 to 1.4 ℃ per hour; the temperature is increased at a slower temperature increase rate, so that the volume density and the strength of the roasted product are improved, and cracks are prevented from being generated when the roasted product shrinks in the polycondensation reaction process; at 850-1150 deg.c, the temperature is raised by 2.2-2.9 deg.c per hour and the temperature is raised at fast rate to densify the structure of the roasted product.
The properties of the impregnated asphalt have important influence on the impregnation effect, and are mainly reflected on asphalt viscosity, quinoline insoluble content and coking value. The higher the coking value is, the larger the bulk density and mechanical strength of the roasted product is, and the coking value is increased along with the increase of the softening point, so that the coal pitch with higher softening point is adopted as the binder, which is beneficial to improving the bulk density and mechanical strength of the product material, but the higher the softening point of the impregnated pitch is, the higher the relative viscosity is, the more the relative viscosity is, the green removing viscosity which is difficult to permeate into the pores of the impregnated product is influenced by the property of the impregnated pitch, and is inversely proportional to the heating temperature. In order to improve the dipping effect, the invention firstly selects the asphalt with the softening point of 83-86 ℃ and the coking value of more than or equal to 48 percent, and secondly heats the dipping asphalt to reduce the viscosity of the dipping asphalt. Generally, after the temperature exceeds 200 ℃, the light component in the asphalt begins to volatilize, 200-400 ℃ is the volatilization stage of the light component in the impregnated asphalt, the molecular weight of the light component volatilized in the impregnated asphalt gradually increases along with the increase of the temperature, the volatilized gas enters the gas in the gas of the impregnated product to hinder the permeation of the asphalt, so in the prior art, the impregnation is started after the impregnated asphalt is heated to 160-180 ℃, the temperature for heating the impregnated asphalt does not exceed 200 ℃, but because the preheating temperature of the carbonaceous product to be impregnated is generally between 300-400 ℃, the light component still volatilizes from the impregnated asphalt in the impregnated carbonaceous product during the impregnation process, the permeation of the impregnated asphalt is hindered, a plurality of gas pores are formed in the impregnated product, and before the impregnation, the impregnated asphalt is heated to 220-320 ℃, the dipping pitch is preferably heated to 260 ℃ of 220-. During impregnation, the carbonaceous product to be impregnated is firstly vacuumized, the purpose of vacuumization is to discharge gas in the pores of the carbonaceous product to be impregnated so as to be beneficial to the permeation of the impregnating pitch, and after the impregnating pitch is added, the impregnating pitch is easy to permeate into the pores of the carbonaceous product to be impregnated under the action of pressure, so that the weight gain rate is ensured; quinoline insoluble substances in the coal pitch are tiny particles, and the quinoline insoluble substances form a layer of film on the surface of the porous material during impregnation to hinder the impregnant from permeating the porous material, so the impregnation pitch with the quinoline insoluble substances of less than or equal to 0.2 percent is selected.
Although only the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art, and all changes are encompassed in the scope of the present invention.
Claims (8)
1. A method for preparing a graphite electrode joint material by utilizing isotropic coke is characterized by comprising the following steps:
s1, grinding: the aggregate is placed in a ball mill for milling at the temperature of 140 ℃ to 160 ℃, the milling time is 6-24 hours, and the speed is 300 ℃ to 600 r/min;
s2, kneading: adding the adhesive into the aggregate for kneading twice, wherein the kneading temperature is 150-170 ℃;
s3, molding: pouring the paste kneaded in the S2 into a forming machine for extrusion forming, wherein the tamping pressure of the extrusion forming is 8MPa, the pre-pressing pressure is 20MPa, the pre-pressing time is 4min, the extrusion pressure is 5-7.5MPa, the extrusion speed length is 1800mm and 150S, the outlet temperature of the extrusion forming machine is 110-3；
S4, primary roasting: the molded green body in S3 is loaded into a roasting furnace to be roasted to obtain a first green body
S5, dipping: preheating the first blank in S4, dipping, vacuumizing the dipping tank, pressurizing to 1.5Mpa, maintaining the pressure at 1.35Mpa for 50-60 minutes, and dipping;
s6, secondary roasting: roasting the impregnated blank in S5 for 330 hours at the temperature of 650-800 ℃;
s7, graphitizing: graphitizing the green body after roasting in S6 for 500 hours at the temperature of 2850 and 3100 ℃;
and S8, electrifying the graphitized motor connector material in S7, heating to 750-900 ℃ under the condition of air isolation, keeping the current intensity at 15A for 8-10 hours, and obtaining the graphite electrode connector material.
2. The method for preparing a graphite electrode tab material using isotropic coke as claimed in claim 1, wherein: the aggregate is made of equal square coke, and the true density is more than or equal to 2.13g/cm3The resistivity of the powder is less than or equal to 55 mu omega m, the ash content is less than or equal to 0.25 percent, and the pore space is 25-55 nm; the binder adopts medium-temperature coal pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 48 percent, and the ash content is less than or equal to 0.3 percent; the impregnant adopts impregnating pitch, the softening point is 83-86 ℃, the coking value is more than or equal to 48 percent, and the quinoline insoluble substance is less than or equal to 0.25 percent.
3. The method for preparing a graphite electrode tab material using isotropic coke as claimed in claim 1, wherein: the weight ratio of the equal square coke to the medium temperature coal pitch is 70:30-75: 25%.
4. The method for preparing a graphite electrode tab material using isotropic coke as claimed in claim 1, wherein: the particle size range and the content of the equirectangular coke are as follows:
the grain diameter is less than or equal to 0.500mm and is 15-20 wt% when the grain diameter is 0.335 mm;
the grain diameter is less than or equal to 0.075mm and is 20-25 wt% of grain diameter;
the grain diameter is less than or equal to 0.075mm and 15-20 wt% in the range of 0.010 mm;
0< particle size <0.075mm 45-50 wt%.
5. The method for preparing a graphite electrode tab material using isotropic coke as claimed in claim 1, wherein: in the kneading process of S2, the adhesive is added twice, the weight of the adhesive added for the first time is 75-85% of the total weight of the adhesive, and the kneading time is 20-25 minutes; the weight of the adhesive added for the second time is 15-25% of the total weight of the adhesive, and the time of the wet mixing for the second time is 20-25 minutes.
6. The method for preparing a graphite electrode tab material by using isotropic coke as claimed in claim 1, wherein the firing temperature-raising procedure in S4 is as follows: the heating rate is 1.2-1.6 ℃/h at the temperature of 150-; the heating rate is 0.8-1 ℃/h at the temperature of 350-550 ℃; the heating rate is 1.2-1.4 ℃/h at the temperature of 850 ℃ below 550-; the temperature rise rate is 2.2-2.9 ℃/h at 850-1150 ℃.
7. The method for preparing a graphite electrode tab material using isotropic coke as claimed in claim 1, wherein: before the S5 impregnation, the impregnant is subjected to moisture removal and impurity removal treatment, the impregnant is heated to 320 ℃ for heat preservation for 1-2.5 hours at 220 ℃, and then the impregnant is heated to 200 ℃ at 180 ℃.
8. The method for preparing a graphite electrode tab material using isotropic coke as claimed in claim 1, wherein: the preheating temperature of the first blank body in the S5 impregnation process is 360-380 ℃, and the weight gain rate after the impregnation process is 13-14%.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911153622.7A CN110981483A (en) | 2019-11-22 | 2019-11-22 | Method for preparing graphite electrode joint material by utilizing isotropic coke |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911153622.7A CN110981483A (en) | 2019-11-22 | 2019-11-22 | Method for preparing graphite electrode joint material by utilizing isotropic coke |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005298231A (en) * | 2004-04-07 | 2005-10-27 | Tokai Carbon Co Ltd | Manufacturing method of isotropic graphite material |
| CN101798080A (en) * | 2010-03-01 | 2010-08-11 | 中钢集团吉林炭素股份有限公司 | Method for manufacturing graphite electrode joint material |
| CN106698414A (en) * | 2015-11-13 | 2017-05-24 | 大同新成新材料股份有限公司 | Raw material composition and method for preparing special graphite material |
| CN109574669A (en) * | 2018-11-30 | 2019-04-05 | 大同新成新材料股份有限公司 | A kind of electrode contact preparation method for material adding graphite cathode material |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005298231A (en) * | 2004-04-07 | 2005-10-27 | Tokai Carbon Co Ltd | Manufacturing method of isotropic graphite material |
| CN101798080A (en) * | 2010-03-01 | 2010-08-11 | 中钢集团吉林炭素股份有限公司 | Method for manufacturing graphite electrode joint material |
| CN106698414A (en) * | 2015-11-13 | 2017-05-24 | 大同新成新材料股份有限公司 | Raw material composition and method for preparing special graphite material |
| CN109574669A (en) * | 2018-11-30 | 2019-04-05 | 大同新成新材料股份有限公司 | A kind of electrode contact preparation method for material adding graphite cathode material |
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Application publication date: 20200410 |