Electrode rod and method for producing the same
By optimizing the particle size distribution of electrode rod raw materials and the calcination, impregnation, and graphitization processes, the quality issues of electrode rod materials were resolved, enabling the preparation of electrode rods with high strength, low resistance, and low coefficient of thermal expansion, thereby improving product quality and performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN CHANGNING CARBON CO LTD
- Filing Date
- 2024-02-26
- Publication Date
- 2026-06-02
AI Technical Summary
Existing electrode rod materials suffer from problems such as high ash content, high brittleness, unreasonable aggregate particle size matching, non-dense microstructure of different carbon phases, and mismatched thermal expansion coefficients, which lead to easy slag shedding during use and poor product quality.
Using needle-shaped petroleum coke powder, electrode rod green waste powder, and coal tar medium-temperature pitch as raw materials with a mass ratio of 3-3.2:0.8-1.2:0.8-1.2, high-strength, low-resistivity, and low-thermal-expansion coefficient electrode rods were prepared by optimizing the particle size distribution and calcination, impregnation, and graphitization treatments.
The strength, density, and purity of the electrode rods were improved, while the resistance and coefficient of thermal expansion were reduced. The problem of internal structural inhomogeneity was solved, the service life was extended, and the production cost was reduced.
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Figure CN118307321B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrode rod manufacturing technology, and particularly relates to an electrode rod and its preparation method. Background Technology
[0002] With the development of the semiconductor and photovoltaic industries, translucent quartz crucibles produced by the electric arc method are indispensable basic materials for pulling large-diameter single-crystal silicon and are essential for the development of large-scale integrated circuits. Electrode rods are the core materials for generating high-temperature electric arcs and transferring heat energy in electric arc furnace metallurgy. Furthermore, electrode rods can be used to manufacture quartz products such as quartz flow guides, indicating a promising future for this industry. However, existing electrode graphite rod materials have high ash content, high brittleness, unreasonable aggregate particle size matching, non-dense microstructures of different carbon phases, and mismatched coefficients of thermal expansion, making them prone to slagging during use. Therefore, the development of electrode rods is crucial for the high-quality development of the manufacturing industry and will greatly promote the transformation and upgrading of the graphite industry.
[0003] Due to the nature of their manufacturing process, raw material composition, and proportions, electrode rods often suffer from poor product quality, particularly in terms of strength, density, resistance, purity, and stability, all of which require further improvement. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide an electrode rod and its preparation method, wherein the electrode rod has high strength, high density, low resistance, low coefficient of thermal expansion and high purity.
[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:
[0006] An electrode rod is provided, the raw materials of which include a needle-shaped petroleum coke powder mixture in a mass ratio of 3-3.2:0.8-1.2:0.8-1.2, electrode rod green waste powder with a particle size of 1-3 mm, and coal tar medium-temperature pitch. The needle-shaped petroleum coke powder mixture includes coarse needle-shaped petroleum coke powder with a particle size of 20 mesh ≤ < 40 mesh, medium needle-shaped petroleum coke powder with a particle size of 40 mesh ≤ < 200 mesh, and fine needle-shaped petroleum coke powder with a particle size of ≤ 200 mesh. The mass of the coarse needle-shaped petroleum coke powder, medium needle-shaped petroleum coke powder, and fine needle-shaped petroleum coke powder accounts for 35-45%, 15-25%, and 35-45% of the mass of the needle-shaped petroleum coke powder mixture, respectively.
[0007] This invention optimizes the particle size distribution of needle-shaped petroleum coke powder. The original particle size and the overall powder mix affect the sintering effect; improper distribution can lead to small defects in the green body, especially in extrusion molding where uneven pressure distribution causes defects to concentrate in the center. The needle-shaped petroleum coke powder gradation follows the principle of "large at both ends and small in the middle," meaning the proportion of coarse and fine powder should be high, while the proportion of medium powder should be low. Based on the principle of close packing, coarse powder is tightly packed, medium powder fills the larger pores between coarse particles, and fine powder, as the main structural material filling the small pores, is fully wetted by medium-temperature pitch and penetrates into the gaps between the powder particles. This results in a more uniform pressing force across the entire process, reducing the probability of internal defects and improving the quality of the green body. If the needle-shaped petroleum coke powder mixture ratio is outside the above range, the green body will crack, and the uniformity and density will not meet the process requirements.
[0008] Preferably, the raw materials include a mixture of needle-shaped petroleum coke powder in a mass ratio of 3:1:1, electrode rod green waste powder with a particle size of 1-3 mm, and coal tar medium-temperature pitch.
[0009] The mass percentages of the needle-shaped petroleum coke coarse powder, needle-shaped petroleum coke medium powder, and needle-shaped petroleum coke fine powder are 40%, 20%, and 40% of the mass of the needle-shaped petroleum coke powder mixture, respectively. This gradation of needle-shaped petroleum coke powder can achieve better results.
[0010] Preferably, the electrode rod green waste powder is prepared by crushing and screening the defective electrode rod greens generated during pressing and / or the cut ends during cooling and cutting through a crusher with a 3mm perforated plate.
[0011] Preferably, the electrode rod has a resistance not exceeding 5 μΩ·m, a flexural strength not less than 40 MPa, a compressive strength not less than 50 MPa, and a bulk density not less than 1.72 g / cm³. 3 The coefficient of thermal expansion at room temperature is not higher than 2.5E-6 / ℃, the oxidation weight loss is less than 5wt.%, and the ash content is not higher than 20ppm.
[0012] As a general inventive concept, the present invention provides a method for preparing an electrode rod, comprising the following steps:
[0013] (1) The needle-shaped petroleum coke powder mixture is mixed with the electrode rod green waste powder and coal tar medium-temperature pitch to make a high-temperature paste. The high-temperature paste is poured into a cooling machine to reduce the temperature to 145-155℃. Then it enters the vertical press cylinder for vacuum pressing and molding. After cooling and cutting, the electrode rod green is obtained.
[0014] (2) The electrode rod blank is repeatedly baked and impregnated with asphalt to obtain a baked electrode rod;
[0015] (3) The electrode rod is graphitized and purified to obtain the electrode rod.
[0016] Preferably, in step (1), the method for preparing the needle-shaped petroleum coke powder mixture is to use a powder with a true density of 2.10 g / cm³. 3 The needle-shaped petroleum coke lumps mentioned above are obtained through crushing and screening. Needle-shaped petroleum coke lumps have high true density, and the smaller their pores, the easier they are to graphitize. They also have lower electrical resistance and a smaller coefficient of thermal expansion, which can improve the performance of electrode rods.
[0017] The preparation method of the needle-shaped petroleum coke powder mixture may specifically include the following steps: crushing the needle-shaped petroleum coke lumps using a disc crusher with a 5mm perforated plate; screening the crushed material to obtain needle-shaped petroleum coke coarse residue with a particle size greater than 20 mesh, needle-shaped petroleum coke coarse powder with a particle size of 20 mesh ≤ particle size < 40 mesh, needle-shaped petroleum coke medium powder with a particle size of 40 mesh ≤ particle size < 200 mesh, and needle-shaped petroleum coke fine powder with a particle size of ≤ 200 mesh; and crushing the needle-shaped petroleum coke coarse powder with a particle size greater than 20 mesh using a roller crusher, and then screening it to obtain needle-shaped petroleum coarse powder with a particle size of 20 mesh ≤ particle size < 40 mesh. Needle-shaped petroleum coke medium powder (40 mesh ≤ < 200 mesh) and needle-shaped petroleum coke fine powder (≤ 200 mesh) are prepared by mixing needle-shaped petroleum coke coarse powder (20 mesh ≤ < 40 mesh), needle-shaped petroleum coke medium powder (40 mesh ≤ < 200 mesh), and needle-shaped petroleum coke fine powder (≤ 200 mesh). The particle size after crushing can be well controlled in the roller crushing step, ensuring all particles meet the process requirements. Integrating this process into the impact crushing and screening system allows for the preparation of all needle-shaped petroleum coke into the different particle sizes required by the process, reducing preparation costs and ensuring particle size quality.
[0018] Preferably, in step (1), the preparation process of the high-temperature paste specifically includes the following steps: needle-shaped petroleum coke powder mixture and electrode rod green waste powder are preheated and mixed in a high-temperature mixing pot at 170–185°C, then mixed for 25–35 minutes using a turbulent three-dimensional mixer, followed by the addition of coal tar medium-temperature pitch and mixing for 15–25 minutes to produce a high-temperature paste with small particles of 1–3 mm in diameter. This invention utilizes turbulent three-dimensional mixing and kneading technology, enabling the materials to achieve thorough mixing in a very short time and producing small particles with a diameter of 1–3 mm, thus achieving homogeneous mixing while saving more than three times the mixing time.
[0019] Preferably, in step (1), during the vacuum pressing molding, the pressing pressure is 15-20 MPa, the vacuum degree is -0.85--0.95 MPa, and the pressing time is 1.5-2.5 minutes.
[0020] Preferably, in step (2), the specific process of preparing the electrode rod calcined part by repeatedly firing and impregnating the electrode rod green blank with asphalt is as follows:
[0021] 1) First, the electrode rod blank is first baked at a temperature of 1080-1150℃ for 4-15 days to obtain a baked electrode rod part.
[0022] During the first firing, the electrode rod blanks are vertically installed at a spacing of 10-20mm using tools, with a distance of more than 50mm from the fire wall. Sand is then filled in and compacted with a vibrator. The sand particle size is controlled to be below 30 mesh. Then the electrode rod blanks are fired for the first time.
[0023] 2) First, preheat the electrode rod calcination part one at 220-250℃ for 22-24 hours, then immerse it in coal tar high-temperature pitch at 170-185℃ and hold it under pressure at 2.5-2.7MPa for 18-21 hours; then place it in a crucible and put it in a single furnace for a second calcination to obtain the electrode rod calcination part two, wherein the temperature of the second calcination is 900-950℃ and the time is 8-9 days;
[0024] 3) First, preheat the electrode rod calcination part two at 220-250℃ for 22-24 hours, then immerse it in coal tar high-temperature pitch at 170-185℃ and hold it under pressure at 2.5-2.7MPa for 18-21 hours; then put it into a crucible and place it in a single furnace for a third calcination to obtain the electrode rod calcination part; wherein, the temperature of the third calcination is 900-950℃ and the time is 8-9 days.
[0025] After the roasted product undergoes high-pressure impregnation with asphalt in the above steps, it is then homogenized and roasted in a single furnace, which ensures an increase in the density of the roasted product and uniformity of its resistance. This invention, through a two-impregnation, three-roasting, graphitization, and purification process, improves the strength, density, and purity of the electrode rod, reduces its resistance, coefficient of thermal expansion, oxidation weight loss rate, and ash content, solves the problem of uneven internal structure, prevents slag and ash shedding during use, extends its service life, and effectively improves the quality of the electrode rod.
[0026] Preferably, in step (3), the graphitization temperature is 2900-2950℃ and the time is 14-15 days;
[0027] The purification process is carried out by introducing chlorine gas at a temperature of 1900–1950°C for 14–15 days.
[0028] At graphitization temperatures, some high-boiling-point impurity compounds in graphite materials are difficult to vaporize and escape. For example, boron carbide has a boiling point of 3500℃, vanadium carbide has a boiling point of 3900℃, and titanium has a boiling point of 3287℃. Removing these high-boiling-point impurities is very difficult. Therefore, chlorine gas is introduced into the furnace at 1900–1950℃ as a purification gas. At high temperatures, chlorine decomposes into elemental chlorine. These chemically active halogen elements react with various impurity elements and their compounds in the graphite products, combining to form halides with very low melting and boiling points, which then vaporize and escape.
[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0030] (1) This invention improves the uniformity of the paste and ensures the density of the green body by scientifically proportioning needle-shaped petroleum coke powder of different particle sizes, and then homogenizing it with electrode rod green waste powder with a particle size of 1-3 mm and coal tar pitch. In addition, the appropriate ratio of needle-shaped petroleum coke powder mixture with electrode rod green waste powder and coal tar pitch results in high strength of the prepared electrode rod.
[0031] (2) The present invention uses electrode rod green blank waste powder as raw material, which can improve product density on the one hand and make full use of waste on the other hand, effectively reducing production costs.
[0032] (3) In the preparation of electrode rods, it is best to control the temperature of the paste cooling material within the range of 145-155℃. Otherwise, if the temperature is too high, it will lead to quality problems such as large elasticity of the green body, out-of-roundness of the outer diameter, and surface blistering. If the temperature is too low, it will also lead to a decrease in product performance. In the pressing process, the vacuum process can be combined to increase the density of the green body and increase the bulk density of the graphitized product and reduce the resistance.
[0033] (4) The electrode rod in this invention has many advantages such as good appearance quality, high strength, high density, high purity, low thermal expansion coefficient, low resistance, low ash content, low oxidation weight loss rate, and long service life. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0035] Figure 1 This is a photograph of the electrode rod prepared in Example 1 of the present invention. Detailed Implementation
[0036] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.
[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.
[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods, as shown in Table 1.
[0039] Example 1:
[0040] An electrode rod of the present invention comprises a needle-shaped petroleum coke powder mixture in a mass ratio of 3:1:1, electrode rod green waste powder with a particle size of 1-3 mm, and medium-temperature coal tar pitch. The needle-shaped petroleum coke powder mixture includes coarse needle-shaped petroleum coke powder with a particle size of 20 mesh ≤ < 40 mesh, medium needle-shaped petroleum coke powder with a particle size of 40 mesh ≤ < 200 mesh, and fine needle-shaped petroleum coke powder with a particle size of ≤ 200 mesh. The mass percentages of the coarse, medium, and fine needle-shaped petroleum coke powders are 40%, 20%, and 40% of the mass of the needle-shaped petroleum coke powder mixture, respectively. The electrode rod green waste powder is prepared by crushing and screening defective electrode rod greens produced during pressing and / or tailings from cooling and cutting through a crusher with a 3 mm perforated plate.
[0041] The method for preparing the electrode rod in this embodiment includes the following steps:
[0042] (1) The true density is 2.11 g / cm³. 3 The needle-shaped petroleum coke lumps are crushed by a flared crusher with a 5mm perforated plate. The crushed material is then screened to obtain needle-shaped petroleum coke coarse residue with a particle size >20 mesh, needle-shaped petroleum coke coarse powder with a particle size ≤200 mesh, needle-shaped petroleum coke medium powder with a particle size ≤200 mesh, and needle-shaped petroleum coke fine powder with a particle size ≤200 mesh. The needle-shaped petroleum coke coarse powder with a particle size >20 mesh is then crushed by a double roller crusher and screened again to obtain needle-shaped petroleum coarse powder with a particle size ≤200 mesh, needle-shaped petroleum coke medium powder with a particle size ≤200 mesh, and needle-shaped petroleum coke fine powder with a particle size ≤200 mesh.
[0043] Then, needle-shaped petroleum coke coarse powder (20 mesh ≤ particle size < 40 mesh), needle-shaped petroleum coke medium powder (40 mesh ≤ particle size < 200 mesh), and needle-shaped petroleum coke fine powder (≤ 200 mesh) were mixed in the following weight percentages to prepare a needle-shaped petroleum coke powder mixture: 40% needle-shaped petroleum coke coarse powder (20 mesh ≤ particle size < 40 mesh), 20% needle-shaped petroleum coke medium powder (40 mesh ≤ particle size < 200 mesh), and 40% needle-shaped petroleum coke fine powder (≤ 200 mesh).
[0044] (2) The needle-shaped petroleum coke powder mixture and the electrode rod green waste powder (obtained from the previous batch of electrode rod green materials produced during vacuum pressing and molding, and the cut-off material from cooling and cutting, which was crushed and screened by a crusher with a 3mm perforated plate) are mixed at a mass ratio of 3:1. After preheating and mixing in a high-temperature mixing pot at 180℃, the mixture is then mixed for 30 minutes using a turbulent three-dimensional mixer. Then, coal tar medium-temperature pitch is added and mixed for 20 minutes. The mass ratio of needle-shaped petroleum coke powder mixture to coal tar medium-temperature pitch is 3:1, resulting in small granular high-temperature high-temperature powder with a particle size of 1-3mm. The paste is prepared by pouring the high-temperature paste into a cooling machine to lower the temperature to 145-155℃. Then, it enters the material cylinder of a vertical press for vacuum pressing and molding. The pressing pressure is 20MPa, the vacuum degree is -0.9MPa, and the pressing time is 2 minutes. After cooling and cutting, electrode rod green blanks are obtained. In the vacuum pressing process, unqualified electrode rod green blanks will be generated, and the head and tail materials generated during cooling and cutting will also be generated. The unqualified electrode rod green blanks and the head and tail materials generated during cooling and cutting are crushed and screened by a crusher with a 3mm perforated plate to obtain electrode rod green blank waste powder, which is used as raw material for the next batch of electrode rods.
[0045] (3) The electrode rod blanks are vertically assembled at 20mm intervals using a special tool, ensuring a distance of at least 50mm from the firewall. Sand is then filled in and compacted using a vibrator, with the sand particle size controlled below 30 mesh. The electrode rod blanks are then fired at 1100℃ for 14 days to obtain electrode rod firing part one. Electrode rod firing part one is preheated at 250℃ for 24 hours, then immersed in coal tar high-temperature pitch at 180℃, and then heated at 2.5M. The electrode rod was held under pressure at 2.5 MPa for 20 hours, then placed in a crucible and placed in a single furnace for a second calcination at 950°C for 8 days, resulting in the second calcined electrode rod. The second calcined electrode rod was preheated at 250°C for 24 hours, then immersed in coal tar high-temperature pitch at 180°C, and held under pressure at 2.5 MPa for 20 hours. It was then placed in a crucible and placed in a single furnace for a third calcination at 950°C for 8 days, resulting in the calcined electrode rod.
[0046] (4) The electrode rod calcination part is placed in a graphitization furnace for graphitization treatment. The graphitization treatment temperature is 2900℃ and the time is 14 days. After the graphitization treatment is completed, chlorine gas is introduced for purification treatment. The purification temperature is 1900℃ and the time is 14 days to obtain graphitized electrode rods. Finally, the electrode rods are processed by intelligent CNC machine tools.
[0047] Photographs of the prepared electrode rods are shown below. Figure 1 As shown. The electrode rod has a resistivity of 4.8 μΩ·m, a flexural strength of 44 MPa, a compressive strength of 55 MPa, and a bulk density of 1.73 g / cm³. 3 The coefficient of thermal expansion at room temperature is 2.4E-6 / ℃, the oxidation weight loss rate is 4.8wt.%, and the ash content is 18ppm.
[0048] Example 2:
[0049] Unlike Example 1, in step (1), the needle-shaped petroleum coke powder mixture was prepared by mixing the following weight percentages: 35% coarse needle-shaped petroleum coke powder with a particle size of 20 mesh ≤ < 40 mesh, 20% medium needle-shaped petroleum coke powder with a particle size of 40 mesh ≤ < 200 mesh, and 45% fine needle-shaped petroleum coke powder with a particle size of ≤ 200 mesh.
[0050] Comparative Example 1:
[0051] Unlike Example 1, in step (1), the needle-shaped petroleum coke powder mixture was prepared by mixing the following weight percentages: 20% coarse needle-shaped petroleum coke powder with a particle size of 20 mesh ≤ < 40 mesh, 50% medium needle-shaped petroleum coke powder with a particle size of 40 mesh ≤ < 200 mesh, and 30% fine needle-shaped petroleum coke powder with a particle size of ≤ 200 mesh.
[0052] Comparative Example 2:
[0053] Unlike Example 1, in step (2), the high-temperature paste is poured into a cooling machine to reduce the temperature to 110-120°C.
[0054] Comparative Example 3:
[0055] Unlike Example 1, in step (2), the mass ratio of needle-shaped petroleum coke powder mixture to electrode rod green waste powder and coal tar medium-temperature pitch is 3:1.3:1.3.
[0056] Comparative Example 4:
[0057] Unlike Example 1, in step (2), no vacuuming is performed during the pressing process.
[0058] Performance testing:
[0059] The resistance, strength, bulk density, coefficient of thermal expansion at room temperature, oxidation weight loss rate and ash content of the electrode rods prepared for the examples and comparative examples were tested according to the following standards.
[0060] The methods for determining resistivity are GB / T 24525-2009; flexural strength is GB / T3074.1-2021; compressive strength is GB / T 1431-2019; bulk density is GB / T24528-2009; coefficient of thermal expansion at room temperature is GB / T 3074.4-2016; oxidation weight loss is ASTM C1179-2015; and ash content is YB / T 5146-2022. Specific results are shown in Table 1.
[0061] Table 1 Performance Test Results
[0062]
[0063] A comparison of Comparative Example 1 and Examples 1-2 shows that when the proportions of each raw material in the needle coke powder mixture exceed the protection scope of this invention, its strength decreases, and its resistivity, bulk density, coefficient of thermal expansion at room temperature, oxidation weight loss rate, and ash content are all poor. However, a comparison of Examples 1 and 2 shows that when the proportions of each raw material in the needle coke powder mixture are: 40% coarse needle coke powder with a particle size of 20 mesh ≤ < 40 mesh, 20% medium needle coke powder with a particle size of 40 mesh ≤ < 200 mesh, and 40% fine needle coke powder with a particle size of ≤ 200 mesh, the obtained electrode rod exhibits better performance.
[0064] As can be seen from the comparison between Comparative Example 2 and Example 1, when the temperature of the paste cooling material is lower than 145-155°C, the resistance and strength of the electrode rod decrease, while the bulk density, room temperature thermal expansion coefficient and oxidation weight loss rate are also poor.
[0065] As can be seen from the comparison between Comparative Example 3 and Example 1, when the mass ratio of needle-shaped petroleum coke powder mixture to electrode rod green waste powder and coal tar medium-temperature pitch exceeds the range of 3-3.2:0.8-1.2:0.8-1.2, its strength will be significantly reduced, and its bulk density and oxidation weight loss rate will not meet the standards.
[0066] As can be seen from the comparison between Comparative Example 4 and Example 1, if the vacuum process is not combined during the compression molding process, the strength, bulk density, and oxidation weight loss rate are poor.
Claims
1. A method for preparing an electrode rod, characterized in that, The raw materials for the electrode rod include a needle-shaped petroleum coke powder mixture in a mass ratio of 3~3.2:0.8~1.2:0.8~1.2, electrode rod green waste powder with a particle size of 1~3mm, and coal tar medium-temperature pitch. The needle-shaped petroleum coke powder mixture includes coarse needle-shaped petroleum coke powder with a particle size of 20 mesh ≤ < 40 mesh, medium needle-shaped petroleum coke powder with a particle size of 40 mesh ≤ < 200 mesh, and fine needle-shaped petroleum coke powder with a particle size of ≤ 200 mesh. The mass percentages of the coarse needle-shaped petroleum coke powder, medium needle-shaped petroleum coke powder, and fine needle-shaped petroleum coke powder are 35~45%, 15~25%, and 35~45% of the mass of the needle-shaped petroleum coke powder mixture, respectively. The method for preparing the electrode rod includes the following steps: (1) The needle-shaped petroleum coke powder mixture is mixed with the electrode rod green waste powder and coal tar medium temperature pitch to make a high temperature paste. The high temperature paste is poured into a cooling machine to reduce the temperature to 145~155℃. Then it enters the vertical press cylinder for vacuum pressing and molding. After cooling and cutting, the electrode rod green is obtained. (2) The electrode rod blank is repeatedly baked and impregnated with asphalt to obtain a baked electrode rod part; (3) The electrode rod is graphitized and purified to obtain the electrode rod.
2. The method for preparing the electrode rod as described in claim 1, characterized in that, The raw materials include a mixture of needle-shaped petroleum coke powder in a mass ratio of 3:1:1, electrode rod green waste powder with a particle size of 1~3mm, and coal tar medium-temperature pitch. The mass percentages of the needle-shaped petroleum coke coarse powder, needle-shaped petroleum coke medium powder, and needle-shaped petroleum coke fine powder are 40%, 20%, and 40% of the mass of the needle-shaped petroleum coke powder mixture, respectively.
3. The method for preparing the electrode rod as described in claim 1, characterized in that, The electrode rod green blank waste powder is prepared by crushing and screening the defective electrode rod green blanks generated during the pressing and molding process and / or the cut ends and tails from the cooling and cutting process through a crusher with a 3mm perforated plate.
4. The method for preparing the electrode rod as described in claim 1, characterized in that, The electrode rod has a resistivity of not more than 5 μΩ·m, a flexural strength of not less than 40 MPa, a compressive strength of not less than 50 MPa, and a bulk density of not less than 1.72 g / cm³. 3 The coefficient of thermal expansion at room temperature is not higher than 2.5 E-6 / ℃, the oxidation weight loss is less than 5 wt.%, and the ash content is not higher than 20 ppm.
5. The preparation method according to claim 1, characterized in that, In step (1), the method for preparing the needle-shaped petroleum coke powder mixture is to use a powder with a true density of 2.10 g / cm³. 3 The above needle-shaped petroleum coke lumps are obtained through crushing and screening.
6. The preparation method according to claim 1, characterized in that, In step (1), the preparation process of the high-temperature paste specifically includes the following steps: the needle-shaped petroleum coke powder mixture and the electrode rod green waste powder are preheated and mixed in a high-temperature mixing pot at 170~185℃, and then mixed for 25~35 minutes using a turbulent three-dimensional mixer. Then, coal tar medium-temperature pitch is added and mixed for 15~25 minutes to make a high-temperature paste with small particles of 1~3mm in diameter.
7. The preparation method according to claim 1, characterized in that, In step (1), during the vacuum pressing molding, the pressing pressure is 15~20MPa, the vacuum degree is -0.85~-0.95MPa, and the pressing time is 1.5~2.5 minutes.
8. The preparation method according to claim 1, characterized in that, In step (2), the specific process of preparing the electrode rod calcined part by repeatedly calcining and impregnating the electrode rod green blank with asphalt is as follows: 1) First, the electrode rod blank is first baked at a temperature of 1080~1150℃ for 14~15 days to obtain a baked electrode rod part. 2) First, preheat the electrode rod calcination part one at 220~250℃ for 22~24 hours, then immerse it in coal tar high-temperature pitch at 170~185℃, and hold it under pressure at 2.5~2.7MPa for 18~21 hours; then put it into a crucible and place it in a single furnace for a second calcination to obtain the electrode rod calcination part two, wherein the temperature of the second calcination is 900~950℃ and the time is 8~9 days; 3) First, preheat the electrode rod calcination part two at 220~250℃ for 22~24 hours, then immerse it in coal tar high-temperature pitch at 170~185℃, and hold it under pressure at 2.5~2.7MPa for 18~21 hours; then put it into a crucible and place it in a single furnace for a third calcination to obtain the electrode rod calcination part, wherein the temperature of the third calcination is 900~950℃ and the time is 8~9 days.
9. The preparation method according to claim 1, characterized in that, In step (3), the graphitization temperature is 2900~2950℃ and the time is 14~15 days; The purification process is carried out by introducing chlorine gas at a temperature of 1900-1950℃ for 14-15 days.