One-time formed graphite box plate and preparation method thereof

Abstract

According to the one-time formed graphite box plate provided by the invention, the old mode that multiple times of repeated machining and cutting need to be performed in the traditional graphite box plate manufacturing process is abandoned, the production cost is remarkably reduced, and the product machining yield and the production efficiency are both improved. According to the method, the blank with the size basically meeting the requirement can be directly generated by means of the one-time forming pressing technology according to the requirement of a personalized design drawing of a client. And the blanks can be directly put into practical application only by being subjected to a very small amount of subsequent processing treatment, so that the generation of waste materials is reduced, and the utilization efficiency of the materials and the yield of finished products are improved. The regenerated graphite is selected as a main raw material, a one-time forming pressing technology is combined, and the production efficiency, environmental protection and energy conservation are both considered. The boxboard disclosed by the invention has the properties of high volume density, few cracks, good resistivity performance, long service time and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite box plate manufacturing, and particularly relates to a one-time formed graphite box plate and a preparation method thereof. Background Art

[0002] Graphitization box furnaces are used for graphitizing materials. As an important component inside the graphitization box furnace, the graphite box plate plays a crucial role in the graphitization effect of materials. However, currently, the graphite box plate is usually prepared by pressing large blanks through multiple processing and cutting steps. Although these techniques can produce box plates with certain properties, there are still the following problem points:

[0003] (1) High cost: Using virgin graphite as the main raw material, the blank size is large and requires multiple processing and cutting. The processing yield is low, resulting in a relatively high production cost;

[0004] (2) Low finished product rate: During the forming process of pressing large blanks, the probability of non-uniformity inside the product is high, and the finished product rate is low;

[0005] (3) Low production efficiency: Traditional preparation methods require multiple processing and cutting, resulting in low production efficiency;

[0006] (4) Limited product performance: Due to inaccurate control of process parameters, the prepared box plates have deficiencies in aspects such as bulk density, electrical conductivity, and service life.

[0007] In view of this, this invention is specifically proposed. Summary of the Invention

[0008] The purpose of the present invention is to provide a one-time formed graphite box plate and a preparation method thereof to solve at least one of the problems mentioned in the background art.

[0009] To achieve the above purpose, the present invention provides the following technical solutions:

[0010] In the first aspect of the present invention, a one-time formed graphite box plate is provided, which includes graphite particle materials and carbonaceous materials for bonding the graphite particle materials; the graphite particle materials include: graphite particles with a particle size of 4 - 2 mm account for 19.8% - 24.2% of the total mass of the graphite particle materials, graphite particles with a particle size of 2 - 1 mm account for 5.4% - 6.6% of the total mass of the graphite particle materials, graphite particles with a particle size of 1 - 0.15 mm account for 37.8% - 46.2% of the total mass of the graphite particle materials, and graphite particles with a particle size less than 0.075 mm account for 27% - 33% of the total mass of the graphite particle materials.

[0011] For further description of the present invention, it includes any one or more of the following conditions:

[0012] (1) The mass ratio of the carbonaceous material to the graphite particle material is 18-19:100;

[0013] (2) The graphite particle material uses recycled graphite material, and the recycled graphite material includes waste graphite of the filler, and / or waste graphite of the resistor material, and / or waste graphite of the insulating material;

[0014] (2) The carbonaceous material includes soft carbon.

[0015] Further description of the present invention includes any one or more of the following conditions:

[0016] (1) The bulk density of the graphite box board is 1.60-1.62 g / cm 3 ;

[0017] (2) The porosity of the graphite box board is not higher than 29%;

[0018] (3) The resistivity of the graphite box board is 17-25 μΩm;

[0019] (4) Randomly select 10 cross-sections of 30 cm × 30 cm at any position of the graphite box board, and the number of cracks is 0. The cracks are cracks with a width of 0.1 mm or more and a length of 10 mm or more;

[0020] (5) Conduct a service life test on the graphite box board, and the service life of the graphite box board ≥ 7 times;

[0021] (6) The thickness of the graphite box board is less than 70 mm.

[0022] Further description of the present invention includes any one or more of the following conditions:

[0023] (1) The bulk density of the graphite box board is 1.60-1.62 g / cm 3 ;

[0024] (2) The porosity of the graphite box board is 27-29%;

[0025] (3) The thickness of the graphite box board is 55-65 mm.

[0026] In the second aspect, the present invention provides a preparation method of a one-time formed graphite box board, including the following steps:

[0028] S1: Batching, including aggregate and binder. The aggregate uses graphite particle material, and the binder accounts for 24 - 26% of the total mass of the graphite particle material. The graphite particle material includes: graphite particles with a particle size of 4 - 2mm account for 19.8% - 24.2% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1mm account for 5.4% - 6.6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15mm account for 37.8% - 46.2% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075mm account for 27% - 33% of the total mass of the graphite particle material;

[0029] S2: Kneading, kneading the batching in step S1 into paste;

[0030] S3: Compression molding, pouring the paste in step S2 into a molding die with a heating function, and cooling the molded green body to room temperature after molding;

[0031] S4: Heat treatment, loading the green body obtained in step S3 into a roasting furnace for firing.

[0032] Further description of the present invention includes any one or more of the following conditions:

[0033] In step S1, the graphite particle material uses recycled graphite material, and the recycled graphite material includes filler waste graphite, and / or resistor waste graphite, and / or insulating material waste graphite;

[0034] (2) In step S1, the binder uses medium-temperature coal tar pitch; preferably, the softening point of the medium-temperature coal tar pitch is 80 - 90°C, the toluene-insoluble content is 15 - 25%, the ash content ≤ 0.3%, the quinoline-insoluble content ≤ 10%, and the coking value ≥ 48%.

[0035] Further description of the present invention: In step S2, first dry-mix the aggregate, the dry-mixing temperature is 170 - 180°C, the dry-mixing time is 30 - 50 min, then add liquid medium-temperature coal tar pitch at one time for wet-mixing, the wet-mixing temperature is 180 - 190°C, and the wet-mixing time is 30 - 50 min to form paste.

[0036] Further description of the present invention includes any one or more of the following conditions:

[0037] (1) In step S3, use a one-step molding process, and the size of the green body matches the finished product size of a single graphite box board; the thickness of the green body is less than 70mm;

[0038] (2) In step S3, the preheating temperature of the die is 50 - 80°C, the compression molding pressure is 18 - 20 Mpa, the holding pressure is 18 - 20 Mpa, and the holding time is 5 - 7 minutes.

[0039] ​

[0040] Further description of the present invention includes any one or more of the following conditions: In step S4, the green body is loaded into an industrial ring-type roasting furnace, covered with a metallurgical coke powder filler, and fired in the heating-up stage; preferably, the particle size composition of the metallurgical coke powder filler is: particles with a particle size of 0.5 - 3 mm account for 30 wt%, and particles with a particle size of 3 - 6 mm account for 70 wt%.

[0041] Further description of the present invention, the heating-up stage includes:

[0042] Initial heating-up stage: Starting from room temperature, gradually heating up to 250°C;

[0043] Stable heating-up stage: The temperature rises from 250°C to 400°C, and the heating rate is 5°C / h - 8°C / h;

[0044] Critical heating-up stage: The temperature rises from 400°C to 750°C, and the heating rate is 1.5°C / h - 3.5°C / h;

[0045] High-temperature stable stage: The temperature rises from 750°C to 850°C, and the heating rate is 2°C / h - 4°C / h;

[0046] Final heating-up: The temperature rises to 1050°C, the heating rate is 4°C / h - 6°C / h, and the heating time is 33 - 50 h;

[0047] Insulation stage: The insulation temperature is 1050°C, and the insulation time is not less than 24 h.

[0048] Further description of the present invention also includes the step of trimming the size and shape of the blank after heat treatment.

[0049] The beneficial effects of the present invention are:

[0050] The one-time formed graphite box board of the present invention, through a reasonable graphite particle size composition, makes the mixture in the preparation process of the graphite box board have a smaller porosity and a higher packing density, ensuring the uniformity and compactness of the mixture, making the graphite box board product have a higher density, creating conditions for improving the mechanical strength, electrical and heat conduction performance, and thermal shock resistance of the graphite box board, etc. Furthermore, when all the graphite particle materials of the present invention adopt recycled graphite particle materials, it can not only reduce costs, be beneficial to environmental protection, but also the performance of the graphite box board is good.

[0051] The present invention provides a one - time - formed graphite box board, which abandons the old mode of multiple repeated processing and cutting in the manufacturing process of traditional graphite box boards, significantly reduces the production cost, and improves both the product processing yield and production efficiency. The present invention can directly generate blank parts with basically required dimensions according to the requirements of customers' personalized design drawings by means of one - time - forming pressing technology. These blank parts only need to be subjected to a very small amount of subsequent processing and then can be directly put into practical application, reducing waste generation and improving the material utilization efficiency and the finished product output rate. The present invention selects recycled graphite as the main raw material and combines with one - time - forming pressing technology, taking into account both production efficiency and environmental protection and energy conservation. The box board of the present invention has properties such as high bulk density, few cracks, good resistivity performance, and long service time. Brief Description of the Drawings

[0052] Figure 1 It is the internal structure diagram after dissecting the large - sized blank pressed in Comparative Example 1;

[0053] Figure 2 It is the internal structure diagram after dissecting the small - sized blank pressed in Example 1;

[0054] Figure 3 It is the internal crack diagram after dissecting the large - sized blank after heat treatment in Comparative Example 1;

[0055] Figure 4 It is the internal crack diagram after dissecting the small - sized blank after heat treatment in Example 1;

[0056] Figure 5 It is the schematic diagram of the preparation method of the box board of the present invention. Detailed Embodiments

[0057] The present invention will be further described below with reference to the accompanying drawings:

[0058] A one - time - formed graphite box board includes graphite particle materials and carbonaceous materials for bonding the graphite particle materials; the graphite particle materials include: graphite particles with a particle size of 4 - 2 mm accounting for 19.8% - 24.2% of the total mass of the graphite particle materials, graphite particles with a particle size of 2 - 1 mm accounting for 5.4% - 6.6% of the total mass of the graphite particle materials, graphite particles with a particle size of 1 - 0.15 mm accounting for 37.8% - 46.2% of the total mass of the graphite particle materials, and graphite particles with a particle size less than 0.075 mm accounting for 27% - 33% of the total mass of the graphite particle materials.

[0059] The one-time formed graphite box board of the present invention enables the mixture during the preparation of the graphite box board to have a smaller porosity and a higher packing density through a reasonable particle size composition of graphite particles, ensuring the uniformity and compactness of the mixture, making the graphite box board product have a higher density, creating conditions for improving the mechanical strength, electrical and heat conduction performance, and thermal shock resistance of the graphite box board, etc. Furthermore, when all the graphite particle materials of the present invention adopt recycled graphite particle materials, not only can the cost be reduced, which is beneficial to environmental protection, but also the performance of the graphite box board is good. Without being restricted by theory, the influence of the particle size composition distribution on the performance of the graphite box board product mainly includes:

[0060] 1. Bulk density:

[0061] Graphite particles with a reasonable particle size distribution can more effectively fill the voids in the box board and help obtain a more uniform microstructure, thereby increasing the bulk density and overall strength of the graphite box board.

[0062] 2. Electrical conductivity and thermal conductivity:

[0063] Electrical conductivity: The particle size distribution of graphite particles has an important influence on the electrical conductivity of the box board. When the particle size is moderate and the distribution is uniform, the contact between graphite particles is closer, which is beneficial to the conduction of electrons, thus improving the electrical conductivity of the box board.

[0064] Thermal conductivity: Graphite particles with a reasonable particle size distribution can form a more effective heat conduction channel, improving the thermal conductivity of the box board.

[0065] In some embodiments, the graphite particle material adopts recycled graphite material, and the recycled graphite material includes filler waste graphite, and / or resistor waste graphite, and / or insulation waste graphite. In some embodiments, the filler resistor, insulation material, recycled waste graphite products, etc. used in the graphitized anode material can be crushed and screened to obtain recycled graphite particle materials.

[0066] It can be understood that based on the above analysis, when using recycled graphite particle materials, although the performance of the recycled graphite material in terms of thermal conductivity, electrical conductivity, etc. decreases significantly compared with the primary graphite material, and the structural defects also increase, the present invention enables the graphite box board to have good performance through a reasonable particle size composition.

[0067] In some embodiments, the mass ratio of the carbonaceous material to the graphite particle material is 18-19:100. It can be understood that the carbonaceous material of the present invention is derived from the binder in the preparation process of the graphite box board and is formed by carbonizing the binder. During the roasting process of the binder, a carbon film bonding bridge is formed between the solid carbonaceous materials, binding the carbonaceous materials into a whole and endowing it with certain mechanical strength. The green body is roasted at a high temperature. At this time, the binder (such as coal tar pitch) participates in the carbonization reaction to generate binder coke and form a good solid-state bond, enabling the product to obtain a fixed geometric shape.

[0068] In some embodiments, the carbonaceous material includes soft carbon. Those skilled in the art know that soft carbon refers to an amorphous carbon material that can be graphitized under high-temperature conditions (usually above 2500 °C). In the present invention, the binder can be converted into soft carbon through carbonization without graphitization, saving costs, and the soft carbon can be converted into graphite material during the use of the graphite box board, thereby improving the performance of the graphite box board.

[0069] In some embodiments, the bulk density of the graphite box board is 1.60 - 1.62 g / cm 3 , for example, it can be 1.60 g / cm 3 , 1.61 g / cm 3 , 1.62 g / cm 3 and so on, as well as any value between any two of them. In some preferred embodiments, the bulk density of the graphite box board is 1.61 - 1.62 g / cm 3 .

[0070] In some embodiments, the porosity of the graphite box board is not higher than 29%, for example, it can be 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20% and so on, as well as any value between any two of them. In some preferred embodiments, the porosity of the graphite box board is 27 - 29%.

[0071] The high bulk density and few internal pores of the graphite box board result in high overall strength of the graphite box board, which also contributes to the improvement of thermal conductivity and electrical conductivity, thereby enhancing the performance of the graphite box board.

[0072] In some embodiments, the resistivity of the graphite box board is 17 - 25 μΩ·m, for example, it can be 17 μΩ·m, 18 μΩ·m, 19 μΩ·m, 20 μΩ·m, 21 μΩ·m, 22 μΩ·m, 23 μΩ·m, 24 μΩ·m, 25 μΩ·m and so on, as well as any value between any two of them.

[0073] It is understandable that the porosity (void ratio), as a key regulatory factor for the performance of graphite box plates, has a profound impact on their bulk density and resistivity. Specifically, an increase in porosity often means the loosening of the internal structure of the material, and this structural change directly leads to a decrease in bulk density. At the same time, the loose internal structure increases the barriers to electron transport, thereby increasing the resistivity of the material. On the contrary, by finely adjusting the porosity to an appropriate range, the bulk density of the recycled graphite box plate can be effectively maintained or even increased, which benefits from the enhanced compactness of the material due to the optimization of the pore structure. In addition, a reasonable reduction in porosity can also promote the smooth transmission of electrons within the material, thereby significantly reducing the resistivity and providing the product with a longer service life and better electrical conductivity.

[0074] In addition, without being bound by theory, porosity also has a non-negligible impact on the mechanical strength of recycled graphite box plates. Excessive porosity often weakens the overall mechanical properties of the material, making the recycled graphite box plate more prone to deformation or damage when facing external forces. This is mainly attributed to the weakening of the rigidity and toughness of the material by the loose structure. However, through scientific porosity design, the mechanical strength of the graphite box plate can be significantly improved. Specifically, reasonable pore distribution and size can optimize the microstructure of the material, enhance the interaction forces within the material, and thus improve its mechanical properties such as compressive strength and flexural strength. This optimization improves the durability of the material.

[0075] In some embodiments, 10 cross-sections of 30 cm × 30 cm are randomly selected at any position of the graphite box plate, and the number of cracks is 0. The cracks are cracks with a width of 0.1 mm or more and a length of 10 mm or more. The graphite box plate of the present invention does not show obvious fractures or gaps, and maintains good integrity and performance. This crack-free state helps to ensure the stability and reliability during subsequent processing and use.

[0076] In some embodiments, a service life test is carried out on the graphite box plate, and the service life of the graphite box plate ≥ 7 times. The graphite box plate of the present invention has a long service life.

[0077] In some embodiments, the thickness of the graphite box plate is less than 70 mm. For example, it can be 65 mm, 60 mm, 55 mm, 50 mm, etc. and any value between any two of them. In some preferred embodiments, the thickness of the graphite box plate is 55 - 65 mm.

[0078] As Figure 5 shown, a preparation method of a one-time formed graphite box plate includes batching, kneading, one-time forming, heat treatment, and size trimming (optional).

[0079] Step S1: Batching, including aggregate and binder.

[0080] The particle size composition of the graphite particle material is as follows:

[0081] Graphite particles with a particle size of 4 - 2 mm account for 19.8% - 24.2% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm account for 5.4% - 6.6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm account for 37.8% - 46.2% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm account for 27% - 33% of the total mass of the graphite particle material.

[0082] Through the above particle size combination, the uniformity and compactness of the mixture are ensured.

[0083] In some embodiments, the aggregate is a graphite particle material composed of recycled graphite material. The recycled graphite material includes waste graphite from fillers, and / or waste graphite from resistor materials, and / or waste graphite from insulation materials, etc. This raw material comes from the recycling and reuse of waste graphite products, which not only reduces production costs but also significantly reduces the exploitation of primary graphite resources and is beneficial to environmental protection.

[0084] In some embodiments, waste graphite products such as those recycled from fillers, resistor materials, and insulation materials are crushed and screened to obtain recycled graphite particles. The characteristics of the particle size composition of the recycled graphite particles are to make the mixture have a smaller porosity and a higher bulk density, in order to make the produced recycled graphite box board products have a higher density, thereby creating conditions for improving the mechanical strength, electrical and heat conduction performance, and thermal shock resistance of the recycled graphite box board.

[0085] The binder is used to bond the graphite particle material and generate a carbonaceous material after reaction. The carbonaceous material includes soft carbon. In some embodiments, the mass ratio of the carbonaceous material to the graphite particle material is 18 - 19:100. In some embodiments, the binder can be medium-temperature coal tar pitch, and the addition amount of the binder accounts for 24 - 26% of the total mass of the recycled graphite particles.

[0086] The medium-temperature coal tar pitch preferably has a softening point of 80 - 90 °C, a toluene insoluble content of 15 - 25%, an ash content ≤ 0.3%, a quinoline insoluble content ≤ 10%, and a coking value ≥ 48%.

[0087] It can be understood that the chemical composition and properties of the medium-temperature coal tar pitch endow it with unique adhesiveness and plasticity. Its softening point, toluene insoluble content, ash content and other indicators meet specific requirements, enabling it to well meet the preparation requirements of the paste to ensure the bonding strength and plasticity of the paste.

[0088] Using medium-temperature coal tar pitch as a binder, one of its functions is to endow the paste with a certain plasticity during the kneading and forming processes, so as to meet the requirements of forming. When the medium-temperature coal tar pitch is in a liquid state, it wets, bonds and kneads the aggregate and powder into a plastic paste. After the paste is pressed into shape and cooled, the binder pitch hardens, solidifying the aggregate and powder into a green body. Another function is to form a carbon film bonding bridge between solid carbonaceous materials during the roasting (heat treatment) process, binding the carbonaceous materials into a whole to endow it with a certain mechanical strength. The green body is roasted at a high temperature. At this time, the binder coal tar pitch participates in the carbonization reaction to generate binding coke and form a good solid bond, enabling the product to obtain a fixed geometric shape.

[0089] Step S2: Kneading, kneading the ingredients in step S1 into a paste.

[0090] In some embodiments, first, the aggregate is dry-mixed at 170 - 180°C for 30 - 50 minutes. The purpose of dry-mixing is to fully preheat and uniformly mix the aggregate. Preheating the aggregate helps the binder to better combine with the aggregate during the subsequent wet-mixing process, and this temperature range can ensure that the aggregate is preheated to an appropriate degree. Then, the medium-temperature liquid asphalt binder is added in one go for wet-mixing. The wet-mixing temperature is 180 - 190°C and the time is 30 - 50 minutes. The purpose of wet-mixing is to ensure that the medium-temperature liquid asphalt binder completely wraps the surface of the aggregate, enabling it to better penetrate into the pores of the aggregate and form a firm bond with the aggregate, forming a uniform paste. This further enhances the bonding strength and plasticity of the paste.

[0091] Step S3: Compression molding, pouring the paste in step S2 into a molding die with a heating function, molding the paste into a green body by die pressing and then cooling it to room temperature.

[0092] In some embodiments, compression molding is carried out by a one-shot molding method. The kneaded paste is poured into a one-shot molding die with upper and lower die heating functions. By starting the heating system, the die is preheated to 50 - 80°C. Under the action of a pressure of 18 - 20 Mpa, the paste is tightly compacted in the die, and the holding pressure is also 18 - 20 Mpa, and the holding time is 5 - 7 minutes. This one-shot molding process has advantages such as high efficiency and energy saving. At the same time, due to the heating function of the die, the paste can be better cured during the pressing process, forming a graphite box board with the required density and shape. After the paste is cooled to room temperature, demolding is carried out to obtain a one-shot molded box board green body.

[0093] In some embodiments, the size of the green body matches the finished size of a single graphite box board. The size of the green body (i.e., the size of the one-time forming die) can be the same as the size of a single graphite box board or slightly larger than the size of a single graphite box board. In some preferred embodiments, the thickness of the green body is less than 70 mm. In some more preferred embodiments, the thickness of the green body is 55 - 65 mm. The present invention directly generates a blank piece with dimensions basically meeting the requirements. Compared with the conventional forming and processing methods of large blank materials (the thickness is usually several hundred mm, for example, usually about 500 mm), the present invention only needs to perform a very small amount of subsequent processing and can be directly put into practical application. Not only the performance of the graphite box board is excellent, but also the generation of waste is reduced, and the utilization efficiency of materials and the output rate of finished products are improved.

[0094] Step S4: Heat treatment, loading the green body obtained in step S3 into a roasting furnace for firing.

[0095] In some embodiments, the specific operation is as follows: loading the pressed green body into an industrial ring-type roasting furnace, and covering the green body with a filler of metallurgical coke powder (the proportion of 0.5 - 3 mm particle size is 30%, and the proportion of 3 - 6 mm particle size is 70% and evenly mixed) to fill the gap to isolate air and prevent the green body from oxidation and deformation. By precisely controlling the temperature and time, a smooth transition of multiple heating stages is achieved. This heat treatment process can not only effectively remove the volatile components and impurities in the paste, but also make the combination between graphite particles closer, thereby improving the thermal stability and mechanical properties of the box board. At the same time, the one-time forming box board can maintain the stability of its shape and size during the heat treatment process, avoiding problems such as deformation and cracks caused by heat treatment.

[0096] In some embodiments, the heating stage of the heat treatment:

[0097] 1. Initial heating stage:

[0098] Starting from room temperature, the temperature is gradually raised to 250 °C. The heating rate in this stage is relatively fast and is free heating.

[0099] 2. Stable heating stage:

[0100] Next, the temperature is slowly raised from 250 °C to 400 °C, and the heating rate is controlled between 5 °C and 8 °C / h, and the duration is about 18 to 30 hours.

[0101] 3. Critical heating stage:

[0102] In the critical stage of 400 °C to 750 °C, the heating rate is significantly slowed down, controlled between 1.5 °C and 3.5 °C / h, and the duration is about 100 to 233 hours.

[0103] 4. High-temperature stable stage:

[0104] Subsequently, the temperature continues to slowly rise to 750°C to 850°C at a heating rate of 2°C to 4°C / h for a duration of approximately 25 to 50 hours.

[0105] 5. Final heating and heat preservation stage:

[0106] Finally, the temperature rises to 1050°C at a heating rate of 4°C to 6°C / h for a duration of approximately 33 to 50 hours.

[0107] 6. Heat preservation stage:

[0108] After reaching the final temperature, heat preservation treatment is carried out for no less than 24 hours to ensure the full realization of the heat treatment effect.

[0109] It can be understood that during the thermal (carbonization) treatment process, a carbon film bonding bridge is formed between the solid carbonaceous materials, binding the carbonaceous materials into a whole to give it a certain mechanical strength. The green body is baked at a high temperature. At this time, the binder coal tar pitch participates in the carbonization reaction to generate binder coke and form a good solid bond, enabling the product to obtain a fixed geometric shape. During the heating process, especially in the critical stage of 400°C to 700°C, the heating rate needs to be particularly slow. This operation can avoid cracks caused by thermal stress, ensure the full overflow of volatile components, and optimize the carbonization process and product performance. These measures are of great significance for improving the overall quality and performance of the product.

[0110] Step S5: Dimension trimming.

[0111] In some embodiments, the heat-treated blank is precision machined, processed (trimmed) by high-precision machining equipment to the dimensions and shapes that meet the design requirements, and strict quality inspection and testing are carried out after the machining is completed to ensure that the finally obtained one-time formed recycled graphite box board has precise dimensions, good surface quality, and stable performance.

[0112] The present invention has the following advantages:

[0113] 1. Resource recycling:

[0114] Using recycled graphite to prepare box boards realizes the recycling of resources, reduces the dependence on primary graphite resources, lowers production costs, and is also beneficial to environmental protection.

[0115] 2. One-time forming:

[0116] Compared with the traditional box board preparation method, the present technical solution adopts a one-time forming process, reducing the production process, lowering production costs, and increasing the product processing yield to 84%.

[0117] 3. Blank dimension optimization:

[0118] During the process of optimizing the blank size, the traditional process of first pressing large blanks and then cutting them into small pieces after heat treatment was abandoned. The core of this transformation lies in directly forming the smallest-sized blanks according to the final processing size of the product, achieving a one-to-one correspondence between the blanks and the finished products, that is, one blank can only be processed into one finished product.

[0119] In the traditional process of pressing large blanks, due to their large size, it is often difficult to achieve complete uniformity in the internal structure and organization during the forming and heat treatment processes. This not only increases the probability of internal non-uniformity of the product but also may affect the overall performance and quality of the product. In the improved process, by directly forming the smallest-sized blanks, the uniformity of the product is effectively improved. This is because small blanks are more easily subjected to a uniform pressure distribution during the forming process, thus ensuring the stability and consistency of their internal structure.

[0120] To more intuitively demonstrate the effect of this improvement, refer to Figure 1 and Figure 2 . Figure 1 shows the internal structure diagram of the traditional large blank pressing. It can be seen that there may be internal non-uniformities and potential defects. And Figure 2 shows the internal structure diagram of the improved small blank pressing, and its structure is more uniform and dense.

[0121] In addition, during the heat treatment stage, the improved small blanks also show obvious advantages. For the large blank box board after heat treatment, 10 sections with an area of 30 cm × 30 cm were randomly selected on its surface for detailed inspection. It was found that there were a large number of cracks inside the large blank. The width of these cracks reached 0.1 mm or more, and the length reached 10 mm or more.

[0122] After the heat treatment of the one-time formed box board of the present invention, multiple sections with an area of 30 cm × 30 cm were randomly selected at any position of the small blank box board for inspection, and no cracks meeting the above standards (width 0.1 mm or more, length 10 mm or more) were found.

[0123] Cracks refer to slender and narrow fractures or gaps formed inside or on the surface of materials. According to the scale and observability of cracks, cracks can be divided into micro-cracks and macro-cracks:

[0124] Micro-cracks: These cracks usually have small sizes and are difficult to directly observe with the naked eye or conventional detection means. They often hide inside the materials and have a potential impact on the overall performance and service life of the materials.

[0125] Macroscopic cracks: These cracks are relatively large in size and can be easily detected by the naked eye or conventional inspection methods. They may penetrate the entire material or form obvious fracture lines on the material surface, significantly affecting the strength and durability of the material.

[0126] Figure 3 Internal crack diagram of the large billet after heat treatment shown in dissection. In Figure 3 we can see that the interior of the large billet after heat treatment is filled with cracks. These cracks are both microscopic and macroscopic, and they are intertwined to form a complex crack network. The presence of these cracks seriously affects the performance and service life of the billet, and may cause the billet to fracture or fail during subsequent processing or use.

[0127] Figure 4 Internal crack diagram of the small billet after heat treatment shown in dissection. In contrast to Figure 3 in Figure 4 the small billet has no internal cracks after heat treatment. This indicates that the small billet did not exhibit obvious fractures or gaps during the heat treatment process, maintaining good integrity and performance. This crack-free state helps to ensure the stability and reliability of the small billet during subsequent processing and use. Due to the reduced size, the volatile components inside the billet are more likely to escape during the heat treatment process, which helps to reduce the generation of internal defects and cracks.

[0128] 4. Performance improvement:

[0129] Through reasonable process control, the prepared box board has better bulk density, good resistivity performance, and long service life. The improvement of these properties enables the box board to meet higher usage requirements.

[0130] The porosity (void ratio) is a key regulatory factor for the performance of the recycled graphite box board and has a profound impact on its bulk density and resistivity. Specifically, an increase in porosity often means the loosening of the internal structure of the material, and this structural change directly leads to a decrease in bulk density. At the same time, the loose internal structure increases the barrier to electron transmission, thereby increasing the resistivity of the material. On the contrary, by finely adjusting the porosity to an appropriate range, the bulk density of the recycled graphite box board can be effectively maintained or even increased, which benefits from the enhanced compactness of the material due to the optimization of the pore structure. In addition, a reasonable reduction in porosity can promote the smooth transmission of electrons inside the material, thereby significantly reducing the resistivity and providing the product with a longer service life and more excellent electrical conductivity.

[0131] The porosity also has a non-negligible impact on the mechanical strength of the recycled graphite box board. An excessively high porosity often weakens the overall mechanical properties of the material, making the recycled graphite box board more prone to deformation or damage when facing external forces. This is mainly attributed to the weakening of the material's rigidity and toughness by the loose structure. However, through scientific porosity design, the mechanical strength of the recycled graphite box board can be significantly improved. Specifically, reasonable pore distribution and size can optimize the microstructure of the material, enhance the internal interaction force of the material, and thus improve its mechanical properties such as compressive strength and flexural strength. This optimization improves the durability of the material.

[0132] As shown in Table 1 below, it is a test data table of the box boards prepared in Examples 1 to 4 and Comparative Examples 1 to 7. See the following text for the specific content of the relevant examples and comparative examples.

[0133] Table 1

[0134]

[0135] Among them:

[0136] The bulk density was tested according to the method of GB / T 24528-2009.

[0137] The porosity was tested according to the method of GB / T24529-2009.

[0138] The resistivity was tested using a GM-II multi-functional resistivity automatic measuring instrument according to the resistivity test method for solid rod-shaped materials.

[0139] Evaluation method of service life:

[0140] Prepare the test equipment and environment: Select a standard-specification graphitization box furnace equipped with precise monitoring and control systems for temperature, pressure, etc., to ensure a stable and precisely controllable test environment. Prepare a sufficient number of one-time formed graphite box board samples produced in the same batch, and the performance indicators of the samples should meet the parameter range specified in the present invention.

[0141] Set the simulated use conditions: According to the actual working parameters of the graphitization box furnace, set the temperature during the test to 3000 °C and the holding time to 72 h. The temperature change simulates the heating, holding, and cooling curves of the graphitization treatment in actual production; the pressure is set within the normal working pressure range of the furnace; the atmosphere is filled with an inert gas or a specific mixed gas according to the actual gas composition in the furnace to simulate the real use environment.

[0142] Conduct cyclic tests: Place the graphite box board sample into a graphitizing box furnace with set conditions, start the equipment, and perform a complete cyclic operation according to the simulated production process. The cyclic process includes steps such as heating to a specific temperature, maintaining that temperature for a period of time, and then cooling to room temperature. After completing one cycle, take the box board out of the furnace. Conduct a comprehensive inspection on the taken-out box board to observe whether there are defects such as cracks and damages on the surface and inside of the box board. At the same time, use professional instruments to measure performance parameters such as the bulk density and resistivity of the box board, and record them in detail. If the box board does not have defects that affect its normal use and all performance parameters are still within the specified range, then put it back into the furnace for the next cyclic test. Repeat the above cyclic test operation until the box board shows serious cracks and damages, or key performance parameters such as its bulk density and resistivity exceed the specified range and cannot meet the actual use requirements, then stop the test.

[0143] Determine the service life: Record the number of cycles experienced by the box board from the start of the test to failure (randomly select 10 areas of 30 cm × 30 cm on the surface of the graphite box board, and when the number of cracks reaches 10 or more, it cannot meet the use requirements). This number of cycles is the service life of the graphite box board samples of this batch. For example, if a box board fails after 7 cyclic tests, then the service life of this box board is 7 times. After testing multiple box board samples, calculate the average value of the service lives of all samples, and use this as the evaluation result of the service life of the one-time formed graphite box board of this batch, so as to more accurately reflect the actual service life of the product.

[0144] The following are the specific contents of Examples 1 to 4 and Comparative Examples 1 to 7. Among them, the sizes of the green compacts obtained by pressing in Examples 1 to 4 and Comparative Examples 2 to 7 are 1100 mm × 450 mm × 60 mm.

[0145] Example 1:

[0146] I. Batching:

[0147] Crush and screen the raw materials (resistance material and insulation material) to obtain graphite particle materials. The composition of the graphite particle materials is as follows: Graphite particles with a particle size of 4 - 2 mm account for 22% of the total mass of the graphite particle materials, graphite particles with a particle size of 2 - 1 mm account for 6% of the total mass of the graphite particle materials, graphite particles with a particle size of 1 - 0.15 mm account for 42% of the total mass of the graphite particle materials, and graphite particles with a particle size less than 0.075 mm account for 30% of the total mass of the graphite particle materials.

[0148] Medium-temperature coal tar pitch is used as the binder. The softening point of the medium-temperature coal tar pitch is 85°C. The addition amount of the medium-temperature coal tar pitch accounts for 25% of the total mass of the graphite particle materials.

[0149] II. Kneading:

[0150] First, dry-mix the aggregates at 175°C for 40 minutes. The purpose of dry-mixing is to fully preheat and uniformly mix the aggregates. Then, add medium-temperature liquid asphalt binder in one go for wet-mixing. The wet-mixing temperature is 185°C and the time is 40 minutes.

[0151] III. One-time forming:

[0152] Pour the kneaded paste into a one-time forming mold with upper and lower mold heating functions. By starting the heating system, preheat the mold to 60°C. Under the action of a pressure of 19 MPa, the paste is tightly compacted in the mold, and the holding pressure is also 19 MPa, and the holding time is 6 minutes.

[0153] IV. Heat treatment:

[0154] Load the pressed green body into an industrial ring-type roasting furnace, and cover the green body and fill the gaps with a filler of metallurgical coke powder (uniformly mixed with 30% of the particle size of 0.5 - 3 mm and 70% of the particle size of 3 - 6 mm) to isolate air and prevent the green body from oxidation and deformation. Then carry out heat treatment, and the heat treatment process is as follows:

[0155] Initial heating stage: Start from room temperature and gradually heat up to 250°C. The heating rate in this stage is relatively fast and is free heating.

[0156] Stable heating stage: The temperature slowly rises from 250°C to 400°C, and the heating rate is controlled at 6°C / h, with a duration of 24 hours.

[0157] Key heating stage: In the key stage from 400°C to 750°C, the heating rate is controlled at 2.5°C / h, with a duration of 166 hours.

[0158] High-temperature stable stage: Subsequently, the temperature continues to slowly rise to 750°C to 850°C, and the heating rate is 3°C / h, with a duration of 38 hours.

[0159] Final heating and holding stage: Finally, the temperature rises to 1050°C, and the heating rate is 5°C / h, with a duration of 41 hours. After reaching the final temperature, carry out heat preservation treatment, and the heat preservation time is 24 hours.

[0160] V. Dimension trimming step:

[0161] Precision process the heat-treated blank, and use high-precision machining equipment to trim it to the dimensions and shapes that meet the design requirements.

[0162] Product performance: The bulk density is maintained at 1.61 g / cm 3 , the porosity reaches 28%, the resistivity is 21 μΩm, the service life is 7 times, and the performance is stable within the reasonable process range.

[0163] Example 2:

[0164] I. Ingredients:

[0165] The raw materials (resistance material and heat insulation material) are crushed and screened to obtain graphite particle material. The composition of the graphite particle material is as follows: graphite particles with a particle size of 4 - 2 mm account for 23.8% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm account for 5.4% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm account for 37.8% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm account for 33% of the total mass of the graphite particle material.

[0166] Medium-temperature coal tar pitch is used as the binder. The softening point of the medium-temperature coal tar pitch is 80 °C. The addition amount of the medium-temperature coal tar pitch accounts for 24% of the total mass of the graphite particle material.

[0167] II. Kneading:

[0168] First, the aggregate is dry-mixed at 170 °C for 50 min. The purpose of dry-mixing is to fully preheat and uniformly mix the aggregate. Then, the medium-temperature liquid asphalt binder is added at one time for wet-mixing. The wet-mixing temperature is 180 °C and the time is 50 min.

[0169] III. One-time molding:

[0170] The kneaded paste is poured into a one-time molding die with the function of heating the upper and lower molds. By starting the heating system, the mold is preheated to 70 °C. Under the action of a pressure of 20 MPa, the paste is tightly compacted in the mold, and the holding pressure is also 20 MPa, and the holding time is 7 minutes.

[0171] IV. Heat treatment:

[0172] The pressed green body is loaded into an industrial ring-type roasting furnace, and the green body is covered with a filler of metallurgical coke powder (the particle size of 0.5 - 3 mm accounts for 30%, and the particle size of 3 - 6 mm accounts for 70% and is uniformly mixed) to fill the gap to isolate air and prevent the green body from oxidizing and deforming. Then heat treatment is carried out, and the heat treatment process is as follows:

[0173] Initial heating stage: Starting from room temperature, the temperature is gradually raised to 250 °C. In this stage, the heating rate is relatively fast and it is free heating.

[0174] Stable heating stage: The temperature is slowly raised from 250 °C to 400 °C, and the heating rate is controlled at 5 °C / h, and the duration is 18 hours.

[0175] Key heating stage: In the key stage from 400 °C to 750 °C, the heating rate is controlled at 1.5 °C / h, and the duration is 100 hours.

[0176] High-temperature stable stage: Subsequently, the temperature continues to slowly rise to 750 °C to 850 °C at a heating rate of 2 °C / h for a duration of 25 hours.

[0177] Final heating and heat preservation stage: Finally, the temperature rises to 1050 °C at a heating rate of 5 °C / h for a duration of 33 hours. After reaching the final temperature, heat preservation treatment is carried out for a heat preservation time of 24 hours.

[0178] Product performance: The bulk density is maintained at 1.62 g / cm 3 , the porosity reaches 29%, the resistivity is 19 μΩm, the service life is 8 times, and the performance is stable within a reasonable process range.

[0179] Example 3:

[0180] I. Batching:

[0181] The raw materials (resistor material and heat preservation material) are crushed and screened to obtain graphite particle material. The composition of the graphite particle material is as follows: graphite particles with a particle size of 4 - 2 mm account for 24.2% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm account for 6.6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm account for 42.2% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm account for 27% of the total mass of the graphite particle material.

[0182] Medium-temperature coal tar pitch is used as the binder. The softening point of the medium-temperature coal tar pitch is 90 °C. The addition amount of the medium-temperature coal tar pitch accounts for 26% of the total mass of the graphite particle material.

[0183] II. Kneading:

[0184] First, the aggregate is dry-mixed at 180 °C for 50 min. The purpose of dry-mixing is to fully preheat and uniformly mix the aggregate. Then, the medium-temperature liquid asphalt binder is added at one time for wet-mixing. The wet-mixing temperature is 190 °C and the time is 50 min.

[0185] III. One-time molding:

[0186] The kneaded paste is poured into a one-time molding die with upper and lower die heating functions. By starting the heating system, the die is preheated to 80 °C. Under the action of a pressure of 18 MPa, the paste is tightly compacted in the die, and the holding pressure is also 18 MPa for a holding time of 5 minutes.

[0187] IV. Heat treatment:

[0188] Load the pressed green body into an industrial ring-type roasting furnace, and cover the green body and fill the gaps with a filler of metallurgical coke powder (with 30% of the particle size of 0.5 - 3 mm and 70% of the particle size of 3 - 6 mm evenly mixed) to isolate the air and prevent the green body from oxidation and deformation. Then, conduct heat treatment, and the heat treatment process is as follows:

[0189] Initial heating stage: Starting from room temperature, gradually heat up to 250 °C. The heating rate in this stage is relatively fast, which is free heating.

[0190] Stable heating stage: The temperature slowly rises from 250 °C to 400 °C, the heating rate is controlled at 8 °C / h, and the duration is 30 hours.

[0191] Key heating stage: In the key stage of 400 °C to 750 °C, the heating rate is controlled at 3.5 °C / h, and the duration is 233 hours.

[0192] High-temperature stable stage: Subsequently, the temperature continues to slowly rise to 750 °C to 850 °C, the heating rate is 4 °C / h, and the duration is 50 hours.

[0193] Final heating and heat preservation stage: Finally, the temperature rises to 1050 °C, the heating rate is 6 °C / h, and the duration is 50 hours. After reaching the final temperature, conduct heat preservation treatment, and the heat preservation time is 24 hours.

[0194] Product performance: Due to the relatively high pitch addition amount and different particle size distributions, the bulk density is 1.62 g / cm 3 , the porosity is 27%, the resistivity is 19 μΩm, the service life is 8 times, and the overall performance of the product is good.

[0195] Example 4:

[0196] I. Batching:

[0197] Crush and screen the raw materials (resistance material and heat preservation material) to obtain graphite particle materials. The composition of the graphite particle materials is as follows: Graphite particles with a particle size of 4 - 2 mm account for 21% of the total mass of the graphite particle materials, graphite particles with a particle size of 2 - 1 mm account for 5.8% of the total mass of the graphite particle materials, graphite particles with a particle size of 1 - 0.15 mm account for 41.2% of the total mass of the graphite particle materials, and graphite particles with a particle size less than 0.075 mm account for 32% of the total mass of the graphite particle materials.

[0198] Medium-temperature coal tar pitch is used as the binder. The softening point of the medium-temperature coal tar pitch is 83 °C. The addition amount of the medium-temperature coal tar pitch accounts for 25.5% of the total mass of the graphite particle materials.

[0199] II. Kneading:

[0200] First, dry-mix the aggregate at 173°C for 35 minutes. The purpose of dry-mixing is to fully preheat and evenly mix the aggregate. Then, add medium-temperature liquid asphalt binder at one time for wet-mixing. The wet-mixing temperature is 183°C and the time is 35 minutes.

[0201] III. One-time forming:

[0202] Pour the kneaded paste into a one-time forming mold with upper and lower mold heating functions. By starting the heating system, preheat the mold to 65°C. Under the action of a pressure of 19 MPa, the paste is tightly compacted in the mold. The holding pressure is also 19 MPa and the holding time is 6 minutes.

[0203] IV. Heat treatment:

[0204] Load the pressed green body into an industrial ring-type roasting furnace, and cover the green body and fill the gaps with a filler of metallurgical coke powder (with a particle size of 0.5 - 3 mm accounting for 30% and 3 - 6 mm accounting for 70% evenly mixed) to isolate air and prevent the green body from oxidizing and deforming. Then carry out heat treatment, and the heat treatment process is as follows:

[0205] Initial heating stage: Starting from room temperature, gradually heat up to 250°C. The heating rate in this stage is relatively fast and is free heating.

[0206] Stable heating stage: The temperature slowly rises from 250°C to 400°C, and the heating rate is controlled at 7°C / h, with a duration of 21 hours.

[0207] Key heating stage: In the key stage from 400°C to 750°C, the heating rate is controlled at 2°C / h, with a duration of 138 hours.

[0208] High-temperature stable stage: Subsequently, the temperature continues to slowly rise to 750°C to 850°C, with a heating rate of 3°C / h and a duration of 33 hours.

[0209] Final heating and heat preservation stage: Finally, the temperature rises to 1050°C, with a heating rate of 5°C / h and a duration of 40 hours. After reaching the final temperature, carry out heat preservation treatment, and the heat preservation time is 24 hours.

[0210] Product performance: Bulk density 1.61 g / cm 3 , porosity 27%, resistivity 21 μΩm. The comprehensive performance meets the expectations, and the service life is 7 times.

[0211] Comparative example 1:

[0212] Ingredients: The same as those in Example 1. Use waste graphite of resistor material and heat preservation material as the aggregate, and medium-temperature coal tar pitch as the binder, with an addition amount accounting for 25% of the total mass of graphite particles.

[0213] Kneading: The same kneading process as in the embodiment, dry kneading at 175°C for 40 min and wet kneading at 185°C for 40 min.

[0214] Forming: Pour the kneaded paste into a mold and press it into a large blank with dimensions of 2500 mm × 500 mm × 500 mm.

[0215] Heat treatment: The same as the heat treatment heating stage in the embodiment.

[0216] Processing treatment: Precision process the blank after heat treatment. According to customer requirements, cut the blank into corresponding sizes and then process it into dimensions of 1100 mm × 450 mm × 60 mm according to the customer's drawing.

[0217] Product performance: Due to the forming and processing methods of the large blank, the internal uniformity of the product is poor, the bulk density is 1.60 g / cm 3 , the porosity is 31%, the resistivity is 22 μΩm, there are many defects inside, the service life is 6 times, and the performance is worse than that of the embodiment.

[0218] Comparative example 2:

[0219] Compared with Example 1, the main difference is the batching. Specifically, for the batching: Graphite particles with a particle size of 4 - 2 mm account for 15% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm account for 6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm account for 42% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm account for 37% of the total mass of the graphite particle material. The softening point of medium-temperature coal tar pitch is 85°C, and the addition amount accounts for 25% of the total mass of the graphite particle material.

[0220] Subsequent processes: The process parameters of the kneading, one-time forming, heat treatment, and size trimming steps are the same as those in Example 1.

[0221] Product performance: Due to the too low proportion of 4 - 2 mm particles, the porosity of the mixture increases, the bulk density drops to 1.58 g / cm 3 , the porosity increases to 33%, the resistivity increases to 24 μΩm, the internal structure of the material is loose, resulting in a decrease in electrical conductivity, and the service life is shortened to 5 times.

[0222] Comparative example 3:

[0223] The formulation is different from that of Example 1. Specifically, the formulation: graphite particles with a particle size of 4 - 2 mm account for 28% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm account for 6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm account for 42% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm account for 24% of the total mass of the graphite particle material. The softening point of medium-temperature coal tar pitch is 85°C, and the addition amount accounts for 25% of the total mass of the graphite particle material.

[0224] Subsequent processes: The process parameters of kneading, one-time forming, heat treatment, and size trimming steps are the same as those in Example 1.

[0225] Product performance: The proportion of 4 - 2 mm particles is too high, affecting the filling effect between particles. The bulk density is 1.60 g / cm 3 , the porosity is 30%, the resistivity is 23 μΩm. Too many large particles are not conducive to electron conduction, the electrical conductivity is affected, and the service life is 6 times.

[0226] Comparative Example 4:

[0227] Compared with Example 1, the formulation is different. Specifically, the formulation: The addition amount of medium-temperature coal tar pitch accounts for 23% of the total mass of the graphite particle material. The particle size distribution of the graphite particle material is the same as that in Example 1, and the softening point is 85°C.

[0228] Subsequent processes: The process parameters of kneading, one-time forming, heat treatment, and size trimming steps are the same as those in Example 1.

[0229] Product performance: Due to insufficient binder, the bonding strength of the paste is insufficient. The bulk density is 1.59 g / cm 3 , the porosity is 32%, the resistivity is 23 μΩm. The internal structure of the product is not dense enough, the mechanical strength and electrical conductivity decrease, and the service life is 5 times.

[0230] Comparative Example 5:

[0231] Compared with Example 1, the formulation is different. Specifically, the formulation: The addition amount of medium-temperature coal tar pitch accounts for 27% of the total mass of the graphite particle material. The particle size distribution of the graphite particle material is the same as that in Example 1, and the softening point is 85°C.

[0232] Subsequent processes: The process parameters of kneading, one-time forming, heat treatment, and size trimming steps are the same as those in Example 1.

[0233] Product performance: Too much binder leaves more impurities after roasting. The bulk density is 1.61 g / cm 3 , the porosity is 29%, but the resistivity increases to 22 μΩm. The impurities affect electron conduction, and the service life is 6 times

[0234] Comparative Example 6:

[0235] Compared with the embodiment, the batching, kneading, and one-time molding are the same as those in Embodiment 1, but the heat treatment steps are different. Specifically, for the heat treatment: in the initial heating stage, it is freely heated to 250°C; in the stable heating stage, it is heated to 400°C at a rate of 8°C / h for 18 hours; in the critical heating stage (400°C - 750°C), the heating rate is controlled at 5°C / h (1.5°C - 3.5°C / h higher than the normal range) for 100 hours; in the high-temperature stable stage, it is heated to 850°C at a rate of 4°C / h for 25 hours; in the final heating and heat preservation stage, it is heated to 1050°C at a rate of 6°C / h for 33 hours and heat-preserved for 24 hours.

[0236] Product performance: During the critical heating stage, the heating rate is too fast, resulting in excessive thermal stress and cracks. The bulk density is 1.60 g / cm 3 , the porosity is 30%, the resistivity is 22 μΩm, the cracks affect the overall performance of the material, and the service life is 6 times.

[0237] Comparative Example 7:

[0238] Compared with Embodiment 1, the batching, kneading, and one-time molding are the same as those in Embodiment 1, but the heat treatment steps are different. Specifically, for the heat treatment: in the initial heating stage, it is freely heated to 250°C; in the stable heating stage, it is heated to 400°C at a rate of 5°C / h for 30 hours; in the critical heating stage (400°C - 750°C), the heating rate is controlled at 1°C / h (1.5°C - 3.5°C / h lower than the normal range) for 350 hours; in the high-temperature stable stage, it is heated to 850°C at a rate of 2°C / h for 50 hours; in the final heating and heat preservation stage, it is heated to 1050°C at a rate of 4°C / h for 50 hours and heat-preserved for 24 hours.

[0239] Product performance: The slow heating rate leads to a significant extension of the production cycle, and some volatile components are not discharged sufficiently. The bulk density is 1.60 g / cm 3 , the porosity is 31%, the resistivity is 22 μΩm, the product performance is affected, and the service life is 6 times.

[0240] The above does not impose any limitation on the technical scope of the present invention. Any modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A one - time - formed graphite box board, characterized in that: It includes graphite particle material and carbonaceous material for bonding the graphite particle material; the graphite particle material includes: graphite particles with a particle size of 4 - 2 mm accounting for 19.8% - 24.2% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm accounting for 5.4% - 6.6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm accounting for 37.8% - 46.2% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm accounting for 27% - 33% of the total mass of the graphite particle material.

2. The disposable molded graphite box board according to claim 1, wherein It includes any one or more of the following conditions: (1) The mass ratio of the carbonaceous material to the graphite particle material is 18 - 19:100; (2) The graphite particle material uses recycled graphite material, and the recycled graphite material includes waste graphite of filler, and / or waste graphite of resistor material, and / or waste graphite of thermal insulation material; (3) The carbonaceous material includes soft carbon.

3. The disposable molded graphite box board according to claim 1, characterized in that, It includes any one or more of the following conditions: (1) The bulk density of the graphite box board is 1.60 - 1.62 g / cm 3 ; (2) The porosity of the graphite box board is not higher than 29%; (3) The resistivity of the graphite box board is 17 - 25 μΩm; (4) Randomly select 10 cross-sections of 30 cm × 30 cm at any position of the graphite box board, and the number of cracks is 0, and the cracks are cracks with a width of 0.1 mm or more and a length of 10 mm or more; (5) Conduct a service life test on the graphite box board, and the service life of the graphite box board ≥ 7 times; (6) The thickness of the graphite box board is less than 70 mm.

4. A one-time formed graphite box board according to claim 3, characterized in that: It includes any one or more of the following conditions: (1) The bulk density of the graphite box board is 1.61 - 1.62 g / cm 3 ; (2) The porosity of the graphite box board is 27 - 29%; (3) The thickness of the graphite box board is 55 - 65 mm.

5. A preparation method of a one-time formed graphite box board, characterized in that: It includes the following steps: S1: Batching, including aggregate and binder. The aggregate uses graphite particle material, and the binder accounts for 24 - 26% of the total mass of the graphite particle material. The graphite particle material includes: graphite particles with a particle size of 4 - 2 mm accounting for 19.8% - 24.2% of the total mass of the graphite particle material, graphite particles with a particle size of 2 - 1 mm accounting for 5.4% - 6.6% of the total mass of the graphite particle material, graphite particles with a particle size of 1 - 0.15 mm accounting for 37.8% - 46.2% of the total mass of the graphite particle material, and graphite particles with a particle size less than 0.075 mm accounting for 27% - 33% of the total mass of the graphite particle material; S2: Kneading, kneading the batching in step S1 into paste; S3: Compacting, pouring the paste in step S2 into a forming mold with a heating function, and molding the paste into a green body and then cooling it to room temperature; S4: Heat treatment, loading the green body obtained in step S3 into a roasting furnace for firing.

6. The preparation method of a one-time formed graphite box board according to claim 5, characterized in that It includes any one or more of the following conditions: (1) In step S1, the graphite particle material uses recycled graphite material, and the recycled graphite material includes waste graphite of filler, and / or waste graphite of resistor material, and / or waste graphite of thermal insulation material; (2) In step S1, the binder used is medium-temperature coal tar pitch; the softening point of the medium-temperature coal tar pitch is 80 - 90 °C, the toluene-insoluble content is 15 - 25%, the ash content is ≤ 0.3%, the quinoline-insoluble content is ≤ 10%, and the coking value is ≥ 48%.

7. The preparation method of a one-time formed graphite box board according to claim 6, characterized in that: In step S2, first, the aggregates are dry-mixed at a dry-mixing temperature of 170 - 180 °C for 30 - 50 min, and then liquid medium-temperature coal tar pitch is added all at once for wet-mixing at a wet-mixing temperature of 180 - 190 °C for 30 - 50 min to form a paste.

8. The preparation method of a disposable formed graphite box board according to claim 5, characterized in that, including any one or more of the following conditions: (1) In step S3, a one-step forming process is adopted, and the size of the green body matches the finished product size of a single graphite box board; the thickness of the green body is less than 70 mm; (2) In step S3, the preheating temperature of the mold is 50 - 80 °C, the molding pressure is 18 - 20 Mpa, the holding pressure is 18 - 20 Mpa, and the holding time is 5 - 7 minutes.

9. The preparation method of a one-time formed graphite box board according to claim 5, characterized in that, (2) including any one or more of the following conditions: In step S4, the green body is loaded into an industrial ring-type roasting furnace, covered with metallurgical coke powder filler, and fired in the heating-up stage; the particle size composition of the metallurgical coke powder filler is: the particles with a particle size of 0.5 - 3 mm account for 30 wt% by weight, and the particles with a particle size of 3 - 6 mm account for 70 wt%.

10. The preparation method of a disposable formed graphite box board according to claim 5, characterized in that: The heating-up stage includes: Initial heating-up stage: Starting from room temperature, the temperature is gradually raised to 250 °C; Stable heating-up stage: The temperature is raised from 250 °C to 400 °C at a heating-up rate of 5 °C / h - 8 °C / h; Key heating-up stage: The temperature is raised from 400 °C to 750 °C at a heating-up rate of 1.5 °C / h - 3.5 °C / h; High-temperature stable stage: The temperature is raised from 750 °C to 850 °C at a heating-up rate of 2 °C / h - 4 °C / h; Final heating-up: The temperature is raised to 1050 °C at a heating-up rate of 4 °C / h - 6 °C / h, and the heating-up time is 33 - 50 h; Insulation stage: The insulation temperature is 1050 °C, and the insulation time is not less than 24 h.

11. A method for preparing a one-step formed graphite box board according to claim 5, characterized in that: It further includes the step of trimming the size and shape of the heat-treated blank.

Images