A baking and forming method for graphite rod stock

Abstract

The present invention discloses a baking and forming method for graphite rod blanks, which can be used for improved auxiliary baking operations on rod-shaped graphite product blanks. When the rod-shaped graphite product blanks are formed, sufficient machining allowances are left in the axial and radial directions respectively. Before baking, they are vertically placed using a baking carrier, and preheating operations are carried out using a previous heating operation before formal baking. After the previous heating operation is completed, baking and high-temperature graphitization treatment are carried out according to the baking process requirements of the graphite rod blanks. After the treatment is completed, it is naturally cooled in the furnace, the rod-shaped graphite product blanks are taken out together with the baking carrier, the bottom of the rod-shaped graphite product blanks is sawed off and then trimmed. After trimming, the finished graphite rod blanks are obtained. The present invention is specifically used for baking and processing graphite rod blanks, with low production costs, high production efficiency, significant economic benefits, and can effectively reduce the impact of pitch in the graphite rod blanks on the quality of the formed graphite rod blanks.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of graphite rods, and particularly relates to a roasting and forming method for graphite rod blanks. Background Art

[0002] Graphite is a natural layered structure mineral with excellent properties such as electrical conductivity, thermal stability, and chemical stability. It is widely used in many fields such as electronics, electric power, metallurgy, and chemical industry, and is widely used in operations such as metal smelting, purification of anode materials for lithium batteries, smelting of polysilicon materials, and ingot casting, and has good technical and economic effects.

[0003] As a common form of use of graphite materials, the main furnace loading method for rod-shaped graphite materials in the roasting and forming stage is to horizontally stack the rod-shaped graphite product blanks in a roasting furnace. Considering that they are prone to rolling, metallurgical coke powder is used as a filler in the gaps between the blanks. The defects of this roasting and forming method are as follows:

[0004] During the roasting operation in the roasting furnace, due to the influence of thermal stress and self-weight, the metallurgical coke powder used as a filler is prone to sink and shift, which will cause the rod-shaped graphite product blanks in the corresponding area to displace accordingly. This displacement may cause the stacked rod-shaped graphite product blanks to fall and collide, resulting in damage;

[0005] The rod-shaped graphite product blanks usually contain a certain proportion of asphalt components before roasting, and the rod-shaped graphite product blanks have a structural characteristic of a large length-to-diameter ratio. This makes the asphalt components soften during the heating process in the roasting process, resulting in local weight gain, and then causing the blanks to deform and bend, requiring an additional blank trimming process; in addition, this part of the softened asphalt components will flow and accumulate towards the gravity side due to gravity flow inside the rod-shaped graphite product blanks, and then cause defects in the internal uniformity of the formed graphite rods during the subsequent graphitization process, directly affecting the quality of the finished graphite rods.

[0006] The above reasons cause the rod-shaped graphite product blanks to be cooled to room temperature after the roasting operation and then go through graphitization. The graphitization process is heated from room temperature to about 2500°C or above, so there is a problem of energy waste in the roasting stage below 850°C. Summary of the Invention

[0007] The technical problem solved by the present invention is to provide a roasting and forming method for graphite rods to solve the defects in the above technical background.

[0008] The technical problem solved by the present invention is achieved by the following technical solutions:

[0009] A roasting and forming method for graphite rods specifically includes the following operation steps:

[0010] S1 Wet-mix graphite powder, petroleum coke, and pitch as raw materials. After uniform wet-mixing, put them into a mold and press them into a rod-shaped graphite product blank.

[0011] When the rod-shaped graphite product blank is being pressed into the mold, leave a machining allowance of 25 - 35% of the length of the finished graphite rod in the axial direction and a machining allowance of 10 - 15% of the radius of the finished graphite rod in the radial direction.

[0012] S2 Load the rod-shaped graphite product blank using a roasting carrier. When placed vertically, use tamped metallurgical coke powder as a bottom lining on the surface of the roasting carrier. Place the rod-shaped graphite product blank vertically on the surface of the bottom lining and set at least two annular support points in the height direction of the rod-shaped graphite product blank.

[0013] S3 Send the rod-shaped graphite product blank together with the roasting carrier into the furnace and perform a roasting operation. Before the roasting operation, perform a preheating operation. The preheating operation is carried out in a vacuum environment with a vacuum degree of 1×10 -2 ~3×10 -2 Pa. The specific steps of the preheating operation include:

[0014] Rapidly heat up to 180 - 230℃ at a heating rate of 60 - 70℃ / h and hold for 80 - 120h.

[0015] Slowly increase the temperature to 400℃ at a heating rate of 10 - 15℃ / h per hour.

[0016] In the temperature range of 400 - 650℃, increase the temperature at a heating rate of 30 - 50℃ / h, hold for 3 - 5h, and then relieve the pressure in the heat preservation state, thus completing the preheating operation.

[0017] S4 After the preheating operation is completed, perform roasting and high-temperature graphitization treatment according to the roasting process requirements of the graphite rod.

[0018] S5 After the treatment, cool naturally with the furnace. Take out the rod-shaped graphite product blank together with the roasting carrier. Saw off the machining allowance in the axial direction at the bottom of the rod-shaped graphite product blank while reserving a trimming allowance of 20 - 30mm. Then trim the rod-shaped graphite product blank with the bottom sawed off. After trimming, the finished graphite rod is obtained.

[0019] As a further limitation, the mixing mass ratio of graphite powder to petroleum coke for preparing the rod-shaped graphite product blank is 3:1 - 1:1; and the mass ratio of the mixture of graphite powder and petroleum coke to pitch is 2:1 - 5:2.

[0020] As a further limitation, after the blank of the rod-shaped graphite product is molded in a mold, it is surface impregnated with phenolic resin or furfuryl alcohol resin to fill the pores on its surface and inside.

[0021] As a further limitation, when preparing the blank of the rod-shaped graphite product, first, the graphite powder and petroleum coke as raw materials are crushed and then dry-mixed, and after the dry-mixing is completed, asphalt is added for wet-mixing. After the wet-mixing is uniform, it is put into a mold and pressed into a blank of the rod-shaped graphite product.

[0022] As a further limitation, the aspect ratio of the blank of the rod-shaped graphite product before leaving the machining allowance is 3:1 to 10:1.

[0023] As a further limitation, when setting the annular support points in step S2, at least one upper annular support point supports at a position 1 / 5L to 1 / 4L downward from the top of the blank of the rod-shaped graphite product, where L is the length of the blank of the rod-shaped graphite product; at least one annular support point supports at the sawing position of the axial machining allowance of the blank of the rod-shaped graphite product.

[0024] As a further limitation, when corresponding roasting and high-temperature graphitization treatment are carried out in step S4, first, roasting operations are carried out according to the roasting process requirements of the graphite rod blank. After the roasting operations are completed, direct heating is carried out under the roasting temperature conditions for graphitization treatment, and after the graphitization treatment is completed, a graphitized blank of the rod-shaped graphite product is obtained.

[0025] As a further limitation, when corresponding roasting and high-temperature graphitization treatment are carried out in step S4, first, roasting operations are carried out according to the roasting process requirements of the graphite rod blank. After the roasting operations are completed, carbonization treatment is carried out to obtain a carbonized intermediate product, which is cooled with the furnace. After cooling, the blank of the rod-shaped graphite product and the roasting carrier are taken out together. Then, the blank of the rod-shaped graphite product is placed in a graphitization furnace alone or together with the roasting carrier for high-temperature graphitization treatment. After the treatment is completed, a graphitized blank of the rod-shaped graphite product is obtained.

[0026] Beneficial effects: The roasting and forming method of a graphite rod blank in the present invention is dedicated to the roasting and forming operations of a graphite rod blank with a relatively large aspect ratio, effectively maintaining the stability of the graphite rod blank during the sintering process, ensuring the stability of the graphite rod blank during the roasting process and at the same time ensuring the forming effect of roasting;

[0027] It can control the duration of softening asphalt through the previous heating operation before roasting the blank of the rod-shaped graphite product, and make the softened and fluid asphalt move downward along the gravity direction and accumulate at the bottom of the blank of the rod-shaped graphite product. By trimming the bottom of the blank of the rod-shaped graphite product after roasting at this position, the internal structure uniformity of the blank of the rod-shaped graphite product above the trimming position can be ensured, and further the quality of the formed graphite rod blank can be ensured. Specific embodiments

[0028] To enable those skilled in the art to better understand the solution of the present invention and to clearly understand the technical means, creative features, achieved purposes and effects of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments.

[0029] This embodiment is only a part of the embodiments of the present invention and does not represent all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention. It should be noted that the terms in the description and claims of the present invention are used to distinguish similar objects. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed.

[0030] In the embodiment, the roasting and forming method of the graphite rod stock is an improved process, which can directly add or modify the process on the basis of the original roasting process of the graphite rod stock, and is specifically realized through the following operation steps:

[0031] In this embodiment, it is necessary to first prepare a blank of the rod-shaped graphite product. The blank of the rod-shaped graphite product is made of graphite powder, petroleum coke and asphalt as raw materials. Among them, the mass ratio of the graphite powder, petroleum coke and asphalt as raw materials is 3:1:2. When preparing, first grind the graphite powder and petroleum coke to obtain a powder with a particle size range of 100-150 μm. The above-mentioned two-component powder is dry-mixed at a temperature of 220 °C for 50 min. During the dry-mixing process, the moisture inside is baked out to keep the dry-mixed material in a completely dry state; then the dry-mixed material and asphalt are added to the kneading pot together for wet mixing, and a semi-solid paste is obtained after 50 min of wet mixing.

[0032] The obtained semi-solid paste is aged at room temperature to ensure the performance of the formed graphite rod stock. The aging treatment duration is 36 h, and then the aged paste is put into the mold and molded by die pressing under the forming pressure condition of 0.3 Mpa to obtain a blank of the rod-shaped graphite product. In this embodiment, when the blank of the rod-shaped graphite product is molded by die pressing, a machining allowance accounting for 20% of the length of the finished graphite rod stock is left in the axial direction of the blank of the rod-shaped graphite product, and a machining allowance accounting for 12-13% of the radius of the finished graphite rod stock is left in the radial direction. At the same time, the length-diameter ratio of the blank of the rod-shaped graphite product before retaining the machining allowance is 6:1.

[0033] Load the rod-shaped graphite product blank after molding by pressing with a roasting carrier. Before loading, form a blind groove on the placement surface of the roasting carrier, fill and tamp the blind groove with metallurgical coke powder, then place the rod-shaped graphite product blank upright on the surface of the tamped metallurgical coke powder, and set three annular support points in the length direction of the rod-shaped graphite product blank. The three annular support points are respectively at the positions 1 / 5L - 1 / 4L (L is the length of the rod-shaped graphite product blank) downward from the top of the rod-shaped graphite product blank, the middle position of the rod-shaped graphite product blank, and the sawing position corresponding to the axial machining allowance of the rod-shaped graphite product blank.

[0034] In this embodiment, the support structure at the annular support point is two semi-circular fixing buckles, which are connected by a hinge and circumferentially hold and limit the rod-shaped graphite product blank. The sawing position corresponds to the upper surface or the lower surface of the fixing buckle, so that the sawing tool can lean against the surface of the fixing buckle for sawing operations. The corresponding sawing position means that after sawing at this position on the rod-shaped graphite product blank, there are 20 - 30 mm of trimming allowances on the upper and lower surfaces of the rod-shaped graphite product blank respectively. After removing this trimming allowance, the removed part on the rod-shaped graphite product blank exactly corresponds to 25 - 35% of the axial machining allowance in the length direction of the finished graphite rod blank.

[0035] After the rod-shaped graphite product blank is loaded using the roasting carrier, directly lift and send the roasting carrier together with the rod-shaped graphite product blank into the furnace for roasting operations using a lifting tool. Before the roasting operation, set the vacuum degree of the roasting furnace to 3×10 -2 Pa for the preheating operation; during the preheating operation, first quickly heat up to 200°C at a heating rate of 65°C / h, hold for 100 h, then slowly increase the temperature to 400°C at a heating rate of 10°C / h per hour, and then heat up at a heating rate of 35°C / h in the temperature range of 400 - 650°C. After heating up to 650°C, hold for 3 - 5 h, and then relieve the pressure under the insulation state, that is, complete the preheating operation. The above preheating operation is mainly used to keep the mobile asphalt component in the rod-shaped graphite product blank under negative pressure for a long time after softening, so that it is concentrated in the bottom area of the rod-shaped graphite product blank.

[0036] After the preheating operation is completed, the roasting operation can be carried out according to the original roasting process of the corresponding graphite rod blank. The process flow and parameters of the roasting process stage and the high-temperature graphitization process stage in the corresponding original roasting process can be directly retained, and two technical paths can be differentiated according to the original roasting process:

[0037] If the original roasting process is directly followed by high-temperature graphitization treatment under this technical background, the technical solution of this embodiment can directly restore all the process flows of the original process after roasting and then performing high-temperature graphitization treatment, or can integrate roasting and high-temperature graphitization treatment and reduce energy consumption. If the latter is chosen, it is necessary to first perform roasting operations according to the roasting process requirements of the graphite rod stock. After the roasting operation is completed, directly raise the temperature under the roasting temperature conditions to perform graphitization treatment, and obtain a graphitized rod-shaped graphite product blank after the graphitization treatment is completed.

[0038] If the original roasting process requires carbonization treatment after roasting, first perform roasting operations according to the roasting process requirements of the graphite rod stock. After the roasting operation is completed, perform carbonization treatment to obtain a carbonized intermediate product, which is cooled in the furnace. After cooling, the rod-shaped graphite product blank and the roasting carrier are taken out together. Then, the rod-shaped graphite product blank is placed in a graphitization furnace alone or together with the roasting carrier for high-temperature graphitization treatment, and a graphitized rod-shaped graphite product blank is obtained after the treatment is completed.

[0039] After the rod-shaped graphite product blanks obtained under the above two technical paths are naturally cooled in the furnace after treatment, the rod-shaped graphite product blanks and the roasting carriers are taken out. While sawing off the machining allowance axially at the bottom of the rod-shaped graphite product blanks, a trimming allowance of 20 - 30 mm is reserved, and then the rod-shaped graphite product blanks with the bottom sawed off are trimmed. After the trimming is completed, the finished graphite rod stock is obtained.

[0040] It should be noted that under the technical background of this embodiment, the corresponding rod-shaped graphite products can be improved according to the original process. Therefore, corresponding other modified / improved components can be added to the corresponding raw materials, such as adding silica white, etc. Without affecting the original ratio of graphite powder, petroleum coke, and asphalt components, and when the content of the above-mentioned modified / improved components does not exceed 5% and does not affect the basic use performance of the rod-shaped graphite products themselves, the improved technical solutions of the above embodiments are still valid.

[0041] In addition, for the improved process of surface impregnation treatment using phenolic resin or furfuryl alcohol resin to fill the surface and internal pores, the improved technical solutions of the above embodiments are also still valid.

[0042] The technical solution of this embodiment can optimize the roasting process of the blank of the rod-shaped graphite product while maintaining a vertical shape, effectively reduce the negative impact of the asphalt component on the roasting process of the blank of the rod-shaped graphite product, obtain a roasted blank of the rod-shaped graphite product with a uniform internal shape, and be used for processing high-quality graphite rod materials. At the same time, during the roasting process in the vertical shape, the softening of the asphalt component will not cause the center of gravity of the blank of the rod-shaped graphite product to shift, effectively reduce the bending deformation of the blank of the rod-shaped graphite product during the roasting process, effectively ensure the straightness of the blank of the rod-shaped graphite product after roasting treatment, so as to reduce the cost of trimming the blank and improve the yield of high-quality graphite rod materials.

[0043] However, the aggregation of the softened asphalt component in the blank of the rod-shaped graphite product caused by gravity flow can be made to concentrate in the lower region of the blank of the rod-shaped graphite product by extending the treatment time of the softening temperature of the asphalt component. At this time, after cutting the lower part of the blank of the rod-shaped graphite product at the corresponding sawing position on the lower annular support point, the uniformity of the internal shape of the upper blank of the rod-shaped graphite product can be effectively ensured, and the finished product quality of the obtained graphite rod material can be ensured after further trimming treatment.

[0044] In this embodiment, the sawn lower blank of the rod-shaped graphite product can be directly used as an intermediate material to re-enter the kneading processing procedure after being crushed, or be crushed and used for other purposes after graphitization treatment.

[0045] In addition, compared with the traditional process of independently completing the two processes of secondary roasting and graphitization during the roasting production process of graphite materials, the technical solution of this embodiment can optimize the subsequent temperature increase operation through the previous temperature increase operation, thereby reducing the need to cool the product to room temperature after secondary roasting and then graphitize it. During the graphitization process, there is also the problem of energy waste during the process of heating the furnace body from room temperature to the roasting temperature when heating from room temperature to above the graphitization temperature. It effectively reduces the equipment energy consumption, improves the processing efficiency and the overall production capacity of the heat treatment system, and can effectively reduce the problem of product scrapping caused by rapid heating during the graphitization process due to insufficient roasting degree.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A baking and forming method for graphite rod stock, characterized in that, Specifically, it includes the following operation steps: S1 Wet-mix using graphite powder, petroleum coke, and pitch as raw materials. After wet-mixing evenly, put it into a mold and press it into a blank of a rod-shaped graphite product; During the process of putting the blank of the rod-shaped graphite product into the mold for pressing, leave a machining allowance of 25-35% of the length of the finished graphite rod in the axial direction and a machining allowance of 10-15% of the radius of the finished graphite rod in the radial direction; S2 Load the blank of the rod-shaped graphite product using a roasting carrier. When placed vertically, use tamped metallurgical coke powder as a bottom lining on the surface of the roasting carrier. Place the blank of the rod-shaped graphite product vertically on the surface of the bottom lining, and set at least two annular support points in the height direction of the blank of the rod-shaped graphite product; S3 sends the blank of the rod-shaped graphite product together with the roasting carrier into the furnace and performs the roasting operation. A preheating operation is carried out before the roasting operation. The preheating operation is carried out in a vacuum environment with a vacuum degree of 1×10 -2 ~3×10 -2 Pa. The specific steps of the preheating operation include: Rapidly heat up to 180-230°C at a heating rate of 60-70°C / h and hold for 80-120h, Slowly increase the temperature to 400°C at a heating rate of 10-15°C / h per hour, In the temperature range of 400-650°C, heat up at a heating rate of 30-50°C / h, hold for 3-5h, and then relieve the pressure under the insulation state, that is, complete the previous heating operation; S4 After the previous heating operation is completed, carry out roasting and high-temperature graphitization treatment according to the roasting process requirements of the graphite rod; After the treatment is completed, let it cool naturally in the furnace. Take out the blank of the rod-shaped graphite product together with the roasting carrier. Saw off the machining allowance in the axial direction at the bottom of the blank of the rod-shaped graphite product while retaining a trimming allowance of 20-30mm, and then trim the blank of the rod-shaped graphite product with the bottom sawed off. After trimming is completed, the finished graphite rod is obtained.

2. The roasting and forming method of the graphite rod material according to claim 1, characterized in that, The mixing mass ratio of the graphite powder and petroleum coke used for preparing the blank of the rod-shaped graphite product is 3:1-1:1; and the mass ratio of the mixture of graphite powder and petroleum coke to pitch is 2:1-5:

2.

3. The roasting and forming method of the graphite rod stock according to claim 1, characterized in that, After the blank of the rod-shaped graphite product is molded by pressing into the mold, it is subjected to surface impregnation treatment with phenolic resin or furfuryl alcohol resin to fill the pores on its surface and inside.

4. The roasting and forming method of the graphite rod stock according to claim 1, characterized in that, When preparing the blank of the rod-shaped graphite product, first dry-mix the graphite powder and petroleum coke used as raw materials after crushing, and then add pitch for wet-mixing after the dry-mixing is completed. After wet-mixing evenly, put it into a mold and press it into a blank of the rod-shaped graphite product.

5. The roasting and forming method of the graphite rod stock according to claim 1, characterized in that, The length-diameter ratio of the blank of the rod-shaped graphite product before retaining the machining allowance is 3:1-10:

1.

6. The roasting and forming method of the graphite rod stock according to claim 1, characterized in that, When setting the annular support points in step S2, at least one upper annular support point supports at a position 1 / 5L-1 / 4L downward from the top of the blank of the rod-shaped graphite product, where L is the length of the blank of the rod-shaped graphite product; at least one annular support point supports at the sawing position of the axial machining allowance of the blank of the rod-shaped graphite product.

7. The roasting and forming method of the graphite rod stock according to claim 1, characterized in that, When corresponding roasting and high-temperature graphitization treatment are carried out in step S4, first carry out roasting operation according to the roasting process requirements of the graphite rod. After the roasting operation is completed, directly heat up for graphitization treatment under the roasting temperature condition, and obtain a graphitized blank of the rod-shaped graphite product after the graphitization treatment is completed.

8. The roasting and forming method of the graphite rod material according to claim 1, characterized in that When performing roasting and high-temperature graphitization treatment correspondingly in step S4, first perform roasting operations according to the roasting process requirements of the graphite rod material. After the roasting operations are completed, perform carbonization treatment to obtain a carbonized intermediate product, which is cooled in the furnace. After cooling, take out the rod-shaped graphite product blank together with the roasting carrier. Then place the rod-shaped graphite product blank alone or together with the roasting carrier in a graphitization furnace for high-temperature graphitization treatment. After the treatment is completed, obtain a graphitized rod-shaped graphite product blank.