阅读说明：本技术 一种使用再生石墨热压冷出一次成型制备坩埚的方法 (Method for preparing crucible by hot-pressing and cold-discharging one-step forming of regenerated graphite ) 是由 李伟 于 2021-09-10 设计创作，主要内容包括：本申请提供了一种使用再生石墨热压冷出一次成型制备坩埚的方法,尤其涉及一种热压冷出法一次性成型石墨坩埚工艺方法。具体包括：将再生石墨粉和石墨化石油焦颗粒制成干料,倒入混捏锅中进行干混,再加入粘接剂湿混制成糊料,将糊料直接倒入加热状态的成型容器中,加压定型,密度达标后立即降温,快速冷却固化后制成生胚,再瞬时加热容器上模,脱模,焙烧即得。本申请中,通过热压冷出一次成型法,有效解决了利用再生石墨为原料制备的坩埚,结构不均匀,使用时易开裂,受力或膨胀后易破损的问题。整体方案工艺简单,混捏后无需晾料,简化制备流程,而且,无需高压成型,具有节能减排,降本增效的效果。(The application provides a method for preparing a crucible by using regenerated graphite through hot-pressing and cold-discharging one-step forming, and particularly relates to a process method for forming a graphite crucible through a hot-pressing and cold-discharging method in one step. The method specifically comprises the following steps: preparing dry materials from regenerated graphite powder and graphitized petroleum coke particles, pouring the dry materials into a kneading pot for dry mixing, adding an adhesive for wet mixing to prepare a paste, directly pouring the paste into a forming container in a heating state, pressurizing and shaping, immediately cooling after the density reaches the standard, quickly cooling and curing to prepare a green body, instantaneously heating an upper die of the container, demoulding and roasting to obtain the graphite catalyst. In the application, the crucible prepared by taking the regenerated graphite as the raw material is formed by hot pressing and cold drawing in one step, so that the problems of nonuniform structure, easiness in cracking during use and easiness in damage after stress or expansion are effectively solved. The whole scheme has simple process, does not need to dry materials after kneading, simplifies the preparation process, does not need high-pressure forming, and has the effects of saving energy, reducing emission, reducing cost and improving efficiency.)

1. A method for preparing a crucible by using regenerated graphite through hot-pressing and cold-discharging one-step forming is characterized in that regenerated graphite powder and graphitized petroleum coke particles are made into dry materials, the dry materials are poured into a kneading pot for dry mixing, then an adhesive is added for wet mixing to prepare a paste material, the paste material is directly poured into a forming container in a heating state, the pressing and the forming are carried out, the temperature is immediately reduced after the density reaches the standard, a green blank is prepared after rapid cooling and solidification, an upper die of the container is instantaneously heated, and the crucible is obtained through demoulding and roasting.

2. The method of claim 1, comprising the steps of:

s1, dry mixing: preparing dry materials from the regenerated graphite powder and the graphitized petroleum coke particles, and pouring the dry materials into a pretreated kneading pot for dry mixing for 40min, wherein the temperature of the dry materials is 120-;

s2, wet mixing: pouring the adhesive into the dry mixture for wet mixing for 40min at the wet mixing temperature of 165-175 ℃ to obtain the paste, wherein the adding amount of the adhesive is 20-30% of the mass of the dry mixture;

s3, profiling: pouring the paste into a forming container with an upper die and a lower die respectively having heating and cooling functions, starting the heating function, pouring the paste into the forming container to form the paste under a pressure state, monitoring the density of the paste, starting a cooling valve when the density index is reached, and repeatedly heating and pressurizing until the density index is reached;

s4, cooling the paste to prepare a green body;

s5, instantaneously heating the upper die of the container, and demolding;

s6, roasting.

3. The method according to claim 2, wherein in step S1, the dry material is a mixture of regenerated graphite powder and graphitized petroleum coke particles in a mass ratio of 1:1,

wherein the particle size of the regenerated graphite powder is less than 0.5mm and accounts for 50 percent of the mass of the dry materials;

the composition of the graphitized petroleum coke particles is as follows: the graphitized petroleum coke particles with the particle size of 0.5-4mm account for 25% of the mass of the dry material, and the graphitized petroleum coke particles with the particle size of 4-8mm account for 25% of the mass of the dry material.

4. The method as claimed in claim 2, wherein in the step S1, the preprocessing step is: the kneading pot is externally heated by heat conducting oil, the heating temperature is 190-200 ℃, and the heat conducting oil is selected from the following types: and (3) adding a dry material into the L-QB300 organic heat carrier when the temperature in the kneading pot is heated to 170-180 ℃, and stirring the dry mixed material by a reamer in the kneading pot.

5. The method of claim 2, wherein in step S2, the binder is medium temperature coal tar pitch, and the mass ratio of the binder to the dry material is 1: 4.

6. The method as claimed in claim 2, wherein in step S3, the upper and lower molds of the forming container are heated and cooled respectively, the heating system is turned on, the upper and lower molds are heated simultaneously at a temperature of 160 ℃ and 170 ℃, the heating is stopped, the mold release agent is coated, the paste is poured in under a pressure of 18-25MPa for a pressing time of 5min and a density index of 1.75-1.80g/cm³。

7. The method of claim 6, wherein the release agent is used oil and the pressure state is 25 Mpa.

8. The method according to claim 2, wherein in step S4, the cooling valve is opened when the density index is reached, and the upper and lower molds are simultaneously cooled to a paste temperature of 40-50 ℃ within 2 minutes.

9. The method as claimed in claim 2, wherein in step S5, only the upper mold is opened for heating, the temperature of the upper mold is heated to 170-.

Technical Field

The invention relates to the technical field of graphite, in particular to a process method for molding a graphite crucible at one time by a hot-pressing cold-discharge method.

Background

Graphite has a crystal structure of a hexagonal system, has weak binding force between planes parallel to a base plane, is easy to shear between the planes, can support load perpendicular to the base plane, and has strong bearing capacity and small friction coefficient. In addition, the graphite also has good thermal conductivity and high temperature resistance, and has small thermal expansion coefficient and certain strain resistance to rapid heating and rapid cooling in the high-temperature use process. Has strong corrosion resistance to acid and alkaline solutions and excellent chemical stability. Because of the excellent performance, the graphite crucible prepared by taking graphite as the raw material is widely used in the operation processes of metal smelting, lithium battery cathode material purification, polycrystalline silicon material smelting, ingot casting and the like, and has better technical and economic effects. When the graphite purification crucible is applied to purification of the lithium battery cathode material, the lithium battery cathode material is filled in the crucible, the cover is sealed, the lithium battery cathode material is placed in Acheson in order, the crucible and the material in the crucible are heated through current, and the temperature is controlled to be 2200-2700 ℃. The impurities such as volatile matters and the like in the material are removed at high temperature, and halogen gas is introduced in a specific temperature interval to oxidize and remove metal ions in the material, so that the purity of the material meets the production requirement.

At present, a main raw material of a graphite crucible is crystalline natural graphite or artificial graphite, and is also formed by mixing the main raw material with other modified materials. Particularly, when the regenerated graphite material obtained by recycling is used for preparing the graphite crucible, an internal system is formed because the regenerated graphite material is subjected to a heat treatment process of roasting in a primary roasting kiln, and after secondary crushing and secondary blank pressing forming, the structural stability of the graphite crucible is poor, and the formed graphite crucible can be normally used according to the use mode of a newly-made graphite crucible, but the service life of the regenerated graphite crucible under the high-temperature use condition is obviously shorter than that of the newly-made graphite crucible. The graphite material is easy to crack in the using process, is easy to bear force and expand unevenly in the temperature rising process, even generates the phenomena of local damage and leakage, leads to potential safety hazards in the using process, and seriously restricts the secondary utilization of the graphite material.

Disclosure of Invention

The invention aims to provide a method for preparing a crucible by using regenerated graphite through hot-pressing and cold-drawing one-step forming, which solves the problems that the crucible prepared by using the regenerated graphite is uneven in structure, easy to crack in use and easy to break after being stressed or expanded. The whole scheme has simple process, does not need to dry materials after kneading, simplifies the preparation process, does not need high-pressure forming, and has the effects of saving energy, reducing emission, reducing cost and improving efficiency.

The invention provides a method for preparing a crucible by hot-pressing and cold-discharging of regenerated graphite through one-step molding, which comprises the steps of preparing dry materials from regenerated graphite powder and graphitized petroleum coke particles, pouring the dry materials into a kneading pot for dry mixing, adding an adhesive for wet mixing to prepare a paste material, directly pouring the paste material into a molding container in a heating state, pressurizing and molding, immediately cooling after the density reaches the standard, quickly cooling and curing to prepare a green blank, instantaneously heating an upper mold of the container, demolding and roasting to obtain the regenerated graphite.

A method for preparing a crucible by hot-pressing and cold-discharging of regenerated graphite through one-step molding specifically comprises the following steps:

s1, dry mixing: preparing dry materials from the regenerated graphite powder and the graphitized petroleum coke particles, and pouring the dry materials into a pretreated kneading pot for dry mixing for 40min, wherein the temperature of the dry materials is 120-;

s2, wet mixing: pouring the adhesive into the dry mixture for wet mixing for 40min at the wet mixing temperature of 165-175 ℃ to obtain the paste, wherein the adding amount of the adhesive is 20-30% of the mass of the dry mixture;

s3, profiling: pouring the paste into a forming container with an upper die and a lower die respectively having heating and cooling functions, starting the heating function, pouring the paste into the forming container to form the paste under a pressure state, monitoring the density of the paste, starting a cooling valve when the density index is reached, and repeatedly heating and pressurizing until the density index is reached;

s4, cooling the paste to prepare a green body;

s5, instantaneously heating the upper die of the container, and demolding;

s6, roasting.

In a preferred embodiment, in step S1, the dry material is a mixture of regenerated graphite powder and graphitized petroleum coke particles in a mass ratio of 1:1,

wherein the particle size of the regenerated graphite powder is less than 0.5mm and accounts for 50 percent of the mass of the dry materials;

the graphitized petroleum coke particles comprise the following components: the graphitized petroleum coke particles with the particle size of 0.5-4mm account for 25% of the mass of the dry material, and the graphitized petroleum coke particles with the particle size of 4-8mm account for 25% of the mass of the dry material.

In a preferred embodiment, in step S1, the preprocessing step is: the kneading pot is externally heated by heat conducting oil, the heating temperature is 190-200 ℃, and the heat conducting oil is selected from the following types: and (3) adding a dry material for dry mixing when the temperature in the kneading pot is heated to 180 ℃ together with 170 ℃ by using an L-QB300 organic heat carrier, and stirring the dry mixed material by using a reamer in the kneading pot.

In a preferred embodiment, in step S2, the binder is medium temperature coal tar pitch, in which the ash content is 0.20% by mass, the volatile matter is 64.2% by mass, the moisture content is 0.06% by mass, and the mass ratio of the binder to the dry material is 1: 4.

In a preferred embodiment, in step S3, the upper and lower molds of the forming container are respectively provided with heating and cooling functions, the heating system is turned on, the upper and lower molds are heated simultaneously at a temperature of 160-170 ℃, the heating is stopped, the mold release agent is coated, the paste is poured into the container under a pressure of 18-25MPa, the pressurization time is 5min, and the density index is 1.75-1.80g/cm³(ii) a Preferably, the release agent is waste engine oil, and the pressure state is 25 Mpa;

when the heating temperature of the upper die and the lower die of the forming container is between 160 ℃ and 170 ℃, the paste is added to fully soften the medium-temperature coal pitch into liquid state, the paste is thoroughly melted from loose state, and the raw materials are fully mixed to be uniform state, which is beneficial to later-stage forming, if the temperature is lower than 160 ℃, fine particles exist in the paste, and the paste is not flat after forming; if the temperature is higher than 170 ℃, the density of the green blank can not reach the standard, and the mechanical strength of the product at the later stage is reduced;

wherein the density index is defined as 1.75-1.80g/cm³The selection basis is that the density of the pressed product determines the density of the roasted product; the higher the compact density of the pressed product is, the higher the compact density of the roasted product is, and the higher the density is, the more durable the product is; more than 1.80g/cm³The technical scheme of the application is difficult to realize, and the product performance is reduced.

In a preferred embodiment, in step S4, the cooling valve is opened to reach the density index, and the upper and lower molds are cooled simultaneously, and the temperature is reduced to 40-50 ℃ within 2 minutes.

In a preferred embodiment, in step S5, only the upper mold is opened to heat the green blank to 170-.

In a preferred embodiment, the upper die and the lower die are respectively provided with a forming container with heating and cooling functions, and a temperature monitoring device is arranged on the upper die and the lower die, so that the difference between the measured actual temperature and the preset temperature can be controlled within 5 ℃.

In a preferred embodiment, in step S6,

firstly, placing a compression green body in an industrial ring type roasting furnace, filling and compacting the compression green body with metallurgical coke powder inside and outside, and gradually heating under the condition of air isolation to obtain a primary roasted product; wherein, the metallurgical coke powder size range is 0.5-2mm 30%, 2-5mm 50%, 5-10mm 20%, and is mixed uniformly.

Heating conditions step by step are as follows: roasting temperature rise interval, first temperature interval: raising the temperature from room temperature to 150 ℃ without any requirement, and freely raising the temperature; 150 ℃ and 350 ℃, the temperature rise speed is 4.4 ℃/h, and the duration time of the first temperature interval is 45 h;

the second temperature interval: raising the temperature from the first temperature interval to 350-400 ℃, wherein the temperature raising speed is 1.7 ℃/h, and the duration time of the second temperature interval is 30 h;

the third temperature interval: the temperature is increased from the second temperature interval to 400-500 ℃, the temperature increase speed is 1.25 ℃/h, and the duration time of the third temperature interval is 80 h;

a fourth temperature interval: the temperature is increased from the third temperature interval to 500-600 ℃, the temperature increase speed is 1.8 ℃/h, and the duration time of the fourth temperature interval is 57 h;

a fifth temperature interval: the temperature is increased from the fourth temperature interval to 600-700 ℃, the temperature increase speed is 3.8 ℃/h, and the duration time of the fifth temperature interval is 27 h;

sixth temperature interval: the temperature is increased from the fifth temperature interval to 800 ℃ below zero, the temperature increase speed is 5.0 ℃/h, and the duration time of the sixth temperature interval is 20 h;

a seventh temperature interval: raising the temperature from the sixth temperature interval to 900 ℃ of 800-.

Compared with the prior art, the method for preparing the crucible by hot-pressing and cold-drawing one-step forming of the regenerated graphite has the following advantages:

the regenerated graphite, namely waste materials generated in the production process of graphite products, is firstly crushed by a crusher and then screened to obtain regenerated graphite powder with the average particle size of 0.5 mm; the method recycles the common waste materials in the carbon industry, can effectively reduce the waste discharge and optimize the resource allocation; in addition, the regenerated graphite has the following advantages: the method has the advantages of stable source, low cost, high economic benefit and physical and chemical indexes: the prepared regenerated graphite composite material has good effects of true density, mechanical strength, elastic modulus, resistivity, thermal conductivity, linear expansion coefficient, graphitization difficulty and the like, and can obtain good stability and heat resistance on the premise of keeping low cost.

Graphitized petroleum coke particles, wherein the petroleum coke is waste residue in the petroleum refining process, the graphitization is the process of processing the petroleum coke into graphite at high temperature, and the process is that the petroleum coke is electrified and then is processed at the high temperature of over 2400 ℃, so that the carbon molecular form of the petroleum coke is changed into a hexagonal uniform arrangement form from an irregular arrangement form. After the graphitized petroleum coke particles are subjected to ultra-high temperature treatment, the content of impurities is less, and the physical and chemical indexes, the linear expansion coefficient, the true density and the like of the graphitized petroleum coke particles are favorable for being fused with regenerated graphite powder, so that the product strength is enhanced, and the cracking rate is reduced.

The binder selection needs to have the following characteristics: 1. the adhesive used in the production of carbon products has two functions, one is that the product is coked when being roasted, and enough strong carbon is left, so that the product obtains necessary mechanical strength and uniform physical and chemical properties; the other is adhesive, which can be used to soak carbon powder particles to form plastic paste, the paste or pressed powder can be pressed into shape, and the pressed piece will not deform under the action of self-weight. 2. Economic, can reduce raw material cost, and on the basis of the principle, the scheme takes the coal tar pitch as the binder for the consideration of effect and cost.

In addition, the application mixes the powder and the raw material particles, and can produce the following effects: 1. the folding strength and the compressive strength of the product are improved. 2. The expansion coefficient, the linear expansion coefficient and the like of the product are reduced. Through a large number of experimental researches, the pure powder product is easy to generate cracks during roasting, and particularly, the regenerated product composite material is easy to cause unstable product properties.

2. In the prior art, after the graphite crucible is prepared by using the regenerated graphite, the materials are dried after generally dry mixing and wet mixing, so as to achieve the effects of reducing the temperature of the paste, increasing the plasticity of the paste and enhancing the strength of a product. And further, the conventional material airing process is omitted, the preparation time is effectively shortened, and the process flow is optimized.

3. In the prior art, only pressure boosting pressing is usually adopted, but in the invention, heating and pressure boosting are combined, the pressure requirement is reduced, temperature reduction and solidification are immediately carried out after one-time pressing forming, repeated pressing steps are reduced, pressure limitation is reduced, forming time is shortened, energy is effectively saved, emission is reduced, cost is reduced, and efficiency is improved.

4. After the green body is made by solidification, the upper die of the container is heated instantaneously, the asphalt on the surface of the green body can be slightly melted by high-temperature heating in a short time, but the internal temperature of the green body is kept at about 40 ℃, the green body still has quite high mechanical strength, the upper die is lifted at the moment, the product is separated from the lower die by the pressure of the upper die after the upper die is separated, the demoulding can be easily carried out, the surface structure of the product is not damaged, and the internal microcrack caused by the expansion after the pressure of a press is removed is prevented. Moreover, the deformation does not occur under the condition of external force conveying, and the product quality is not influenced.

5. In the invention, the formed container with the functions of heating and cooling the upper die and the lower die respectively is adopted, and the formed container is provided with modules for heating, pressurizing, density monitoring, cooling and the like, and heating or cooling can be realized by separating the upper die and the lower die, so that single-side heating or cooling is completed. All the forming processes are completed in one device, so that the consistency of products is improved, and the production efficiency is improved.

Drawings

FIG. 1 is a schematic flow chart of a method for manufacturing a disposable graphite crucible according to an embodiment of the present invention.

Detailed Description

Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are commercially available.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1

A method for preparing a crucible by hot-pressing and cold-drawing one-step molding of regenerated graphite,

s1, dry mixing: preparing dry materials from the regenerated graphite powder and the graphitized petroleum coke particles, and pouring the dry materials into a pretreated kneading pot for dry mixing for 40min, wherein the temperature of the dry materials is 120-;

wherein the particle size of the regenerated graphite powder is less than 0.5mm and accounts for 50 percent of the mass of the dry materials;

the graphitized petroleum coke particles comprise the following components: the graphitized petroleum coke particles with the particle size of 0.5-4mm account for 25% of the mass of the dry material, and the graphitized petroleum coke particles with the particle size of 4-8mm account for 25% of the mass of the dry material;

the pretreatment steps are as follows: the kneading pot is externally heated by heat conducting oil, the heating temperature is 190-200 ℃, and the heat conducting oil is selected from L-QB300 organic heat carriers. When the temperature in the kneading pot is heated to 170-180 ℃, dry materials are added for dry mixing, and a reamer is arranged in the kneading pot for stirring the dry mixed materials;

s2, wet mixing: pouring the adhesive into the dry mixture for wet mixing for 40min at the wet mixing temperature of 165-175 ℃ to obtain paste;

wherein the adhesive is medium-temperature coal pitch, the ash content in the medium-temperature coal pitch is 0.20 percent by mass, the volatile matter is 64.2 percent by mass, the water content is 0.06 percent by mass, and the mass ratio of the adhesive to the dry materials is 1: 4.

S3, profiling: pouring the paste into a forming container with an upper die and a lower die respectively having heating and cooling functions, starting the heating function, simultaneously heating the upper die and the lower die at a heating temperature of 160-; specifically, the density index is 1.75-1.80g/cm³；

S4, opening a cooling valve when the density index is reached, simultaneously cooling the upper die and the lower die, and cooling the paste within 2 minutes until the temperature of the paste is 40-50 ℃ to prepare a green body;

s5, only opening the upper die to heat the green body, rapidly heating the upper die to 170-175 ℃ within 1 minute, rapidly lifting the upper die when the internal temperature of the green body is about 40 ℃, and separating the green body from the lower die by means of the pressure of the upper die after the upper die is separated;

s6, roasting, namely, putting the pressed green body into an industrial ring type roasting furnace, filling and compacting the pressed green body with metallurgical coke powder inside and outside, and gradually heating under the condition of air isolation to obtain a primary roasted product; wherein, the metallurgical coke powder size range is 0.5-2mm 30%, 2-5mm 50%, 5-10mm 20%, and is mixed uniformly.

Heating conditions step by step are as follows: roasting temperature rise interval, first temperature interval: raising the temperature from room temperature to 150 ℃ without any requirement, and freely raising the temperature; 150 ℃ and 350 ℃, the temperature rise speed is 4.4 ℃/h, and the duration time of the first temperature interval is 45 h;

the second temperature interval: raising the temperature from the first temperature interval to 350-400 ℃, wherein the temperature raising speed is 1.7 ℃/h, and the duration time of the second temperature interval is 30 h;

the third temperature interval: the temperature is increased from the second temperature interval to 400-500 ℃, the temperature increase speed is 1.25 ℃/h, and the duration time of the third temperature interval is 80 h;

a fourth temperature interval: the temperature is increased from the third temperature interval to 500-600 ℃, the temperature increase speed is 1.8 ℃/h, and the duration time of the fourth temperature interval is 57 h;

a fifth temperature interval: the temperature is increased from the fourth temperature interval to 600-700 ℃, the temperature increase speed is 3.8 ℃/h, and the duration time of the fifth temperature interval is 27 h;

sixth temperature interval: the temperature is increased from the fifth temperature interval to 800 ℃ below zero, the temperature increase speed is 5.0 ℃/h, and the duration time of the sixth temperature interval is 20 h;

a seventh temperature interval: raising the temperature from the sixth temperature interval to 900 ℃ of 800-.

The graphite crucible prepared in this example had performance test results

As can be seen, the average volume density of the graphite crucible prepared by the embodiment of the application reaches 1.62g/cm³Other indexes are also obviously superior to those of the regenerated graphite crucible prepared by the prior art, and the problems that the crucible prepared by using the regenerated graphite as the raw material is uneven in structure, easy to crack in use and easy to damage after being stressed or expanded are effectively solved through a hot-pressing and cold-forming one-step forming method. The whole scheme has simple process, does not need to dry materials after kneading, simplifies the preparation process, does not need high-pressure forming, and has the effects of saving energy, reducing emission, reducing cost and improving efficiency.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.