A special graphite sealing material for aviation and its preparation method

Abstract

The present invention belongs to the technical field of special graphite sealing materials, and particularly relates to a special graphite sealing material for aviation and a preparation method thereof. The preparation method of the special graphite sealing material for aviation comprises the following steps: S1. successively performing kneading treatment and powder grinding treatment on raw materials to obtain powder materials; pressing the powder materials into a shape to obtain a green body; S2. baking the green body and cooling to obtain a baked material; S3. successively performing graphitization treatment, impregnation treatment and purification treatment on the baked material to obtain the special graphite sealing material for aviation; the special graphite sealing material for aviation described in the present invention has relatively high flexural strength, compressive strength, hardness and density; has relatively low resistivity, porosity and ash content, and the preparation process is simpler, reducing the production cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of special graphite sealing materials, and particularly relates to a special graphite sealing material for aviation and a preparation method thereof. Background Art

[0002] Special graphite materials refer to graphite with a carbon mass fraction greater than 99%, which has high strength, high density, and high purity, and is also known as "three-high graphite". Special graphite sealing materials have the advantages of high temperature resistance, corrosion resistance, pressure resistance, and low leakage, so they are widely used in various industrial fields, especially in sealing applications under high temperature, high pressure, and corrosive environments. For example, they are used for sealing various chemical containers, pipelines, and valves in the chemical industry; for sealing oil well equipment, pipelines, and valves in the petroleum industry; and for sealing equipment such as engines, hydraulic systems, and fuel systems in the aerospace industry.

[0003] The Chinese patent with the publication number CN113372118A in the prior art discloses a preparation method of special graphite materials. The raw materials selected are the most representative Jinzhou needle coke and Baosteel needle coke in the petroleum-based and coal-based domestic cokes. The binder selected is medium-temperature modified pitch with a high coking value and strong operability. An enhanced treatment process after graphitization is added to the process flow, and the formula is improved as well as the control of other processes. The raw material selection is reasonable, and the process control is targeted. The special graphite material produced by this method has a high volume density, high mechanical strength, and a low thermal expansion coefficient, is suitable for use under high temperature and rapid temperature change conditions, and can be widely used in technical fields such as aerospace, ships, and national defense weapons.

[0004] The Chinese patent with the publication number CN118145633A discloses a special graphite material and a preparation method thereof, including successively performing kneading treatment, hot rolling treatment, and grinding treatment on the raw materials; then performing pressing treatment on the powder; performing a first roasting treatment on the pressed formed blank; then performing cyclic impregnation-roasting treatment on the blank after the first roasting treatment; and finally performing graphitization treatment on the blank after the cyclic impregnation-roasting treatment to obtain the product. The volume density and graphitization degree of the special-purpose graphite material of this technical solution are significantly improved. The products prepared from the graphite material of this technical solution have high mechanical strength; the prepared products have good self-lubricating and antioxidant properties; the microstructure of the material is closer to the theoretical graphite structure, with a low high-temperature thermal oxidation weight loss rate, can be used in high-temperature and radiation-proof fields, and can significantly extend the service life of the material.

[0005] However, in the preparation process of the above technical solutions, multiple impregnation-roasting treatments are adopted, the process is cumbersome, and the cost is high. Summary of the Invention

[0006] In view of the above problems, the present invention provides a special graphite sealing material for aviation and a preparation method thereof. The special graphite sealing material for aviation of the present invention has high flexural strength, compressive strength, hardness and density; has low resistivity, porosity and ash content, and the preparation process is simpler, reducing the production cost.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a preparation method of a special graphite sealing material for aviation, comprising the following steps:

[0009] S1. The raw materials are successively subjected to kneading treatment and grinding treatment to obtain powder; the powder is pressed into a green body.

[0010] S2. The green body is baked and cooled to obtain a baked material.

[0011] S3. The baked material is successively subjected to graphitization treatment, impregnation treatment and purification treatment to obtain the special graphite sealing material for aviation.

[0012] The working curve of baking is:

[0013] The first stage: room temperature - 350 °C, free heating.

[0014] The second stage: 350 - 450 °C, heating rate 3 - 5 °C / h.

[0015] The third stage: 450 - 500 °C, heating rate 2 - 3 °C / h.

[0016] The fourth stage: 500 - 550 °C, heating rate 1.4 - 1.8 °C / h.

[0017] The fifth stage: 550 - 750 °C, heating rate 1 - 1.5 °C / h.

[0018] The sixth stage: 750 - 810 °C, heating rate 1 - 3 °C / h.

[0019] The seventh stage: 810 - 900 °C, heating rate 2 - 4 °C / h.

[0020] The eighth stage: 900 - 940 °C, heating rate 4 - 6 °C / h.

[0021] The ninth stage: 940 - 1200 °C, heating rate 8 - 12 °C / h.

[0022] The tenth stage: 1200 ± 50 °C, heat preservation for 75 - 85 h.

[0023] In some preferred embodiments, the raw materials, by mass parts, include 50-55 parts of green petroleum coke powder, 6-8 parts of natural graphite powder, 24-27 parts of binder, and 12-15 parts of oleic acid mixture.

[0024] In some preferred embodiments, the mass ratio of the green petroleum coke powder to the natural graphite powder is 5-10:1, preferably 7-7.5:1.

[0025] In a preferred embodiment, the raw materials, by mass parts, include 52.8 parts of green petroleum coke powder, 7.2 parts of natural graphite powder, 27 parts of binder, and 13 parts of oleic acid mixture.

[0026] In a preferred embodiment, D50 of the green petroleum coke powder is ≤10 μm, preferably 5-10 μm.

[0027] In some preferred embodiments, the physical property parameters of the natural graphite powder are: ash content ≤0.5%, moisture content ≤1%, volatile matter content ≤1%, pH value is 6.5-7.5, and the screening particle size of -320# is 80-90%.

[0028] Preferably, the natural graphite powder is T399 graphite powder produced by Qingdao Nanshu Ruiying Graphite Co., Ltd.

[0029] In the present invention, +160# represents the powder content above the 160-mesh sieve; -320# represents the powder content below the 320-mesh sieve.

[0030] In some preferred embodiments, the binder is a mixture of medium-temperature pitch and coal tar, and the mass ratio of the two is 1-2:2-4, preferably 1-1.5:2.5-3.5, and further preferably 1.4:3.

[0031] In some preferred embodiments, the oleic acid mixture is a mixture of oleic acid and alcohol.

[0032] Preferably, the mass ratio of the oleic acid to the alcohol is 1:100-120.

[0033] In some preferred embodiments, the kneading treatment method is: heating the green petroleum coke powder, natural graphite powder and oleic acid mixture to 100-120 °C and mixing for 120-150 min, adding the binder (the binder is pre-stirred evenly), and closing the cover and mixing for 60-70 min.

[0034] In some preferred embodiments, the physical property parameters of the powder after grinding treatment are: ash content ≤0.5%, moisture content ≤1%, volatile matter content is 15-25%, +160# ≤2%, and -320# is 70-80%.

[0035] In a preferred embodiment, the physical properties of the powder after grinding treatment are as follows: ash content is 0.3%, moisture content is 0.7%, volatile matter content is 24%, the screening particle size of +160# is 1%, and the screening particle size of -320# is 77%.

[0036] In a preferred embodiment, the method of pressing and forming is cold isostatic pressing.

[0037] Preferably, the pressure of the cold isostatic pressing is 120 - 140 MPa, and the time is 8 - 12 min.

[0038] In a preferred embodiment, the working curve of roasting is as follows:

[0039] The first stage: room temperature - 350°C, free heating;

[0040] The second stage: 350 - 450°C, heating rate 4°C / h;

[0041] The third stage: 450 - 500°C, heating rate 2.5°C / h;

[0042] The fourth stage: 500 - 550°C, heating rate 1.67°C / h;

[0043] The fifth stage: 550 - 750°C, heating rate 1.25°C / h;

[0044] The sixth stage: 750 - 810°C, heating rate 2°C / h;

[0045] The seventh stage: 810 - 900°C, heating rate 3°C / h;

[0046] The eighth stage: 900 - 940°C, heating rate 5°C / h;

[0047] The ninth stage: 940 - 1200°C, heating rate 10°C / h;

[0048] The tenth stage: 1200 ± 50°C, holding for 80 h.

[0049] Preferably, the time for free heating is 10 h.

[0050] In some preferred embodiments, the method of graphitization treatment is as follows: placing the roasted material in an Acheson graphitization furnace, heating by electricity to 2500 - 2600°C, and the total electricity heating time is 130 - 150 h.

[0051] In some preferred embodiments, the curve of heating by electricity is as follows:

[0052] The first stage: 0 - 85 h, the power rises uniformly from 120 Kw to 360 Kw;

[0053] The second stage: 85 - 120 h, the power rises uniformly from 360 Kw to 750 Kw;

[0054] The third stage: 120 - 150 h, the power drops uniformly from 750 Kw to 550 Kw.

[0055] In some preferred embodiments, the method of impregnation treatment is as follows: Place the graphitized product in an impregnation tank, heat it to 200 - 220 °C, keep it warm for 3 - 5 h, add an impregnating agent, and keep the pressure at 1.5 - 2 MPa for 8 - 10 h.

[0056] Preferably, the impregnating agent is impregnating pitch.

[0057] In some preferred embodiments, the method of purification treatment is as follows: Place the impregnated product in a graphitization furnace, feed chlorine gas when the core temperature of the furnace is 2000 - 2200 °C; feed Freon when the temperature is 2200 - 2400 °C; treat it at 2800 - 3000 °C for 40 - 50 h.

[0058] Preferably, the method of purification treatment is as follows: Place the impregnated product in a graphitization furnace, feed chlorine gas when the core temperature of the furnace is 2000 °C; feed Freon when the temperature is 2200 °C; treat it at 2800 - 3000 °C for 48 h.

[0059] In some other preferred embodiments, the method of purification treatment is as follows: Place the impregnated product in a graphitization furnace, feed chlorine gas when the core temperature of the furnace is 2000 - 2200 °C; feed chlorine gas and Freon together after 6 h; treat it at 2800 - 3000 °C for 40 h.

[0060] Preferably, during the process of feeding chlorine gas and Freon together, the amount of chlorine gas is slightly greater than that of Freon.

[0061] The second aspect of the present invention provides an aviation special graphite sealing material obtained by the preparation method of the above-mentioned aviation special graphite sealing material.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] The preparation method of the aviation special graphite sealing material provided by the present invention only requires one roasting treatment and one impregnation treatment, the preparation process is simpler, and the production cost is reduced; moreover, the obtained aviation special graphite sealing material has higher flexural strength, compressive strength, hardness and density; and has lower resistivity, porosity and ash content. Detailed Embodiments

[0064] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0065] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0066] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0067] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0068] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0069] In the following examples, unless otherwise specified, the raw materials used are all commercially available or prepared by conventional methods in the art.

[0070] The sources of the raw materials involved in the examples and comparative examples are shown in Table 1:

[0071] Table 1

[0072]

[0073]

[0074] Example 1

[0075] By mass, the raw materials of the special graphite sealing material for aviation consist of 52.8 parts of raw petroleum coke powder, 7.2 parts of natural graphite powder, 27 parts of a binder (a mixture of medium-temperature pitch and coal tar, with a mass ratio of 1.4:3), and 13 parts of oleic acid mixture.

[0076] Preparation method of special graphite sealing material for aviation, comprising the following steps:

[0077] S1. Kneading treatment: Heat the mixture of raw petroleum coke powder, natural graphite powder and oleic acid solution to 110°C and mix for 130 min, add the binder (the binder is pre-stirred evenly), close the cover and mix for 65 min;

[0078] Grinding treatment: Use a 4R Raymond mill to grind the powder to obtain powder; the physical properties of the powder are: ash content 0.3%, moisture content 0.7%, volatile matter 24%, +160# 1%, -320# 77%.

[0079] Pressing the powder into shape: Perform cold isostatic pressing at a pressure of 140 MPa, keep the pressure for 10 min and then slowly release the pressure to obtain a green body;

[0080] S2. Place the green body in a down-draft kiln for roasting, and cool to obtain a roasted material; the working curve of roasting is:

[0081] The first stage: room temperature - 350°C, free heating for 10 h;

[0082] The second stage: 350 - 450°C, heating rate 4°C / h;

[0083] The third stage: 450 - 500°C, heating rate 2.5°C / h;

[0084] The fourth stage: 500 - 550°C, heating rate 1.67°C / h;

[0085] The fifth stage: 550 - 750°C, heating rate 1.25°C / h;

[0086] The sixth stage: 750 - 810°C, heating rate 2°C / h;

[0087] The seventh stage: 810 - 900°C, heating rate 3°C / h;

[0088] The eighth stage: 900 - 940°C, heating rate 5°C / h;

[0089] The ninth stage: 940 - 1200°C, heating rate 10°C / h;

[0090] The tenth stage: 1200 ± 50°C, keep the temperature for 80 h;

[0091] The properties of the obtained calcined material are shown in Table 2: The test standard for flexural strength is JB / T 8133.7 Test Methods for Physicochemical Properties of Electrical Carbon Products - Part 7; the test standard for compressive strength is JB / T 8133.8 Test Methods for Physicochemical Properties of Electrical Carbon Products - Part 8; the test standard for resistivity is JB / T 8133.2 Test Methods for Physicochemical Properties of Electrical Carbon Products - Part 2; the test standard for Shore hardness is JB / T 8133.4 Test Methods for Physicochemical Properties of Electrical Carbon Products - Part 4; the test standard for bulk density is JB / T 8133.14 Test Methods for Physicochemical Properties of Electrical Carbon Products - Part 14; the test standard for open porosity is JB / T 8133.15 Test Methods for Physicochemical Properties of Electrical Carbon Products - Part 15.

[0092] Table 2

[0093]

[0094] S3. Graphitize the calcined material in sequence: Place the calcined material in an Acheson graphitization furnace and heat it by electricity to 2600 °C; the curve of heating by electricity is as follows:

[0095] The first stage: 0 - 85 h, the power rises uniformly from 120 Kw to 360 Kw;

[0096] The second stage: 85 - 120 h, the power rises uniformly from 360 Kw to 750 Kw;

[0097] The third stage: 120 - 150 h, the power drops uniformly from 750 Kw to 550 Kw.

[0098] The properties of the graphitized product are shown in Table 3:

[0099] Table 3

[0100]

[0101] Impregnation treatment: Place the graphitized product in an impregnation tank, heat it to 210 °C, keep it warm for 4 h, add impregnating pitch, and keep the pressure at 1.8 MPa for 9 h;

[0102] Purification treatment: Place the impregnated product in a graphitization furnace, feed chlorine when the core temperature of the furnace is 2000 °C; feed Freon when it is 2200 °C; treat it at 3000 °C for 48 h to obtain the special graphite sealing material for aviation.

[0103] Example 2

[0104] The difference from Example 1 is that, by mass, the raw materials of the special graphite sealing material for aviation consist of 53.9 parts of green petroleum coke powder, 6 parts of natural graphite powder, 27 parts of binder (a mixture of medium-temperature pitch and coal tar, with a mass ratio of 1.4:3 between the two), and 13.1 parts of oleic acid mixture.

[0105] The working curve for roasting is as follows:

[0106] The first stage: room temperature - 350°C, free heating for 10 h;

[0107] The second stage: 350 - 450°C, heating rate 3°C / h;

[0108] The third stage: 450 - 500°C, heating rate 2°C / h;

[0109] The fourth stage: 500 - 550°C, heating rate 1.4°C / h;

[0110] The fifth stage: 550 - 750°C, heating rate 1°C / h;

[0111] The sixth stage: 750 - 810°C, heating rate 1°C / h;

[0112] The seventh stage: 810 - 900°C, heating rate 2°C / h;

[0113] The eighth stage: 900 - 940°C, heating rate 4°C / h;

[0114] The ninth stage: 940 - 1200°C, heating rate 8°C / h;

[0115] The tenth stage: 1200 ± 50°C, heat preservation for 75 h; the rest are the same.

[0116] Example 3

[0117] The difference from Example 1 is that, by mass, the raw materials of the special graphite sealing material for aviation consist of 50.9 parts of green petroleum coke powder, 9 parts of natural graphite powder, 27 parts of binder (a mixture of medium-temperature pitch and coal tar, with a mass ratio of 1.4:3 between the two), and 13.1 parts of oleic acid mixture.

[0118] The working curve for roasting is as follows:

[0119] The first stage: room temperature - 350°C, free heating for 10 h;

[0120] The second stage: 350 - 450°C, heating rate 5°C / h;

[0121] The third stage: 450 - 500°C, heating rate 3°C / h;

[0122] Fourth stage: 500 - 550 °C, heating rate 1.8 °C / h;

[0123] Fifth stage: 550 - 750 °C, heating rate 1.5 °C / h;

[0124] Sixth stage: 750 - 810 °C, heating rate 3 °C / h;

[0125] Seventh stage: 810 - 900 °C, heating rate 4 °C / h;

[0126] Eighth stage: 900 - 940 °C, heating rate 6 °C / h;

[0127] Ninth stage: 940 - 1200 °C, heating rate 12 °C / h;

[0128] Tenth stage: 1200 ± 50 °C, heat preservation for 85 h; the rest are the same.

[0129] Comparative example 1

[0130] The difference from Example 1 is only that the T399 graphite powder is replaced with the same mass of artificial graphite powder, and the rest are the same.

[0131] Comparative example 2

[0132] The difference from Example 1 is only that the raw petroleum coke powder is replaced with the same mass of needle coke powder, and the rest are the same.

[0133] Comparative example 3

[0134] The difference from Example 1 is only that the mass ratio of raw petroleum coke powder to natural graphite powder is 11.5:1. That is, by mass fraction, the raw materials of the special graphite sealing material for aviation consist of 55.2 parts of raw petroleum coke powder, 4.8 parts of natural graphite powder, 27 parts of binder (a mixture of medium-temperature pitch and coal tar, with a mass ratio of 1.4:3), and 13 parts of oleic acid mixture.

[0135] Comparative example 4

[0136] The difference from Example 1 is only that the roasting working curve is:

[0137] First stage: 130 - 350 °C, heating rate 4.4 °C / h, duration 40 h;

[0138] Second stage: 350 - 400 °C, heating rate 1.7 °C / h, duration 40 h;

[0139] Third stage: 400 - 500 °C, heating rate 1.2 °C / h, duration 80 h;

[0140] The fourth stage: 500 - 600 °C, heating rate 1.5 °C / h, duration 70 h;

[0141] The fifth stage: 600 - 700 °C, heating rate 3.0 °C / h, duration 35 h;

[0142] The sixth stage: 700 - 800 °C, heating rate 4.5 °C / h, duration 20 h;

[0143] The seventh stage: 800 - 1000 °C, heating rate 8.0 °C / h, duration 25 h;

[0144] The eighth stage: 1000 - 1250 °C, heating rate 8.5 °C / h, duration 30 h;

[0145] The ninth stage: 1250 ± 25 °C, heat preservation 20 h; the rest are the same.

[0146] Comparative Example 5

[0147] The difference from Example 1 is only that the roasting working curve is:

[0148] The first stage: room temperature - 200 °C, free heating 48 h;

[0149] The second stage: 200 - 400 °C, heating rate 1 °C / h;

[0150] The third stage: 400 - 600 °C, heating rate 1.5 °C / h;

[0151] The fourth stage: 600 ± 10 °C, heat preservation 24 h;

[0152] The fifth stage: 600 - 1000 °C, heating rate 2.0 °C / h;

[0153] The sixth stage: 1000 ± 50 °C, heat preservation 72 h; the rest are the same.

[0154] Comparative Example 6

[0155] The difference from Example 1 is only that the curve of electrified heating is:

[0156] The first stage: 0 - 50 h, power uniformly rising from 120 Kw to 330 Kw;

[0157] The second stage: 50 - 100 h, power uniformly rising from 330 Kw to 700 Kw;

[0158] The third stage: 100 - 120 h, power uniformly dropping from 700 Kw to 500 Kw; the rest are the same

[0159] Comparative Example 7

[0160] The difference from Example 1 is that in S3, the calcined material is successively subjected to impregnation treatment, graphitization treatment, and purification treatment; the rest are the same.

[0161] Performance tests were carried out on the special graphite sealing materials for aviation of Examples 1-3 and Comparative Examples 1-7, and the results are shown in Table 4.

[0162] Table 4

[0163]

[0164] The special graphite sealing material for aviation in the embodiment of the present invention has been applied to the dynamic sealing device of a certain type of aeroengine. After application, it has the characteristics of low leakage, low heat generation, long life, and high reliability.

[0165] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a special graphite sealing material, characterized in that: The following steps are involved: S1, kneading and grinding the raw materials in sequence to obtain powder; The powder is pressed into shape to obtain a green body; S2, calcining the green body and cooling it to obtain a calcined material; S3, sequentially subjecting the calcined material to graphitization, impregnation and purification to obtain a special graphite sealing material; The working curve of roasting is: Stage 1: room temperature - 350°C, free heating; The second stage: 350-450℃, heating rate 3-5℃ / h; The third stage: 450-500℃, heating rate 2-3℃ / h; The fourth stage: 500-550℃, heating rate 1.4-1.8℃ / h; The fifth stage: 550-750℃, heating rate 1-1.5℃ / h; Stage 6: 750-810°C, heating rate 1-3°C / h; Stage 7: 810-900°C, heating rate 2-4°C / h; Stage 8: 900-940°C, heating rate 4-6°C / h; The ninth stage: 940-1200℃, heating rate 8-12℃ / h; Stage 10: 1200±50℃, keep warm for 75-85h; The raw materials in step S1 include, by mass, 50-55 parts of raw petroleum coke powder, 6-8 parts of natural graphite powder, 24-27 parts of binder, and 12-15 parts of oleic acid mixed solution.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the raw petroleum coke powder to the natural graphite powder is 7-7.5:

1.

3. The preparation method according to claim 2, characterized in that: The raw materials include, by mass, 52.8 parts of raw petroleum coke powder, 7.2 parts of natural graphite powder, 27 parts of binder, and 13 parts of oleic acid mixed solution.

4. The preparation method according to claim 1, characterized in that: The D50 of the raw petroleum coke powder is ≤10 μm.

5. The preparation method according to claim 1, characterized in that: The binder is a mixture of medium-temperature asphalt and coal tar, and the mass ratio of the two is 1-2:2-4.

6. The preparation method according to claim 1, characterized in that: The physical property parameters of the powder after grinding are: ash content ≤0.5%, moisture ≤1%, volatile matter 15-25%, screening particle size +160# ≤2%, screening particle size -320# 70-80%.

7. The preparation method according to claim 6, characterized in that: The physical properties of the powder after grinding are as follows: ash content is 0.3%, moisture content is 0.7%, volatile matter is 24%, sieve particle size +160# is 1%, and sieve particle size -320# is 77%.

8. The preparation method according to claim 1, characterized in that: The working curve of roasting is: Stage 1: room temperature - 350°C, free heating; The second stage: 350-450℃, heating rate 4℃ / h; The third stage: 450-500℃, heating rate 2.5℃ / h; Stage 4: 500-550°C, heating rate 1.67°C / h; The fifth stage: 550-750℃, heating rate 1.25℃ / h; Stage 6: 750-810°C, heating rate 2°C / h; Stage 7: 810-900°C, heating rate 3°C / h; The eighth stage: 900-940℃, heating rate 5℃ / h; The ninth stage: 940-1200℃, heating rate 10℃ / h; The tenth stage: 1200±50℃, keep warm for 80h.

9. The preparation method according to claim 1, characterized in that: The method of graphitization treatment is: placing the roasted material in an Acheson graphitization furnace, heating it to 2500-2600° C. by applying power, and the total power-on time is 130-150 hours.

10. The preparation method according to claim 9, characterized in that: The curve of heating after power on is: The first stage: 0-85h, the power increases from 120Kw to 360Kw at a constant speed; The second stage: 85-120h, the power increases from 360Kw to 750Kw at a constant speed; The third stage: 120-150h, the power drops from 750Kw to 550Kw at a constant speed.

11. The preparation method according to claim 1, characterized in that: The purification method is: placing the impregnated product in a graphitization furnace, supplying chlorine when the furnace core temperature is 2000-2200°C; supplying Freon when the furnace core temperature is 2200-2400°C; and treating at 2800-3000°C for 40-50 hours.

12. The special graphite sealing material obtained by the preparation method according to any one of claims 1 to 11.

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