RU2266867C2 - Method of production of graphitized material - Google Patents

Abstract

FIELD: metallurgy; semiconductor and aeronautical engineering; manufacture of electrodes, seals for aircraft engines and super clean articles.

SUBSTANCE: coke at yield of volatile agents of 4.0-12.0 mass-% in which fraction of size lesser than 0.09 mm is no less than 97 mass-% and fraction of size lesser than 0.045 mm is no less than 91 mass-% is mixed with 30-40 mass-% of coal-tar pitch, 0.015-2.0 mass-% of sterically hindered phenols and/or phenyl phosphites and 0.015-2.0 mass-% of stearic acid. Mass ratio of stearic acid to sterically hindered phenols and/or phenyl phosphites ranges from 1:1 to 2:1. Mixing with coal-tar pitch is performed at temperature of 110-160°C. Mass thus obtained is cooled to room temperature, crushed, ground and blanks at density of 1.01-1.25 g/cm³ are molded and roasted at 1000°C. Roasted blanks are graphitized at temperature rise by the following scheme: to 800°C, 30-60°C/h; to 1500, 5-25°C/h; to 2200°C, 15045°C/h. Holding time at each stage is equal to 3/7 h. Material thus obtained has apparent density of 1650-1870 kg/m³ at compressive strength of 103-160 Mpa and bending strength of 81-88 Mpa.

EFFECT: enhanced efficiency.

2 tbl, 1 ex

Description

The invention relates to a technology for producing carbon materials that can be used in electric discharge machining of metals, for the manufacture of electrodes used in foundry in the smelting of metals, for example aluminum, calcium, for the production of mechanical seals in aircraft gas turbine engines, as well as in the manufacture of highly pure products for semiconductor technology, etc.

A known method of producing graphitized materials by grinding calcined petroleum coke to a particle size of 1-2 mm, mixing coke and pitch in a ratio (wt.%) 65:35, using a vibratory grinding machine of a coke pitch mixture to produce at least 95% of the powder passing through a sieve with openings 0 , 09 mm, molding blanks with their subsequent firing and graphitization (Tyrina L.Ya., Nikolaev A.I., Sigarev A.M., Sat. tr. "Structural materials based on graphite. M: Metallurgy, No. 3, 1967, pp. 11-18).

Material with increased density, strength and uniformity is obtained by a technology that includes the same operations, but grinding calcined petroleum coke to a particle size of less than 40 microns and mixing it with 28-35 wt.% High-temperature pitch and then grinding the coke-pitch composition to a grain size of less than 150 microns (patent RU No. 2035396, 01 B 31/04, publ. 1995).

Both technical solutions considered use calcined petroleum coke as a basis, which during firing and graphitization has a slight shrinkage, which ensures a high yield of products during firing and graphitization. However, the density of coke in the process of obtaining graphitized material varies from 2.08 to 2.18 g / cm ³ and the binder - coal tar pitch - from 1.35 to 2.18 g / cm ³ . As a result of this, stresses occur in the material that reduce the strength characteristics of the metal and its resistance to oxidation.

A known method of producing graphitized material, including grinding non-calcined petroleum coke grades KNPS-SM and KNPS-KM to a fractional composition containing at least 85 wt.% Of the fraction passing through a sieve of 0.3-0.8 mm, mixing crushed coke with coal tar pitch and the addition of a surfactant in a ratio (wt.%), respectively, 61: 39: 0.7 at a temperature of 120-130 ° C, molding the mass followed by its grinding into a powder, pressing the blanks, burning them and graphitizing (TU 48- 20-51-84). With this method of obtaining, simultaneous shrinkage of coke and pitch occurs, which allows one to obtain materials with increased density and strength. However, the implementation of the described process is currently impossible in connection with the cessation of production of petroleum coke of these grades.

Closest to the technical nature and the achieved result to the proposed solution, the method of obtaining high-strength graphitized material according to patent RU No. 2160704, 01 B 31/04, publ. 2000, adopted as a prototype.

Formally, in the prototype patent, the object of protection is a graphitized material containing fine calcined non-calcined shale tar coke, coal tar pitch and an organic additive, and the fractional composition of the coke used is as follows: fraction with a particle size of 0.02-0 mm — at least 80 wt.%, fraction 0.09-0.02 - the rest. The composition of the material in the formula is not given, however, judging by example 1, the composition and method of production is identical to the method of obtaining material according to TU 48-20-51-84, namely: the method consists in grinding shale tar coke to the above fractional composition, mixing crushed coke with coal tar pitch and organic additive in the ratio (wt.%) respectively 62.3: 37: 0.7 at a temperature of 120-130 ° C, molding the mass followed by grinding into fresh powder, pressing with a density of 1.08-1.15 g / cm ³ , firing blanks at a temperature of 2500-3000 ° C. Moreover, only through the use of coke of shale resin of a certain fractional composition, the authors of the prototype patent were able to obtain high-strength graphite material superior to the material according to TU 48-20-51-84 in compressive strength by 5-6% and bending strength by 20-30 % at a density of 1.65-1.75 g / cm ³ against 1.65 of the prototype.

The technical result consists in a further increase in the strength characteristics of graphitized material.

The technical result is achieved due to the fact that in the method of producing graphitized material, including mixing crushed coke with coal tar pitch and an organic additive by heating, mass pressing, firing and graphitization, coke is used with a yield of volatile from 4.0 to 12.0 wt.% in which the fraction of a fraction of less than 0.09 mm is not less than 97 wt.% and the fraction of a fraction of less than 0.045 mm is not less than 91 wt.%, a mixture of stearic acid and spatially hindered phenols and / or phenylphosphites in a mass ratio, respectively, from 1: 1 to 2: 1, mixing with pitch is carried out at a temperature of from 110 to 160 ° C, after which the mass is cooled to room temperature, crushed, finely ground and pressed blanks with a density of 1.01-1, 25 g / cm ³ followed by firing the workpiece at temperatures up to 1000 ° C and graphitization to a temperature of 2200 ° C according to the mode: up to 800 ° C - at a speed of 30-60 ° C / h, up to 1500 ° C - at a speed of 5-25 ° C / hour and up to 2200 ° C - at a speed of 15-45 ° C / hour, with holding at each stage for 3-7 hours with the following ratio of the initial components of the mixture (wt.%) :

Coal tar pitch 30-40 Spatially hindered phenols and / or Phenylphosphites 0.015-2.0 Stearic acid 0.015-2.0 Coke rest.

As spatially hindered phenol or phenylphosphite, tetra- (methylene-4-hydroxy-3,5-di-tert-butyl-phenylpropionate methane (MOBPPM), 4,4'-dimethyl-6,6'-di-tert can be used -butyl-2,2'-methylene-bis-phenylphosphite (MBMFF), 2,4-bis- (1,1'-dimethylethyl) phenylphosphite (BFF) diarylpentaerythritol diphosphite and other similar compounds produced on an industrial scale in a wide range of brands , known as Irganox 1010, Stafor 11, Irgafos 168, and Ultranoks 624 (626) brands, respectively, used in foreign and domestic (import) practice in the plastics industry (Journal of High-Molecular Compounds, Series A, 1981, 23 (b), pp. 1275-1281; ibid., 1983, 25 (b), pp. 1302-1306; Japanese application No. 61 -225191, 1986 (Chemical abstracts, T. 106, ref. 120065 d, 1987)

As coke, oil and shale tar coke can be used, preferably non-calcined, as in the process of producing graphitized materials due to the simultaneous shrinkage of coke and pitch, the strength characteristics of the materials increase (compared with materials based on calcined cokes).

The invention is illustrated by the following examples.

Example 1

Shale tar coke not calcined according to technical specifications EE-1300542 TU 8:94 with a yield of volatile 4 wt.% Was dried and crushed to pieces 4 mm in size, and then grinded at a vibratory mill. The content of the fraction passing after grinding through a sieve of 0.09 mm was 97 wt.% And through a sieve of 0.045 mm - 91 wt.%. 38 wt.% Of medium temperature coal tar pitch (GOST 10200-83) is mixed in a mixer with 0.04 wt.% Of a mixture of MOBFPM and stearic acid, taken in a mass ratio of 1: 1 (0.02 wt.% Each) and 61, 96 wt.% Crushed coke for 50 min at a temperature of 110-160 ° C, after which the mass is cooled to room temperature. The cooled mass is crushed in a crusher, and then fine grinding is carried out in a vibratory mill. In the mold at a specific pressure of 60 MPa, blanks with a density of 1.15 g / cm ^{3 are} pressed (specific pressure is selected based on the interval of the required density of blanks 1.01-1.25 g / cm ³ ). The billets are fired at temperatures up to 1000 ° C in an electric furnace, and graphitization is carried out in an electric vacuum furnace (imported equipment) according to the regime: at a speed of 50 ° C / h until a temperature of 800 ° C is reached, at a speed of 10 ° C / h - up to 1500 ° With and at a speed of 30 ° C / hour - up to 2200 ° C, with a shutter speed of 5 hours at each stage.

Information on examples 2-11 are presented in tables 1 and 2.

Examples 1-5 illustrate the method in accordance with the invention, examples 6-11 are control, justifying the claimed compounds:

- example 6 - the composition does not contain spatially hindered phenols and / or phenylphosphites;

- example 7 - the composition does not contain stearic acid;

- example 8 - the ratio between the mixture of spatially hindered additives MOBFPM and MBMFF and stearic acid is 1: 3, i.e. goes beyond the declared limits;

- example 9 - the fraction of the coke fraction of less than 0.09 mm is 9 5%, i.e. below stated;

- examples 10 and 11 - the pitch content is respectively higher and lower than stated.

Table 1 Recipes for the composition of graphitized material Components Examples of the invention, wt.% Test cases 1 2 3 4 5 6 7 8 nine 10 eleven Coal tar pitch 38 35 40 38 thirty 38 38 38 38 41 29th Organic supplement: MOBFPM 0.02 2.0 0.01 1,0 1,5 0.25 0.01 MBMFF 0.015 0.5 0.25 0.015 FFT 0.01 2.0 2.0 Stearic acid 0.02 0.015 2.0 0.02 2.0 2.0 1,5 2.0 2.0 0,03 Coke: Shale tar, with the release of volatile 4 wt.% 61.96 10 wt.% 56.0 60 60 60 58 55 70,955 12 wt.% 61.96

1 2 3 4 5 6 7 8 nine 10 eleven Fraction fraction size

less than 0.09 mm,%


97.0


99


98


98


98


98


95


98


98 less than 0,045 mm,% 91 98 92 Petroleum coke, volatile

4 wt.%


64.97 12 wt.% 67 The fraction fraction less than 0.09 mm,% 98 99 less than 0,045 mm,% 93 96

Table 1 presents the formulations of the claimed and control compounds.

Table 2 - characteristics of the materials obtained on their basis (in comparison with the prototype).

table 2 Characteristics of graphitized materials No. of examples The apparent density, Kg / m ³ Tensile strength, MPa under compression when bending 1 2 3 4 1 1650 108 81 2 1720 130 82

1 2 3 4 3 1830 152 86 4 1660 103 81 5 1870 160 88 Control 6 1680 90 78 7 1600 98 75 nine 1690 73 78 10 1700 90 77 eleven 1620 78 70 prototype 1670-1750 74-78 45-52.6

The presented examples indicate that the proposed method has achieved a significant technical result - a significant increase in strength indicators compared to the prototype. So, compressive strength (the most important indicator) increased by 105%, and bending strength - by 67% when comparing the maximum values of indicators; when comparing the minimum values of the indicators, the growth was 39% and 80%, respectively.

None of the control examples gave a noticeable improvement in performance compared to the prototype; they are all inferior to the claimed material.

It should be noted the significant role of the parameters of the method of manufacturing graphitized material, especially the graphitization stage, the hardware design of which ensured the strict fulfillment of the specified mode, without which it would be impossible to achieve such a high effect on improving strength indicators. The combination of the claimed - both qualitative and quantitative - compositions and operating parameters of the method, which allowed to obtain the technical result described above.

Claims (1)

A method of producing graphitized material, comprising mixing crushed coke with coal tar pitch and an organic additive by heating, pressing the mass, calcining and graphitizing, characterized in that coke is used with a yield of volatile 4.0-12.0 wt.%, In which the fraction fraction is of size less than 0.09 mm is not less than 97 wt.% and the fraction of a fraction of less than 0.045 mm is not less than 91 wt.%, as an organic additive use a mixture of stearic acid and spatially hindered phenols and / or phenylphosphites in a mass ratio, accordingly, from 1: 1 to 2: 1, mixing with the pitch is carried out at a temperature of 110-160 ° C, after which the mass is cooled to room temperature, crushed, ground and pressed blanks with a density of 1.01-1.25 g / cm ³ followed by firing the workpiece at temperatures up to 1000 ° C and graphitization to a temperature of 2200 ° C according to the mode: up to 800 ° C - at a speed of 30-60 ° C / h, up to 1500 ° C - at a speed of 5-25 ° C / h and up to 2200 ° С - at a speed of 15-45 ° С / h, with holding at each step for 3-7 hours, with the following ratio of the initial components of the mixture, wt.%: Coal tar pitch 30-40 Spatially hindered phenols and / or phenylphosphites 0.015-2.0 Stearic acid 0.015-2.0 Coke Rest