JPH0147426B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing carbonaceous sliding materials. Carbon materials generally have excellent properties such as good lubricity, low coefficient of friction, no seizure, and good chemical resistance, so they are used in various mechanical bearings, mechanical seal parts, packing, and rotating parts. It is widely used as a sliding material for pump vanes, etc. However, as technology advances, improvements in the properties of these carbonaceous sliding materials are required, and in particular, vanes for rotary vacuum pumps are strongly required to have longer lifespans and lower noise from the viewpoint of maintenance-free operation and improved working environments. The following will mainly explain the vacuum pump vane. Recent trends in dry-type rotary vacuum pumps include demands for higher vacuums and higher rotation speeds, and the use conditions for carbonaceous sliding materials are becoming increasingly severe. In other words, an increase in the PV value due to an increase in the sliding speed V due to higher speeds and an increase in the pressing pressure P due to centrifugal force, together with high vacuum and sliding heat generation, decreases friction performance, accelerates vane wear, and reduces sliding noise. The increase is becoming a problem. According to frequency analysis of sliding noise, it is 4.3KHz and 10.6K
The abnormal metallic noise of Hz is felt to be significantly more unpleasant than general sliding noise, and has a negative impact on not only humans but also animals. For example, dry pumps are used for dairy farming, but this abnormal metallic sound is one of the fatal flaws, as there is concern that it may have an adverse effect on dairy cows' milk collection. The present invention has been made to solve the above-mentioned problems. The present inventors investigated various compounding ratios for various raw materials for carbonaceous sliding materials, and discovered a method for manufacturing carbonaceous sliding materials that provides an optimal combination to achieve the above-mentioned objectives. The present invention consists of 45 to 50 parts by weight of an artificial graphite mixture powder in which the ratio of coke-based artificial graphite powder to oil smoke-based artificial graphite powder is 90:10 to 50:50, 1 to 4 parts by weight of talc, and 4 parts by weight of natural graphite powder. The following relates to a method for producing a carbonaceous sliding material, which involves adding 45 to 55 parts by weight of tar pitch and/or coal tar as a binder, sintering, crushing, shaping, and firing. In the present invention, the material (aggregate) that forms the skeleton is obtained by kneading petroleum-based or coal-based pitch coke with tar pitch and/or coal tar, crushing, shaping, and calcining, and then graphitizing it at a high temperature of 2500°C or higher. The coke-based artificial graphite obtained by the same process using oil smoke instead of the pitch coke and the oil smoke-based artificial graphite obtained by the same treatment are pulverized. The particle size is preferably 150 mesh or less in order to maintain mechanical strength. Since these materials are highly graphitized, most of the impurities in the raw materials that cause noise are removed. Coke-based artificial graphite has excellent lubricity, and oil-smoke-based artificial graphite contributes to improving the wear resistance of sliding materials, and one feature of the present invention is to combine the two.
The mixing ratio of coke-based artificial graphite powder and oil-smoke-based artificial graphite powder is 90:10 to 50:50 by weight; If the amount is too high, wear will increase,
On the other hand, if there is a large amount of oil smoke-based artificial graphite, the overall sliding noise will increase. A preferred blending ratio of coke-based artificial graphite and oil smoke-based artificial graphite is 80:20 to 70:30 by weight. Use 45 to 50 parts by weight of this mixed powder. If it is less than 45 parts by weight, the overall sliding noise will become louder, and if it exceeds 50 parts by weight, abnormal metallic noise will occur. Addition of talc is effective in eliminating abnormal metallic sounds, and calcined talc is preferably added in an amount of 1 to 4 parts by weight. 1
If it is less than 4 parts by weight, it will not be effective, and if it exceeds 4 parts by weight, it will accelerate wear. Since natural graphite has better lubricity than artificial graphite, adding a small amount contributes to reducing sliding noise, but adding more than 4 parts by weight reduces the mechanical strength of the carbonaceous sliding material. Natural graphite is phosphorous graphite from Ceylon with particle size
Preferably 150 meshes or more. The binder used is tar pitch and/or coal tar, and in order to improve the sliding properties, tar pitch and/or coal tar with a softening point of 60 to 85 °C by IJS mercury method is used.
Alternatively, it is preferable to use purified tar. If there is less binder, the bonding force between aggregates will decrease and wear will be accelerated. On the other hand, if there is too much, the sliding noise will become louder. 45 to 50 parts by weight of these raw material powders, that is, artificial graphite powder,
A mixture of 1 to 4 parts by weight of talc, up to 4 parts by weight of natural graphite powder, and 45 to 55 parts by weight of a binder is thoroughly kneaded using a double-arm type or screw type ricer machine using a conventional method, and the binder is volatilized. about 10-15% by weight
Until = After heating and drying in the washer and dryer
After crushing to 150 mesh or less and press forming, it is fired in a non-oxidizing atmosphere to a final temperature of 900 to 1200°C. The temperature increase rate is desirably 5°C or less per hour. Finally, the fired body is processed into a sliding material having a desired shape. Next, an example will be described. Example Four samples A, B, C, and D were prepared as follows. That is, the raw materials were weighed according to the proportions shown in Table 1, and placed in a double-armed washer.
The mixture was mixed for 4 hours at ℃, cooled, and then ground to a total size of 150 meshes. After mixing this in a mixer, a brick-like block is formed at a pressure of 1000 kg/ ^cm2 , and the green compact is embedded in coke powder and heated to approximately 950°C at a rate of 2°C per hour in a non-oxidizing atmosphere furnace. It was heated to obtain a fired body.

【table】

[Table] Comparative example Samples EF and G were blended with the raw material composition shown in Table 1,
It was created by the same method as in the example. The fired body thus obtained was processed into the shape of a vane for a commercially available dry type vacuum pump, and was installed in a vacuum pump at a rotation speed of 1240 rpm and a sliding speed of 10.
A sliding test was conducted for 3,000 hours under the conditions of m/sec, vacuum level of 400 mmHg, and number of vanes of 6, and the results of investigating the amount of wear on the vane height, abnormal metallic noise, sliding noise, and surface roughness of the pump casing. Shown in Table 2. These characteristics were measured during the course of the test, and the test was discontinued if it seemed difficult or pointless to continue the test. For the measurement results in Table 2, where the test time is less than 3000 hours, the time when the test was stopped is indicated, and the amount of wear is 3000 hours from the amount of wear at that point.
This is the value converted after hours.

[Table] It can be seen from Table 2 that the carbonaceous sliding material obtained in the example had a small amount of vane wear and had twice the life of the vane of the comparative example. The roughness of the casing surface of samples A, B, C, and D was 1 to 2 μm or less when finished, and the one using the carbonaceous material vane obtained in the example was different from the one using the vane of the comparative example. In comparison, it does not roughen the surface of the casing. Figure 1 shows the relationship between test time and blade wear amount.
Figure 2 shows an example of the casing surface roughness measurement results. As shown in Figure 1, the number of wear increases with time for Sample E, which is a comparative example, and this is shown in Figure 2 c.
This seems to be related to the progress of surface roughness of the casing shown in . On the other hand, as shown in FIG. 1, sample A of the example has a substantially constant wear coefficient, indicating steady wear. Furthermore, as shown in FIG. 2b, the surface roughness of the casing due to the use of sample A was unchanged from before use. From the above results, it can be seen that the vanes of the above examples are excellent as vanes for dry type vacuum pumps. According to the present invention, it is possible to obtain a carbon sliding material in which an optimal combination is selected that takes advantage of the characteristics of various raw materials, and since the carbonaceous sliding material has excellent lubricity, it does not roughen the sliding surface of the mating member. Since it has advantages such as wear resistance and low sliding noise, it can be widely used as a dry sliding member.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between test time and vane wear amount using a dry type vacuum pump, and Figure 2 is a diagram showing the surface roughness of the pump casing before and after the test, where 1 is before the test and 2 is the example. 3 is the surface roughness after the test of Comparative Example E.

Claims (1)

[Claims] 1. Artificial graphite mixture powder in which the ratio of coke-based artificial graphite powder to oil smoke-based artificial graphite powder is 90:10 to 50:50 by weight.
To 45 to 50 parts by weight, 1 to 4 parts by weight of talc, 4 parts by weight or less of natural graphite powder, and 45 to 55 parts by weight of tar pitch and/or coal tar as a binder are added, which is then combined, pulverized, shaped, and then fired. A method of manufacturing a carbonaceous sliding material.