JPS5849484B2 - Method for manufacturing self-lubricating graphite parts - Google Patents

Description

[Detailed Description of the Invention] This invention uses only natural graphite powder as a raw material powder without containing any binder or any other ingredients, and moreover, it is molded without any firing or graphitization treatment. , density 1. with pressure molding only. 9 f/ffl or more,
The present invention relates to a method for manufacturing a self-lubricating graphite member having a radial crushing strength of 0.5 kg/mA or more.

Conventionally, graphite members generally contain one or more of artificial and/or natural graphite powder, coke powder, carbon black powder, etc., and one or more of tar, pitch, synthetic resin, etc. After blending and mixing a binder consisting of at least one species, and then applying pressure thereto to produce a press-molded body, the press-molded body is heated to a temperature of iooo to
Calcinate at 1500℃, and further increase the temperature to about 280℃ if necessary.
It is manufactured by graphitizing at around 0°C.

As described above, the conventional manufacturing of graphite members requires processes such as mixing, firing, and graphitization treatment, which not only lengthens the manufacturing process but also requires various types of equipment.
Higher costs cannot be avoided.

In addition, conventional graphite members have a friction coefficient of 0.1
Because the bearing is as high as ~0.3, it can only be used as a normal oil-impregnated bearing, and it can be used for household electrical appliances, acoustics, automobiles, etc.
Moreover, it cannot be applied as a bearing for office machines, etc., and its surface roughness is about 50μ, making it unsuitable for use as a sliding member.

Furthermore, conventional graphite members had poor machinability, so
Even when manufacturing general oil-impregnated bearings that require dimensional accuracy of S7 class or higher, the required dimensional accuracy cannot be satisfied.

The present inventor conducted research to solve the above-mentioned drawbacks of conventional graphite members in terms of manufacturing and properties.
When only commercially available natural graphite powder with a particle size of 50 mesh or less is used as a raw material powder and a graphite member is manufactured from this only by pressure molding, the natural graphite powder has poor fluidity and cannot be press molded. Since it is difficult to fill the powder into the die and the apparent density is low, a large filling depth is required during press forming, resulting in a large density at the top, center, and bottom of the formed graphite member. However, (a) when the natural graphite powder is mixed with a 2 ~1. O ton /
In this case, it is difficult to fill the powder into the molding die due to the poor fluidity of the natural graphite powder, and the primary pressure molded body is manufactured with a pressure of crrt. The problem of local density differences and the occurrence of slips and cracks still remains, but the difficulties in powder filling can be solved by using a forming die with a diameter as large as possible, and Density differences, slips and cracks will be pulverized in the next step, so there will be no problem.
A secondary powder is produced by crushing it to have a particle size distribution in which 70% by weight or more has a particle size within the particle size range of esh;
on /cwtJJ. ．． When a graphite member is manufactured only by pressure molding at the above molding pressure, the graphite member has 1
．． Density of 997 crl or more and 0. Knowledge that it has a radial crushing strength of 5 kg/1 or more, has significantly superior surface roughness and dimensional accuracy compared to conventional graphite members, and shows good results in practical use even when used as a sliding member. I got it.

Therefore, this invention has been made based on the above knowledge, and the reason for limiting the numerical values as described above will be explained below.

(l) Pressure force of the primary press-formed body is 0. If the pressing force is less than 2 ton/crtf, the interparticle bonding force of the primary press-formed product will be weak, and many of the particles will return to the starting particle size in the next step of pulverization, resulting in 2 particles having the desired particle size range.
On the other hand, 1. O ton /
If the pressing force exceeds cnl, the interparticle bonding force in the primary compacted body will become too strong and more energy than necessary will be required for the secondary powder compaction, so the pressing force should be reduced to 0. 2 ~1. O ton /crtl
It was determined that

(2) Particle size distribution of secondary powder If fine particles with a particle size exceeding 200 mesh are contained in a large amount exceeding 30%, the difficulty in powder filling as described above,
In addition, problems such as density differences, slips, and cracks occur, and on the other hand, if the coarse particles with a particle size of less than 20 mesh exceed 30%, the powder filling into the forming die becomes uneven and the density balance is lost. Therefore, the particle size distribution of the secondary powder was limited so that 70% or more of the powder had a consistency within the particle size range of 20 to 200 mesh.

(3) The density and radial crushing strength or pressing force of the graphite member are 0. If it is less than 5 ton/crA, the density of the graphite member will be less than 1.9 flI, and the bonding force between particles will be insufficient, making it impossible to secure a high radial crushing strength of 0.5 kg/xi or more, and the graphite member will have a density of less than 1.9 fl. When assembling and handling the parts, chipping may occur at the edges, so by pressure forming with a molding force of 0.5 ton/cat or more, the density can be reduced to t. 9
By setting P/d or more, it is possible to ensure a radial crushing strength of 0.5 kg/xlB or more.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 From Ceylon natural graphite powder with a particle size of 150 mesh or less, 0. A cylindrical primary press-molded body having dimensions of 80 mm in outer diameter and 30 mm in height was produced under a pressure of 5 ton/crti, and then the primary press-molded body was pulverized using a stamp mill. , secondary powders 1 to 3 having the particle size distribution of this invention (hereinafter referred to as secondary powders 1 to 3 of the invention)
Then, secondary powders 1 and 2 (hereinafter referred to as comparative secondary powders 1 and 2) having a particle size distribution different from that of the present invention were produced.

The particle size distribution of these secondary powders is shown in Table 1.

Next, from the above-mentioned secondary powders 1 to 3 of the present invention and comparative secondary powders 1 and 2, 0.2, 0.5, and 1. O
At a pressure of ton/cr/l, it was shaped into the shape shown in the schematic cross-sectional view in Figure 1, with a center hole diameter of 4.8 mmφ and an outer diameter of 1.
A bearing test piece (graphite member) having dimensions of a 1111φ ball and a height of 8 mm was press-molded.

In addition, when the bearing specimen was pressure-formed, the molding form was observed and the results shown below were obtained.

In other words, (a) When using Comparative Secondary Powder 1, the powder had good fluidity, but the powder supply to some of the upper and lower corners of the bearing specimen was insufficient, resulting in the formation of these parts. Moreover, the density was also non-uniform.

(b) In the case of using the secondary powder 1 of the present invention, the powder was uniformly and sufficiently supplied to some of the upper and lower corners of the bearing specimen, and a bearing specimen with uniform density was obtained.

(c) In the case of using the secondary powder 2 of the present invention, both the fluidity and moldability of the powder were good, and bearing specimens could be manufactured in ideal conditions.

(d) When using the secondary powder 3 of the present invention, some powder flying was observed, and the workability was slightly worse (although the formability was good and bearing specimens with uniform density were obtained. .

(e) When Comparative Secondary Powder 2 was used, the fluidity of the powder was poor and it was difficult to fill the powder into the molding die, making it impossible to obtain a satisfactory bearing specimen.

From the above observation results, graphite members can be pressure-molded without any problems if the secondary powder of the present invention, which has a particle size distribution in which 70% or more is within the -20+200 mesh particle size range, is used. On the other hand, it is clear that it is extremely difficult to manufacture a graphite member from a comparative secondary powder having a particle size distribution that deviates from the above particle size distribution.

Next, present invention 2 in which pressure molding was performed in a satisfactory state
The density and radial crushing strength of bearing specimens using the following powders 1 to 3 were measured, and the measurement results are shown in Table 2.

From the measurement results shown in Table 2, 0. 2 tons/
At a pressing force of crA, the radial crushing strength of the obtained bearing specimen was 0.
．． 1 2 ~ 0. It has a low weight of 15 kg/yni and cannot withstand use as a bearing, and generally has a minimum weight of 0.1 kg/yni to be used as a bearing. Since a radial crushing strength of 5 kg/ml is required, 0. 5 tons/crA
It is clear that it is necessary to mold with a pressure greater than the above.

Next, secondary powder 2 of the present invention, which had the best pressure molding properties,
From 1. A bearing specimen of the present invention (with a density of 1.94 f/cII and a radial crushing strength of 0.77 kg/ml) molded under a pressure of O ton/crrt was mixed with a binder and mixed according to a conventional method. Figure 2 shows a schematic diagram of a graphite bearing specimen (hereinafter referred to as a conventional bearing specimen) manufactured into the shape and dimensions shown in Figure 1 through the processes of pressing, firing, graphitization, and cutting. Using the practical test machine shown, (a) Bearing test piece mounting mode: horizontal no-load dry method, (b
) Rotation speed: 280Or. p. m. , (c) test temperature: 2-30°C, 20°C, 200°C, (d) test time: 1500 hours.A practical test was conducted under the following conditions.

In FIG. 2, 1 is a bearing specimen, 2 is a shaft having an outer diameter of 4.8 mφ on which the bearing specimen to be tested is mounted, 3 is a rotor, and 4 is a winding.

In this practical test, the test results shown in Table 3 were obtained.

Note that Table 3 also shows the states of water resistance, oil resistance, and water absorption.

As is clear from the results shown in Table 3, the bearing specimens of the present invention exhibit the same amount of wear, water resistance, and oil resistance as the conventional bearing specimens, while exhibiting lower noise, water absorption, and friction coefficient. It has better properties.

Example 2 From Ceylon natural graphite powder with a particle size of 150 mesh or less. A cylindrical primary press-molded body having dimensions of an outer diameter of 100 mm and a height of 25 mm was produced with a pressure of 7 ton/crA, and then the primary press-molded body was pulverized using a stamp mill. , +20mesh: O%, -20+60mesh: 6%, -60+100mesh: 22%, -1
0 0+1 5 0mesh: 3 5%, -1 5
0+2 0 0mesh: 2 3%, -2 0
0+2 5 0mesh: 1 2%, -25 0+
350mesh: 2%, -350mesh
2 with the particle size distribution of this invention consisting of: 0%, (more than % by weight)
The following powder was produced.

Next, from the above secondary powder, 1. A square graphite member (hereinafter referred to as the graphite member of the present invention) having dimensions of 1 1 mm x 2 6 ml x 7 mm was pressure-molded using a pressure of O ton/crA. 9 3?
It had a density of /air.

Next, the above-mentioned graphite member of the present invention and a graphite member of the same size (
(hereinafter referred to as conventional graphite member), using the testing machine schematically shown in FIG. 3, (a) Rotation speed of commutator: 2880 r. p. m. , (b) Circumferential speed of commutator:
1 1.9 1 m/see, (c) Spring pressure:
4 0 0? /crA, (d) PV value: 4 7
A wear test was conducted under the following conditions: 6 k9/crrr-m/sec, (e) Test time: 20 hours.

In Fig. 3, a is a graphite member, b is a commutator with an outer diameter of 79 mm that rotates in contact with the graphite member a to be tested, and C is a commutator for pressing the graphite member against the commutator. A spring body, b a bearing, e a stage pulley IJ-f a motor, respectively.

This abrasion test showed the test results shown in Table 4,
It is clear from Table 4 that the graphite members of the present invention exhibit superior wear resistance compared to conventional graphite members.

As mentioned above, according to the present invention, only natural graphite powder is used as a raw material powder without containing a binder or other components, and by performing only a pressure molding process on this powder, high density and high strength can be obtained. Furthermore, it is possible to manufacture a self-lubricating graphite member with a simple process and low cost, which also has superior noise characteristics, wear resistance, and water absorption properties compared to conventional fired graphite members.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a bearing to be subjected to a practical test, FIG. 2 is a schematic diagram of a practical test machine, and FIG. 3 is a schematic diagram of a wear test machine. In the drawings, 1...bearing specimen, 2...
・Shaft, 3... Rotor 4...
Winding wire, a... graphite member, b... commutator, C... spring body, d... bearing,
e... Stage pulley f... Motor.

Claims (1)

[Claims] 1. 0.2 to 1 from raw material powder consisting only of natural graphite powder
．． After producing a primary press-molded body at a pressing force of O ton/crA, 70% by weight or more of the primary press-molded body has a particle size within a particle size range of 20 to 200 mesh. A secondary powder is produced by pulverizing it so that it has a particle size distribution, and then the secondary powder is pulverized to have a particle size distribution of 0.000. Density is 1.9 f/d or more and radial crushing strength is 0 by only pressure molding at a molding pressure of 5 ton/crA or more.
．． A method for producing a self-lubricating graphite member, the method comprising producing a graphite member having an electric current of 5 kg/mA or more.