JPS63282221A - Manufacture of composite sintered material - Google Patents

Abstract

PURPOSE:To develop a Cu-base composite material excellent in wear resistance even in lubricant free state, by mixing a graphite powder of a specific grain size whose surface is plated with Cu with a metallic powder mixture composed principally of Cu powder and by subjecting the resulting powder mixture to compacting, to sintering, and further to recompacting. CONSTITUTION:A uniform powder mixture consisting of, by weight, 3-20% of graphite powder which is coated with Cu by electroplating or electroless plating and in which aspect ratio and grain size are regulated to 4-8 and 50-400mum, respectively, and respective powders of Sn, Pb, Zn, Bi and Fe and the balance Cu powder is compacted at 4-7ton/cm<2> pressure into the prescribed shape. The resulting green compact is sintered at 700-850 deg.C, and the sintered compact is recompacted under 4-7ton/cm<2> pressure again. By this method, the Cu-base composite material in which graphite acts as solid lubricant and, as a result, which has superior wear resistance even in lubricant free state and is suitable for bearing, etc., can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to friction-free applications where it is difficult to introduce lubricating oil and which require wear resistance, such as non-lubricated pumps and various types of non-lubricated bearings. C with excellent wear resistance that can be used as a mechanical component
The present invention relates to a u-based composite material and a method for producing the same.

[Conventional technology]

In mechanisms that operate without lubrication, for example, there are self-lubricating materials as various bearing materials into which lubricating oil cannot be introduced. Examples of these materials include JP-A-51-45603, JP-A-56-13451, and JP-A-56-16973.
No. 9, etc., and is a wear-resistant material containing graphite and molybdenum disulfide, which are solid lubricants.

However, the manufacturing method of an optimal wear-resistant sintered material based on the relationship between the aspect ratio of graphite powder particles, which is a solid lubricant, and wear characteristics has not been studied or considered yet.

[Problem that the invention seeks to solve]

Further, in the conventional technology described above, when operated without lubrication, the molybdenum disulfide, which is a solid lubricant, changes in quality due to generation of excessive frictional heat, resulting in unstable wear characteristics.

An object of the present invention is to provide a method for producing a sintered material with excellent wear resistance that contains graphite as a solid lubricant and is sufficiently stable even in the absence of lubrication.

[Means for solving problems]

As a result of research into sintered materials with excellent wear resistance, the inventors used graphite, which has solid lubricating properties, as a component that imparts wear resistance to the outer surface of the carbon particles to ensure good wettability during sintering. Electrolytic and electroless Cu plating is applied to disperse Cu in the Cu matrix, and lead has a low melting point and provides wear resistance, and tin contributes to improving the overall mechanical strength of the sintered body.
zinc.

By making a composite material containing bismuth and iron, a material that satisfies the above objective wear resistance was obtained.

In addition, as a method for obtaining the composite material, a weight ratio of 3 to 2
0% by weight of Cu-plated graphite powder with a particle size of 50 to 400 μm, Su, and pb.

After uniformly mixing a composition in which Zn, Bi, and Fe are appropriately mixed and the remainder Cu, 4 to 7 ton/c! A compact is formed at a pressure of lf, and then the compact is heated to 700 to 850°C.
A sintered composite with excellent wear resistance is obtained by sintering at a temperature of We were able to develop a manufacturing method for the material.

[Effect]

The reason for limiting the composition and manufacturing method of the composite material of the present invention as described above will be explained.

During sintering, carbon acts as a solid lubricant without thermally decomposing, and has the effect of lowering the coefficient of friction and adhesion.
If the range is smaller, the effect of lowering the friction coefficient and preventing adhesion cannot be exhibited, resulting in a decrease in smearing and abrasion resistance. Moreover, if it exceeds 20%, the bending strength decreases significantly as shown in FIG. 4, making it unsuitable as a structural material. Therefore, it is necessary to keep the carbon content in the range of 3 to 20%. Furthermore, in order to obtain a composite material that has a particularly low coefficient of wear and high single bending strength, it is desirable that the amount of carbon be 3 to 6%.

Further, this carbon component can be mixed in the form of graphite powder or carbon fiber, and the particle size of graphite powder is 50 to 400.
μ is easily mixed, and the action of graphite as a solid lubricant is most effectively exhibited.

The carbon component is graphite powder to improve sinterability and bonding strength (wettability) with the matrix component (Cu).

Alternatively, it is necessary to coat the carbon fiber surface with Cu by electroplating or electroless plating.

First, as an example, looking at the effects of each powder component of the Sn-Pb-C copper-based sintered material, the tin component acts to improve the overall mechanical strength of the sintered body, but as shown in Figure 5. As is clear from the above, if it is less than 5%, there is no effect, and if it is more than 15%, it promotes embrittlement and the strength decreases.
A range of 15% to 15% is desirable, and a range of 8 to 10% is particularly favorable.

Since the lead component is a low melting point metal, it forms a lead skin without lubrication and prevents adhesion, and is particularly effective under high load conditions. A suitable amount of lead is 2 to 10%; less than 2% has no effect of improving conformability, that is, plastic fluidity, and more than 10% reduces the strength of the composite. Moreover, in the range of 3 to 5%, the best results in friction coefficient, galling resistance, and wear resistance are obtained due to the synergistic effect with the components.

Next, as mentioned above, C consisting of Sn, Pb, C and Cu
The technical/technical reasons for adding numerical limitations to the compaction pressure and sintering temperature in the manufacturing method of the u-based composite material are as follows.

After uniformly mixing the amount of each powder that satisfies the above composition range, 4 to 7 tons/a! The reason why powder compacting was performed at a pressure of This is because cracks occur in the molded product during the process, and the shape of the molded product is not maintained.

In addition, if it is 7 ton/a #1 or more, even if it is higher than that, the effect of improving the density and strength of the molded product cannot be expected to be large.

Next, the reason why the sintering temperature is set to 700 to 850°C is related to recompression molding, and this is because density and strength are low at temperatures below 700°C even if recompression molding is performed in that process. Further, even if the temperature is 850° C. or higher, no significant improvement effect in terms of density and strength is observed.

If the re-compression pressure after sintering is set to 4 to 6 ton/ai, the density and strength will be similarly low if it is less than ±4 ton/'cj, and even if it is 6 ton/a#, no significant improvement can be expected. It's for a reason. In addition, if we look at the changes in graphite powder and Cu-coated graphite in each process, that is, the aspect ratio of graphite particles in the direction of molding pressure (the ratio of the maximum crushed weight of graphite to the thickness with respect to pressure), Figure 2 shows that As shown, the relationship between the pressure during the -th molding and the aspect ratio of the graphite particles is about 4 to 8. In addition, the graphite particle size is 50~
After 400 μm. Figure 13 shows the pressure during recompression and the aspect ratio of graphite particles. Although there is no drastic change from the first time, the ratio is between 5 and 6, and the Cu coating is better than the untreated one. Also, the aspect ratio tends to be 1/3. This is because graphite powder not coated with Cu gets into each component powder particle during molding and deforms by directly receiving pressure stress, resulting in a large aspect ratio. but,
In the case of Cu-coated graphite, the aspect ratio becomes small because the Cu coating firmly protects the graphite against the pressure during molding and can also be firmly bonded to other powder component particles.

Next, 5n-Zu-C, 5u-Pb-Zu-CeP b
Looking at the effects of each powder component of the copper-based sintered material -B i -C-F e -C, the zinc component, like tin,
It becomes a sintered alloy, and brass is alloyed with bronze to form a copper-zinc-tin alloy, increasing the strength of the base and improving wear resistance due to the synergistic effect with graphite. The amount is 1 to 10
Good weight percentage.

Next, like the lead component, the bismuth component is a low melting point metal, so it forms a skin of lead and bismuth in the absence of lubrication to prevent adhesion. The amount is preferably 1 to 3% by weight.

Next, iron is dispersed in the sintered alloy without forming a solid solution, increasing the hardness and strength of the base. The amount should be 0.5 to 2 times the weight.

Having described the effects of each component, the technical reasons for adding numerical limitations to the compaction pressure and sintering temperature in the manufacturing method of the Cu-based composite material of each composition are as follows.

First, regarding the powder compaction pressure, the sintered compacts of each composition can be used at a pressure of 4 to 7 ton/a under the same conditions as described above for the 5u-PbC copper-based sintered material. Good range. Further, a sintering temperature of 700 to 850°C is sufficient, and a repressing pressure of 4 to 6 ton/d after sintering is sufficient. The aspect ratio of the graphite powder in this case also shows approximately the same ratio.

Next, there is a correlation between the size of graphite powder and its wear characteristics.
For example, if the size of the graphite powder is 50 μm or less, the coefficient of friction will be high, the amount of wear will be large, and the lubricating effect of graphite will not be exhibited. Furthermore, if the particle size exceeds 400μ, the mixed powder tends to segregate, making uniform dispersion difficult and resulting in poor wear resistance. Therefore, the optimum graphite particle size is 50 to 400 microns.

【Example〕

<Example 1> Table 1 shows the chemical composition of the materials used in this example.

In Table 1, samples Na 1 to Nα8 satisfy the requirements defined by the present invention, and Arashi 9 to 17 contain Su and Pb.

Any of C is a comparative material outside the range defined by the present invention. After mixing the raw material powders having the chemical compositions shown in Table 1 (next page) in a V-type mixer for 30 minutes,
It was molded at a pressure of 5 tons/al, sintered at 760°C, and then re-press molded at a pressure of 5 tons/al. Figure 1 shows the galling wear resistance limit surface pressure of the sample. J
I! The rubbing conditions were as follows: eutectic cast iron (Fe12) was used as the mating material, the atmosphere was air, and the friction surface pressure was changed as appropriate. As is known from this result, the galling wear resistance limit surface pressure of the invention material is higher than that of other materials, and it can be seen that when Su and C (graphite) are less than the invention composition range, the galling limit surface pressure is low.

<Example 2> Table 1 Figure 2 shows the friction coefficients obtained when ct was varied in a composite material of Su: 9%, Pb: 4%, Cu and C. The manufacturing methods for these composition materials are the same as those for the invention materials of Examples. Moreover, the wear test conditions are also the same.

In Su, Pb, Cu, and C composite materials, between c-t and friction coefficient, the friction coefficient shows a constant value at C-f+t 3% to 15%, but below 3%, the friction coefficient shows a constant value. It can be seen that even if the friction coefficient is large, or 20% or more, the friction coefficient becomes similarly high and unstable.

Figure 3 shows the relationship between the coefficient of friction when the amount of pb is changed in the same (Su, C, Cu and Pb composite material).The relationship between the amount of pb and the friction coefficient is Pbt: 3~
It can be seen that the friction coefficient is the lowest in the range of 5% and is stable, showing an approximately constant value, but the friction coefficient increases in other areas.

<Example 3> Figure 4 shows C in the same test piece as the sample shown in Figure 2.
This shows the relationship between the amount and bending strength.

As is clear from this, the strength decreases as the C:t increases, and decreases rapidly when the C content exceeds 20%. Therefore, in terms of strength, it can be seen that the C content is preferably 20% or less, preferably 10% or less.

Figure 5 shows Su added to Pb: 4%, C: 5%, and Cu.
This figure shows the relationship between the amount of Sum and the bending strength. The bending strength decreases as the amount of Su increases, but
It can be seen that when it exceeds 15%, the rate of decrease becomes large and this is not a desirable state.

From the above results, in a composite material made of Su, Pb, C and Cu, the maximum content of Su, Pb and C is Su:15
%, Pb: 10%, and C: 20%.

<Example 4> Figures 6 to 8 show the compounding ratio of Su: 9% and Pb.
4%, C: 10%, and residual Cu composition materials, and the manufacturing method and characteristics thereof are shown. Figure 6 shows the following manufacturing process: forming (5 ton/cd) - + sintering (760°C) → repressing (5 ton/al), changing the forming process from 2 to 1° ton/cj, and increasing the strength. This study investigated the relationship between density and density. From this result, if the molding pressure is less than 3 ton/aJ, the shape of the molded product cannot be maintained in the manufacturing process, and if the molding pressure is 7 ton/a# or more, neither strength nor density is improved.

Figure 7 shows the process of forming (5 ton/a#) → sintering → repressing (
5 ton/cxl) shows the relationship between strength and density when the sintering temperature is changed from 600 to 950°C. Both strength and density are low at sintering temperatures of 700°C or lower, but at 750°C to 850°C
℃, both strength and density are high, but 8
It can be seen that the strength does not reach an upper limit even when the temperature exceeds 50°C.

Figure 8 shows molding (5 tons/cal) → sintering (760
℃) → In the recompression molding manufacturing process, the recompression molding pressure is increased by 2 to
Showing the relationship between strength and density when changing from n/d to 10 ton/ad, both strength and density are low when the recompression pressure is 4 ton/csJ or less, and when the recompression pressure is 6 ton/a# or higher. It can be seen that both the strength and density show approximately constant values.

<Example 5> Figures 9 and 10 show the compounding ratio of Su: 9%.

The relationship between the particle size of C, strength, and density when produced by the invention manufacturing method of Example 1 is shown for Pb: 4%, C: 5%, and residual Cu composition material.

Looking at the relationship between the particle size of C and the coefficient of friction in Figure 9, we find that C
When the particle size is 50 μm or less, the friction coefficient shows a high value, but from 50 to 400 μm, the friction coefficient remains constant and low.

However, it can be seen that when the particle size becomes larger than that, a high value is obtained, which is not good.

Looking at the relationship between the cm diameter and strength and density in Figure 10, it can be seen that when the C grain size becomes less than 50μm and more than 400μm, the bending strength decreases significantly.The results above 0 indicate that the maximum C grain size The size is limited to 400μ,
In view of the coefficient of friction, the minimum size is preferably 50μ.

Looking at the results of the dry type seizure test shown in Figure 11, when comparing each combination in the dry type, it can be seen that the seizure resistance is better than the three types of sintered oil-impregnated bearing materials of the JIS standard, and is about five times better.

Figures 12 and 13 show molding pressure and graphite particle size of 50 to 40.
It shows an aspect ratio of 0 μm, and the Cu-coated graphite has a molding pressure of 4 to 7 tons/aJ and a remolding pressure of 4 to 7 tons/aJ.
When carried out at 6 ton/ad, the aspect ratio of graphite coated with Cu is 5 to 7, which indicates that the aspect ratio is smaller than that of graphite not coated with Cu.

Figure 14 shows graphite-containing C produced in Figures 12 and 13.
The results show the results of a friction and wear test using a U-based sintered composite material. From these results, the molding pressure was 4 to 7 ton/aJ.
, the friction coefficient and wear amount of the copper-coated graphite and uncoated graphite-containing sintered composite materials obtained at 4 to 6 ton/cwt using a thin acid type pressure crab are as follows. It turns out that the material is better.

〔Effect of the invention〕

According to the present invention, a Cu-based composite material has been developed that has excellent wear resistance even under no lubrication conditions, which was not possible with conventional materials, and has excellent wear resistance even under oil lubrication.
The base composite material can be stably obtained industrially.

[Brief explanation of drawings]

Claims (1)

[Claims] 1. In a graphite-containing Cu-based composite sintered material containing Su, Pb, Zn, Bi, Fe and coated graphite powder, with the remainder being substantially Cu, the aspect of graphite in the sintered body A method for producing a composite sintered material with excellent wear resistance, characterized in that the ratio is in the range of 4 to 8. 2. The method for producing a composite sintered material according to claim 1, wherein the amount of graphite in the composition is 3 to 20% by weight, and the particle size is 50 to 400 μm. 3. The method for producing a composite sintered material according to claim 1, wherein the graphite in the composition is Cu-coated graphite formed by electroplating or electroless plating. 4. After uniformly mixing the mixed powders of each powder combination described in claim 1, a compacted body is formed at a pressure of 4 to 7 tons/cm^2, and then the compact is formed at a pressure of 700 to 850 tons/cm^2.
A method for producing a composite sintered material, which comprises sintering at a temperature of 0.degree. C. and then repressing at a pressure of 4 to 6 tons/cm^2.