JPS591781B2 - Porous aluminum sintered alloy sliding member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a porous aluminum sintered alloy sliding member.

Conventionally, sintered alloy sliding members mainly made of aluminum have advantages such as relatively excellent speed characteristics, corrosion resistance, and light weight, but on the other hand, they have poor mechanical strength, wear resistance, There are problems such as insufficient load resistance and difficulty in setting sintering conditions, and satisfactory results are not always obtained.

This invention has succeeded in greatly improving these conventional problems, and the weight ratio is 0.5 to 6% copper, 0.2 to 2% magnesium, 5 to 30% silicon, The present invention provides a porous aluminum sintered alloy sliding member comprising 0.5 to 8% of a boron compound selected from boron sesquioxide, borax, colemanite, and boronatrocalcite, and the balance aluminum. A sliding member whose conformability and seizure resistance are further improved by adding 10% or less of one or both of tin and antimony to the above components, and/or 20Cfl7 or less of lead as an alloying component. It can also be provided as

The porous aluminum sintered alloy sliding members described above are all characterized by being able to be sintered in the atmosphere and having excellent mechanical strength.

Regarding this invention, especially regarding the fact that it contains a large amount of silicon, the inventors of the present invention et al.
As already disclosed in detail in the invention related to No. 1-35364, the present invention is capable of improving moldability as well as improving sliding properties such as seizure resistance and load resistance as a sliding member.

If the silicon content is less than 5% by weight, the present invention does not improve the load resistance, resistance, and seizure resistance, making it difficult to use as a sliding member.

When the content is around 10% by weight, both the Rockwell hardness and the radial crushing strength constant show maximum values, but when the content is increased beyond that, these values gradually decrease. The inclusion of silicon also increases the porosity (expressed in this invention by oil content) of the sintered alloy.

. In particular, the oil content increases almost linearly when the silicon content is around 10% by weight, but the upper limit was set at 30% by weight in view of the reduction in mechanical strength. Regarding boron compounds, boron sesquioxide (B2O3), borax (Na
2B407・10H20), Colemanite (Ca, B,
O,... 5H, O), pandermite (Ca, B6O
ll-3H20), boronatrocalcite (CaB4O
7.NaBO, .6H,0), etc. are used, but boron sesquioxide and borax are particularly effective.

When using a borate containing water of crystallization, it is important to remove all the water of crystallization before use. Otherwise, the effect will not appear. The boron compound has the effect of improving the sinterability of the green compact and significantly increasing the mechanical strength of the sintered alloy. According to the inventor's experiments, boron sesquioxide has 0
．． Effects are already visible when around 5% by weight is added, and 2% by weight
It was confirmed that the before and after additions also contributed to the improvement of mechanical strength, and the strength increase was approximately twice that of the one without additives. If more than 2% by weight is added, the strength will begin to decrease, and if around 10% by weight is added, the strength will be the opposite of that of an alloy without boron sesquioxide.

The boron compound mentioned above has the effect of dissolving metal oxides and also has the effect of preventing the oxidation of components during compact sintering, so it improves the sinterability of aluminum powder, especially in the atmosphere. It is thought that this makes sintering possible, but an even greater effect is that it promotes the diffusion of copper and magnesium and/or a compound of magnesium and silicon (Mg2Si) into the aluminum.
By making the alloy structure uniform, the present inventor confirmed this fact as a result of analysis using an X-ray microanalyzer.

In other words, in the case of alloys without the addition of boron compounds, for example, copper components are present in large quantities at the grain boundaries in the sintered alloy or around the board, but when such compounds are added, the distribution of copper becomes extremely uniform, and the copper component in the aluminum becomes more uniform. It was confirmed that the spread was progressing smoothly.

Therefore, it can be considered that the strength of the sintered body is significantly improved due to the degree of alloying strength of the sintered body. The addition of this boron compound also tends to increase the porosity of the sintered body.

The effect on mechanical strength is slightly different, and there is no significant change when added up to about 2% by weight, but as the amount added is further increased, the oil content gradually increases. However, as mentioned above, when 10% by weight of boron compounds is added, the strength decreases to almost the same level as that without additives or even lower.
In consideration of this strength, 0.5 to 8% by weight, especially 1 to 8% by weight.
The content is preferably 6% by weight. The copper component contributes to improving the strength of the alloy. In the composition of this invention,
If it is less than 0.5% by weight, it has almost no effect, and if it exceeds 6% by weight, it tends to make the material brittle, so the amount added is set to 0.5 to 6% by weight. The magnesium component coexists with copper and contributes to improving the mechanical strength of the alloy.

Magnesium also contributes to the age hardenability of the aluminum sintered alloy in the form of silicon and Mg2Si. In the composition of the present invention, if it is less than 0.2% by weight, there is almost no effect, and if it exceeds 2% by weight, the strength will decrease and the sinterability will deteriorate. The tin, antimony, and lead components contribute to improving the conformability and seizure resistance of the alloy as a sliding member.

Tin and antimony are used individually or in a total amount of 0.
The content is preferably 3 to 10% by weight. The effect of addition is not clear below 0.3% by weight.

Moreover, if it is added in an amount exceeding 10% by weight, the strength of the alloy will be reduced. When lead is added in an amount of 5 to 20% by weight, it not only contributes to improving conformability but also improves seizure resistance.

If it is less than 5% by weight, the effect of addition is poor in reproducibility, and if it is added in excess of 20% by weight, the strength of the alloy will be impaired.

These metal components that contribute to improving conformability and seizure resistance can be used alone or in combination of two or more, depending on the purpose of use.

When obtaining the sintered alloy of the present invention, the compacting pressure is preferably 1 to 5 tons/C77l, particularly 2 to 4 tons/~.

When the molding pressure is increased, the mechanical strength such as the radial crushing strength constant improves, but the porosity (oil content) decreases. Sintering temperature is 5
The temperature is 50 to 640°C, which is below the melting point of aluminum,
Sintering time is 5-60 minutes.

Sintering may proceed in a neutral or cyclic atmosphere, but the feature of this invention is that sintering can be performed in the atmosphere, and the mechanical strength of the obtained sintered body is moderate. This means that there is no significant difference compared to those sintered in a neutral or cyclic atmosphere. Furthermore, even when compared to an aluminum sintered alloy of a similar composition that does not contain a boron compound, its strength is significantly greater despite being sintered in the air.

In air sintering, there is no benefit in taking too long a sintering time.

It is desirable to rapidly proceed with sintering in a furnace adjusted to a predetermined temperature. The mechanical strength of the sintered body almost reaches its maximum strength after about 30 minutes of sintering time. The outer surface of the obtained sintered body is also almost comparable to that of one sintered in a neutral or reducing atmosphere.

The table shows how the radial crushing strength constant and elongation content are affected when the content of boron sesquioxide as a boron compound is changed using 4% by weight of copper, 0.5% by weight of magnesium, and 10% by weight of silicon. This is what is shown.

The molding pressure was 3 tons/o/l, and the sintering conditions were 580°C in the air.
It was sintered for 10 minutes in a furnace maintained at a temperature of ±10°C. As described above, the porous aluminum sintered alloy sliding members of the present invention (black 2 to black 8 in the table above) have high mechanical strength and excellent sliding properties, and are easy to sinter in manufacturing. It has the advantages of being able to be sintered in the atmosphere without the need for special atmosphere adjustment.

The following description will be made based on examples.

(Example 1) 4% by weight of electrolytic copper powder passing through 200 meshes, 0.5% by weight of agnesium powder passing through 200 meshes, 10% by weight of silicon powder passing through 250 meshes,
2% by weight of boron sesquioxide powder passing through 200 meshes
, and the remainder is atomized aluminum powder that passes through 250 meshes, and a small amount of lubricant such as lauryl alcohol and zinc stearate '2 for all alloy powders.
% by weight), the resulting mixed powder was compacted in a mold at a compacting pressure of 3 tons/d, taken out from the mold, and placed in a furnace maintained at a temperature of 580°C ± 10°C in the atmosphere. sintered for 10 minutes.

The radial crushing strength constant of the sintered alloy thus obtained was 20.5k9/
Md, oil content 3.2% by weight, initial coefficient of friction (μR) 0.
120, coefficient of friction in steady state (μc) 0.100
Met.

(Example 2) Borax was used instead of boron sesquioxide as a boron compound.
Sodium tetraborate obtained by baking at 00℃ and removing crystallization water (
A sintered alloy was obtained in the same manner as in Example 1 by pulverizing Na2B4O7) into a powder that passed through 200 meshes and adding 2% by weight of this powder.

This material has a radial crushing strength constant of 16.0 kg/M77f, an oil content of 3.0% by weight, and a μRO. l2O, μCO. It was lOO. (Example 3) Copper, magnesium, silicon, boron sesquioxide in Example 1
A sintered alloy was obtained in the same manner as in Example 1, using the same blending ratio as above, adding 2% by weight of crushed tin powder that passed through 250 meshes and using the remainder as aluminum powder.

This product has a constant radial crushing strength of 19.0 kg/Md, an oil content of 3.0% by weight, and a μRO. They were llO, μCO, and O95. (Example 4) In Example 3, 2% by weight of antimony powder that passes through 250 meshes was added in place of the tin powder, and the remainder was made into aluminum powder, and a sintered alloy was obtained in the same manner.

This product has a radial crushing strength constant of 18.5 kV and an oil content of 3.0.
Weight %, μRO. llO,μCO. It was O95. (
Example 5) In Example 3, 250 ml of tin powder was used instead of tin powder. 10% by weight of the lead powder passing through the thread was added and the remainder was made into aluminum powder, and a sintered alloy was obtained in the same manner.

This product has a radial crushing strength constant of 14.0 kg/M7l, an oil content of 2.7% by weight, and a μRO. O95, μCO. It was O9O. As a comparative example, a mixed powder consisting of the sintered alloy of cliff 1 shown in the table above, ie, 4% by weight of copper, 0.5% by weight of magnesium, 10% by weight of silicon, and the balance aluminum was molded under the same conditions as in the example.・The radial crushing strength constant of the sintered alloy obtained by sintering is 9.5 kg/7n7i, oil content 3, 1% by weight,
μRO. l5,μCO. It was l2.

Further, as a comparative example of Example 3, the sintered alloy disclosed in the prior art Japanese Patent Publication No. 47-32163 was adjusted to have the same composition as Example 3, that is, 4% by weight of copper and 0.0% by weight of magnesium. 5% by weight, 10% by weight of silicon, 2% by weight of tin, and the balance aluminum, and the sintered alloy obtained by molding and sintering this under the same conditions as in the example had a radial crushing strength constant of 18.
5k9/M7i, oil content 1.5% by weight, μRO. l3,
μCO. It was hot. Oxidation was observed in the sintered alloys of these comparative examples during sintering.

In addition, μR and μc shown in each example and comparative example are measured at a circumferential speed of 20 m/day and a load of 10
The results of a test using a thrust friction and wear tester using carbon steel for machine structures as a mating material at 0 kg/C-FL are shown below.

It can be seen that the sintered alloys of the examples described above have high mechanical strength and excellent sliding characteristics when compared with the comparative examples.

In addition, although the method of sintering the mixed powder after molding was described in the example, depending on the intended use of the sintered alloy, it is possible to achieve even higher density and higher density by adopting a method of proceeding with sintering while applying pressure. It is also possible to obtain a strong sintered alloy.

Claims (1)

[Claims] 1. Copper 0.5-6%, magnesium 0.2-2% by weight
%, silicon 5-30%, boron sesquioxide, borax, colemanite, boronatrocalcite 0.5-8%, and the balance aluminum. 2 Copper 0.5-6%, magnesium 0.2-2% by weight
%, silicon 5-30%, the total amount of one or both of tin and antimony is 10% or less, and/or lead 20% or less, boron sesquioxide, borax, colemanite,
Boron compound selected from boronatrocalcite 0.
A porous aluminum sintered alloy sliding member consisting of 5 to 8% aluminum and the balance aluminum.