JP2517675B2 - Sintered copper alloy for high load sliding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sintered copper alloy suitable for a bearing component that slides under a high load.

[Conventional technology]

Sintered alloys for sliding such as plain bearings have been widely used for a long time since tin bronze materials have been used since they have good sliding characteristics and are easy to manufacture. Further, for high surface pressure, there are materials to which solid lubricants such as lead, graphite and molybdenum disulfide are added.

By the way, when comparing the maximum surface pressures that do not cause seizure within a predetermined time at a constant sliding speed for the main copper-based materials, it is known that the latter is higher in the order of brass, tin bronze, and aluminum bronze.

For example, the mating material is 0.4% C carbon steel and the sliding speed is 90m.
The seizure resistance limit surface pressure of various oil-impregnated sintered copper alloys when sliding at a speed of approx./min is about 60 kgf / cm ^{2 for} brass or tin bronze,
Aluminum bronze is about 80 kgf / cm ² , and aluminum bronze is preferable as a sliding material for higher loads.

Aluminum bronze alloys are also excellent in corrosion resistance, and in the case of ingot materials, practical aluminum bronze alloys to which Ni, Fe, Mn are usually added in order to improve mechanical properties are known.

[Problems to be Solved by the Invention]

As mentioned above, the sintered aluminum bronze alloy has excellent wear resistance even under relatively high surface pressure, but the higher 100 kgf / cm ²
If it is slid with a certain surface pressure, it will seize in a short time.

For example, as seen in sintered oil-impregnated bearings, it is difficult to form a lubricating oil film on the sliding surface at the time of starting, resulting in metal contact, causing abrasive wear (scratch wear) or adhesive wear, and eventually seizure. To be

The present invention is to obtain a sintered aluminum bronze alloy capable of withstanding a surface pressure of 100 kgf / cm ² or more.

[Means for solving the problem]

The present inventors, as a result of repeated studies to solve the above problems, have reached the present invention, the present invention contains Al: 6-15 wt%, Co: 1-10 wt%, The balance is Cu
And a sintered copper alloy for high-load sliding, comprising at least one unavoidable impurity and having a Co phase interspersed in a copper-aluminum alloy matrix, at least one of Ni, Fe or Mn, The above-mentioned two types of high-load sliding sintered copper alloys containing at least 2% by weight in total and at least one of graphite and boron nitride in a total amount of 1 to 5% by weight. The present invention provides a copper alloy.

[Action]

 The limited use of the composition in the present invention will be described below.

Al alloys with Cu. If the Al content is less than 6% by weight, the mechanical strength is low, plastic flow easily occurs during high surface pressure sliding, and the pores on the sliding surface are closed, making it difficult to supply the lubricating oil impregnated in the pores. Become.

On the other hand, when it is added in excess of 15% by weight, the precipitation of γ ₂ phase increases, the copper-aluminum alloy matrix becomes brittle, and the mating material tends to be easily worn.

Cobalt acts to prevent the abrasive wear when it is scattered in the copper-aluminum alloy base without being completely dissolved. The size of the cobalt phase scattered is not particularly limited, but in consideration of making the mating material less likely to be worn, it is preferable that the particle size be as small as several μm rather than several tens μm.

If the cobalt content is less than 1% by weight, the abrasive wear resistance is insufficient, and even if it exceeds 10% by weight, the cost is not expensive.

The aluminum bronze alloy base containing Ni, Fe or Mn is tougher than the Cu-Al alloy base and has further improved surface pressure resistance.

Ni, Fe and Mn alloy with Al and Cu, respectively, to strengthen the matrix.

Further, Ni, Fe and Mn have the property of expanding the α phase region and suppressing the precipitation of the γ ₂ phase to impart toughness, and Mn makes the crystal grains finer and improves the strength.

The addition method is performed in the form of a copper alloy powder containing Ni, Fe or Mn, or an aluminum bronze alloy powder, which is an industrial commercial aluminum bronze alloy Cu-Al-Fe alloy system or Cu-Al-. Fe-Ni
The -Mn alloy system is preferred.

However, the total amount of Ni, Fe and Mn added is 10% by weight.
Aluminum bronze alloy powders exceeding 10% have high hardness and poor powder formability, so considering the powder formability, aluminum bronze alloys with a total addition amount of these three elements of 10 wt% or less, for example, 50% Al -Used by mixing with Cu alloy powder and copper powder, and the mixed amount should be 20% by weight or less. Therefore, the total content of Ni, Fe, and Mn in the sintered copper alloy is set to 2% by weight or less.

Graphite and boron nitride act as solid lubricants. Sintering of aluminum bronze alloys is usually performed in vacuum. Molybdenum disulfide is easily decomposed during heating, whereas graphite and boron nitride are not decomposed during heating. If the addition amount of each of graphite and boron nitride is less than 1% by weight, the improvement of lubricity is small, and if it exceeds 5% by weight, the strength of the material decreases.

〔Example〕

Below, it demonstrates in comparison with the comparative example of the Example of this invention.

 The following raw material powders were prepared.

(1) 50% Al copper alloy powder, grain size 350 mesh or less (2) 10% Al-4% Fe copper alloy powder, grain size 350 mesh or less (3) 10% Al-3% Ni-4% Fe-1% Mn copper alloy Powder Particle size 350 mesh or less (4) Cobalt powder Particle size 350 mesh or less (5) Copper powder Particle size 100 mesh or less (6) Tin powder Particle size 250 mesh or less (7) Graphite powder Particle size 100 mesh or less (8) Boron nitride powder particle size 350 mesh (9) Molybdenum disulfide powder with a grain size of 350 mesh or less These powders are mixed so as to have the composition shown in Table 1, compacted into a bearing having a predetermined size, and then in vacuum at a temperature of 950 ° C. After sintering, normal sizing was performed and turbine oil was impregnated into a sample. The dimensions of the sample are 10 mm inside diameter, 16 mm outside diameter, and 10 mm total length.

The tin bronze of sample No. 29, which is a comparative example, was sintered in an ammonia decomposition gas.

The structures of the sintered aluminum bronze alloy bases of sample numbers 1 to 28 are
Precipitates that are considered to be the κ phase are observed in Sample Nos. 11 to 18 that exhibit the α phase.

In addition, the cobalt-added sample has gray-blue cobalt particles scattered in the matrix, and sample Nos. 19 to 28 show solid lubricants near the grain boundaries.

In addition, in sample numbers 14 to 18, the compressibility of the mixed powder gradually deteriorates from sample number 14 to 18,
In No. 18, molding workability was not preferable.

Next, a bearing durability test was conducted on each sample. Using a rotating shaft obtained by heat treatment of S45C carbon steel, the surface pressure at which the friction coefficient sharply rises was calculated by increasing the surface pressure at a sliding speed of 94 m / min. The results are shown in Table 1 as the limit surface pressure. The normal friction coefficient during operation is 0.02 to 0.04.

As shown in Table 1, the alloys according to the present invention and the alloys containing Ni, Fe, Mn and the solid lubricant are higher than the tin bronze of the comparative example and the aluminum bronze containing too little or too much aluminum or cobalt. You can see that the surface pressure does not cause seizure.

[Effects of the Invention] As described above, the sintered alloy of the present invention is more excellent in load bearing capacity than conventional aluminum bronze or tin bronze, and therefore, a starter bearing of an internal combustion engine to which a high load is applied at the time of starting, etc. , The life of sliding parts can be improved, and
It is possible to expand the use to high load sliding parts.

Claims (3)

(57) [Claims] 1. A composition comprising Al: 6 to 15% by weight Co: 1 to 10% by weight, the balance being Cu and inevitable impurities, and having a structure in which a Co phase is scattered in a copper-aluminum alloy matrix. Sintered copper alloy for high load sliding characterized by 2. At least one of Ni, Fe or Mn
The sintered copper alloy for high-load sliding according to claim 1, which contains 2% by weight or less in total. 3. The sintered copper alloy for high load sliding according to claim 1, which contains at least one of graphite and boron nitride in a total amount of 1 to 5% by weight.