JP4757460B2 - Pb-free copper alloy composite sliding material with excellent seizure resistance - Google Patents

Description

  The present invention relates to a copper-based sintered sliding material. More specifically, the present invention relates to a Pb-free copper alloy composite sliding material having excellent seizure resistance.

  As the copper-based sliding material, a Cu—Pb alloy, a Cu—Sn alloy, or a Cu—Sn—Pb alloy sintered material is generally used. Pb in the copper alloy forms a low melting point phase, and Pb is melted by the temperature rise during sliding, and seizure resistance is ensured by the effect of cooling the sliding surface and the self-lubricating action of Pb. Other than Pb, there is a copper alloy composite sliding material to which a small amount of Ag is added as a component for preventing the copper alloy from adhering to the counterpart material during boundary lubrication (see Patent Document 1, US Pat. No. 6,348,114). ). A small amount of Ag reacts with S in the lubricating oil, and the Ag-S concentrated layer formed on the sliding surface due to frictional heat under boundary lubrication extends thinly on the sliding surface, suppressing adhesion between the shaft and the bearing. .

Copper alloys containing Pb are corroded by components in the lubricating oil, and the sliding properties are reduced. Moreover, since Pb is an environmentally hazardous substance, Pb-free requirements are high, but Cu and Cu—Sn alloys not containing Pb are inferior in sliding characteristics, particularly seizure resistance under boundary lubrication. In order to overcome this point, a sintered copper alloy which does not contain Pb and has improved sliding characteristics by adding a tribo material such as MoS ₂ is known as described later.
Furthermore, when an Ag-added copper alloy is slid under lubricating oil with a large amount of S, such as ATF or engine oil, Ag-S is generated on the surface. The effect of can not be fully demonstrated.

Patent Document 2 (Patent No. 3042539) proposes to use a sintered layer of Sn: 5 to 16%, MoS ₂ : 5 to 16% and the balance Cu as a sliding layer for automobile parts bushes and washers. Has been. MoS ₂ may be plated with Ni or Cu.

Also, a bushing material in which 1 to 10% of graphite, MoS ₂ and WS ₂ and at least 1 to 30% of hard materials such as Fe ₃ P and Fe-Ni are dispersed in a Cu-based sintered alloy (patented) Document 3, see Patent No. 3042539), and a bushing material (Patent Document 4, Patent No. 2974738) in which 1 to 10% graphite and 0.05 to less than 1% Al ₂ O ₃ are dispersed are also proposed. ing.

Patent Document 5 (WO96 / 27685) discloses a copper alloy having the following composition and excellent in sulfidation corrosion resistance. Essential ingredients: Ni: more than 5% and 50% or less, Ag: 0.1-2%. Optional component (1) Sn: 20% or less, P: 0.5% or less, Al: 5% or less, Si: 1% or less, Mn: 5% or less, Zn: 30% or less, Fe: 10% or less, Sb: 1 (2) Pb and / or Bi in a total amount of 30% or less; (3) MoS ₂ , WS ₂ , BN in a total amount of 30% or less; (4) 20% or less in a total amount Al ₂ O ₃ , SiC, SiO ₂ , Fe ₃ P, AlN, Si ₃ N ₄ , TiC, WC, BN, NiB; (5) S: 0.001 to 1%.
US Pat. No. 6,348,114 Japanese Patent No. 3013946 Japanese Patent No. 3042539 Japanese Patent No. 2974738 WO96 / 27685 publication

It has been found that the tribo material conventionally compounded with the copper-based sintered material has the following problems.
(1) MoS ₂ and WS ₂ : Sintering of copper-based sintered materials is generally performed in a reducing atmosphere, but MoS ₂ and WS ₂ may be partially oxidized even under such conditions. Are known. For this reason, the lubricating performance commensurate with the amount added is not exhibited. However, increasing the amount of MoS ₂ and WS ₂ added as a countermeasure decreases the strength of the copper-based sintered material.
(2) Graphite (graphite): Since graphite does not react with copper, it is originally used for copper alloy molds and the like, so it has poor compatibility with sintering to copper alloy. Therefore, the holding force in the copper matrix is weak, and there is a risk that the graphite particles fall off during sliding.
Therefore, an object of the present invention is to provide a copper-based sintered sliding material that can exhibit the same or better performance as a Pb-containing copper-based sintered alloy without adding a conventional tribo material.

The present invention, in mass percentage, Sn: 20% or less, P: contained 0.5% or less, further Ag: 5 wt% or less (including zero), Ni: 10 wt% or less (including zero), Bi : 20% by mass or less (including zero), In: 10% by mass or less (including zero), and Zn: 30% by mass or less (including zero), containing one or more, and the balance Cu and Combining 0.1-10 parts by mass of CuS, Cu ₂ S, Ag ₂ S, K ₂ S, CaS, NiS and FeS with respect to 100 parts by mass of inevitable impurities. The present invention provides a Pb-free copper alloy composite sliding material having excellent seizure resistance.
The present invention will be described in detail below.

The kind of sulfide that is a composite component of the sintered sliding material of the present invention is CuS, Cu ₂ S, ZnS, Ag ₂ S, K ₂ S, CaS, NiS, and FeS , and the sintering temperature is 700 to 700. It is a sulfide that does not decompose at 1000 ° C. If the amount of the sulfide added is 0.1 parts by mass or less with respect to 100 parts by mass of the copper alloy, the effect is not obtained, and if it is 10 parts by mass or more, the strength decreases. A preferable addition amount of sulfide is 1 to 5 parts by mass. If sulfide is added, the surrounding Cu matrix tends to be sulfided, and wear resistance and strength are expected to decrease. Therefore, the following components such as Sn and Ni are added to the Cu matrix to prevent this. It is preferable to do.

    Sn increases the strength of the Cu matrix and is effective in improving fatigue resistance and wear resistance. Further, there is an effect of preventing the sulfidation of the copper alloy due to the addition of the sulfide. If the Sn content in the copper alloy exceeds 20% by mass, the copper alloy becomes brittle. Therefore, Sn content is 20 mass% or less, Preferably it is 1-15 mass%.

  P lowers the melting point of the copper alloy and increases the sinterability. When the content of P in the copper alloy exceeds 0.5% by mass, the copper alloy becomes brittle. Therefore, the P content is 0.5% by mass or less, preferably 0.01 to 0.2% by mass, more preferably 0.01 to 0.1% by mass.

Optional additive elements such as Ag, Ni, Zn, In, Bi that may be added to the copper alloy that is a composite component of the sintered sliding material of the present invention: Ag, Ni, etc. increase the strength of the Cu matrix, Effective in improving fatigue and wear resistance. In addition, it suppresses the copper matrix from undergoing sulfidation corrosion due to heat generated during sliding and S in the lubricating oil. In particular, it is desirable to add Zn or Ni in a sliding material used in a part where the amount of S in the lubricating oil is large or in a part where the temperature is high. Bi does not dissolve in Cu but exists as secondary phase particles. Since Bi has a low melting point, it melts onto the sliding surface by the heat generated during sliding, lowering the temperature of the sliding surface and preventing seizure.
However, when Ag: 5% by mass or more, Ni: 10% by mass or more, Zn: 30% by mass or more, and In: 10% by mass or more, the hardness of the copper alloy increases so that the conformability decreases and the seizure resistance decreases. To do. If Bi: 20% by mass or more, the melting point of the copper alloy is too low and the strength is lowered. Preferable addition amounts are Ag: 0.1 to 2.0 mass%, Ni: 1.0 to 5.0 mass%, Zn: 5.0 to 30 mass%, and In: 1.0 to 5.0 mass%.

Graphite, MoS ₂ , WS ₂ : These substances are known solid lubricants that exhibit self-lubricating properties, but supplementary addition in the present invention is not a problem. If the amount added exceeds 10 parts by mass with respect to 100 parts by mass of the copper alloy, the solid lubricants tend to aggregate together, resulting in poor adhesion with Cu. Leads to. In addition, the strength decreases. A preferable addition amount is 1 to 5 parts by mass. The average particle size of these solid lubricants is preferably 10 to 30 μm.

Fe ₃ P, FeB, AlN, Al ₂ O ₃ , SiC, SiO ₂ , Si ₃ N ₄ : Further, in the present invention, one or more of these hard materials may be added to improve wear resistance. it can. If the addition amount of these hard materials exceeds 10 parts by mass with respect to 100 parts by mass of the copper alloy, the strength of the sliding material decreases. A preferable addition amount is 0.1 to 5.0 parts by mass. The particle size of these hard materials is preferably 10 to 50 μm on average.

The sulfide, which is a composite component of the sliding material of the present invention, has a higher coefficient of friction than MoS ₂ and WS ₂ and does not improve the sliding characteristics by the cleavage mechanism like the latter, but because it is brittle, it adheres to the counterpart material. Difficult to improve the adhesion resistance of the entire copper alloy. If a large amount of sulfide, which is a composite component of the sliding material of the present invention, is present, there is a concern that the wear resistance of the copper alloy may be reduced. However, if the Cu matrix is reinforced with Sn, Ag, Ni, Zn or the like, the sliding performance does not deteriorate. In addition, if these elements are present in the alloy, Cu sulfidation due to heat generated during sliding is suppressed, so even if sulfides are added, surrounding Cu will not undergo sulfidation corrosion.
Since the lubricating performance of the sulfide itself, which is a composite component of the sliding material of the present invention, is lower than that of Pb, it is preferable to add a solid lubricant such as Bi, graphite, MoS ₂ or the like.
Hereinafter, the present invention will be described in more detail with reference to examples.

  Sulfide powder was mixed with copper alloy atomized powder (particle size of 180 μm or less) having the composition shown in Table 1 at a ratio shown in Table 1, and sprayed on a steel plate to 1 mm, followed by high-frequency heat sintering. Sintering conditions for high-frequency heat sintering are as follows. In a reducing atmosphere, the temperature is raised to a sintering temperature of 700 to 1000 ° C. within 2 minutes, and the holding time at the sintering temperature is 3 minutes or less. Or / and quickly cooled to room temperature within 2-3 minutes by roll cooling. Thereafter, it was rolled and sintered again under the same conditions, and the obtained material was used as a test piece.

The test method was as follows.
Testing machine: Pin-on-disk testing machine Load: 4M Pa / 10min gradual increase Oil type: Paraffin base oil Oil temperature: Room temperature Counterpart material: SUJ2
The test results are shown in Table 1. No. 8 is a reference example.

As shown in Table 1, Example No. Although the seizure surface pressure of No. 3 was slightly low, performance almost equal to or higher than that of the Pb-containing copper alloy was obtained.

  As described above, since the sliding material of the present invention does not contain Pb and has excellent seizure resistance, it is very suitable as a bush for a fuel injection pump and a bush for an automatic transmission.

Claims (3)

In mass percent, Sn: 20% or less, P: contained 0.5% or less, further Ag: 5 wt% or less (including zero), Ni: 10 wt% or less (including zero), Bi: 20 wt% Contains one or more of the following (including zero), In: 10% by mass or less (including zero), and Zn: 30% by mass or less (including zero), and the remainder from Cu and inevitable impurities It is characterized in that 0.1 to 10 parts by mass of CuS, Cu ₂ S, Ag ₂ S, K ₂ S, CaS, NiS and FeS are combined with one or more of 100 parts by mass of the resulting copper alloy. Pb-free copper alloy composite sliding material with excellent seizure resistance. _2. Excellent seizure resistance according to claim 1 , characterized by further combining one or more of graphite, MoS ₂ and WS ₂ of 10 parts by mass or less with respect to 100 parts by mass of the copper alloy. Pb-free copper alloy composite sliding material. One or more of Fe ₃ P, Fe ₂ P, FeB, AlN, Al ₂ O ₃ , SiC, SiO ₂ and Si ₃ N ₄ of 10 parts by mass or less with respect to 100 parts by mass of the copper alloy. 3. The Pb-free copper alloy composite sliding material having excellent seizure resistance according to claim 1 or 2, further comprising a composite.