SLIDING ELEMENT COMPOSED OF A COPPER ALLOY

Abstract

The invention relates to a sliding element composed of a copper alloy which contains the following constituents (in % by weight): from 2.0 to 3.0% of Ni, from 0.45 to 1.0% of Si, up to 1.5% of Ti and/or Cr, where the sum of the Ni content [Ni] and the Ti content [Ti]: [Ni]+[Ti] is 0.2%, optionally from 0.05 to 1.5% of Co, optionally in each case from 0.05 to 0.1% of Mg, Al, Fe, optionally from 0.01 to 0.1% of Pb, optionally from 0.002 to 0.01% of P, a balance of Cu and unavoidable impurities,
wherein the ratio of the sum of the Ni content [Ni], Ti content [Ti] and Cr content [Cr] to the Si content [Si] is such that:

4.3([Ni]+[Ti]+[Cr])/[Si]6.5.

Claims

1. Sliding element composed of a copper alloy which contains the following constituents (in % by weight): from 2.0 to 3.0% of Ni, from 0.45 to 1.0% of Si, up to 1.5% of Ti and/or Cr, where the sum of the Ni content [Ni] and the Ti content [Ti]: [Ni]+[Ti] is 0.2%, optionally from 0.05 to 1.5% of Co, optionally in each case from 0.05 to 0.1% of Mg, Al, Fe, optionally from 0.01 to 0.1% of Pb, optionally from 0.002 to 0.01% of P, a balance of Cu and unavoidable impurities, characterized in that the ratio of the sum of the Ni content [Ni], Ti content [Ti] and Cr content [Cr] to the Si content [Si] is such that:
4.3([Ni]+[Ti]+[Cr])/[Si]6.5.

2. Sliding element according to claim 1, characterized in that the ratio is such that:
5.1([Ni]+[Ti]+[Cr])/[Si]6.2.

3. Sliding element according to claim 1, characterized by from 2.3 to 2.7% of Ni and/or from 0.45 to 0.65% of Si.

4. Sliding element according to claim 1, characterized in that at least one fraction of precipitates where the precipitates having a volume-equivalent sphere diameter of at least 1.0 m have a density of from 5000 to 20 000 particles per mm.sup.2 is present.

5. Sliding element according to claim 4, characterized in that at least one fraction of precipitates where the precipitates having a volume-equivalent sphere diameter of at least 1.0 m have a density of from 10 000 to 20 000 particles per mm.sup.2 is present.

6. Sliding element according to claim 5, characterized in that at least one fraction of precipitates where the precipitates having a volume-equivalent sphere diameter of at least 1.0 m and not more than 3.0 m have a density of from 10 000 to 18 000 particles per mm.sup.2 is present.

7. Sliding element according to claim 4, characterized in that the precipitates are Cr-containing and/or Ti-containing silicides.

8. Sliding element according to claim 1, characterized in that the Ti content and/or Cr content is not more than 1.0% by weight.

9. Sliding element according to claim 8, characterized in that the Ti content and/or Cr content is at least 0.45% by weight and not more than 0.95% by weight.

10. Sliding element according to claim 1, characterized in that the electrical conductivity after a thermal treatment in the range from 300 C. to 600 C. is at least 25 MS/m.

11. Sliding element according to claim 1, characterized in that the ratio of the coefficient of thermal expansion in the temperature range from 20 C. to 300 C. to the thermal conductivity at room temperature, /, is from 0.09 to 0.20 m/W.

12. Sliding element according to claim 1, characterized in that the hardness after a final thermal treatment in the range from 300 C. to 600 C. is at least 150 HBW 2.5/62.5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 is Graph 1 which contains Coefficients of friction (samples No. 1 and 4 with comparative samples); and

[0049] FIG. 2 is Graph 2 which contains Wear (samples No. 1 and 4 with comparative samples).

[0050] The coefficients of friction in graph 1 and the degrees of wear in graph 2 for the samples 1 and 4 and also samples of comparative alloys were determined by means of a tribometer during long-term running. The friction pairing consists of a flat plate of the alloy and annular segments composed of the steel 100Cr6. The steel rotates at a sliding speed of 1 m/sec on the sheet of the copper material. The friction partners are lubricated with a commercial engine oil at a temperature of 120 C. After a running-in phase in two stages, a constant load of 600 N is applied for 5.5 h. Here, the force applied per unit area is 9 N/mm.sup.2.

[0051] Compared to copper-based bearing materials being used today, the alloys of the invention display a lower average coefficient of friction. Both working examples 1 and 4 wear significantly less than the tin-nickel bronze and a tried-and-tested iron-containing specialty brass with mixed silicides.