LEAD-FREE CUNI2SI SLIDING BEARING MATERIAL WITH THE ADDITION OF A METAL HAVING A CHIP-BREAKING EFFECT

Abstract

The invention relates to a sliding bearing material with a matrix material which consists of 0.5-5 wt. % nickel, 0.25-2.5 wt. % silicon, <0.1 wt. % lead, impurities that result from the metallurgical smelting process, and the rest being copper, with optionally at least one hard material and optionally at least one solid lubricant, and which has at least one tellurium additive. The invention also relates to a sliding bearing composite material which has a carrier layer, a bearing metal layer and a sliding layer applied to said bearing metal layer, the bearing metal layer consisting of such a sliding bearing material, as well as to a sliding element or sliding bearing that consists of such a sliding bearing composite material.

Claims

1. A sliding bearing material with a matrix material, consisting of 0.5-5 wt. % nickel, 0.25-2.5 wt. % silicon, <0.1 wt. % lead, impurities that result from the metallurgical melting process, with the rest being copper, with optionally at least one hard material and optionally at least one solid lubricant, characterized by at least an additive of tellurium.

2. A sliding bearing material according to claim 1, characterized in that the weight ratio of nickel to silicon is between 2.5 and 5.

3. A sliding bearing material according to one of the claim 1 or 2, characterized in that the additive is dispersed within the matrix material with a total amount of between 0.01 and 2.0 wt. %.

4. A sliding bearing material according to one of the aforementioned cams, characterized in that the additive is present in the matrix material in the form of particles, whereby 90% of the measurable particles have a maximum dimension of 30 m, preferably of 15 m.

5. A sliding bearing material according to one of the aforementioned claims, characterized in that below the limit of 800 MPa m/s, preferably below 850 MPa m/s, no adhesive wearing occurs.

6. A sliding bearing material according to one of the aforementioned claims, characterized by at least one hard material selected from a group consisting of silicides, oxides, carbides and nitrides, in particular AlN, Al.sub.2O.sub.3, SO.sub.2, TiO.sub.2, ZrO.sub.2, Mo.sub.2C, MoSi.sub.2, SiC, B.sub.4C, Si.sub.3N.sub.4 and c-BN.

7. A sliding bearing material according to one of the aforementioned claims, characterized by at least one solid lubricant selected from a group consisting of h-BN and graphite.

8. A sliding bearing composite material with a backing layer, a bearing metal layer and a sliding layer applied to said bearing metal layer, characterized in that the bearing metal layer consists of a sliding bearing material according to one of the patent claims 1 to 7.

9. A sliding bearing composite material according to claim 8, characterized in that the bearing metal layer is a sinter layer.

10. A sliding bearing composite material according to claim 8, characterized in that there is, if necessary via an intermediate layer, a roll cladding connection between the bearing metal layer and the backing layer.

11. A sliding bearing composite material according to claim 8, characterized in that the bearing metal layer is a cast layer.

12. A sliding element or sliding bearing with a sliding bearing material according to one of the patent claims 1 to 7.

13. A sliding element or sliding bearing made from a sliding bearing composite material according to one of the patent claims 8 to 10.

Description

[0038] Other properties and features of the invented sliding bearing material are explained in the following drawings. These are:

[0039] FIG. 1 a light microscope picture of the surface of the invented sliding bearing material,

[0040] FIG. 2 a diagram to illustrate a test program for determining wear on a sliding bearing, and

[0041] FIG. 3 a diagram of determined wear values of the invented and various other copper alloys.

[0042] FIG. 1 shows a light microscope picture of the cross-section of the invented sliding bearing material. The scale is 500:1 so that the ranges of m orders of magnitude are visible. The specimen shown has a composition of 2.14 wt. % nickel, 0.73 wt. % silicon, 1.52 wt. % tellurium with the rest copper, whereby the materials nickel, silicon and copper form the matrix material and tellurium is present in its undissolved phase.

[0043] The pure matrix material is depicted by the pale area (2), whilst the darker coloured areas (4) mark the added tellurium in the form of localized particles. In FIG. 1, the spatial separation of the tellurium phases or particles of the matrix material are clearly visible. The tellurium phases appear as clearly defined, mostly elongated patches, preferably with a maximum dimension of up to 15 m in 90% of measurable cases.

[0044] This type of invented material and comparative materials underwent a wear test according to the diagram shown in FIG. 2. The test bench on which the measurements were carried out is similar to a combustion engine, equipped with original pistons, connecting rods, crankshafts and sliding bearings. During the test, the crankshaft's rotational speed is incrementally increased from 1900 rotations per minute to a maximum of 8000 rotations per minute. The latter value is equivalent to the maximum relative speed between the crankpin surface and the sliding bearing surface of 19.7 m/s. Here, the sliding bearing is subjected to a sinusoidal load in the large eye of the connecting rod, which is depicted in two parts in the form of two bearing shells. At the same time as the rotational speed, the load is increased incrementally due to the centrifugal forces that occur. In the diagram, the product of the load (in MPa) and the relative speed (in m/s) is plotted as curve 20 and scaled to the y-axis on the left hand side of the diagram. The bearing is initially lubricated with oil at a constant oil flow rate of 500 ml/mm. After a period of 250 mins, but still before the maximum load is reached, the oil flow is reduced incrementally, while the load or rotational speed is increased incrementally even further. The oil flow is also plotted on the diagram as curve 22 and scaled to the y-axis on the right-hand side of the diagram. The maximum load and sliding speed at which the bearing scuffs under these conditions is measured in each of at least three tests per bearing material under the same conditions, and is plotted as an average value in the diagram according to FIG. 3.

[0045] In FIG. 3, the measured value of the maximum load and sliding speed is shown as an indication of the seizure behaviour of four different CuNi2Si microstructure modifications. The matrix material has the same composition in all four variants: 2 wt. % Ni, 0.6 wt. % Si, rest Cu. Only material no. 12 contains an additional 0.5 wt. % tellurium and thus represents the inventive sliding bearing material.

[0046] Material 10 is a recrystallized CuSi2Ni material, cast onto steel and then subjected to the thermomechanical treatment described above. After it has undergone thermomechanical treatment, the microstructure is characterized by fine, evenly and isotropically distributed, intermetallic precipitates (recrystallized) on a NiSi basis within the copper matrix. In this material, an average load limit of 720 MPa m/s was measured.

[0047] Material 12 is a CuNi2Si solid bearing material with a chip-breaker that is recrystallized using thermomechanical treatment, without steel backings. Compared to all other tested CuNi2Si materials, it has the greatest load-bearing capacity without seizure at a value of 830 MPa m/s.

[0048] Material 14 is a roll cladded CuNi2Si material, which was initially rolled out as a band and then joined to a steel backing in a subsequent roll cladding process in the manner described above, and also underwent thermomechanical treatment. For this, an average load limit of 770 MPa m/s was recorded.

[0049] Material 16 is a CuNi2Si cast material that was cast onto a steel backing in the manner described above. This material did not undergo any subsequent thermomechanical treatment and is therefore not recrystallized. It therefore achieves an average load limit of just 270 MPa m/s.

[0050] The inventive sliding bearing materials therefore have an improved level of machinability compared to known sliding bearing materials without additives, as well as a surprisingly significantly reduced susceptibility to seizure. They are therefore especially suitable for use in the event of insufficient lubrication, even without solid lubricants.