Patent Application
20070254180
For the tests, the applied material was CuNi6Sn6 in the as-rolled and soft-annealed state, and the base material used was steel in various states. The specimens were treated with brushes and then cleaned.
This was immediately followed by rolling with different reductions per pass. The starting thickness of the strips of the copper multicomponent alloy was approx. 3 mm. The different strip thicknesses of the base material were 1.5, 3 and 5 mm. The width of the copper multicomponent alloy was approx. 0.1-0.3 mm less than that of the base material. Rolling forces, moments and outlet temperatures were measured. In each case five variations per combination were carried out for each material state having the above-mentioned thicknesses of the base material. The rolling tests showed that CuNi6Sn6 can be readily plated onto steel with good material bonding.
The following text describes a process for producing a material composite comprising the copper multicomponent alloy for sliding elements, such as thrust washers and bearing liners. In this process, a lead-free bearing material from the Cu—Ni—Sn system is applied to deep-drawing steel by melting and casting. The lead-free bearing material was cast on at a temperature of 1000 to 1200° C., with the layer microstructure being formed from α-phase with continuous and discontinuous precipitations. The material composite comprising steel and the Cu—Ni—Sn alloy was annealed at temperatures between 600 and 800° C., and then the surface of the layer was removed by milling. These layer bearing materials can be used both in the as-cast state and in the age-hardened state for sliding bearing elements. The age-hardening was carried out at temperatures between 300 and 500° C.
The cast microstructure of the bearing layer was wrought by thermomechanical treatments, such as rolling and annealing. The strips can be cold-rolled with degrees of deformation of between 10 and 60% and then annealed at temperatures between 500 and 800° C. It has been found that the composite bearing material can be used in all its various states, i.e. in the as-cast state, in the wrought state and in the age-hardened state, for sliding elements.
In further series of tests, ingots with different Mn—Si ratios were cast and then cold-worked further. The alloy variants tested are summarized in Table 1. The cast ingots were homogenized in the temperature range between 700 and 800° C. and then milled. Strips with thicknesses of between 2.5 and 2.85 mm were then produced by a plurality of cold-forming stages and intermediate annealing steps. The strips were cold-rolled and then annealed in the temperature range between 700 and 800° C. in order to achieve sufficient cold-formability.
As expected, it was confirmed that the cold-formability of the Cu—Ni—Sn alloy modified with silicides is slightly lower than that of a Cu—Ni—Sn alloy without further silicide phases.
In a further process step, strips of this type are combined to form a strong material composite by roll-cladding processes. The tribological tests demonstrated that the silicide-modified Cu—Ni—Sn alloys had a significantly lower coefficient of friction than the unmodified variant. This new modified alloy is therefore suitable in particular as a primary material for use as a sliding element (liners, thrust washers, etc.) in the automotive industry for engines, transmissions and hydraulics.
However, over and beyond the values indicated in the table, it has been found that modified Cu—Ni—Sn variants with an Si content of up to 1.5% by weight and a Mn content of up to 2.5% by weight can be manufactured with improved materials properties. Further laboratory tests to demonstrate this have likewise already been carried out, confirming the limit values.
In particular, it has been ensured that with an Si content of up to 0.7% by weight and an Mn content of up to 1.6% by weight manufacturing is actually possible without problems from a manufacturing technology perspective. If higher silicon and manganese contents are used, corresponding adjustments in line with standard measures should be performed with regard to the casting parameters.
However, difficulties, in particular caused by cracks at the edges of the strip material, are likely during further processing if the silicon and/or manganese contents exceed the indicated maxima of 3% by weight and 5% by weight, respectively.
The CuNiSn alloy contains finely distributed manganese-nickel silicides which are embedded in the alloy matrix. These silicides, as the first precipitation in the melt, are formed as early as the temperature range around 1100° C. If the melt composition is selected appropriately, the available silicon and manganese are precipitated with a nickel content which is present in excess to form the silicide. The nickel content consumed in the silicide can be correspondingly taken into account for the subsequent formation of the matrix by using a higher nickel content in the melt.
The composition of the silicides does not necessarily have to correspond to a predetermined stoichiometry. Depending on the procedure adopted, determined in particular by the cooling rate, ternary intermetallic phases precipitate in the form of the silicides of type (Mn,Ni)xSi, which are in the range between the binary boundary phases Mn5Si3 and Ni2Si.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102006019826.3 | Apr 2006 | DE | national |
