THREE-MATERIAL ROLL-BONDED SLIDING BEARING HAVING TWO ALUMINIUM LAYERS

Abstract

A sliding bearing element has a steel supporting layer onto which a 2-layer composite is applied which consists of an aluminum-based substrate having a layer thickness hs of 0.2 to 0.4 mm and an aluminum-based sliding layer having a layer thickness hG of 0.005 to 0.1 mm. The substrate and the sliding layer are joined by roll bonding. A sliding bearing is made from two sliding bearing elements of this kind, which are predominately used for applications in high-performance engines, principally for connecting-rod bearings, crankshaft main bearings and connecting rod bushes, but also in applications in mounting camshafts and counterbalance shafts as well as transmissions.

Claims

1. A sliding bearing element comprising a steel supporting layer, a 2-layer composite applied to the supporting layer comprising a lead-free aluminum-based substrate layer having a layer thickness hs of 0.2 to 0.4 mm, and a lead-free aluminum-based sliding layer having a layer thickness hG of 0.005 to 0.1 mm, and wherein the substrate layer and the sliding layer are joined by roll bonding.

2. The sliding bearing element according to claim 1, wherein the substrate layer comprises a first aluminum alloy which, in addition to unavoidable impurities, comprises one or a plurality of the following components 0.1-8.0 wt. % copper, 0.1-2.0 wt. % manganese, 0.2-5 wt. % nickel, 1.0-8.0 wt. % zinc, 0.1-5.0 wt. % magnesium, 0.1-2.0 wt. % silicon, 0.05-1.0 wt. % chromium, 0.05-1.0 wt. % vanadium, and the rest aluminum.

3. The sliding bearing element according to claim 2, wherein the first aluminum alloy in combination has 0.4-6.0 wt. % copper, 0.3-2.0 wt. % manganese.

4. The sliding bearing element according to claim 3, wherein the first aluminum alloy further has 0.5-3 wt. % nickel and 0.05-1.0 wt. % vanadium.

5. The sliding bearing element according to claim 3, wherein the first aluminum alloy further has 0.2-2.5 wt. % magnesium and 0.1-2.0 wt. % silicon.

6. The sliding bearing element according claim 1, wherein the sliding layer comprises a second aluminum alloy which, in addition to unavoidable impurities, comprises one or more of the following components 1.0-10.0 wt. % silicon, 5.0-30.0 wt. % tin, 0.1-5.0 wt. % copper, 0.1-3.0 wt. % manganese, 0.05-1.0 wt. % vanadium, 0.05-1.0 wt. % chromium, and the rest aluminum.

7. The sliding bearing element according to claim 6, wherein the second aluminum alloy in combination has 1.0-6.0 wt. % silicon, 5.0-25.0 wt. % tin and 0.3-2.5 wt. % copper.

8. The sliding bearing element according to claim 7, wherein the second aluminum alloy further has 0.1-1.5 wt. % manganese.

9. The sliding bearing element according to claim 7, wherein the second aluminum alloy further has 0.05-1.0 wt. % vanadium and 0.05-1.0 wt. % chromium.

10. The sliding bearing element according to claim 1, wherein the substrate layer has a Brinell hardness of 50-100 HBW 1/5/30.

11. The sliding bearing element according to claim 1, wherein the substrate layer has tensile strength of 200-300 MPa.

12. The sliding bearing element according to claim 1, wherein the sliding layer has a Brinell hardness of 25-60 HBW 1/5/30.

13. The sliding bearing element according to claim 1, wherein the sliding layer has a tensile strength of 100-200 MPa.

14. The sliding bearing element according to claim 1, wherein the sliding bearing element is formed as sliding bearing shell.

15. The sliding bearing element according to claim 14, wherein the sliding bearing shell has a nominal diameter of <100 mm.

16. A sliding bearing composed of two sliding bearing shells, of which at least one sliding bearing shell is formed according to claim 15.

Description

[0075] The sliding bearing element according to the invention will be explained in greater detail with reference to the drawings and examples. In the drawing:

[0076] FIG. 1 shows a basic layer structure of the sliding bearing element according to the invention.

[0077] FIG. 1 is a perspective sectional view of a sliding bearing element in the form of a sliding bearing shell according to the invention. The sliding bearing shell has a total of three layers. The lowest layer is a supporting or carrier layer 10 made of steel. A substrate layer 12 is applied to the carrier layer 10. A sliding layer 14 is in turn arranged on the substrate layer 12. The substrate layer 12 and the sliding layer 14 each have the aluminum-based composition discussed above. The sliding layer has a thickness hG of 0.005 to 0.1 mm. The following applies: The thinner the sliding layer, the higher the contribution of the thicker substrate layer to the fatigue strength. The substrate layer has a thickness hs of 0.2 to 0.4 mm.

[0078] Table 1 below shows two embodiments of the aluminum alloy of the substrate layer and Table 2 shows two embodiments of the aluminum alloy of the sliding layer.

TABLE-US-00001 TABLE 1 Sample composition substrate layer (proportions in wt. %) Al Cu Mn Ni Mg Zn Cr Si V S1 REST 0.6 0.6 1.5 0.2 S2 REST 4.5 0.7 0.7 0.5

TABLE-US-00002 TABLE 2 Sample composition sliding layer (proportions in wt. %) Al Sn Cu Si Cr V Mn G1 REST 21.5 1.0 4.0 0.35 G2 REST 10.0 0.8 2.4 0.2 0.2

[0079] The tensile strengths and hardness of the embodiments listed above are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Hardness and tensile strengths R.sub.m of substrate layers (S1 and S2) and sliding layers (G1 and G2) at different points in the manufacturing process Before Before Before Finished roll-bonding roll-bonding final bearing on aluminum on steel annealing shell Hard- Hard- Hard- Hard- R.sub.m ness R.sub.m ness R.sub.m ness R.sub.m ness [MPa] [HBW] [MPa] [HBW] [MPa] [HBW] [MPa] [HBW] S1 238 71 166 45 265 75 250 70 S2 190 51 180 48 240 63 225 60 G1 181 55 130 35 175 57 130 38 G2 193 56 146 44 190 59 150 42

[0080] The hardness and tensile strengths were determined in accordance with DIN specifications EN ISO 6506 and DIN EN 10002.

[0081] In the following, the production of the bearing elements according to the invention and in particular the adjustment of the material properties of the aluminum alloys of the substrate layer and the sliding layer are described.

[0082] Through individual fine tuning of the composition and the process sequences during the production of the individual layers, the focus of the properties between load-bearing capacity, fatigue strength and/or sliding properties is set in the above parameter range depending on the requirement profile of the planned application.

[0083] A strip material made of a first aluminum alloy, which forms the substrate layer in the later composite material, and a strip material made of a second aluminum alloy, which forms the sliding layer in the later composite material, are provided. As can be seen from Table 3, these materials may initially have similar properties in terms of hardness and tensile strength. The casting of the strip materials is followed by annealing at a temperature between 400 and 550 C. for homogenisation. The precipitates of the easily soluble elements in the alloys, such as copper, magnesium, silicon or zinc, dissolve and are distributed evenly. All in all, the material properties are homogenised in this way. Precipitates of less soluble elements such as manganese increase become coarser and lose their angular shape (moulding). The strip materials can, for example, be cast on site and then rolled in alternating annealing and forming steps (rolls) to a desired thickness, for example 1.4 to 2 mm in each case, to form strips.

[0084] The two strip materials are then joined by cold roll bonding. The thickness of the joined layers after this first roll bonding is about 0.7 to 1 mm, which corresponds to a degree of deformation of about 50%. This is followed by one or more annealing treatments for recrystallisation at a temperature between 200 and 400 C. for 8 to 15 hours. This breaks down the internal energy of the dislocations created by the deformation by rearrangement and formation of a new grain structure, with recrystallisation starting at lower temperatures, the greater the cold deformation and the longer the annealing time. In addition, this leads to an overall decrease in tensile strength and hardness of the individual layers (cf. Table 3). The fine-grained and ideally completely recrystallised microstructure has the best forming properties.

[0085] The two-layer composite thus produced is then also applied to a steel strip by cold roll bonding, i.e. joined to form a three-layer composite, with the substrate layer arranged on top of the steel layer. This is followed, if necessary, by further rolling steps in which the thickness of the substrate layer and the sliding layer is further reduced to the desired final dimension (the substrate layer). Here, degrees of deformation of at least 50% are achieved, whereby high degrees of deformation are accompanied by a better bond between the two-layer composite and the steel back. The substrate thickness and the sliding layer thickness then each amount to about 0.2 to 0.4 mm.

[0086] After roll bonding and individual further rolling steps, recrystallisation annealing can follow again, if required. At the end of the deformation process, whether after roll bonding to the steel strip or after the further rolling pass(es), a final annealing is performed at temperatures between 150 and 450 C., preferably between 200 and 350 C. for 4 to 12 hours, during which a bonding zone between the steel strip and the substrate material is formed by diffusion, which leads to an improvement in the bond between the layers.

[0087] In addition, the final annealing serves to adjust the material properties required above with regard to hardness and tensile strength. Due to the different chemical composition, the final annealing temperature can be selected above or below the recrystallisation threshold of one of the two layers, so that recrystallisation optionally takes place in the corresponding layer at the same time. Preferably the temperature is selected so that the substrate layer will survive the final annealing without significant tensile strength and hardness losses, while the sliding layer loses hardness.

[0088] Finally, the bearing element is formed from the 3-layer composite material by, for example, cutting off blanks, forming them into sliding bearing shells or bushes in a next process step and finally machining the sliding bearing shells or bushes, whereby a final dimension of the sliding layer thickness of 0.005 to 0.1 mm is achieved.

LIST OF REFERENCE SIGNS

[0089] 10 Steel back [0090] 12 Substrate layer [0091] 14 Sliding layer [0092] 16 Sliding surface [0093] hG Thickness of the sliding layer [0094] hs Thickness of the substrate layer