METHOD FOR PRODUCING PLAIN-BEARING COMPOSITE MATERIALS, PLAIN-BEARING COMPOSITE MATERIAL AND SLIDING ELEMENT COMPRISING PLAIN-BEARING COMPOSITE MATERIALS OF THIS TYPE

Abstract

A method for producing plain-bearing composite materials (30) includes applying a powder of a bearing metal to a strip material of steel and then sintering the bearing metal. The composite material (25) consisting of the strip material (6) and the bearing metal (14) subsequently undergoes a heat treatment. After the sintering process the composite material (25) is quenched, directly followed by an ageing process. The plain-bearing composite material (30) has a substrate (32) consisting of steel and a sintered bearing metal layer (34) consisting of a copper alloy, the bearing metal layer (34) having a hardness of 100 HBW 1/5/30 to 200 HBW 1/5/30.

Claims

1. A method for producing plain-bearing composite materials, in which a powder of a bearing metal is applied to a strip material made of steel, and the bearing metal undergoes at least one sintering process, and the composite material consisting of the strip material and the bearing metal subsequently undergoes heat treatment, the composite material is quenched following the sintering process, and an ageing process subsequently follows.

2. The method according to claim 1, wherein the ageing process is carried out at a temperature of between 350 C. and 520 C. for four to ten hours.

3. The method according to claim 2, wherein the ageing process is carried out at a temperature of between 350 C. and 420 C.

4. The method according to claim 2, wherein the ageing process is carried out at a temperature of between >420 C. and 520 C.

5. The method according to claim 1, wherein an austenitic steel is used as the steel.

6. The method according to claim 5, wherein a steel having a carbon content of from 0.15% to 0.40% is used.

7. The method according to claim 1, wherein a bearing metal consisting of a powder of a copper alloy is applied.

8. The method according to claim 7, wherein the copper alloy is hardenable.

9. The method according to claim 7 wherein the copper alloy consists of a copper-nickel alloy, a copper-iron alloy, a copper-chromium alloy or a copper-zircon alloy.

10. The method according to claim 1, wherein the quenching process begins immediately after the sintering process.

11. The method according to claim 1, wherein the quenching process begins within 15 to 25 seconds following the sintering process.

12. The method according to claim 1, wherein the composite material is quenched to a temperature T.sub.1 of from 150 C. to 250 C.

13. The method according to claim 1, wherein the quenching process is carried out at a quenching rate of from 10 K/s to 30 K/s.

14. The method according to claim 1 the quenching of the copper-nickel alloy is carried out at a quenching rate of from 15 K/s to 25 K/s.

15. The method according to claim 1, wherein the quenching of the copper-iron alloy is carried out at a quenching rate of from 15 K/s to 25 K/s.

16. The method according to claim 1, wherein the quenching of the copper-chromium alloy is carried out at a quenching rate of from 10 K/s to 20 K/s.

17. The method according to claim 1, wherein the quenching of the copper-zircon alloy is carried out at a quenching rate of from 10 K/s to 20 K/s.

18. The method according to claim 1, wherein the quenching is carried out using a quenching medium.

19. The method according to claim 18, wherein a nitrogen-hydrogen gas mixture is used for the quenching.

20. The method according to claim 1, wherein the rear face of the composite material is sprayed with the quenching medium.

21. A plain-bearing composite material comprising a steel substrate layer and a sintered bearing metal layer consisting of a copper alloy, wherein the bearing metal layer has a hardness of from 100 HBW 1/5/30 to 200 HBW 1/5/30.

22. The plain-bearing composite material according to claim 21, wherein the substrate layer has a hardness of from 150 HBW 1/5/30 to 250 HBW 1/5/30.

23. The plain-bearing composite material according to claim 21, wherein the bearing metal layer has a tensile strength of from 380 MPa to 500 MPa.

24. The plain-bearing composite material according to claim 21, wherein the bearing metal layer has a yield strength of from 250 MPa to 450 MPa.

25. The plain-bearing composite material according to claim 21, wherein the copper alloy is a copper-nickel alloy, a copper-iron alloy, a copper-chromium alloy or a copper-zircon alloy.

26. The plain-bearing composite material according to claim 21, wherein the copper-nickel alloy comprises 0.5 to 5 wt. % nickel.

27. The plain-bearing composite material according to claim 21, wherein the copper-iron alloy comprises 1.5 to 3 wt. % iron.

28. The plain-bearing composite material according to claim 21, wherein the copper-chromium alloy comprises 0.2 to 1.5 wt. % chromium.

29. The plain-bearing composite material according to claim 21, wherein the copper-zircon alloy comprises 0.02 to 0.5 wt. % zircon.

30. The plain bearing element comprising a plain-bearing composite material according to claim 21.

31. The plain bearing element according to claim 30, including a sliding layer that is applied to the bearing metal layer.

32. The plain bearing element according to claim 31, wherein the sliding layer consists of a galvanic layer.

33. The plain bearing element according to claim 32, wherein the galvanic layer consists of a tin-copper alloy, a bismuth-copper alloy or of bismuth.

34. The plain bearing element according to claim 32, wherein the sliding layer consists of a plastics layer.

35. The plain bearing element according to claim 32, wherein the sliding layer consists of a layer applied by means of a PVD method.

36. The plain bearing element according to claim 32, wherein the sliding layer consists of a sputter layer.

37. The plain bearing element according to claim 30, wherein the plain bearing element is formed as a plain bearing shell, as a valve plate or as a sliding segment.

Description

[0092] Exemplary embodiments will be explained in greater detail in the following, with reference to the drawings, in which:

[0093] FIG. 1 schematically shows the production method according to the prior art,

[0094] FIG. 2 schematically shows the procedure according to the invention,

[0095] FIG. 3 schematically shows a conveyor system according to the invention,

[0096] FIGS. 4a and b are perspective views of two sliding elements,

[0097] FIG. 5 is a graph showing the hardness as a function of the structural state, for a comparative example,

[0098] FIG. 6 is a graph showing the bearing metal strength as a function of the structural state, for the comparative example,

[0099] FIG. 7 is a graph showing the hardness for examples 1 to 3 according to the invention,

[0100] FIG. 8 is a graph showing the bearing metal strength for examples 1 to 3 according to the invention.

[0101] FIG. 9 is an iron-carbon phase diagram for steel,

[0102] FIG. 10 is the phase diagram for the bearing metal alloy CuNi2Si.

[0103] FIG. 2 schematically shows the procedure according to the invention, the temperature T of the individual method steps being plotted against the time t. The sintering is carried out for example at a temperature T.sub.s of 940 C. and immediately thereafter the composite material is quenched to a temperature T.sub.1 of approximately 150 C. to 250 C. If two sintering steps are carried out at temperatures T.sub.s1 and T.sub.s2, T.sub.s represents the temperature T.sub.s2. The quenching process lasts approximately t.sub.a=1 to 3 minutes. This is followed by ageing at a temperature T.sub.A of from 350 C. to 520 C. The total time duration of the method t.sub.g2 is thus shorter than the method according to the prior art (see FIG. 1, t.sub.g1). The shortening results from full homogenisation annealing (solution annealing) being omitted. In the case of CuNi2Si for example, according to the prior art this in particular requires heating times of several hours to a target temperature of from 750 C. to 800 C. and holding times of several hours, followed by the quenching.

[0104] FIG. 3 schematically shows a conveyor system 1. A steel strip roll 3 from which the steel strip material 6 is unwound is located in the unwinding station 2. The strip material 6 is smoothed in a subsequent alignment station 8a.

[0105] A powder storage container 10, in which the bearing metal powder 11 is stored and from which the powder 11 is applied to the strip material 6, is located in the subsequent powder spreading unit 9.

[0106] In a following first sintering station 13a, the powder 11 is sintered by means of a heating apparatus 14 arranged above the strip material 6. The composite material 25 thus produced is cooled in a cooling station 15 by means of a gas consisting of a nitrogen-hydrogen mixture. The gas mixture is ejected from the spray nozzles 17. The spray nozzles 17 are arranged under the strip material 6, such that the rear face 26 of the composite material 25 can be sprayed with the gas jet 18a consisting of the cooling gas mixture.

[0107] The composite material 25 is compressed in the following rolling station 8b and subsequently undergoes a further sintering process in a second sintering station 13b.

[0108] The quenching of the composite material 25 is in turn carried out in the quenching station 16, using a nitrogen-hydrogen mixture that is ejected from the spray nozzles 17 of a jet cooler. The spray nozzles 17 are arranged under the strip material 6, such that the rear face 26 of the composite material 25 is sprayed with the gas jet 18b consisting of the quenching medium 18.

[0109] The composite material 25 is subsequently wound in a winding station 4. The composite material roll 5 is subsequently transported to an ageing station 24 where the final ageing is carried out in a top hat furnace in order to set the desired mechanical properties of the bearing metal. The ageing time is between 4 hours and 10 hours at temperatures of from 350 C. to 520 C.

[0110] The plain-bearing composite material 30 thus produced is then further processed. For example, plain bearing shells can be produced therefrom by means of shaping. FIG. 4a shows a sliding element 40 in the form of a plain bearing shell 42. The plain bearing shell 42 comprises a steel substrate layer 32, a plain-bearing metal layer 34, and a sliding layer 36.

[0111] The structure of the valve plate 44 shown in FIG. 4b is that of a steel back 32 and the bearing metal layer 43 produced according to the invention. In the case of applications of this kind, for reasons of stress a sliding layer 36 is generally omitted. The thickness D.sub.1 may be between 1.5 mm and 8 mm. The bearing metal thickness D.sub.2 is 0.5 to 3.0 mm.

COMPARATIVE EXAMPLE

[0112] A plain-bearing composite material consisting of C22+CuNi2Si was produced, the production method according to DE 10 2005 063 324 B4 being carried out as follows: [0113] application of the powder of the bearing metal CuNi2Si [0114] first sintering at T.sub.s1=960 C. for 8 minutes [0115] cooling at a cooling rate of <1 K/s [0116] rolling [0117] second sintering at T.sub.s2=920 C. for 8 minutes [0118] cooling at a cooling rate of <1 K/s

[0119] FIG. 5 shows the hardness values of the steel and of the bearing metal following the second sintering.

[0120] At the end of the production method, the plain-bearing composite material has a steel hardness of 138 HBW 1/5/30 and a bearing metal hardness of 100 HBW 1/5/30. The corresponding strength values are shown in FIG. 6. The electrical conductivity is given in IACS units.

EXAMPLES ACCORDING TO THE INVENTION

[0121] If higher strengths for both steel and the bearing metal are required for particular applications, i.e. for applications in which wear-resistance and fatigue strength are required primarily, this is achieved using the method according to the invention. The method according to the invention was likewise carried out using the same materials, steel C22 and bearing metal CuNi2Si: [0122] spreading of the bearing metal powder onto a steel strip [0123] first sintering at T.sub.s1=960 C. for 8 minutes [0124] cooling at a cooling rate of <1 K/s [0125] second sintering at T.sub.s2=920C for 8 minutes [0126] quenching from 920 C. to 200 C., i.e. 720 C. in 0.7 minutes, corresponding to a quenching rate of 20 K/s

[0127] Following the second sintering, the steel is quenched and hardened by means of the rapid cooling from the austenite region (see FIG. 9).

[0128] Following the rapid setting (see FIG. 10) by means of the high cooling rate, the bearing metal CuNi2Si is present in the form of a supersaturated -solid solution, has low strengths, and has very high elongation at break values (see FIG. 8, cast state).

[0129] The plain-bearing composite material does not subsequently undergo homogenisation annealing, but instead ageing at temperatures of 380 C./8 hours (example 1), 480 C./4 hours (example 2) or 480 C./8 hours (example 3), i.e. ageing in the two-phase region of the CuNi2Si alloy (see FIG. 10), as a result of which nickel silicides form in the -solid solution, which cause a significant increase in hardness of the bearing metal. The hardnesses of the steel are reduced slightly, but still remain significantly higher than in the comparative example (see FIG. 7).

[0130] The corresponding strength values are summarised in FIG. 8.

LIST OF REFERENCE SIGNS

[0131] 1 conveyor system [0132] 2 unwinding station [0133] 3 steel strip roll [0134] 4 winding station [0135] 5 composite material roll [0136] 6 steel strip material [0137] 8a alignment station [0138] 8b rolling station [0139] 9 powder spreading unit [0140] 10 powder storage container [0141] 11 powder [0142] 13a first sintering station [0143] 13b second sintering station [0144] 14 heating apparatus [0145] 15 cooling station [0146] 16 quenching station [0147] 17 spray nozzle [0148] 18 quenching medium [0149] 18a gas jet [0150] 18b gas jet [0151] 24 ageing station [0152] 25 composite material [0153] 26 rear face of the composite material [0154] 30 plain-bearing composite material [0155] 32 substrate layer [0156] 34 bearing metal layer [0157] 36 sliding layer [0158] 40 plain bearing element [0159] 42 plain bearing shell [0160] 44 valve plate [0161] D.sub.1 steel layer thickness [0162] D.sub.2 bearing metal layer thickness [0163] T.sub.s sintering temperature [0164] T.sub.s1 sintering temperature [0165] T.sub.s2 sintering temperature [0166] T.sub.1 temperature after quenching [0167] T.sub.A ageing temperature [0168] t.sub.s quenching time [0169] t.sub.g1 total time of the method according to the prior art [0170] t.sub.g2 total time of the method according to the invention