WO2006131129A1

WO2006131129A1 - Aluminium plain bearing alloy

Info

Publication number: WO2006131129A1
Application number: PCT/EP2005/006091
Authority: WO
Inventors: Babette Tonn; Juri Moiseev; Hennadiy Zak; Lorenz Ratke; Heinz Palkowski; Hubert Schwarze
Original assignee: Technische Universität Clausthal; Deutsches Zentrum für Luft- und Raumfahrt e. V.
Priority date: 2005-06-07
Filing date: 2005-06-07
Publication date: 2006-12-14
Also published as: EP1888798A1; DE502005006241D1; ATE417132T1; JP2008542548A; US20100221141A1; EP1888798B1

Abstract

The invention relates to a monotectic aluminium plain bearing alloy, comprising 5 to 20 wt. % bismuth, 3 to 20 wt. % zinc, 1 to 4 wt. % copper and additionally several of the components manganese, vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten, chromium, silver, calcium, scandium, cerium, beryllium, antimony, boron, titanium, carbon and zirconium in amounts up to 5 wt. % and aluminium to make 100 wt. %, produced by strip casting and during the subsequent production process for plain bearings, after rolling or roll-bonding, subjected to a heat treatment at ca. 270 to 400 °C. Long bismuth particles or sheets, produced by rolling or roll-bonding can thus be recoagulated to give finely-distributed spherical drops with a size in the 20 νm range and smaller.

Description

Aluminum antifriction alloy

description

The invention relates to a heavy-duty aluminum sliding bearing alloy, in particular for multilayer bearings, a method for their preparation and associated plain bearing shells and plain bearings.

Highly stressed plain bearings are constructed of several layers to meet the variety of requirements placed on the bearings and partly contradictory. Mostly steel-aluminum composites are used.

While the steel support shell ensures the absorption of the mechanical stress and the tight fit, the sliding bearing materials must withstand the manifold tribological stresses and be fatigue-proof. To meet this requirement, the sliding bearing materials in the aluminum matrix on the one hand contain hard phases, such as silicon and intermetallic precipitates, and on the other soft phases, such as lead or tin. The heavy duty

Multi-layer bearings often additionally have a highly lead-containing sliding layer applied galvanically on the functional layer. This soft sliding layer ensures the good emergency running properties of the bearing. It can embed abrasion particles and thus remove from the sliding surface.

An environmentally friendly alternative to leaded aluminum plain bearing alloys are slide bearings based on aluminum-tin, which are used without additional sliding layer. However, the mechanical properties of these alloys, for example fatigue strength and heat resistance, are limited. The relatively high tin content during casting leads to the formation of a grain boundary-related tin network, which significantly affects the strength of these alloys, especially at higher temperatures.

Unlike tin, bismuth has some advantages as a soft phase in the aluminum matrix. Thus, bismuth has a higher melting point and can be used at higher temperatures. In addition, it is possible by special casting and heat treatment measures a massive accumulation of the To avoid bismuth at the grain boundaries of the sliding bearing alloys and to obtain a sufficiently uniform and fine distribution of bismuth droplets in the structure, which leads in the end to improve their resilience and tribological properties compared to aluminum-tin alloys.

It has been proposed in DE 4003018 A1 that an aluminum alloy comprises one or more of the components 1 to 50% by weight, preferably 5 to 30% by weight lead, 3 to 50% by weight, preferably 5 to 30% by weight. % Bismuth and 15 to 50 wt .-% indium and additionally one or more of the components 0.1 to 20 wt .-% silicon, 0.1 to 20 wt .-% tin, 0.1 to 10 wt .-% zinc , 0.1 to 5% by weight of magnesium, 0.1 to 5% by weight of copper, 0.05 to 3% by weight of iron, 0.05 to 3% by weight of manganese, 0.05 to 3 Wt .-% nickel and 0.001 to 0.30 wt .-% titanium. This alloy known from DE 4003018 A1 is cast in continuous casting vertically to a strip or wire of 5 to 20 mm thickness or diameter, wherein the melt is cast at a cooling rate of 300 to 1500 K / s. Due to the rapid cooling rate, it is intended to prevent large-volume precipitations of a minority phase from being formed in the period between when the demixing temperature has fallen below and after complete solidification of the matrix metal. From the practice of continuous casting of aluminum alloys, however, it is known that, as a result of the very high cooling rates, there is a considerable risk of crack formation and the process stability required for series production is difficult to ensure.

By the method described in EP 0 940 474 A1, a cast aluminum difficult to control monotectic aluminum sliding bearing alloy with up to 15 wt .-% bismuth and with at least one element selected from the group silicon, tin, lead in total from 0.5 to 15 wt .-% and possible additives from the group of copper, manganese, magnesium, nickel, chromium, zinc and antimony in a total amount of up to 3% in reproducible quality by casting tapes are cast. A homogeneous distribution of the minority phase is achieved in this case by intensive stirring of the melt in the electromagnetic field. In addition, the texture of this alloy is softened by addition of fining agents. Among other things, this has an advantageous effect on the size of the drop-shaped bismuth precipitates, which in casting a Diameter of 40 microns maximum. The addition amount of the grain refining agent is calculated according to EP 0 940 474 A1 with a formula which takes into account the bismuth content in the melt. This invention contains no indication of the type of Komfeinungszusätze used, leading to the results described in the patent.

EP 0 190 691 discloses an alloy containing 4 to 7% by weight bismuth, 1 to 4.5% by weight silicon, 0 to 1, 7% by weight copper, 0 to 2.5% by weight Lead and at least one element from the group nickel, manganese, chromium in a total amount of up to 1% and additionally at least one element from the group tin, zinc, antimony of a total of up to 5 wt .-% known. Although high silicon contents reinforce the aluminum matrix, they have a negative influence on the size of the minority phase and lead to a significant worsening of the droplet distribution in the strand. When rolling such a cast structure, the originally spherical lead or bismuth phase is deformed into very thick threads which considerably reduce the mechanical strength and the tribological properties of the material.

One possible solution for setting the desired material properties is the transformation of the elongated precipitates of the minority phase into compact structural forms by a subsequent heat treatment. For example, according to DE 4014430 A1 is a monotectic aluminum-silicon bismuth alloy heat-treated at temperatures of 575 ⁰ C to 585 ⁰ C, in order to achieve a fine distribution of the plate-like elongated after rolling bismuth.

As a further advantage, the heat treatment offers the possibility of improving the strength values of the aluminum sliding bearing alloy by means of hardening effects. The elements suitable for achieving the possible curing effects are, for example, silicon, magnesium, zinc and zirconium. The addition of copper increases the cure rate and can be used in combination with these elements. From US Pat. No. 5,286,445 an aluminum sliding bearing alloy with a bismuth content of 2 to 15% by weight, 0.05 to 1% by weight of zirconium and a copper content and / or magnesium content of up to 1.5% is known. In addition, this alloy contains at least one element from the group of tin, lead and indium in the sum of 0.05 to 2 wt .-% or at least one element selected from the group silicon, manganese, vanadium, antimony, niobium, molybdenum, cobalt, iron, Titanium, chromium in the sum of 0.05 to 5 wt .-%. The additions of tin, lead and indium support the re-coagulation of stretched bismuth drops to finer precipitates at temperatures of 200 ⁰ C to 350 ⁰ C. The elements zirconium, silicon and magnesium cause after annealing in the temperature range 480 ⁰ C to 525 ⁰ C, the is carried out shortly before the Walzplattiervorgang after US 5,286,445, the actual hardening effect. The transition elements should ensure an additional increase in the mechanical strength of the material.

The unfavorable effect of silicon on the size and distribution of the minority phase has already been reported. The addition of magnesium additionally has the disadvantage that magnesium with bismuth preferably forms the intermetallic compound Mg ₃ Bi ₂ . This accumulates in the bismuth drops and significantly reduces the embedding capacity of the bismuth drops for abrasive particles. By adding tin, the mechanical strength of the sliding bearing material is significantly impaired at higher temperatures. Furthermore, in DE 4014430 A1 and US 5,286,445 proposed in the heat treatment temperatures of about 480 ⁰ C in view of the formation of brittle intermetallic phases between the steel shell contactor and aluminum are very unfavorable selected. According to the state of the art, the temperature range acceptable for the cladding of aluminum with steel is below 400 ^° C.

The bismuth-containing alloys described so far have all not acquired any practical significance, since the complex processes occurring during their production by continuous casting and subsequent further processing to the sliding bearing shell have not yet been sufficiently controlled. As a prerequisite for an optimal property profile of

In addition to a fine distribution of the minority phase in the casting state, aluminum sliding bearing alloys also have the option of following the necessary forming and Walzplattiervorgängen to produce a fine distribution of the minority phase can. Other requirements are high strength, mechanical strength - including at high temperatures - wear resistance of the aluminum matrix and a good formability.

The invention is therefore an object of the invention to provide a heavy-duty aluminum sliding bearing alloy, which avoids the disadvantages of the prior art, and makes it possible to achieve a uniform and fine distribution of the bismuth phase and to obtain during the subsequent processing of the tapes in the manufacturing phase to slide bearing shell and possibly to improve.

This object is achieved by an aluminum sliding bearing alloy containing the following constituents: about 5 to 20 wt .-% bismuth, about 3 to 20 wt .-% zinc, about 1 to 4 wt .-% copper and additionally one or several of the components manganese, vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten, chromium, silver, calcium, scandium, cerium, antimony, boron, beryllium, titanium, carbon, zirconium in total up to about 5% by weight. % and remainder aluminum, but without tin, lead and silicon, except in quantities caused by melting-induced impurities, or in a quantity of not more than 1% by weight each. This means that the alloy according to the invention should in principle not contain tin and silicon as alloying constituents. In contamination-related amounts up to about 0.3 wt .-% or otherwise in small amounts up to about 1 wt .-%, but better to about 0.5 wt .-% can both tin (Sn), lead (Pb) as well as silicon (Si), however, without unduly compromising the advantages of the invention. The plain bearing alloy according to the invention is preferably continuously cast and is already characterized in the cast state by a fine distribution of the bismuth phase, which is largely independent of the withdrawal and cooling rate. In the course of a further treatment during rolling and roll cladding long bismuth plates may subsequently be fully re-coagulated by heat treatment at temperatures of 270 ⁰ C to 400 ⁰ C to finely divided spherical droplets, which are present at a corresponding procedure less than 20 microns. Preferably, the alloy contains between about 7 and 12 weight percent bismuth. The proportion of zinc may preferably be between about 3 and 6 wt .-%, of copper between about 2 and 4, in particular between about 2 and 3 wt .-%. The proportions of the different elements are independently variable within the given limits.

The alloy of the invention differs from the known by the use of bismuth as the only soft phase, ie there is no combination of bismuth with lead and / or tin, and by a max. 20 wt .-% increased zinc and up to max. 4 wt .-% increased copper content. Although the stated additions of zinc and copper lead to a slight deterioration in the size of the bismuth drops in the cast state compared to binary Al-Bi alloys, but allow complete re-coagulation of bismuth strands strongly stretched after the cladding into fine up to 20 microns large spherical droplets. These anneals are provided up to 400 ⁰ C. The glow time depends on the chemical composition. In addition, increased copper contents increase the strength of the aluminum matrix and, according to our own experience, improve the corrosion resistance of the bismuth-containing plain bearing material.

It has been found that the use of the commercial grain refining agent AITΪ5B1 or AITi3C0,15 in addition amounts of about 0.3 to 2 wt .-% exerts a strong grain refining effect on the alloy according to the invention and reliably prevents the formation of hot cracks during continuous casting at different cooling rates , The addition of the mentioned grain refining agent also causes a significant reduction in the size of the minority phase. The maximum diameter of the bismuth drops could be reduced to less than 30 microns by using Komfeinungszusätzen in the cast state even at relatively low cooling rates of about 5 K / s.

With the help of the elements manganese, vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten, chromium, silver, calcium, scandium, cerium, beryllium, antimony, boron, titanium, zirconium, carbon it is possible to determine the properties of the alloy according to the invention specially adapted to the respective purpose. The invention further comprises a process for producing an aluminum sliding bearing alloy using the composition of the invention as described above. Preferably, the alloying ingredients are combined in a casting process to form an alloy in which the cooling rate is 5 to 1000 K / s. Otherwise, the alloy can also be produced by other customary production methods, in particular by other casting methods. At present, production by continuous casting is preferred. The conditions are then adapted so that preferably drop-shaped Bismuteinlagerungen arise. In continuous casting, the take-off speed is preferably 2 to 15 mm / s.

The alloy obtained by casting is subjected to at least one heat treatment at temperatures between about 270 and 400 ⁰ C according to the preferred embodiment of this invention in the course of subsequent forming processes. Such heat treatment preferably follows a rolling and / or roll plating process, wherein multiple rolling and / or plating operations may be performed within the manufacturing process between the casting of the alloy and the final product and at least one heat treatment at the final rolling and / or roll plating operation or connect to several or all of these operations.

For the provision of a semi-tool or during the production of products such as u.a. Plain bearings, the cast alloy can be provided with at least one support layer. The support layer may in particular be a steel layer. Other layers, e.g. Adhesive layers or coatings may be added.

The invention further comprises a sliding bearing shell which contains or consists of an alloy according to the invention as one of the materials used therein.

Finally, the invention comprises a sliding bearing with such a plain bearing shell or the use of the sliding bearing shell according to the invention in a sliding bearing. The invention is explained in more detail below with reference to an embodiment.

Show it:

Fig. 1 cast structure of a AIZn5Cu3Bi7 alloy

Fig. 2 rolling structure of AIZn5Cu3Bi7 alloy, Gesamtformformgrad 94%, before the heat treatment

Fig. 3 rolling structure of AIZn5Cu3Bi7 alloy, Gesamtumformgrad 94%, after the heat treatment at 360 ° C / 3 h.

To produce the sliding bearing material, cast strips with a cross-section of 10 mm × 100 mm with the addition of 0.6% by weight of AITi5B1 are produced in this example on a vertical continuous casting plant, as known in the prior art. During the production of the belts, the take-off speed is 8 mm / s and the cooling speed is 600 K / s. First, the strands are milled horizontally on the broad sides to a thickness of about 8 mm.

Next, a brushed and degreased aluminum alloy primer is first roll-coated onto the brushed and degreased AIZn5Cu3Bi7 alloy in the mill stand. The thickness of the plated starting material strip is 4 mm. This is then rolled to 1, 3 mm in several rolling passes. For this purpose 5 rolling passes are necessary. To improve the plating capability of the aluminum bearing material strip, it is subjected to a Erhohlungsglühung at 370 ⁰ C of up to 3 hours duration. In the next processing step, the steel strip and the aluminum bearing material strip are joined together in a plating mill.

Subsequently, the produced material compound is subjected to a 3 hour heat treatment at a temperature of 360 ^° C., wherein the bond between the steel and the aluminum bearing material is increased by a diffusion process and that after plating in the aluminum-zinc-copper matrix is strong stretched bismuth threads to fine up to 20 microns large spherical droplets are completely transformed. The likewise from the Heat treatment resulting high hardness of at least 43 HB 2.5 / 62.5 / 30 is also beneficial. After this heat treatment, the plated strip can be divided and formed into bearing shells.

FIGS. 1 to 3 show, by way of example, how an alloy according to the invention, in this case an AIZn5Cu3Bi7 alloy, changes its structure during processing. FIG. 1 shows the structure of the alloy after production by continuous casting. The bismuth phase, which is in the form of droplets, is shown in the dark.

FIG. 2 shows the structure of the alloy after rolling. In the rolling structure, the bismuth plates elongated by the rolling can be recognized.

Figure 3 shows the rolled structure after a heat treatment at 360 ⁰ C for 3 hours. The elongated Bi plates could be effectively recoagulated by the heat treatment. In Figure 1, still occasionally to be recognized larger drops were divided by the stretching and re-coagulation, so that the degree of fine distribution by the treatment is increased overall.

It should be noted that the example is illustrative only and does not limit the invention. The person skilled in the art also knows how slide bearings and bearing shells are produced and how, thus, the production of the alloy according to the invention can be included in the usual bearing manufacturing processes.

Claims

claims

1. monotectic aluminum plain bearing alloy with 5 to 20 wt .-% bismuth,

3 to 20 wt .-% zinc, 1 to 4 wt .-% copper and additionally one or more of the components manganese, vanadium, niobium, nickel, molybdenum,

Cobalt, iron, tungsten, chromium, silver, calcium, scandium, cerium, beryllium, antimony, boron, titanium, carbon, zirconium in total up to 5 wt .-% and aluminum ad 100 wt .-%.

2. Monotectic aluminum plain bearing alloy according to claim 1, characterized in that the alloy contains between 7 and 12 wt .-% bismuth.

3. Monotectic aluminum plain bearing alloy according to claim 1 or 2, characterized in that the alloy between 3 and 6 wt .-%

Contains zinc.

4. Monotectic aluminum plain bearing alloy according to one of claims 1 to 3, characterized in that the alloy contains between 2 and 4 wt .-%, in particular between 2 and 3 wt .-% copper.

5. Monotectic aluminum plain bearing alloy according to one of claims 1 to 4, characterized in that the alloy contains up to 2 wt .-% Al-Ti-B or Al-Ti-C grain refining agent.

6. A method for producing an aluminum plain bearing alloy using the composition according to any one of claims 1 to 5, characterized in that the alloying components are bonded in a casting process to an alloy in which the cooling rate is 5 to 1000 K / s.

7. The method according to claim 6, characterized in that the withdrawal speed is 2 to 15 mm / s.

8. The method according to claim 6 or 7, characterized in that a continuous casting is used as the casting process.

9. The method according to any one of claims 6 to 8, characterized in that the alloy for the provision of a semi-finished product is provided with at least one support layer.

10. The method according to any one of claims 6 to 9, characterized in that the alloy in the course of subsequent forming processes at least one heat treatment at temperatures of 270 ⁰ C to 400

° C is made.

11. The method according to claim 10, characterized in that the heat treatment follows a rolling and / or Walzplattiervorgang.

12. plain bearing shell containing or consisting of one of the materials used therein an alloy according to any one of claims 1 to 5.

13. plain bearing with a shell according to claim 11.