JP2008542548A - Aluminum sliding bearing alloy - Google Patents

Abstract

The present invention relates to 5 to 20% by weight of bismuth, 3 to 20% by weight of zinc, 1 to 4% by weight of copper, manganese, vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten, chromium, Made by strip casting, including 5% by weight total of several components of silver, calcium, scandium, cerium, beryllium, antimony, boron, titanium, carbon and zirconium and 100% by weight aluminum, and later The invention relates to a monoclinic aluminum slide bearing alloy that has been subjected to a heat treatment of approximately 270 to 400 ° C. after rolling or roll bonding during the manufacturing process of the present invention. Long bismuth particles or sheets made by rolling or roll bonding can be re-solidified to give finely distributed spherical droplets with a size of 20 μm or less.
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Description

  The present invention relates to a highly durable aluminum bearing alloy (especially a multi-layer bearing), a method of manufacturing the same, and related sliding bearing shells and sliding bearings.

  High durability sliding bearings are made of several layers that meet the various requirements of the bearing and are somewhat incompatible. Mainly steel-aluminum composite material is used. Steel support shells absorb mechanical loads and ensure a tight fit, but the plain bearing material must withstand various friction loads and fatigue. To meet this requirement, the material of the sliding bearing in the aluminum matrix contains on the one hand a hard phase such as silicon and intermetallic precipitates and on the other hand a soft phase such as lead and tin. High durability multilayer bearings often have a high lead content sliding layer that is further electrolytically coated on the functional layer. This soft sliding layer provides good emergency operating characteristics of the bearing. This can embed the wear particles and release them from the sliding surface.

  An environmentally friendly alternative to lead-containing aluminum sliding bearing alloys is aluminum tin-based sliding bearings, which are used without an additional sliding layer. However, the mechanical properties of these alloys, such as fatigue resistance and heat resistance, are limited. The relatively high tin content results in the formation of tin networks that are bonded together at grain boundaries during casting. This significantly impairs the load carrying capacity of these alloys, especially at relatively high temperatures.

  In contrast to tin, bismuth has several advantages as a soft phase in the aluminum matrix. For example, bismuth has a high melting point and can be used at higher temperatures. In addition, by special casting and heat treatment means, it is possible to avoid mass concentration of bismuth at the grain boundaries of the sliding bearing alloy and to obtain a sufficiently homogeneous and fine distribution of bismuth droplets in the microstructure. This ultimately results in improved load carrying capacity and friction properties compared to aluminum tin alloys.

  Thus, in DE 4003018 A1, the aluminum alloy is 1 to 50 wt.%, Preferably 5 to 30 wt.% Lead, 3 to 50 wt.%, Preferably 5 to 30 wt.% Bismuth, and 15 to 50 wt. % One or more components of indium and 0.1 to 20% by weight silicon, 0.1 to 20% by weight tin, 0.1 to 10% by weight zinc, 0.1 to 5% by weight % Magnesium, 0.1-20% copper, 0.05-3% iron, 0.05-3% manganese, 0.05-3% nickel and 0.001-0. It has been proposed that one or more components of 30 wt% titanium may be included. This alloy, known from DE 4003018 A1, is cast vertically by continuous casting into strips or wires with a thickness or diameter of 5 to 20 mm, and the melt is cast at a cooling rate of 300 to 1500 K / s. The quenching rate is intended to avoid the formation of large volume precipitates of minor phase at a time between the temperature drop below the segregation temperature and the complete solidification of the matrix metal. However, practical experience in continuous casting of aluminum alloys gives the result that very fast cooling rates are a significant risk of crack formation and only guarantee the processing stability required for mass production. I know.

  The method described in EP 0940474 A1 comprises a total of 0.5 to 15% by weight of at least one component from the group comprising 15% by weight of bismuth and silicon, tin and zinc, copper, manganese, Reproducible quality by strip casting of difficult-to-cast hard aluminum alloy bearings containing up to 3% by weight of possible additives from the group including magnesium, nickel, chromium, zinc and antimony So that it can be cast in. A homogeneous distribution of the minor phase is in this case achieved by vigorously stirring the melt in an electromagnetic field. By adding a crystal refiner, the microstructure of this alloy is further refined. Among the effects this has is also an advantageous effect on the size of bismuth precipitates in the form of droplets with a diameter of up to 40 μm in the cast state. According to EP 0940474 A1, the addition amount of the crystal refining agent is calculated by a formula that takes into account the bismuth content in the melt. This invention does not include any indication of the type of refinement additive used to obtain the results described in the patent.

  EP 090691 describes 4 to 7% by weight of bismuth, 1 to 4.5% by weight of silicon, 0 to 1.7% by weight of copper, 0 to 2.5% by weight of lead, nickel, manganese and Disclosed is an alloy comprising at least one element from the group comprising chromium to a total extent of less than 1% by weight, and further comprising at least one element from the group comprising tin, zinc and antimony to a total of less than 5% by weight. ing. High silicon contents strengthen the aluminum matrix, but they have a detrimental effect on the size of the minor phase and clearly impair the droplet distribution in the strands. While rolling such a cast structure, the originally spherical lead or bismuth phase is transformed into a very thick filament. This significantly reduces the mechanical load carrying capacity and frictional properties of the material.

  One possible solution for setting the desired material properties is to transform the minor phase elongated precipitates into a dense structure by subsequent heat treatment. For example, according to DE 4014430 A1, a twin crystal aluminum silicon-bismuth alloy is heat-treated at 575-585 ° C. to achieve a fine distribution of the bismuth phase and is drawn into a lamellar form after rolling.

  As a further advantage, the heat treatment offers the possibility of improving the strength value of the aluminum plain bearing by a hardening effect. Suitable elements for achieving possible hardening 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.

  US 5,286,445 contains bismuth with a content of 2 to 15% by weight, zirconium with a content of 0.05 to 1% by weight and copper and / or magnesium with a content of 1.5% by weight or less. An aluminum slide bearing alloy is disclosed. In addition, this alloy has a total of 0.05 to 2% by weight of at least one element from the group comprising tin, lead and indium, or silicon, manganese, vanadium, antimony, niobium, molybdenum, cobalt, iron, titanium and A total of 0.05 to 5% by weight of at least one element from the group comprising chromium. The addition of tin, lead and indium assists in re-solidification of the stretched bismuth droplets into finer precipitates at temperatures of 200-350 ° C. The elements zirconium, silicon and magnesium provide an actual hardening effect after annealing in the temperature range of 480 to 525 ° C. This is carried out according to US 5,286,445 shortly before the rolling coating. The transition elements are intended to ensure a further increase in the mechanical load bearing capacity of the material.

The undesirable effects of silicon on minor phase size and distribution have already been reported. The addition of magnesium is further accompanied by the disadvantage that magnesium preferentially forms the intermetallic compound Mg ₃ Bi ₂ with bismuth. This is inserted between the bismuth droplets and clearly reduces the ability of the bismuth droplets to embed the wear particles. Adding tin significantly impairs the mechanical load bearing capacity of the sliding bearing material at high temperatures. Furthermore, the temperature of the heat treatment above 480 ° C. proposed in DE 40144 30 A1 and US Pat. No. 5,286,445 is very disadvantageously selected for the formation of a brittle intermetallic phase between the steel support shell and aluminum. ing. According to the prior art, the acceptable temperature range for coating aluminum with steel is less than 400 ° C.

  None of the above-described alloys containing bismuth has gained any practical significance. This is because it is still impossible to adequately overcome the complex processes that occur during continuous casting and their production by subsequent further processing to form sliding bearing shells. In addition to the minor phase fine distribution in the cast state, the requirements for optimal properties of the aluminum plain bearing alloy can establish a minor phase fine distribution, especially even after the necessary forming and rolling coating operations. It is sex. Other requirements are high strength, mechanical load capacity (including high temperatures), aluminum matrix wear resistance and good formability.

  The present invention is therefore based on the object of providing a highly durable aluminum sliding bearing alloy, which avoids the disadvantages of the prior art and achieves a homogeneous and fine distribution of the bismuth phase, and a sliding bearing shell. This can be maintained during further processing of subsequent strips in the processing stage to form and improve if possible.

  This object is achieved by an aluminum plain bearing alloy comprising the following components: Approximately 5 to 20% by weight bismuth, approximately 3 to 20% by weight zinc, approximately 1 to 4% by weight copper, and manganese, vanadium, niobium, nickel, molybdenum, cobalt, iron, tungsten, chromium, silver , Calcium, scandium, cerium, antimony, boron, beryllium, titanium, carbon and zirconium, and the remaining aluminum is a total of 5% by weight or less, but tin, lead and silicon are derived from scouring In addition to the amount produced by the impurities, it is not more than 1% by weight. This means in principle that the alloys according to the invention are intended not to contain tin and silicon as alloying components. However, not only tin (Sn) but also lead (Pb) and silicon (Si) are produced by impurities of about 0.3 wt% or less, or in small amounts of about 1 wt% or less, but better It may be present at about 0.5% by weight or less and does not excessively detract from the advantages of the present invention. The plain bearing alloy according to the invention is preferably continuously cast and is already distinguished in the cast state by the fine distribution of the bismuth phase, which does not depend greatly on the drawing and cooling rates. Long bismuth lamellae produced during further processing during rolling and roll coating are then completely re-solidified by heat treatment at temperatures of 270-400 ° C. to form finely distributed spherical droplets, which are If the process is properly performed, it is smaller than 20 μm.

  The alloy preferably contains approximately 7-12% by weight of bismuth. The zinc content is preferably approximately 3 to 6% by weight and the copper content is approximately 2 to 4% by weight, in particular 2-3% by weight. The content of the various elements can be varied independently of each other within a given range.

  The alloys according to the invention differ from known alloys by the use of bismuth as a single soft phase former. That is, there is no combination of bismuth and lead and / or tin, the zinc content increases to a maximum of 20 wt% or less, and the copper content increases to a maximum of 4 wt% or less. The stated amounts of added zinc and copper cause a slight deterioration in the size of the bismuth droplets in the cast state compared to the binary Al-Bi alloy, but they were highly stretched after the coating pass. Enables complete re-coagulation of the bismuth filament and forms fine spherical droplets of 20 μm or less in size. The annealing time depends on the chemical composition. In addition, the increased copper content results in increased strength of the aluminum matrix, and our experience improves the corrosion resistance of bismuth-containing plain bearing materials.

  The use of the commercially available crystal refiner AlTi5B1 or AlTi3CO, 15 added in an addition amount of approximately 0.3 to 2% by weight has an excellent crystal refinement effect in the alloys according to the invention, and various cooling It has been found to reliably prevent the formation of heat cracks during continuous casting at speed. The addition of the mentioned crystal refiner has the further effect of clearly reducing the size of the minor phase. The use of grain refiner additives makes it possible to reduce the maximum diameter of bismuth droplets in the cast state to less than 30 μm, even at a relatively slow cooling rate of approximately 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 and carbon, the properties of the alloys according to the invention are particularly It can be adapted to each intended use.

  The present invention further includes a method of producing an aluminum plain bearing alloy using the composition according to the present invention described above. Preferably, the alloying components are combined in a casting process with a cooling rate of 5 to 1000 K / s to form an alloy. Alternatively, the alloy can be manufactured by other conventional manufacturing methods, in particular by other casting methods. Production by continuous casting is currently preferred. The conditions are therefore preferably adapted so that a droplet-shaped bismuth intercalation is formed. During continuous casting, the drawing speed is preferably 2 to 15 mm / s.

  According to a preferred embodiment of the invention, the alloy obtained by casting is subjected to at least one heat treatment at a temperature of approximately 270 to 400 ° C. during the subsequent forming step. Such heat treatment is preferably done after rolling and / or roll coating, several rolling and / or coating operations can be carried out in the manufacturing process between the casting of the alloy and the final product, and At least one heat treatment can be performed after the final rolling and / or roll coating operations or after some or all of these operations.

  For the preparation of a semi-finished product or in the course of the manufacture of a product such as a sliding bearing, the cast alloy may be provided with at least one support layer. The support layer may in particular be a steel layer. Additional layers, such as adhesion promoting layers or coatings may be added.

  The invention further includes a plain bearing shell comprising the alloy according to the invention as one of the materials used therein or consisting of this alloy.

  Finally, the invention includes a sliding bearing with such a sliding bearing shell, or the use of a sliding bearing shell according to the invention in a sliding bearing.

  The invention is explained in more detail below on the basis of exemplary embodiments.

  In order to produce a plain bearing material, a cast strip having a cross section of 10 mm × 100 mm in this example is added in a vertical continuous casting apparatus as known in the prior art with 0.6 wt% AlTi5B1. create. In the production of the strip, the drawing speed is 8 mm / s and the cooling rate is 600 K / s. The strand is first rolled horizontally on a wide surface to a thickness of approximately 8 mm.

  Subsequently, the matte and degreased AlZn5Cu3Bi7 alloy is similarly coated with the matte and degreased aluminum alloy adhesion promoter in the first rolling pass in the rolling stand. The thickness of the coated raw material strip is 4 mm. This is subsequently rolled to 1.3 mm in several rolling passes. This requires five rolling passes. In order to improve the coating properties of the aluminum bearing material strip, it is subjected to a regenerative annealing operation at 370 ° C. for up to 3 hours. In the next processing step, the steel strip and the aluminum plain bearing material strip are bonded together in a coated rolling mill.

  The resulting material combination is then subjected to a heat treatment lasting 3 hours at a temperature of 360 ° C. to increase the bond between the steel and the aluminum plain bearing material by a diffusion process, and the aluminum-zinc-copper matrix after cladding. The bismuth filaments that are highly stretched therein are completely modified to form fine spherical droplets having a size of 20 μm or less. Similarly, a high hardness of at least 43 HB 2.5 / 62.5 / 30 resulting from heat treatment is advantageous. After this heat treatment, the coated strip may be subdivided and formed into a bearing shell.

  1 to 3 show by way of example how an alloy according to the invention (here AlZn5Cu3Bi7 alloy) changes in its microstructure during processing. FIG. 1 shows the microstructure of the alloy after production by continuous casting. The droplet-shaped bismuth phase is shown as dark.

  FIG. 2 shows the microstructure of the alloy after rolling. Bismuth lamellae stretched by rolling are visible in the rolled structure.

  FIG. 3 shows the rolled structure after heat treatment at 360 ° C. for 3 hours. The stretched Bi lamella can be effectively re-solidified by heat treatment. Because large droplets (an isolated example of which is still seen in FIG. 1) are destroyed by stretching and re-solidification, the process increases the degree of overall fine distribution.

  It should be mentioned that the examples are merely illustrative and do not limit the invention. The person skilled in the art knows how slide bearings and bearing shells are manufactured and how the manufacture of the alloy according to the invention is consequently incorporated into the normal bearing manufacturing process.

FIG. 1 shows the cast structure of AlZn5Cu3Bi7 alloy. FIG. 2 shows a rolled structure of an AlZn5Cu3Bi7 alloy having a total forming degree of 94% before heat treatment. FIG. 3 shows a rolled structure of an AlZn5Cu3Bi7 alloy having a total forming degree of 94% after heat treatment at 360 ° C./3 hours.

Claims (13)

  A monolithic aluminum sliding bearing alloy comprising 5 to 20% by weight bismuth, 3 to 20% by weight zinc, 1 to 4% by weight copper, and manganese, vanadium, niobium, nickel, molybdenum, cobalt, One or more components of iron, tungsten, chromium, silver, calcium, scandium, cerium, beryllium, antimony, boron, titanium, carbon, and zirconium are combined in total to 5% by weight or less, and aluminum that makes the alloy 100% by weight. Including monoclinic aluminum sliding bearing alloy.   2. The monoclinic aluminum sliding bearing alloy according to claim 1, wherein the alloy contains 7 to 12% by weight of bismuth.   3. The monoclinic aluminum plain bearing alloy according to claim 1, wherein the alloy contains 3 to 6% by weight of zinc.   4. A monoclinic aluminum sliding bearing alloy according to claim 1, wherein the alloy contains 2 to 4% by weight of copper, in particular 2 to 3% by weight of copper.   5. The twinned aluminum sliding bearing alloy according to claim 1, wherein the alloy contains 2% by weight or less of Al—Ti—B or Al—Ti—C crystal refining agent.   A method for producing an aluminum plain bearing alloy using the composition according to claim 1, wherein the alloying component is combined in a casting process with a cooling rate of 5 to 1000 K / s. Forming a method.   7. The method according to claim 6, wherein the drawing speed is 2 to 15 mm / s.   The method according to claim 6 or 7, wherein a continuous casting process is used as the casting process.   9. Process according to one of claims 6 to 8, characterized in that the alloy is provided with at least one support layer for the preparation of a semifinished product.   10. The method according to claim 6, wherein at least one heat treatment is performed on the alloy at a temperature of 270 to 400 [deg.] C. during the subsequent forming step.   11. A method according to claim 10, characterized in that the heat treatment is carried out after the rolling and / or rolling coating operation.   6. A plain bearing shell comprising the alloy according to claim 1 as one of the materials used therefor or consisting of this alloy.   A plain bearing comprising the shell according to claim 11.

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