GB2066846A - Aluminum-tin base bearing alloy - Google Patents

Abstract

The Al-Sn base bearing alloy comprises 3 to 7% by weight of Sn; 0.1-1.0% by weight of Cr; 1 to 10% by by weight in total of one or more constituents selected from a group of specified additives consisting of Si, Mn, Sb, Ti, Zr, Ni, Fe, W, Ce, Nb, V, Mo, Ba, Ca and Co; 0.1 to 0.8, the latter exclusive, % by weight of Cu and/or Mg; and the remainder of aluminium. The alloy can further contain 9% by weight in total of one or more constituents selected from a group consisting of Pb, Bi, Tl, Cd and In, thereby improving the bearing characteristics. Steel-backed allots according to the invention may be used for the bearings of internal combustion engines in which spheroidal (nodular) graphite cast iron is used for crankshafts.

Description

SPECIFICATION Aluminium-tin base bearing alloy The present invention relates to an aluminium-tin (Al-Sn) base bearing alloy which is prepared by adding tin to an aluminium matrix and to a bearing material which is made by applying the Al-Sn base bearing alloy to a backing steel by pressure welding. More particularly, the Al-Sn base bearing alloy of the invention is characterized in that the bearing alloy may be improved in several properties thereof by adding various kinds of additive elements. That is, the fatigue strength may be much improved by reducing the lowering of the hardness at high temperatures and, especially, by avoiding the coarsening of tin particles. Furthermore, the wear resistance of the bearing alloy may be also raised in order to improve the durability relative to the shaft to be supported which has a hard and coarse surface.

Accordingly, in the case that the bearing alloy of the present invention is used for the bearing devices around the crank shafts of internal combustion engines which require severe conditions, remarkable advantages can be expected.

In recent years, the automobile internal combustion engines are required to be made compact and to have high power. Further, as the countermeasure to the regulation of exhaust gas, they must be provided with blow-by-gas recirculation devices or the like. Therefore, the use conditions for the bearing materials in the internal combustion engines have become severe at high loads and high temperatures.

Under such severe conditions, the conventional bearing materials are liable to cause fatigue failure and abnormal wearing which bring the engines to several troubles.

In connection with the shafts to be brought into engagement with the bearing materials, there is a tendency that the hitherto produced forged shafts are changed into less expensive shafts made of spheroidal graphite cast iron or other coarse material in order to reduce the production costs. Therefore, the improvement in the wear resistance, seizure resistance and fatigue resistance at high temperatures are required much more.

Exemplified as the Al-Sn base alloy used for making the bearings of internal combustion engines in the prior art are: Al(remainder) - Sn(3.5-4.5) - Si(3.5-4.5) - Cu(0.71.3); Al(remainder) - Sn(4-8) - Si(i-2) - Cu(O.i-2) - Ni(O.i-i); Al(remainder - Sn(3-40) - Pb(O.i-5) - Cu(0.2--2)- Sb(O.i-3) - Si(0.2--3)- Ti(O.Oi-i); Al(remainder) - Sn( 5-30) - Cu(0.5--2);; and Al(remainder) - Sn(i-23) - Pb(1 .5-9) - Cu(0.3--3)- Si(1-8), in which the values in parentheses denote the percentages by weight of the component materials.

When these conventional alloys are used for the bearings of automobile internal combustion engines under severe conditions as described above, fatigue failure is sometimes caused to occur in a short time if the engines are continuously operated under heavy loads. This is considered to be due to the fact that the temperature of the lubricant oil in an internal combustion engine becomes very high during the continuous full-load running thereof, for example, the temperature of the lubricant oil in an oil pan reaches 1 300C-i 500 C, so that the temperature of sliding surfaces of bearings is also raised very high.As the result, since the eutectic point of such the alloy is about 2250C or so, the hardness of the alloy becomes rapidly low under the high temperature conditions, which causes the fusion and the migration of the Sn component and the fatigue strength is resultantly lowered. The inventors of the present invention have prepared an alloy, the hardness of which is not lowered at high temperatures and the Sn component of the alloy is hardly movable. The alloy was worked into the shapes of bearings for internal combustion engines and they were subjected to fatigue tests under dynamic loads at high oil temperatures. As a result, the improvement in fatigue strength was recognised, which substantiated the above-mentioned consideration.

Further, in addition to the lowering of the fatigue strength due to the loss of hardness at high temperatures as mentioned above, the coarsening of tin particles in the texture of conventional Al-Sn alloy also causes lowering of the fatigue strength. That is, the aluminium bearing material is generally formed by applying Al-Sn alloy to a backing steel through pressure welding, in which an annealing step is required after the pressure welding in order to improve the adhesive strength between both metals.

The annealing is generally done at a temperature below the point at which an Al-Fe inter-metallic compound deposits and the higher the treating temperature is and the longer the treating time is, the larger the adhesion strength becomes. As a matter of fact, when the conventional Al-Sn alloy is placed in a high temperature condition during annealing, the coarsening of aluminium grain boundaries and tin particles is disadvantageously caused to occur in the alloy texture. That is, when the conventional aluminium bearing alloy is subjected to annealing in order to improve the adhesive strength to the backing steel, the coarsening of tin particles is brought about, which results in the lowering of the fatigue strength of the Al-Sn alloy at high temperatures.

Further, these conventional Al-Sn bearing alloys may not have sufficient wear resistance.

Especially, when shafts having hard and coarse surfaces, such as those made of spheroidal graphite cast iron, are brought into engagement with the bearing alloys, the wear resistance is greatly lowered and fatigue failures are liable to occur and this has been a serious problem.

The present invention aims to reduce or eliminate one or more of the above-described disadvantages in the conventional Al-Sn base bearing alloys. Accordingly, one object of the present invention is to provide an Al-Sn base bearing alloy which exhibits relatively small loss of hardness at high temperatures, and as a result, has a relatively high fatigue strength.

Another object of the present invention is to provide an improved Al-Sn base bearing alloy in which the coarsening of the tin particles is avoided or moderated during the annealing step or during use under high temperature conditions, which results in a higher fatigue strength.

A further object of the present invention is to provide an Al-Sn base bearing alloy having a relatively high wear resistance, especially when employed with shafts which are made of hard and coarse materials such as spheroidal graphite cast iron that is used for making the crankshafts of internal combustion engines.

Yet a further object of the present invention is to provide a bearing material which is made by applying the above bearing alloy to the surface of a backing steel sheet and bearings for internal combustion engines which are made of the above bearing material.

According to the present invention, the Al-Sn base bearing alloy basically comprises 3 to 7% by weight of Sn; 0.11.0% by weight of Cr; 1 to 10% by weight in total of one or more constituents selected from a group of specified additives consisting of Si, Mn, Sb, Ti, Zr, Ni, Fe, W, Ce, Nb, V, Mo, Ba, Ca and Co; 0.1 to 0.8, the latter exclusive, % by weight of Cu and/or Mg; and the remainder of aluminium. The alloy can further contain 9% by weight in total of one or more constituents selected from a group consisting of Pb, Bi, TI, Cd and In, thereby improving the bearing characteristics.

The objects, features and advantages of the present invention will be more clearly understood from the following detailed description, examples and accompanying drawings, in which: Fig. 1 is a graph showing the changers in wear losses of alloys with the increases of loads applied to steel shafts which are in contact with the alloys; and Fig. 2 is a graph showing the changes in wear losses of alloys with the increase of loads applied to the shafts made of spheroidal graphite cast iron which are in contact with the alloys.

The Al-Sn base bearing alloy of the present invention is prepared by adding the above-mentioned Sn, Cr, one or more members of the foregoing specified additive group and Cu and/or Mg to the matrix - of aluminum.

In connection with the quantity of tin, the conformability and lubricating property may generally be improved with the increase of tin, however, the hardness is lowered. Therefore, the load carrying property as a bearing becomes low. To the contrary, when the quantity of tin becomes small, the load carrying property is increased, however, the alloy becomes too hard as the bearing material and the conformability becomes worse. In the conventional art, the upper limit of tin content was generally about 15% and the lower limit, about 3%. In the present invention, the tin content is restricted to the range of 3 to 7% in which the load carrying property is good.

The addition of chromium (Cr) is effective in that the hardness of the alloy is raised to prevent the alloy from softening at high temperatures and thus the coarsening of tin particles is not caused to occur even in annealing. In the first place, the effects to raise the hardness and to avoid the softening of alloy at high temperatures will be described. When the quantity of chromium is less than 0.1 wt.%, the improvement in high temperature hardness cannot be expected. If the addition quantity of chromium exceeds 1.0 wit.%, the Al-Cr inter-metallic compound cannot be dispersed finely and evenly as described later on, therefore, the effect of the addition becomes low.Accordingly, the addition quantity of chromium is limited in the range of 0.1 to 1.0 wt.%. More particularly in connection with the improvement in the high temperature hardness, the chromium forms a solid solution in aluminium which raises the recrystallization temperature of aluminium and, in addition, the solid solution itself improves the hardness of the aluminium matrix. At the same time, the hardness of the alloy containing chromium becomes higher even when it is subjected to rolling several times which is contrasted to casting. With the rise of the recrystallizing temperature of aluminium, the bearings of engines that are exposed to high temperatures can maintain their mechanical properties.Especially, the lowering of hardness at high temperatures can be reduced and the softening of bearings in a high temperature range can well be avoided, thereby improving the durability of bearings. Further, the Al-Cr intermetallic compound that is deposited over the limit of solid solution, has a Vickers hardness of more than 370 so that the dispersion of such the compound aids the bearing alloy in maintaining the hardness at high temperature. Therefore, the dispersion of such the inner-metallic compound in a proper quantity gives a good effect. The preferable range of the quantity of chromium is, as described above, 1.0 wt.% or less, and if the quantity of chromium is within such the range, fine and uniform deposition of the inter metallic compound is formed and it increases the hardness of the bearing alloy.

The effect of the addition of chromium to avoid the coarsening of tin particles will be described in 5 the following. The coarsening of tin particles is a phenomenon owing to the migration of aluminium grain boundaries and tin particles in a high temperature condition of the Al-Sn alloy. Since the chromium is precipitated as the above-mentioned Al-Cr inter-metallic compound which is finely dispersed in the aluminium alloy matrix, this inter-metallic compound inhibits directly the migration of aluminium grain boundaries and, at the same time, it obstructs the growth of aluminium crystal grains.

Therefore, the migration of tin particles is also hindered and, as the result, the coarsening of tin particles can be avoided. This is related to the fact that the finely divided tin particles are retained as they stand during the repeat of rolling and annealing, and the above-described various effects can be obtained.

Furthermore, the liquidation of tin particles having a low melting point of about 2320C can be prevented effectively under high temperature conditions because the tin particles are well maintained in a finely divided state in the aluminium matrix. From this viewpoint, the effect of the prevention of lowering in hardness will be understood.

In the above passage, the effect for preventing the coarsening of tin particles in the annealing step is described. This effect can also be expected in the working condition of the bearing material in which the temperature is equal to the annealing condition. Accordingly, the fatigue strength in practical uses can also be improved with the inhibition of softening.

In order to improve mainly the wear resistance, it is effective to add one or more members of the group of the specified additives such as silicon (Si), manganese (Mn), antimony (Sb), titanium (Ti), zirconium (Zr), nickel (Ni), iron (Fe), tungsten (W), cesium (Ce), niobium (Nb), vanadium (V), molybdenum (Mo), barium (Ba), calcium (Ca) and cobalt (Co). The addition quantity of each of these elements is within the range of a trace to 10 wt.%, while the total quantity of these elements is not more than 10 wt.%, and preferably in the range of 1 to 6 wt%, which quantity may be determined in accordance with the purpose of use. The reason for the above restriction is as follows.The precipitated substances (or crystallized substances, the same shall apply hereinafter) of these elements are dispersed in the aluminium matrix, therefore, the wear resistance can be improved. If the addition quantity of the specified additive is less than 1 wt.% the effect of addition cannot be exhibited on the contrary, if the addition quantity is more than 10 wt.%, the precipitated substance becomes too much, so that the adaptability to rolling becomes worse and the repeating of rolling and annealing becomes difficult, further, the formation of the fine particles of tin is inhibited. In order to eliminate these undesirable effects completely, the preferable upper limit is made 6 wt.% or so.

The forms of precipitation of these specified additives are the precipitated substance of each added element, those of inter-metallic compounds between the added elements, those of inter-metallic compounds of aluminium and added elements, and those of inter-metallic compounds of aluminium and the inter-metallic compound of added elements. The wear resistance can be improved by the precipitated substances in any forms of the above.

The Vickers hardnesses of these precipitated substances reach several hundreds, so that the precipitated substances are very hard and the wearing of bearings caused by the friction with shafts can be reduced notably by the precipitated substances. Accordingly, a quite good result can be obtained when a proper quantity of the precipitated susbtance exists in the aluminium matrix. The range of the proper quantity is 1 to 10 wt.% as described above, and if the quantity of the precipitated substance is in this range, the precipitated substance can be dispersed uniformly and the wear resistance can effectively be improved without causing any ill effects such as the lowering of conformability.

The effect to improve the wear resistance is remarkably when the bearing supports a shaft having a hard and coarse surface. The performance of bearing generally depends upon the hardness and coarseness of the material to be supported to a great extent. For example, when the conventional Al-Sn base bearing material is used for supporting a shaft made of spheroidal graphite cast iron, the properties of the bearing such as antiseizing property and wear resistance are markedly lowered. Since the shafts made of spheroidal graphite cast iron can be produced at low cost, such shafts have been widely employed recently in place of the steel shafts. In the iron matrix of the shaft, soft graphite particles are scattered, therefore, when the shaft surface is scraped, blade-like grinding burrs are formed around the particles of graphite.When the shaft having such grinding burrs is slid relative to the bearing under a heavy load in which the coarsenesses of the shaft and the bearing and the thickness of the oil film between them equals with each other, the bearing surface which is softer than the shaft is ground. If such condition is continued, the surface of the bearing becomes coarse and the clearance between the bearing and the shaft becomes large, which causes the breakage of oil film or the lack of oil film. As a result, the direct contact between the shaft and the bearing (the metal-to-metal contact) is caused to occur, which results in the occurrence of seizure of both the parts.

While in the alloy according to the present invention, the precipitated substance which is formed in the aluminium matrix by the addition of one or more members of the above specified additives, is harder than the above-mentioned grinding burrs of the shaft of spheroidal graphite cast iron. Therefore, the precipitated substance removes the above-mentioned grinding burrs from the surface of the shaft and, in addition, the metal transfer and adhesion of the precipitated substance is hard to occur.

Therefore, the course of wearing of the bearing surface can be suppressed within a relatively short time to cause the formation of stable oil film. As a result, in relation to the shaft made of the spheroidal graphite cast iron, the wear resistance and the antiseizing property of the bearing can be improved.

By the way, among the group of specified additives, the most desirable one is Si in the first place which is followed by Mn and Sb, next Zr, Mo, Fe and Co, then, Ni, Ti and Ce, and further, Nb, W and V, and the last of Ba and Ca. This depends upon the fact that the hardness and castability of Si are excellent so that Si is most desirably used. The order of other elements is taken in view of the degree of uniform dispersion of the inter-metallic compounds with aluminium of other elements and the easiness in casting. While, Mo and Co is a little worse in anticorrosiveness, so that, when anticorrosiveness is especially required in the use, it is necessary to consider that the addition quantity of them may be reproduced and other elements are employed.

In addition to the above-described compositions of the present invention, the bearing alloy can further contain 0.1 to 0.8, the latter exclusive, wt.% in total of copper (Cu) and/or magnesium (Mg). The copper and/or magnesium are added in view of the fact that they reduce the lowering of the hardness at high temperatures. When the addition quantity of them is less than 0.1 wt.%, the rise of hardness cannot be expected so much. When the quantity of Sn is restricted to the above-described narrow range of 3 to 7%, if the quantity of Cu and/or Mg is made large, the alloy becomes too hard and it causes the wearing of the material in contact. Therefore, the quantity of Cu and/or Mg is desirably less than 0.8 wt.%.

Further, the effect of the addition of copper and/or magnesium is exhibited when the chromium is added simultaneously, and the effect to raise the hardness at high temperatures cannot be expected when only the copper and/or magnesium are added. In other words, if copper and/or magnesium are added to the aluminium matrix, the hardness in the rolling is much raised, which is remarkable as compared with the case in which other elements are added to the aluminium matrix. It is to be noted, however, that the aluminium matrix containing the copper and/or magnesium is easily softened at about 2000C, therefore, it cannot be expected to maintain the hardness at high temperatures.On the contrary, when the copper and/or magnesium are added together with the chromium, the hardness which is raised during the rolling by the effect of the addition of the copper and/or magnesium is not so much lowered by the annealing, which is brought about by the addition of the chromium. This hardness can be maintained under high temperature conditions, therefore, as compared with the prior art alloys, the bearing alloy of the present invention has a higher hardness at high temperatures, which results in the improvement in the fatigue strength.

Further, in the bearing alloy of the present invention, the property as a slidable metal containing tin can be further improved by adding more than zero to 9 wt% in total of one member or more of lead (Pb), bismuth (Bi), thallium (TI), cadmium (Cd) and indium (In). The effect of the addition of these lead, bismuth, thallium, cadmium and indium is exhibited when they are added together with chromium. In the prior art, it has been considered that these elements are added to Al-Sn base alloys and the addition has been practised in some cases. However, when only these elements are added to the Al-Sn base alloy, they form alloys so that the disadvantage that the melting point of tin becomes low cannot be avoided.Thus, the fusion and the migration of tin at low temperatures is liable to occur in the prior art Al-Sn base alloy, which causes the growth of tin particles into larger and coarse ones. When such alloy is employed as a bearing material, partial fusion and scraping are caused to occur under continuous heavy load running. On the contrary, the tin particles are made fine by the addition of chromium and such texture is maintained at high temperatures in the bearing alloy of the present invention. Therefore, even when one or more of the above lead, bismuth, thallium, cadmium and indium are added to the alloy, the lubricating property of tin can be improved without causing the above troubles in the prior art.Further, the bearing alloy of the invention can be used for the bearing of which a high fatigue strength is required, in addition, it becomes possible to improve the conformability of the bearing material. As described above, the addition quantity of one or more of the lead, bismuth, thallium, cadmium and indium having the above effects is in the range of more than zero to 9 wt.% in total. Among these elements, lead and indium are most preferable which are followed by bithmuth and cadmium, and then thallium. This depends upon the fact that lead and indium are most flowable under pressure so that sliding property and conformability become good. The next bithmuth and cadmium are somewhat harder and higher in melting points as compared with the lead and indium.The last thallium has similar properties as those of lead and indium, however, the production quantity of thallium is small and it is expensive. The one or more of lead, bismuth, thallium, cadmium and indium are added together with the above-mentioned copper and/or magnesium, in which the lowering of the high temperature hardness can be reduced, at the same time, the lubricating property of the tin can be improved.

The above described Al-Sn base bearing alloy is mainly used as the sliding bearings of automobile internal combustion engines or the like, in which the bearing alloy is generally applied to backing steel sheets by pressure welding and, in order to increase the adhesive strength, the annealing is done after the pressure welding. However, in the prior art Al-Sn base alloys, the lowering of the hardness, the fusion of tin particles and so forth are caused to occur because the migration of aluminium grain boundaries and tin particles in the alloy texture is brought about which causes the coarsening of the tin particles. While in the present invention, the migration of aluminium grain boundaries and the growth of aluminium crystal particles are effectively avoided by the precipitated substance of Al-Cr inter-metallic compound which is generated in the pressure welding and the annealing steps. Therefore, the bearing alloy of the present invention is free from the above ill influences of annealing and, as a result, the adhesion strength between the Al-Sn base alloy and backing steel sheets can be made high by raising the temperature of annealing. Since the above fact can be applied to the case in which the bearing alloy of the present invention is placed under the circumstances which correspond to the temperature of annealing, it is quite meaningful that the fatigue strength can be improved by the prevention of softening.Furthermore, the improvement in the wear resistance is also observed, especially, the bearing alloy is quite effective when it is used for the shafts made of spheroidal graphite cast iron.

In the foilowing, the present invention will be described further in detail by several examples.

The following Table A shows the compositions of the alloys (specimens) 1 to 1 7 of the present invention and comparative alloys (specimens) 1 8 to 22.

In the preparation of the alloys 1 to 17, aluminium material was melted in a gas furnace and, in accordance with the formulae of Table A, the base alloys of Al-Cu, Al-Mg and Al-specified additives were dissolved into the molten aluminium, respectively. After that, Sn and Pb, Bi, In, TI and Cd were added and degassing was performed.

Then, metal mold casting was performed, which was followed by repeated rolling and annealing (35O0C) to obtain specimens. The high temperature hardnesses of the specimens were then measured.

In the next step these specimens were subjected to rolling and after that, the alloy specimens were fixed to backing steel sheets by pressure welding to obtain bimetallic specimens. These were then subjected to annealing and worked into plain bearings and the fatigue resistance under dynamic loads of them were tested. In like manner as the above, alloys 1 8-22 for comparative tests, were also prepared and they were subjected to the same tests.

The Table B shows the results of measurement of Vickers hardnesses of several alloys at an ordinary temperature and at 2000C, the results of fatigue tests under dynamic loads, and the results of seizure tests with steel shafts and spheroidal graphite cast iron shafts. The above fatigue tests were carried out by applying each alloy with 10' times repetition of loads under the following conditions and measured the intensity of loads at which the fatigue occurs, that is, the pressure at fatigue limit by that number of repetitions.

Test machine: Soda Dynamic Load Tester Sliding speed: 400-470 m/min.

Lubricant oil: SAE 10W30 Lubrication: Forced Lubrication Oil temperature: 140 + 50C Oil pressure: 5 Kg/cm2 Material in contact: Kind: S 55 C Coarseness: 1 Mm Hardness: Hv 500-600 Shape,of bearing: Dia. x width: 52 x 20 mm Half-split metal Coarseness: 13 4m In the above seizure tests, the loads at seizure were measured with increasing loads by 50 Kg/cm2 at every 20 minutes under the following conditions. The following material (1) in contact with the bearing was used as a steel shaft and the material (2) in contact with the bearing was used as a spheroidal graphite cast iron shaft.

Test machine: Ultra-high pressure seizure tester Sliding speed: 468 m/min Load: 50 Kg/cm2/20 min, gradual increase Lubricant oil: SAE 10W30 Lubrication: Forced lubrication Oil temperature: 140 + 50C Material (1) in contact: Kind: S 50 C Coarseness: 0.3-0.8 ym Hardness: Hv 500-600 Material (2) in contact: Kind: Spheroidal graphite cast iron (DCI) Coarseness: 0.3-0.8 Mm Hardness: Hv 200-300 Shape of bearing:Dia. x width: 52 x 20 mm Half-split metal Coarseness: 1-3 ym As will be understood from Table B, the alloys 1-1 7 of the present invention have higher hardness in the high temperature range as compared with the comparative alloys 1 8-22. Especially, in view of the fact that the comparative alloy has an ordinary temperature hardness that is higher than those of some alloys of the present invention, it will be understood that the rates of lowering of hardnesses in the high temperature range in connection with the alloys of the present invention are relatively low.

Further, as compared with the comparative alloys 1 8-22, the alloys 1-1 7 of the present invention gave relatively good results in view of the fatigue resistances. Further, in the seizure tests with using spheroidal graphite cast iron shafts, the alloys of the present invention gave excellent results. TABLE A

Alloy Constltuent Elements (Wt.%) Example Numbers Al Sn Cu Mg Pb Bi In Tl Cd Cr Si Mn Sb Ti Ni Fe Zr W Ce Nb V Mo Ba Ca Co 1 Re 3.0 0.2 1.5 0.5 3.0 2 " 6.0 0.5 2.0 0.4 2.5 3 " 6.5 0.2 0.2 0.2 3.0 4 " 6.0 0.2 1.0 1.0 7.0 0.5 2.0 5 " 6.0 0.5 2.0 1.0 2.0 6 " 4.5 0.5 1.5 0.3 2.5 7 " 4.0 0.7 0.1 2.0 2.0 8 " 6.0 0.2 1.5 0.5 2.0 9 " 6.5 0.2 1.5 0.8 2.0 10 " 4.5 0.1 1.6 0.8 0.5 11 " 4.5 0.2 1.5 0.3 6.0 12 " 4.5 0.2 0.4 2.0 13 " 8.0 0.3 3.0 3.0 0.2 0.4 5.0 4.0 14 " 6.0 0.3 3.0 0.3 2.0 15 " 6.0 0.5 4.5 0.3 16 " 6.0 0.5 3.0 0.5 2.0 1.0 17 " 4.5 0.2 0.5 0.4 5.5 18 " 6.0 1.0 0.4 1.2 19 " 4.0 1.0 1.5 0.5 20 " 4.5 1.0 4.0 21 " 6.0 1.0 1.5 2.5 22 " 1.0 1.5 Note : Re - Remainder.

TABLE B

Hardness (Hv) Load at Seizure (Kg /cmZ) Al loy Fatigue 00C resistance (Kg/cm2) Example Ordinary Numbers Temperature Kg /cm2 Steel Shaft D C I 1 1 46 32 600 900 800 2 44 30 680 1050 950 3 41 26 540 900 650 4 44 29 560 1000 600 5 40 24 540 900 650 6 43 29 640 1000 800 7 40 25 640 700 650 8 8 44 29 580 900 600 l > 9 44 29 600 850 650 Co .c 10 43 29 660 900 600 11 43 29 580 800 600 12 43 29 600 850 i 600 13 40 25 600 900 600 14 40 25 640 900 700 15 42 26 620 1000 800 16 40 24 580 1000 900 17 47 34 720 950 700 18 42 19 540 800 100 19 62 22 540 800 300 fCL 20 52 22 520 950 300 21 35 17 560 800 300 22 35 17 540 800 100 Shown in Fig. 1 are the results of friction tests, in which the alloys 2, 3 and 1 7 of the present invention and the comparative alloys 21 and 22 were compared with using steel shafts (material (1) in contact). In Fig. 2, the results of other friction tests are shown, in which alloys are the same as those of Fig. 1 and the shafts made of spheroidal graphite cast iron (surface roughness: 1 ssm, hardness: Hv 200-300) were used under the same test conditions. From Figs. 1 and 2, it will be understood that the wear losses of the alloys 2, 3 and 1 7 of the present invention are quite little as compared with those of the comparative alloys 21 and 22. Further, it will be understood from Figs. 1 and 2 that the effect in the improvement of wear resistance is quite clear when the spheroidal graphite cast iron is used as the material in contact as compared with the case of steel shaft.

By the way, it should be noted that in the composition of the alloy of the present invention, the aluminium (Al) may of course contain a trace quantity of impurities which cannot be eliminated by the ordinary refining technique.

Claims (11)

1. An Al-Sn bearing alloy containing substantially 3 to 7 wt.% of Sn; 0.1 to 1.0 wt.% of Cr; 1 to 10 wt.% in total of one or more elements selected from the group of specified additives consisting of Si, Mn, Sb, Ti, Zr, Ni, Fe, W, Ce, Nb, V, Mo, Ba, Ca and Co; not less than 0.1 wt.% but less than 0.8 wt.% in total of Cu and/or Mg; and the remainder of Al.

2. The bearing alloy as claimed in claim 1, wherein Si is selected from said group of specified additives.

3. A bearing material which is made by applying said bearing alloy as claimed in claim 1 or 2 to a backing steel sheet by pressure welding.

4. The bearing alloy or the bearing material as claimed in any one of claims 1 to 3, wherein said bearing alloy or said bearing material is employed in a bearing in contact with a shaft of spheroidal graphite cast iron.

5. An Al-Sn bearing alloy containing substantially 3 to 7 wt.% of Sn; 0.1 to 1.0 wt.% of Cr; 1 to 10 wt.% in total of one or more elements selected from the group of specified additives consisting of Si, Mn, Sb, Ti, Zr, Ni, Fe, W, Ce, Nb, V, Mo, Ba, Ca and Co; not less than 0.1 wt.% but less than 0.8 wt.% in total of Cu and/or Mg; 9 wt.% or less in total of one or more of the elements Pb, Bi, TI, Cd and In; and the remainder of Al.

6. The bearing alloy as claimed in claim 5, wherein Si is selected from said group of specified additives.

7. A bearing material which is made by applying said bearing alloy as claimed in claim 5 or 6 to a backing steel sheet by pressure yielding.

8. The bearing alloy or the bearing material as claimed in any one of claims 5 to 7, wherein said bearing alloy or said bearing material is employed in a bearing in contact with a shaft of spheroidal graphite cast iron.

9. A bearing alloy according to any one of claims 1 to 5 and substantially as described herein.

10. A bearing material comprising a bearing alloy according to claim 9.

1 A shaft bearing comprising a bearing alloy according to any one of claims 1, 2, 4, 5, 6, 8 or 9 and/or a bearing material according to any one of claims 3, 4, 7, 8 or 10.

1 2. An internal combustion engine having a rotary shaft of spheroidal graphite cast iron supported in a plurality of bearings according to claim

11.