JPS6045701B2 - Composite aluminum-tin bearing alloy material - Google Patents

Description

Detailed Description of the Invention The present invention provides an aluminum (Al) bearing alloy that exhibits less growth of Sn (tin) particles and less decrease in hardness in high-temperature conditions, has excellent fatigue resistance, and has excellent wear resistance. The present invention relates to a composite aluminum-tin bearing alloy material formed by pressure welding, and provides a bearing alloy material suitable for use after being rolled and annealed several times after casting.

Conventional aluminum bearing alloys are mainly Al-
Sn-based alloys, such as Al-SΠ (20%)-Cu (copper) 1%, Al-Sn (20%)-Pb (lead) 3%-Cu
(1%)-Si (silicon) 3% etc. are used,
When a bearing alloy material made by press-bonding this alloy to a copper backing plate is used in a bearing for an automobile internal combustion engine, fatigue failure may occur in a short period of time, such as when the internal combustion engine continues to operate under high load. This is because the oil in the internal combustion engine becomes particularly hot during continuous high-load operation, for example, the temperature of the oil in the oil pan reaches 130°C to 150°C, so it is expected that the bearing will reach a considerably high temperature on its sliding surface. As a result, in conventional Al-Sn alloys, the hardness rapidly decreases at high temperatures, causing melting and movement of Sn, which is thought to be the cause of the decrease in fatigue strength. The inventors of the present invention fabricated an alloy with high hardness or an alloy in which Sn does not easily move under high temperatures into the shape of an internal combustion engine bearing, and conducted a dynamic load fatigue test under high temperature oil. As a result, the fatigue strength improved. The fact that this was observed supports the above consideration. Further, regarding the decrease in fatigue strength due to the above-mentioned decrease in high-temperature hardness, (11), in conventional A1-Sn alloys, the coarsening of Sn particles in the alloy structure is also a cause of the decrease in fatigue strength.

In other words, the aluminum bearing alloy material is formed by pressure-bonding an N-Sn alloy to a backing steel plate, but in order to increase the bonding strength of both metals, it is essential to anneal the material after pressure-welding, and the general method is This annealing is performed at a temperature below the precipitation temperature of the A1-Fe intermetallic compound (approximately 475° C.), and the higher the temperature and the longer the time, the greater the adhesive strength. However, when conventional A1-Sn alloys are subjected to high temperatures during annealing, movement of A1 grain boundaries and Sn particles occurs in the alloy structure.
As a result, there was a drawback that the Sn particles became coarser with the passage of time. In other words, in conventional aluminum bearing alloy materials, annealing to increase the adhesive strength with the back metal steel plate causes the Sn particles to become coarser, and this coarsening causes a decrease in the fatigue strength of the A1-Sn alloy. ing. The inventors of the present invention have added various additive elements to the N-Sn alloy to improve its high-temperature hardness and fatigue strength. As a result, the inventors have already added a required amount of Cr (chromium) or We have developed an alloy containing Zr (zirconium), Cu, etc., and have filed a patent application (Japanese Patent Application No. 1982-26 (6)).

Furthermore, in addition to Sn, Cr, Cu, etc., Pb or In(
Indium) was added to develop an alloy with particularly improved conformability while maintaining the same fatigue resistance, and a patent application (Japanese Patent Application No. 52-18255) was filed. As a result of further research, the present invention has revealed that by increasing the Cr content in the A1-Sn alloy, the phase can be reduced. This was achieved by discovering a material that can significantly improve wear resistance regardless of the material used.

The A1-Sn bearing alloy material of the present invention basically contains 3.5% to 35% Sn in terms of weight percent, and more than 1.0% Sn and 7.0% by weight.
% of Cr.
Cu and/or Mg (magnesium) 3.0
% or less (including 0), 9% or less (not including 0) of Pb
, In, and Bi (bismuth), and the amount of Sn is the largest among the added elements. Cr, Pb compared to A1-Sn bearing alloy material
, Bi, and In made the Sn finer and improved the conformability. In addition, the hardness increased, and it was observed that there was almost no movement or growth of Sn, especially at high temperatures. Also, there is little decrease in high temperature hardness. Furthermore, when a dynamic load fatigue test was conducted, it was confirmed that the fatigue strength was improved under high oil temperatures. It was also confirmed that the material has sufficient wear resistance regardless of the material of the bearing, that is, the material of the shaft, which has a particularly large effect on the sliding performance of the bearing. The reason for limiting the Sn content to 3.5 to 35% by weight is that Sn is an elemental dust added primarily for lubrication, but adding 35% or more of this improves compatibility and lubricity. However, the hardness decreases, and if this is less than 3.5%, the conformability as a bearing alloy will be poor.

The upper limit of the amount of Sn added in conventional A1-Sn alloys is about 15% in order to disperse Sn vertically, and the reason for this is that if more than 15% is added, the Sn particles in the alloy It was believed that this was because the hardness decreased because the particles could no longer be dispersed in A1 and began to exist in a continuous state, but in the present invention, this could be reduced to 35% by the effect of adding other elements, which will be described later. Even when it was added, the Sn particles were dispersed vertically and there was no practical problem. In addition, the amount of Sn added was 3.5
- 35% should be determined appropriately depending on the application, but in general, when the load applied to the bearing is large, the amount of Sn should be reduced, and when the load is small. If this occurs, it is better to increase the amount of Sn. From another point of view, when used in conditions where seizure is a concern, Sn
It is better to increase the amount of Sn, and reduce the amount of Sn when there is no concern about this. However, recently, bearings have become hot due to high oil temperatures.
Since this causes the bearing to deform, seize, and cause fatigue, it is necessary to determine the amount of Sn from the viewpoint of minimizing deformation at high temperatures. Cr is particularly effective in that it prevents increase in hardness and softening at high temperatures, does not cause coarsening of Sn particles even during annealing, and has sufficient wear resistance regardless of the material used. Additive effect is high.

First, let's talk about increasing hardness and preventing softening at high temperatures.
If the amount of Cr added is less than 1.0% by weight, improvement in high temperature hardness can be expected, but improvement in wear resistance cannot be expected. 7.0
If more than % is added, A1-Cr intermetallic compounds such as Cr and Al will precipitate too much, making the bearing alloy too hard, and although the wear resistance may be improved, the conformability will be extremely low. It exceeds 1.0 and is limited to 7.0%.

To explain this improvement in high-temperature hardness in more detail, Cr increases the recrystallization temperature of A1 by being dissolved in Al, and the solid solution itself increases the hardness of the N base.
At the same time, the hardness also increases by rolling several times compared to when it is cast. Increasing the recrystallization temperature is effective in maintaining stable mechanical properties even in the high temperature range to which internal combustion engine bearings are exposed. This can prevent the bearing from softening in this region, which in turn improves fatigue strength. In addition, N-Cr intermetallic compounds that precipitate beyond the solid solubility limit are
It has a Utzkers hardness of about 370, and therefore, the dispersion and precipitation of this compound helps maintain high-temperature hardness, and dispersing an appropriate amount of this compound produces a good effect. Next, the effect of inhibiting the coarsening of Sn particles by adding Cr will be described.

The coarsening of Sn particles is a phenomenon that occurs due to the movement of N grain boundaries and Sn particles when an N-Sn alloy is exposed to high temperatures, but as mentioned above, Cr Precipitates of compounds are formed and these precipitates are finely dispersed in the A1 metal, so this intermetallic compound directly prevents the movement of Al grain boundaries and at the same time prevents the growth of N crystal grains. It is thought that this is because it prevents the movement of Sn particles, that is, the coarsening of Sn particles. This leads to keeping the Sn particles that have been refined by rolling, annealing, etc.
It has the various effects mentioned above. This phenomenon occurs when the amount of Sn is relatively large (approximately 10% or more).
Further, a more significant effect occurs when Sn starts to exist continuously at about 15% or more. However, even if the amount of Sn is 10% or less, the effect of the addition of Cr may still be required depending on the usage conditions and applications. In addition, the Sn particles are kept fine and A
Existing in one bullion means 23' at the same time! 'C
It is also considered to be effective for preventing the elution phenomenon of Sn particles having a low melting point at high temperatures, and from this point of view as well, the effect of preventing a decrease in hardness is significant. The above is a description of the effect of inhibiting the coarsening of Sn particles in relation to annealing, but the above effect is also valid even when the environment in which this bearing material is used is at a high temperature comparable to that of annealing. By preventing softening, fatigue strength can be improved. Next, the effect of improving wear resistance by adding Cr will be described. Cr is N-Cr in N metal as mentioned above.
This compound produces a precipitate of an intermetallic compound, which has a Utzkers hardness of approximately 370, and is a very hard precipitate, so this precipitate can significantly reduce the wear of the bearing due to friction with the shaft. Dispersing this in an appropriate amount produces good effects. As mentioned above, the appropriate amount range here means 7.0% or less of Cr, and within this range, the above precipitates will be uniformly dispersed and the wear resistance will be improved without adversely affecting other properties such as conformability. Improved effects can be obtained. In addition A
1-Cr precipitates also have the following effects. In other words, the mating material of a bearing greatly influences the bearing performance, and for example, when a conventional N-Sn bearing is used in combination with a spheroidal graphite cast iron shaft, the bearing performance in terms of seizure resistance, wear resistance, etc. is significantly impaired. Recently, spheroidal graphite cast iron shafts, which are cheaper to process, have been increasingly used in place of steel shafts. However, in spheroidal graphite cast iron, soft graphite is scattered within the iron base, and for this reason, when the shaft is ground, grinding burrs with sharp edges are generated around the graphite. When a bearing is slid against a shaft with such abrasive burrs under such a high load that the oil film thickness is the same as the shaft and bearing surface roughness, the burrs will cut the bearing surface, which is softer than the shaft. As this situation progresses, the bearing surface accuracy becomes rougher, the clearance between the shaft and the bearing increases, and the oil film pressure is no longer formed, or the oil film is no longer formed due to oil film rupture. As a result, more direct contact, or metal contact, between the shaft and the bearing occurs, leading to seizure.
However, in the bearing alloy material according to the present invention, A1-Cr precipitates, which are harder than the burrs on the spheroidal graphite cast iron shaft, are dispersed in the A1 ground, and these A1-Cr precipitates can eliminate the polishing burrs on the spheroidal graphite cast iron shaft. It also has the effect of removing N-Cr precipitates and making it difficult for N-Cr precipitates to migrate and adhere, thereby suppressing the progress of wear on the bearing surface in a relatively short period of time and forming a stable oil film. As a result, wear resistance and seizure resistance are improved, especially for spheroidal graphite cast iron shafts. Next, in the present invention, Cu or (and) Mg is added in an amount of 3% or less by weight in addition to the above composition.

Among these, when Cu is used, the amount added is 3% or less. This is because adding 3% or more of Cu improves hardness, but as Cu increases, rollability and corrosion resistance decrease, which is not preferable.

Here, a more preferable addition ratio is 2.0 or less. As for Mg, if it is added in an amount of 3% or more, the hardness improves, but the increase in hardness due to rolling becomes too large, making it impossible to perform sufficient rolling, making it difficult to obtain a fine Sn structure. Further, during annealing, Mg dissolved in N is likely to precipitate, and the excess amount added will precipitate, so strengthening of the A1 base by solid solution cannot be expected. Here, a more preferable addition ratio is 2.0 or less. This Cu (5M
The above effect of g occurs when it is added simultaneously with Cr, and C
U or Mg alone cannot be expected to have the effect of increasing hardness at high temperatures. In other words, when Cu or Mg is added to N, the hardness increases significantly during rolling. Even at the same rolling rate, the increase in hardness is remarkable compared to Al materials with other elements added, but at 200°C It easily softens when heated to near high temperatures and cannot be expected to maintain its hardness at high temperatures. On the other hand, when Cr and Cu or Mg are added at the same time, the hardness increased during rolling due to the effect of adding Cu or Mg is maintained even after annealing.
It does not decrease much due to the effect of adding r, that is, the increase in recrystallization temperature. This hardness is maintained even at high temperatures, resulting in an alloy with higher high-temperature strength than conventional alloys, which in turn leads to improved fatigue strength. In addition, when adding Cu and Mg at the same time, the total amount should be within 3%, of which Cu
is preferably within 2%. Next, Pb, Bj, I
The purpose of adding at least one type of n is to improve the properties of Sn as a lubricating metal, and the effect is observed when it is added together with Cr. Adding these elements to the A1-Sn alloy has been thought of and has been done in some cases, but if these elements are added alone, they will not be alloyed into the A1-Sn alloy. Due to storage, the disadvantage that the melting point of Sn becomes low cannot be avoided. For this reason, in conventional N-Sn alloys, Sn melts and moves easily at low temperatures, resulting in easy growth into coarse Sn grains.
If this is used as a bearing, it may partially melt and peel during continuous high-load operation. On the other hand, if the Sn grains are made finer by adding Cr as in the present invention, and the structure is maintained even at high temperatures, even if at least one of Pb, Bi, and In is added, It is possible to improve the Sn(7) lubricity without causing the adverse effects such as, and it can be used in bearings that require high fatigue strength, and it also aims to improve conformability in addition to fatigue resistance. I can do it. Furthermore, N-C precipitated
rThe surface layer exposed on the bearing surface of the intermetallic compound contains Pb, B.
Frictional characteristics are improved by forming a thin film of Sn-based low melting point metal whose lubricating performance has been improved by adding i,In. Pb, which can obtain such effects,
The amount of at least one of Bi and In added is 9% or less (
(b)), and preferably about 15% or less based on the amount of Sn contained.

Note that Pb and Bi. (The total amount of 51n may be 9% or less. Furthermore, the total amount of Sn (with at least one of 5Pb, Bi, and In) is preferably 35% or less. In addition, in order to make the lubricating metal exist finely in A1, The amount of Sn must be the highest among the additive elements.N bearing alloys with the above structure are mainly used as full bearings for internal combustion engines for vehicles, but in this case they are usually used by being pressure-welded to a backing steel plate. After this pressure bonding, annealing is performed to increase adhesive strength.

However, as mentioned above, in the conventional A1-Sn alloy, the N grain boundaries and Sn particles in the alloy structure move due to several times of annealing after rolling, and the Sn particles become coarser, resulting in a decrease in hardness. There were drawbacks such as a decrease in the amount of water and elution of Sn particles. In contrast, in the present invention, AI-
Since the precipitates of Cr intermetallic compound impede the movement of A1 grain boundaries and inhibit the growth of A1 crystal grains, the above-mentioned adverse effects due to annealing do not occur. It can increase the adhesive strength with steel plate. Note that this also means that this bearing alloy material remains valid even when it is placed under high temperatures comparable to annealing, so it can also contribute to improving fatigue strength by preventing softening. Next, the present invention will be explained with reference to Examples. The following table shows the chemical composition values of Alloys 1 to 17 constituting the bearing alloy material according to the present invention and Alloys 18 to 21 as comparative materials. Alloys 1 to 17 are produced by melting A1 base metal in a gas furnace, and then melting A1-Cr master alloy or AI-C.
U master alloy Al5-Mg master alloy was melted according to the target components, and finally Sn and Pb were added, followed by degassing treatment and casting into a mold at a hot water temperature of 720°C, followed by rolling. Samples were prepared by repeated annealing (350'C) and high temperature hardness measurements were performed.

Next, this sample was further rolled, and then these alloys and a backing steel plate were pressure-welded to form a bimetallic material, which was then annealed (3
After heating the bearings to 80°C, they were processed into flat bearings and subjected to dynamic load fatigue tests. For convenience of comparison, Alloys 18 to 21 were prepared using conventional compositions using the same manufacturing method as the above-mentioned alloys, and were subjected to the same tests. Figure 1 shows the above alloy 1.
This shows the results of measuring the hardness at high temperatures of 21 to 21 using Witzkers hardness.

As is clear from these graphs, Alloys 1 to 17 of the bearing alloy material according to the present invention have higher hardness in all temperature ranges than conventional Alloys 18 to 20, and have higher hardness than conventional Alloy 21. Although there are cases where Alloy 21 has higher hardness in the low temperature range, the hardness of Alloy 21 decreases rapidly as the temperature rises, whereas the hardness of Alloys 1 to 17 of the present invention materials decreases as the temperature increases. The degree of decrease in hardness is gradual, which has the effect of reducing changes in the bearing condition due to changes in temperature. Also, especially Pb
, Bi, and In, alloys 5 to 13, 16, and 17 in which Cu or (and) Mg were added were found to have particularly high hardness in the entire temperature range, and compared to alloy 21, the hardness increased with increasing temperature. There is little decrease in hardness, and high hardness is maintained even at a temperature of 200°C. This is clearly Cu,M
This is the effect of adding g. Moreover, from the alloy structure, no coarsening of S electrons was observed in Alloys 1 to 17 of the bearing alloy materials according to the present invention even after annealing after joining with the backing steel plate. Figure 2 shows alloy 2 of the material of the present invention,
The results of a dynamic load bearing fatigue test are shown for alloys No. 5, 9, 14, and 16 and conventional alloys 18, 19, and 20.

This test was conducted at a shaft rotation speed of 3000 r. p. S55C hardened material was used as the m1 shaft material, and the fatigue resistance surface pressure was measured under forced lubrication at a constant oil temperature and with different oil temperatures under 107 stress repetition conditions to determine the fatigue state of steel materials. As is clear from this graph, alloys 2, 5, 9, 1
4, 16, 18, 19, and 20, the fatigue resistance surface pressure decreases as the temperature increases, but alloy 2, the bearing alloy material according to the present invention,
In alloys 5, 9, 14, and 16, the degree of decrease in fatigue resistance surface pressure was not as large as in conventional alloys 18, 19, and 20, and alloys 2, 5, and
The difference in fatigue bearing pressure on the low temperature side between Alloys 2, 5, 9, 14, and 16 is not that large, but the fatigue bearing pressure on the high temperature side is higher than that of Alloy 18. ,19,2
It is clearly recognized that 0 is being overtaken. In addition, the second
The figure shows alloys 2, 5, 9, 14, 16 representing the bearing alloy material according to the present invention, and 18, representing conventional alloys.
19 and 20, but results showing similar trends have been obtained for other alloys as well. Further, the following table shows alloys 2, 9, and 12 of the bearing alloy material according to the present invention and conventional alloys 18 and 1.
9 shows the seizure load when a seizure test was conducted on No. 9.

In this experiment, the shaft rotation speed was 1000 r'. P. ml S55C hardened material was used as the shaft material, and the load (static load) up to seizure was measured under forced lubrication at a constant oil temperature (140 ° C.). ,12
shows a much better seizure load than Alloys 18 and 19, and this is recognized to be the effect of the additives that improve conformability, namely Pb, Bi, and In.

Further, FIG. 3 shows a bearing alloy material according to the present invention. Alloy 2
, 9 and the conventional alloy 19 are graphs showing the results of measuring changes in friction torque when the load is increased.

In this experiment, the situation during the load increase during the seizure test was measured using an oscillograph. According to this graph, in the conventional alloy 19, the friction torque increases with a large fluctuation with the occurrence of a peak every time the load is increased.
Furthermore, in Alloy 2, no large fluctuations accompanied by peaks were observed, and the fluctuations were smooth, but chevron-shaped friction torque fluctuations occurred when the load stopped increasing. On the other hand, in Alloy 9, which is a material of the present invention, the friction torque increases extremely smoothly following the increase in load, and no harmful friction torque fluctuations occur. This indicates that the alloy of the material of the present invention has excellent conformability and is less prone to seizure. In other words, the peak waveform with large fluctuations seen in conventional Alloy 19 means that the oil film on the sliding surface is partially destroyed, solid contact occurs, and if this is repeated, total destruction (seizing/seizing) will occur. Alloys 2 and 9, which are materials of the present invention that do not produce such corrugations, have high conformability and seizure load resistance. In addition, in the alloy composition of the bearing alloy material according to the present invention, it goes without saying that Al contains impurities that cannot be avoided by ordinary scouring techniques.

Next, FIG. 4 shows alloys 1, 5, and 1 of bearing alloy materials according to the present invention.
14 is a graph showing the results of measuring changes in the amount of wear when the load is increased when performing a wear test on Alloys No. 14 and conventional Alloys No. 18 and No. 19. FIG.

According to this graph, it is recognized that compared to the conventional alloy 18, 1, 5, and 14 to which Cr is added and 19 to which Si is added to the conventional alloy have an extremely small amount of wear. Further, even in alloys to which Cr is added, differences in the amount of wear are observed depending on the difference in Cr content. In other words, 5, which has a large amount of Cr added,
No. 14 has less wear than No. 1. In this experiment, the shaft rotation speed was 1000 r'. P. The amount of wear at each load was measured when S55C hardened material (shaft roughness 1μ) was used as the shaft material and the load was increased under forced lubrication at a constant oil temperature (120'C). Alloy 1 of the material of the present invention,
Alloy Nos. 5 and 14 exhibited much better wear resistance than Alloy 18, and this was recognized to be the effect of the addition of Cr.

Next, FIG. 5 shows an experiment similar to that shown in FIG. 4 conducted using spheroidal graphite cast iron as the shaft material.

Compared to the case of the copper shaft shown in Fig. 4, alloys 1, 5, and 16 of the bearing alloy material according to the present invention have a large difference in wear amount from the conventional alloy 18, and the wear resistance due to the addition of Cr. The effect of improving properties is more obvious when a spheroidal graphite cast iron shaft is used than when a copper shaft is used. In addition, in the results shown in FIGS. 4 and 5, the present invention product and some of the conventional materials show similar results, but the conventional materials have drawbacks as shown in FIGS. 1 to 3. In the end, it cannot be said to be a sufficient alloy.

Next, FIG. 6 shows alloys 1, 2, and bearing alloy materials according to the present invention.
9 is a graph showing the surface pressure at the time of seizure when a seizure test was conducted using a spheroidal graphite cast iron shaft as the mating material for Alloy No. 9 and conventional alloys 18, 19, and 20.

According to this graph, it is recognized that Cr-added alloys 1, 2, and 9 have higher seizure surface pressures than the conventional alloy 18. Furthermore, even in alloys to which Cr is added, differences in seizure load are observed depending on the difference in Cr content. In other words, Alloy 2 with a large amount of Cr added has better seizure resistance than Alloy 1. Among them, Alloy 9 containing Pb shows excellent seizure resistance. In addition, the conventional alloy 19 shows improved seizure resistance, which is thought to be due to S1 in its chemical components, and the alloy 20 to which Pb is added exhibits the same superior effect as the present invention. However, as mentioned above, these conventional materials can prevent a decrease in high-temperature hardness, which is one of the characteristics of the alloy of the present invention material.
No improvement in fatigue resistance was observed. As described above, the composite aluminum-tin bearing alloy material according to the present invention is A1-
Addition of Cr to Sn-based alloys improves hardness, prevents reduction of high-temperature hardness, prevents coarsening of Sn particles, improves fatigue resistance and wear resistance through these, and improves especially spheroidal graphite. When using cast iron shafts, it is possible to improve wear resistance and seizure resistance, and Pb, Bi, and In, which are effective when added with Cr, can improve conformability and seizure resistance. Addition of Cu and Mg further improves high temperature strength.

Further, since rolling annealing after pressure bonding with the backing steel plate can be performed at high temperature for a long time, the adhesion between the two can be improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the change in hardness due to temperature change between the alloy constituting the composite aluminum-tin bearing alloy material according to the present invention and a conventional similar bearing alloy.
Figure 2 is a graph plotting the change in fatigue resistance surface pressure, Figure 3 is a graph showing the change in friction torque when the load is increased, and Figure 4 is a graph plotting the change in fatigue resistance against the steel shaft. FIG. 5 is a graph showing how the amount of wear changes when the load is similarly increased, and FIG. 5 is a graph similarly showing the amount of wear on the spheroidal graphite cast iron shaft.

Claims (1)

[Claims] 1 3.5 to 35% tin by weight, more than 1.0 chromium 7
．． 1. A composite aluminum-tin bearing alloy material made by press-welding a backing steel plate to an aluminum-tin bearing alloy consisting essentially of 0% aluminum and the remainder aluminum. 2 3.5 to 35% tin by weight, over 1.0 chromium 7
．． A composite aluminum-tin bearing made by press-welding a backing steel plate to an aluminum-tin bearing alloy consisting essentially of 0% copper and/or magnesium, 3.0% or less (excluding 0), and the balance essentially aluminum. Alloy material. 3 3.5 to 35% tin by weight, more than 1.0 chromium 7
．． 0%, 3.0% or less (excluding 0) of copper and/or magnesium, 9.0% or less (excluding 0) of at least one of Pb, Bi, In, and the remainder essentially aluminum A composite aluminum-tin bearing alloy material made by press-welding a backing steel plate to an aluminum-tin bearing alloy. 4 3.5 to 35% tin by weight, over 1.0 chromium 7
．． 0%, at least one of Pb, Bi, In 9.0%
A composite aluminum-tin bearing material made by press-welding a backing steel plate to an aluminum-tin bearing alloy, the following (excluding 0) and the remainder being essentially aluminum.