US2852365A - Aluminum base bearing - Google Patents

Description

p 16, 1958 A. w. SCHLUCHTER 2,852,365

ALUMINUM BASE BEARING Filed Deg. 19, 1955 575a ALUMl/VUM Auor L540 0/? L540 ALLOY mvmrdn mdd zwwih aq?w ATTORNEY Unite States Patent ALUMINUM BASE BEARING Alfred W. Schluchter, Hazel Park, Micln, assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Application December 19, 1955, Serial No. 561,974

3 Claims. (Cl. 75-148) This invention relates to bearings and particularly to an aluminum base bearing having good corrosion resistance and excellent anti-score properties.

Aluminum and most of its alloys are generally quite unsuitable for use in bearings for ferrous metal parts because the aluminum tends to adhere to, or combine with, the ferrous metal, thereby causing scoring or seizing. I have found, however, that by suitable combination of alloying constituents, this difiiculty can be overcome and a bearing alloy produced having not only anti-friction properties but other characteristics especially suitable in a bearing material. Many aluminum base alloys, such as the type disclosed in Pat-ent No. 2,338,399, which issued April 15, 1941, in the name of Alfred W. Schluchter, are satisfactory bearing materials in most respects. However, many of these alloys do not possess sufiicient resistance to corrosion to enable them to be satisfactorily used under highly acidic conditions, such as are sometimes found in lubricating oils during use. The bearing material of the present invention, therefore, is an improvement in that respect on the alloy disclosed in the aforementioned patent.

Accordingly, a principal object of this invention is to providean aluminum base bearing alloy which has excellent corrosion resistance, as well as satisfactory hardness and high score resistance. A further object of this invention is to provide a corrosion-resistant aluminum base alloy which possesses desirable frictional properties when used as either a cast alloy or a wrought alloy.

In accordance with my invention, therefore, the foregoing objects and advantages are attained with an aluminum base alloy containing minor proportions of indium, silicon and silver. Inasmuch as an alloy of this composition is a stronger metal than many of the aluminum alloys generally heretofore used for beating purposes, solid bearings may be formed from it and no backing of steel or similar metals is necessary for many applications. If desired, a bearing formed from my alloy may be advantageously provided with a thin overlay of lead or a lead base alloy. Examples of these overlays include the lead-tin and lead-indium alloys which are used for this purpose and in which lead is the major constituent. It is therefore obvious that, as Well recognized by the trade, the term bearing is used herein as meaning an element which performs a bearing function regardless of the presence or absence of such an overlay.

Thus I have found that satisfactory bearing properties are obtained with an alloy comprising, by weight, approximately 0.05% to 5% indium, 0.5% to silicon, 0.05% to 5% silver, and the balance substantially all aluminum. Various incidental impurities may be included in this alloy in the usual small amounts without any substantial detrimental effects. Hence the term aluminum, as used herein, embraces the usual impurities which are found in aluminum ingots of commercial grade or which are introduced during the handling operations incident to ordinary melting practice. For

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example, iron, which together with silicon is found in commercial aluminum, may be present in amounts not greater than approximately 0.5% without causing any harmful results. For optimum results I have found that an alloy should be'used which consists essentially of 0.08% to 0.5% indium, 2.5% to 5% silicon, 0.2% to 1% silver, and the balance substantially all aluminum.

Under severe test conditions, alloys having the above composition show excellent anti-friction properties so that bearings formed of this alloy not only do not score or gall when in contact with a rotating steel shaft, but neither the shaftnor the bearings show an appreciable amount of wear after long and severe use. I have also found that the resistance of this alloy to cracking or crumbling is extraordinarily high.

The addition of indium greatly improves the corrosion resistance and score resistance of the aluminum base bearing. Despite the fact that it has been generally recognized that the addition of indium to aluminum causes slight loss of strength, I have found that indium, in the presence of silicon, may be beneficially introduced in amounts as large as 5% without causing a measurable loss of strength. In fact, the resultant alloy is remarkably resistant to disintegration under impact or pounding such as occurs in severe bearing service. Moreover, the presence of indium does not affect the hardness if the alloy is subsequently heat treated. Although the effect of indium on both strength and hardness is negligible in any event if added in quantities no greater than 5%, indium is a relatively soft metal and hence the indium content'should not be higher than this amount.

I have also found that an indium content greater than 5% tends to cause this element to segregate out and settle to the bottom of the casting during the solidification thereof in the form of the apparently nearly pure metal. Thus, too high an indium content raises the cost of the alloy by increasing personnel expenses because of increased handling costs and the necessity of more detailed and careful supervision. Moreover, if the final aluminum base alloy is to be used as a wrought alloy to form a bearing, it is particularly important that the indium content does not exceed approximately 0.5 inasmuch as greater amounts of indium make the alloy too brittle. Therefore, in order that the material may be properly rolled, the indium content should not exceed the afore mentioned maximum amount.

There is a marked improvement in score properties if indium is added in quantities up to 0.5 but increasing the indium content beyond this amount does not proportionately increase the score resistance of the alloy. Hence, I prefer to use about 0.08% to 0.5% indium. An indium content of at least 0.05% should be used in all instances to provide adequate score resistance.

The inclusion of silicon in my aluminum base bearing alloy also enhances its score resistance. This property of silicon, plus the manner in which it influences the effects of the indium present in the alloy and the fact that solidification shrinkage is lower as the silicon content is raised, dictates that the alloy contain at least 0.5% silicon. Inasmuch as a high silicon content increases the brittleness of the final alloy and interferes with rolling processes, however, the maximum amount of silicon to be added necessarily is governed by the method in which the bearing is formed. Accordingly, silicon should not be present in amounts greater than approximately 5% in the wrought alloy because such an alloy needs to be rolled, while it may be added in amounts as high as about 10% in the cast alloy. While an increased silicon content improves score resistance, the addition of silicon in amounts greater than 5% provides only slight additional beneficial properties in this respect. Accordingly, best results are obtained for most purposes when the silicon content is kept within a preferred range of 2.5% to 5%.

The score properties of the alloy are further improved by the presence of silver. However, since silver is an expensive and relatively rare metal, it is desirable to add only as much of this metal as is necessary to produce the desired results.

An example of the above alloy which possesses the aforementioned desirable characteristics to an outstanding degree, therefore, is one consisting of 0.5% indium, 3% silicon, 0.5% silver, and the balance substantially all aluminum. As hereinbefore stated, various incidental impurities may be present in the above alloy, but for best results the amounts of these other elements should be confined to relatively low proportions.

In order to obtain the high degree of resistance to pounding, such as is encountered in a bearing, it is preferable that the alloy have a physical structure typified by the absence of continuous networks of relatively brittle eutectic mixtures. Conventional alloy procedures may be employed with intermediate alloys, such as aluminumsilicon, being used to introduce the silicon. For example, I have found that the aluminum and silicon may advantageously be fused at a temperature in the order of approximately 1200 F., the melt then preferably being removed from the furnace. The silver and indium next may be successively or simultaneously added to the melt, whichis subsequently stirred and cast, usually in metal or graphite molds. Casting temperatures below 1400 F. have proved to be satisfactory. The alloy may be either cast in the desired form for use in bearings or it may be cast in ingots, rolled down to strip material of the desired thickness, and bearing liners or other bearing elements formed from the rolled stock.

Cast articles having a metallographic structure showing a continuous network of segrated metal compounds may be improved as to strength and fatigue resistance by suitable heat treatrnent. For example, I have found that a solution treatment at a temperature between approximately 800 F. and 1100" F. for a period of five to twenty hours is particularly effective to increase the amount of constituent elements in solid solution. Upon removing the alloy from the furnace following the solution treatment, it is preferable to cool it immediately by quenching in water. This treatment provides the alloy with the high degree of ductility, such as is desirable for 4 rolling operations; and it may then be easily rolled down to strip material of the desired thickness.

The above-described bearing has better resistance to fatigue and to cracking under pounding action than tinbronze bearings. Hence my bearings may be used as connecting rod bearings and main bearings for an automobile engine. In addition, this hearing is highly resistant to corrosion by acid constituents of lubricating oils which attack many other bearing compositions.

A slipper or sleeve bearing embodying the invention described above is shown in the accompanying drawing. This bearing 10 comprises an aluminum base alloy layer 12 of the composition hereinbefore set forth having a steel backing 14. The aluminum alloy in the bearing shown is provided with a thin overlay 16 of lead or lead alloy as previously described.

It is to be understood that, while the invention has been described in conjunction with certain specific examples, the scope of the invention is not to be limited thereby except as defined in the appended claims.

I claim:

1. A hearing formed of an alloy comprising approximately 0.05% to 5% indium, 0.5% to 10% silicon, 0.05 to 5% silver, and the balance substantially all aluminum.

2. A corrosion-resistant bearing formed of an alloy capable of being rolled into sheet form from cast ingots and having high anti-friction properties and fatigue resistance, said alloy consisting essentially of 0.08% to 0.5% indium, 2.5% to 5% silicon, 0.2% to 1% silver, and the balance substantially all aluminum.

3. A bearing characterized by high anti-friction properties and resistance to disintegration under impact, said bearing being formed of an alloy consisting of 0.05% to 5% indium, 2.5 to 5% silicon, 0.05% to 5% silver, iron not in excess of 0.5%, and the balance substantially all aluminum, the physical structure of said alloy being substantially free of continuous networks of segregated metallic constituents.

References Cited in the file of this patent UNITED STATES PATENTS 1,079,035 Tebetts Nov. 18, 1913 1,908,023 Kempf May 9, 1933 2,746,136 Rich May 22, 1956

Claims (1)

1. A BEARING FORMED OF AN ALLOY COMPRISING APPROXIMATELY 0.05% TO 5% INDIUM, 0.5% TO 10% SILICON, 0.05% TO 5% SILVER, AND THE BALANCE SUBSTANTIALLY ALL ALUMINUM.

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