US2531910A - Aluminum thallium bearing - Google Patents

Description

NGV 28, 1950 F. R. HENsl-:L ET AL 2,531 910 ALUMINUM THALLIUM BEARING Filed NOV. 23, 1945 INVENTORS jfwnz j? Hemsf Earl [dfse/ BYM mi HTTORNEY Patented Nov. 28, 1950 ALUMINUIVI THALLIUM BEARING Franz R. Hensel and Earl I. Larsen, Indianapolis,

Ind., assignors to E'. R. Mallory & Co. Inc., Indianapolis, Ind., a corporation of Delaware Application November 23, 1945,V Serial No. 630,354

(Cl. 'l5- 138) Claims.

The present invention relates to bearings, and, more particularly, to bearings composed of aluminum base alloys containing thallium.

This application is a continuation-in-part of our co-pending application Serial No. 539,794, l'lled on June 10, 1944, for Sintered Aluminum Bearings, now Pat. No. 2,418,881, issued April 15, 1947. In the said patent, We have disclosed that sintered aluminum bearings having improved properties can be obtained from aluminum or aluminum alloy powders in combination with thallium or thallium base alloys, which cannot be alloyed directly in substantial quantities with aluminum, and that the range of thallium percentages in such bearings may be from 0.5% to 45%. The addition of thallium or thallium base alloy may be made by various procedures, such -as impregnating the compacted and sintered aluminum base with thallium or a thallium base alloy, or adding the thallium powder or thallium alloy powder to the aluminum powder, mixing, pressing and sintering the same, or by providing a coating of aluminum on the particles of thallium or thallium base alloy. The aluminum coated particles are then pressed into suitable forms and sintered. In addition to thallium or thallium alloys, some of the Babbitt type materials comprising alloys of tin, antimony, copper, lead and arsenic may be likewise added. Bearings of the described character provide numerous advantages of which the most important are low coefficient of friction, low specific weight, good thermal conductivity and high resistance to corrosion.

We have now discovered that the bearing properties of aluminum thallium alloys may be further improved to a substantial extent by preparing the -alloys by casting which may be rollowed by rolling or other working operations.

It is an object of the present invention to provide bearings composed of aluminum thallium alloys having improved anti-frictional properties.

It is another object of the invention to pro-.- vide aluminum base bearing alloys containing thallium particles uniformly distributed in an aluminum. matrix which are characterized by excellent seizure resistance.

The invention also contemplates novel aluminum thallium bearings having a cast and rolled structure combining the advantage of high embeddability with sufficient mechanical strength to resist deformation under operating conditions.

Other and further objects and advantages of the invention will become apparent from the following description and the accompanying drawing, in which:

Fig. 1 is a longitudinal sectional View of a bearing blank embodying the principles of the invention;

Fig. 2 is an end view of a bearing half shell formed of the bearing blank shown in Fig. l;

Fig. 3 is a longitudinal sectional view of a bearing blank comprising a layer of aluminum thallium alloy having a layer of pure aluminum clad thereon and bonded to a steel backing layer by means of an interposed layer of silver; and

Fig. 4 is a similar View of a bearing blank comprising a layer of aluminum thallium alloy combined with a reinforcing layer of duralumin.

Broadly stated, we have found that in accordance with the present invention aluminum thallium alloys may be prepared by such methods as casting with or without subsequent rolling or other working operations, provided that the thallium content is limited to about 10% of the composition by weight. While aluminum and thallium are substantially immiscible in the solid state, they are partially miscible in the liquid state. The resulting alloys are characterized by a structure wherein thallium particles are uniformly distributed in an aluminum matrix.

In the preparation of these alloys, the aluminum is usually melted rst and is superheated. A predetermined percentage of thallium is then added and the .molten mixture is poured into suitable molds or it may be poured directly into bearing shells. It is also possible and in some cases desirable to subject the cast alloy to working, such as rolling, in order to improve its bearing properties and to produce the alloy in the form of strips which may be readily converted into bearing shells by means of forming operations.

Experiments have indicated that thallium within the percentage ranges set forth in the foregoing does not segregate in the yaluminum matrix. In this respect thallium as an alloying element is superior to some of the alloying elements used in prior aluminum base bearing alloys such as tin, lead, cadmium, and the like, having a decided tendency to segregate in the nished product. We have found that the addition of thallium to aluminum base bearing alloys containing such elements as tin, lead and cadmium will greatly reduce segregation, will thus produce a more uniform structure in the as cast condition and will improve the workability of the alloys when it is desired to produce the alloys in the form of strips or sheets. Y y

Bearing tests were carried out on a number of aluminum thallium alloys and it was found that a material containing 4% of thallium by weight,

balance aluminum, had excellent seizure resistance when subjected to the Amsler seizure test. The alloys consisting of high purity aluminum and thallium, however, are extremely soft and in order to improve their mechanical strength, it is desirable to add hardening ingredients to the aluminum base material or to use the aluminum thallium alloys as bearing liners bonded to a reinforcing backing of steel or some other suitable backing material.

The preferred composition range of the aluminum thallium alloys of the invention is from about 0.1% to about of thallium by Weight, balance aluminum and particularly good results are obtained within the specific range of alloys containing from about 2% to about 4% of thallium by weight. Other elements may be added for further improving the bearing properties of the aluminum thallium alloys such as 0.1% to about 10% of lead by weight, 0.1% to about 5% of cadmium by weight, 0.1% to about 10% of tin by weight and 0.1% to about of silicon by weight.

The preferred hardening elements are copper and nickel which may be employed individually or in combination. The hardening elements should be present only in comparatively small quantities, in most cases not exceeding 2% of the composition by weight. For example, if copper and nickel are added for the purpose of strengthening the matrix, 1% of copper and 1% of nickel will be sufllcient. In addition to copper and nickel, such other elements as chromium, manganese, titanium, magnesium and beryllium may be incorporated for the purpose of strengthening the aluminum matrix or otherwise improving the properties of the alloys.

The elements incorporated into the aluminum thallium bearings for the purpose of improving the bearing properties usually form eutectic alloys with the thallium except in the case of lead. The diiiiculties experienced in connection with aluminum lead alloys are caused by the very limited liquid solubility of lead in aluminum. This results in the formation of two liquid layers and,

unless the melt is properly controlled and vigorously stirred, a very inhomogeneous material characterized by extensive lead segregation is produced upon casting. This difficulty is one of the reasons why aluminum lead alloys are not employed extensively in commercial applications. Aluminum thallium alloys are much less subject to this type of segregation.

It has been found that the addition of tin to aluminum thallium alloys is particularly helpful in preventing segregation and producing uniform distribution of the thallium tin phase within the aluminum matrix. For this reason, the following compositions have shown excellent bearing properties:

2% thallium, 4% tin, balance aluminum;

4% thallium, 3% tin, 2% silicon, balance aluminum;

0.5% thallium, 5% tin, 1.5% silicon, balance aluminum.

The distribution of the ingredients of low melting point within the aluminum is of particular importance when the bearing alloys of the invention are produced in the form of strip or sheet. The rolling temperatures must be closely controlled in order to avoid the formation of liquid phases between the crystal boundaries as such a condition would cause cracks and fractures in the material.

In most cases it is desirable to fabricate the aluminum thallium bearing alloys in the form of a liner which is bonded to a reinforcing backing of steel, or some other suitable material having suicient mechanical strength. Preferably, the bonding is carried out by means of the methods disclosed in the co-pending application Serial No. 607,993 of Franz R. Hensel, filed July 31, 1945, and entitled Art of Metal Bonding, which is a continuation-impart of co-pending applications Serial Numbers 557,703 and 579,992, iiled October 7, 1944, and February 27, 1945, respectively, and both entitled Aluminum Clad Steel. The essence of these methods of bonding aluminum to steel comprises applying a thin coating of silver at least to the surface of the steel, preheating the steel and aluminum strips preferably in a reducing atmosphere, and then effecting a strong, fatigue-resistant bond by the application of pressure. A bimetal suitable for the fabrication of bearings and made in accordance with these methods is illustrated in Fig. 1 wherein reference numeral Ill denotes the strip or layer of aluminum thallium bearing alloy, numeral Il denotes the steel strip or backing layer, and numeral l2 the interposed bonding layer of silver. This bimetal strip may be readily cut into unit lengths which are formed into bearings, such as the bearing half shell shown in Fig. 2 in which similar reference numerals have been employed to denote corresponding parts.

In carrying out the bonding process in accordance with the methods disclosed in the aforesaid (zo-pending applications, accurate control of the preheating and bonding temperatures is of great importance. To further promote the formation of a strong bond between the aluminum thallium alloy layer and the steel, it is in some cases also desirable to subject the bonding face of the said alloy to a preliminary etching treatment of the type disclosed in the co-pending application of Lynch and Strain, Serial No. 617,246, filed September 19, 1945, and entitled Method of Bonding Aluminum Alloys to Steel.

It is also possible to first clad the aluminum thallium bearing alloys with a layer of pure aluminum and then bond the said pure aluminum layer to steel by means of an interposed silver bonding layer in accordance with the method disclosed in the co-pendng application of Larsen and Doty, Serial Number 617,526, led September 20, 1945, and entitled Method of Bonding Aluminum Clad Alloys to Steel. A bearing blank prepared in accordance with this method is shown in Fig. 3 wherein I3 is the layer of aluminum thallium bearing alloy, I4 the layer of pure aluminum clad thereon, l5 is the steel backing layer, and i6 the silver bonding layer interposed between layers I4 and l5.

Instead of using a steel backing layer, the layer of aluminum thallium bearing alloy may be combined with other aluminum alloys having suiicient mechanical strength such as alloys of the duraluminum type. As those slrilled in the art know, alloys of this type are composed of a major portion of aluminum with approximately 4% copper, fractional percentages of magnesium and manganese, and small amounts of iron and silicon. A bearing blank including a layer of aluminum thallium alloy l? and a layer of duraluminum I8 clad thereon is shown in Fig. 4.

The term aluminum as used in the specication and in the claims is intended to cover the materials known in the trade as high purity aluminum and commercially pure aluminum.

The principal advantages of the aluminum thallium alloys of the invention are their good anti-friction properties, good embeddability, high fatigue and seizure resistance. Further important advantages are loW specific Weight, high heat conductivity and excellent resistance to corrosion.

Although the present invention has been disclosed in connection With a few preferred embodiments thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the invention. All of these Variations and modiiications are considered to be within the true spirit and scope of the present invention as disclosed in the foregoing description and dened by the appended claims.

What is claimed is:

1. A bearing formed of a cast alloy composed of about 0.1 to percent thallium by Weight and the balance substantially all aluminum, said bearing being characterized by low coeiiicientof friction and high resistance to seizure.

2. A bearing formed of a cast aluminum base alloy composed of about 0.1 percent to about 10 percent thallium by weight, and of a hardening addition of copper and nickel not exceeding 2 percent by weight, the balance being substantially all aluminum, said bearing being characterized by low coeicient of friction and high fatigue and seizure resistance.

3. A bearing formed of a cast and rolled aluminum base alloy containing from about 0.1 percent to about 10 percent of thallium by weight, about 1 percent of copper by weight, and about 1 percent of nickel by Weight, the balance being aluminum, said bearing being characterized by low coefficient of friction and high fatigue and seizure resistance.

4. A bearing formed of a cast aluminum base alloy containing about 2 percent of thallium by weight, and about 4 percent of tin by Weight, the balance being aluminum.

5. A bearing formed of a cast aluminum base alloy containing about 4 percent of thallium by weight, about 3 percent of tin by weight, and about 2 percent of silicon by weight, the balance being aluminum.

6. A bearing formed of a cast aluminum base alloy containing about 0.5 percent of thallium by Weight, about 5 percent of tin by weight, and about 1.5 percent of silicon by Weight, the balance being aluminum.

7. A bearing formed of a cast aluminum base alloy containing from about 0.1 percent to about 10 percent of thallium by weight, and from about 0.1 percent to about 10 percent by Weight of a lubricating metal selected from the group consisting of lead and tin, the balance being aluminum.

8. A bearing formed of a cast aluminum base alloy containing from about 0.1 percent to about 10 percent of thallium by weight, and from about 0.1 percent to about 5 percent of cadmium by weight, the balance being aluminum.

9. A bearing formed of a cast aluminum base alloy containing from about 0.1 percent to about 10 percent of thallium by weight, and from about 0.1 percent to about 15% of silicon by Weight, the balance being aluminum.

10. A bearing formed of a cast aluminum base alloy containing from about 0.1 percent to about 10 percent of thallium by Weight, and an eiective amount of at least one hardening element selected from the group consisting of copper, nickel, chromium, manganese, titanium, magnesium and beryllium not exceeding 2 percent of the alloy by weight, the balance being aluminum.

FRANZ R. HENSEL. EARL I. LARSEN.

REFERENCES CITED rThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,026,546 Kempf et al. Jan. 7, 1936 21,026,572 Kempf et al Jan. 7, 1936 2,026,549 Dean et al Jan. 7, 1936 2,170,039 Steudel Aug. 22, 1939 2,241,789 Queneau et al May 13, 1941 2,277,023 Steiner et al Mar. 17, 1942 2,329,483 Queneau et al Sept. 14, 1943 FOREIGN PATENTS Number Country Date 487,401 Great Britain June 20, 1938

Claims (1)

1. A BEARING FORMED OF A CAST ALLOY COMPOSED OF ABOUT 0.1 TO 10 PERCENT THALLIUM BY WEIGHT AND THE BALANCE SUBSTANTIALLY ALL ALUMINUM, SAID BEARING BEING CHARACTERIZED BY LOW COEFFICIENT OF FRICTION AND HIGH RESISTANCE TO SEIZURE.

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