US2260247A - Method of making bearings - Google Patents

Description

Patented, Oct. 21, 1941 UNITED STATES PATENT OFFICE 2,250,247 METHOD or MAKING BEARINGS Ernest R. Darby and Carlos-M. Heath, Detroit, Mich., assig'nors to Federal-Mogul Corporation, Detroit, Mich., a corporation of Michigan Application December 29, 1939, Serial No. 311,525

4Claims.

where the lining is applied in the form of metal 5 powder. The use of a bronze liner in a steel back as a bearing *is not new. The lining bronze has been made of various alloys. One such alloy or class of alloys is copper and lead with the lead content ranging from to 45%. Another alloy is composed of copper and lead with a small percentage of tin. Another alloy is one of copper and lead with a small amount of nickel. Small amounts of, silver have been used along with If) copper and lead.

Bearings with liners of these alloys, as well as others having a copper base, have been made by diflerent methods. One method comprises the 1 pouring of the melted copper base alloy into a heated steel shell in a suitable mold followed by rapid chilling. whereby the alloy is bonded or fused to the steel. Another method comprises the spinning of the melted bearing alloy in the heated shell followed by rapid cooling. Still another method has been used where the bronze or. copper-lead bearing metal is melted in a closed tube or shell in a reducing atmosphere and the whole rotated to spin the bearing alloy into position. I

Metal powder has been used in the application of the bearing liner to the steel supporting back of the bearing. One method makes use of a powder composed of particles of lead enveloped in a shell of copper. powder is compressed upon a steel bearing back which has been electroplated or otherwise coated with a thin layer of copper. The powder layer is sintered into position under pressure at relatively high temperature, thereby bonding the particles 4 of powder together and the layer as a whole to the copper plated steel back. Another method employs a mechanical mixture of copper and lead powder or of copper, lead and tin powders. The

powder mixture is compressed upon a steel backing which has been coated with a thin lead-tin layer. A very high pressure is used whereby the compressed powder layer imbeds in the lead-tin layer suillcientiy to be held in place during handling and sinterlng. Sintering under pressure at a temperature around 1500 F, afl'ects bonding of the bearing layer to the steel and a union of the metal particles in the bearing layer. Other methods similar in nature have been used and powders of various compositions have been This copper coated lead 35 employed. One composition contains graphite particles along with the copper, tin and lead, and a chemical is frequently added for the purpose oi producing porositywhich later is supposed to absorb lubricating oil. p

All of the bronze or copper-lead lined bearings as herebefore described have characteristics which are more or less undesirable either from a manufacturing standpoint or in actual bearing service. It has been found by experimental tests that the iron which is dissolved into the bronte or the copper-lead when the melted alloy is poured into a steel bearing shell, lowers the bearing properties of the finished bearing. Other impurities dissolve in the bearing alloy during the melting process, and with some melting units and processes it is necessary to add' metallic or nonmetalllc elements or substances known as fluxes to remove gas or oxide and in other manners improve the castability of the melted metal. These fluxes, if allowed to remain in the alloy, are in some instances harmful to bearing performance.

- The high temperature employed when the melted bearing alloy is cast or spun into position on the steel backing material, necessitates operations which are expensive and, in addition, considerpowder upon the steel bearing member followed by sintering under pressure, several serious manufacturing diiiiculties are encountered. If the powder used be copper coated lead powder and the sintering temperature employed be low enough to prevent lead sweating under pressure, the time necessary to properly bond the particles of powder together and the whole bearing layer to the steel backing-is very long and the operation becomes expensive. This is also true when the powder used is a mechanical mixture of copper and lead or of copper, lead and tin, and in this case it is impossible with very high lead mixtures to sinter under pressure without sweating a large amount of lead. If sintering is attempted without pressure being applied at the same time, blistering will occur-resulting in excessive porosity and very poor bond or union between the bearing metal layers and the steel back.

We have found that a satisfactory and superior bearing can be made with the use of metal powder whereby the dimculties encountered in other methods are eliminated. In our process we may employ either copper coated lead powder or a mechanical mixture of copperand lead powders or copper. tin and lead powders. In addition, we may use a mixture of copper coated lead powder and copper or lead powder added for the purpose of controlling the chemical composition. We have also found thatsmall amounts of tin may be added which, under certain conditions. is advantageous to our process.

The accompanying drawing illustrates dia-' grammatically the steps in the preferred form of our method. In this drawing: a

Figure 1 is a section through a portion of an unplatedmetal backing for the bearing produced by our method. I

Figure 2 shows .the backing plated with a coating of bonding material.

Figure 3 shows the powdered bearing material applied to the plated bearing backing.

tion.

Figure 5 illustrates a rolling operation which may be performed after the first sintering operation.

" Figure 6 is a view similar to Figure 4 illus- :trating the second sintering operation.

. Figure 7 illustrates another rolling operationbearing blank is sintered in a suitable atmosphere to prevent oiddation, at a temperature of about 11-00 F., as indicated in Figure 4. The time of sintering will vary with the thickness of the layer of powder and the thickness of the steel backing member. However, under average con- Figure 4 illustrates the first sintering opera- A yer 3 F re 3) of the metal.

ditions, this time should not exceed thirty'minutes. After the bearing blank has been sintered,

it is cooled to room temperature while still main-" taining' a reducing atmosphere, and 'removed It is then put in a suitable from the furnace. I die and pressed or rolled between suitable rollers, as indicated in Figure 5, under a pressure be:-

tween 2500 and 20,000 lbs. per sq. in. depending upon the nature of the powder-and the thickness of the layer. This pressing-operation serves to compact the metal powder layer without danger of causing blistering or sweating in the sintering operation which is to follow. The bearing blank is then again sintered,as shown in Figure 6, for

exceeding 1700 F. Cooling is effected as before in the reducing atmosphere.

"By the above operation we have provided a bearing blank upon which the copper-1ead*- or bronze layer is securely bonded without danger of lead sweating or blistering during any of the operations. In addition, such a bearing blank is remarkably free from porosity and will require but a slight amount of rolling or pressing before the'tlnishing or machining operations necessary to complete the bearing. r A modification of this method may be employed with a certain type bearing whereby the properly platedsteel bearing member is placed in a die and the metal powderas above is compressed upon all surfaces under a light'pressure not ex- .a period of 10 to 30 minutes in a reducing at- .mosphere in. a furnace held at a temperature not ceeding 7500 lbs. per sq. in.; the desired pressure depending upon the density and other characteristics of the powder. serves to density the metal powder layer to an extent whereby the bearing blank with the powder layer upon it may be handled in subsequent operations. After this pressing operation, the

blank is sintered in a reducing atmosphere at a temperature of about 1100 F. and cooled as before mentioned. It is then again compressed in a suitable die under a pressure of from 2500 lbs. per sq. in. to 20,000 lbs; per sq. in. depending upon the thickness of the steel backing and the metal powder layer. Final sintering then follows in a reducing atmosphere at a temperature of about 1700 F., whereby the metal powder layer is bonded to the plated steel backing and the particles of powder are thoroughly united. Cooling is then eflected as before in a reducing atmosphere.

Another modification has been found practical with certain types of bearing blanks, wherein the metal powder layer is spread loosely upon "the plated steel back and then sintered at a temperature not exceeding 1700'. F. The blank is then cooled in a reducing atmosphere as before."

After the bearing blanks have been prepared as above, a pressing operation may. or may not be necessary" depending upon the density desired in the finished bearing. In the case of theaverage bearing. such as used in internal combustion engines, apressing operation is desirable and it has been found that a pressure of as high as 40 T. per sq. in. can be safely applied to the fingered metalsurface for the'purpose of densiflcation and for the purpose of sizing the blank to the desired thickness. This operation may be a rolling operation, as shown in Figure 7. We have' found that by our process this final pressingoperationproduces a surface which may be used in many, applications without any machining. It of course is understood that where the bearing blank has been made in strip "or other flat form,

a forming operation is required 'to produce thedesired shape, for example, that of Figure 8.

One of the advantages of our method is that the metal powder may be applied as-a loose layer on the steel back, and sinteredwithout lateral or longitudinal shrinkage and without the formation of shrinkage cracks in the sintered and slightly bonded to the plated steel, back, but not enough diffusion has taken place to cause appreciable shrinkage of the layer. The pressing operation then so compacts the layerthat it can not shrink or crack in final sintering. In fact, a slight expansion is 'noticeable in the final sinterlng operation.

The advantages of this process are particularly evident when thick bearing layers are desired and when sintering under pressure causes blistering andlead sweating. 4

Although we have described our process as using a platedlsteel backing membenwe do not wish to confine ourselves to that alone. It is within the spirit of our invention to use any strong rigid material plated as described or any copper base alloy such as argentiferous copper, bronze, brass or leaded bronze as' a backing member.

Having thus. described our invention, what we claim is:

This pressing operation surface. During our first or low temperature sintering, the particlesof powder are slightly knit together v booting-forming metallic material on the in non-compacted powdered form and then in a non-oxidizing atmosphere at a hire of from about 1100 to 1700 F. in 1J1 to partially bond the particles of nqnpowder together and the layer as a mic to the back. then pressing or rolling the a blank thus formed to compact the sintered layer eliminste-mbstantially all voids therefrom,

y sintering said bearing blank in a nonatmosphere at a temperatur of from t 1100 to 1700' 1". in order to complete of the particles together and the layer a whole to the back, and cooling in a nonpxiniisinga ere. q 2. The method of producing a bearing memfber which consists essentially in placing a layer the bearing-taming metallic material in nonpowdered form on the back and then mtering in a non-oxidizing atmosphere at a temperature of from about 1100 to 1700 F. in

1 'gpacted powder together and the layer as a whole v, M the back, cooling the blank thus formed ina finch-oxidising atmosphere. then pressing or rolling said blank to compact the sintered layer to ;eliminat e substantially all voids'theretrom, again faring said bearinglblank in a non-oxidizing atmosphere at a temperature of about 1700' F.

in order to complete bonding of the particles gender to partially bond the particles of non-com-- together and the layer as a whole to the back, and cooling in a non-oxidizing atmosphere.

3. The method of producing a bearing member which consists essentially in applyinga coating of bonding metallic materialto a bearing blank,

placing a layer of the bearing-forming metallic sintered layer to eliminate'substantially all voids therefrom, again sintering said bearing blank in a non-oxidizing atmosphere at a temperature of about 1700" F. and cooling in a non-oxidizing atmosphere. v

4. A method according to claim 3 wherein the said bearing lblank is subjected to an additional pressing or rolling operation after the second sintering operation under a pressure not exceeding 40 tons per square inch to density the hearing metal layer and size the blank to the desired thickness.

ERNEST R. LDARBY. CARLOS M, HEATH.

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