US2597461A - Lead base alloy - Google Patents

Description

Patented May 20, 1952 ass 7 ,461

LEAD BASE-ALLOY James F. :Ednie, BellevuefPa a'ssignor "to *{Ijhe American Metal Companyf-Ltd iYurk, N. Y., ascorporationof New Zlotk No.-'Draiving. -Application Augustlli, I947,

serial'No. 769,519

1 Claim. (01. #5 1156) LI'hislinventionrelates to leadbase alloys having -:characteristics comparable to those of tin base alloys, and :more especially it deals with alloys consisting of suitable proportions of lead, tin, antimony, :manganese and iron.

In the field of so-called Babbitt metals,-a mate- -rial distinction is recognized between tin base alloys on theonehand and lead base alloys on the other. Though both types havefound extensive-usatin basealloys are generally. regarded .as possessing the more desirable properties -for use .in-antisfrietion bearings and for other purposes for which such alloys areutilized. One of the chi-efvadvantagesof the-tin base'alloys as a group is the considerably =-greater rduotility they 5 possess, as-compared with the leadbase alloys. Howevendueto-the greater cost of -tin base alloys, it .has long been recognized that :it would be commercially and technically desirable to providea lead base alloy having properties comparable to thosezof the tin basetype.

I have succeeded inlaccomplishing the'foregoing object by my present invention. I have found that when small amounts of manganese and iron are added to an alloy composed of a substantial proportion of lead and minor proportions of tin and antimony, the resulting alloy-exhibits properties which are substantially equivalent to those of the tin base alloys. In addition, my novel alloy is materially lower in cost than tin base alloys.

The above mentioned alloys can be produced by first melting tin in a kettle and bringing the temperature up to about 1500 F. or more then 1 adding powdered manganese and stirring in. "Afterthe'prop'er amount of manganese has-been dissolved, the powdered iron is added in the amount required. When'this-mixture has been thoroughly alloyed, the antimony is added during which period :the temperature drops slowly --and the lleadlis then added. The alloyis then poured -D s (at atemperatureofiabout.80'O .F.

However, lgpre'fer tOPIOdlICB my-bearing metal alloys by vfirst makingx-an iron-manganese-tin hardener or individuallrardeners "of iron-tin and manganese-tin. The ilnal bearing-metal alloy is madabymddingthe correctamounts of hammer to a'previously. prepared bath OfzlBHid and anti- .imony. EI'heidesiredzhardenerismade bymelting tin to a tempera-ture for about :1'500" .or lmo're and adding enough .ipowdered manganese and powdered iron to make :an -alloy around ironmnd'somewhatilessrnranganese, al-thoughthis .proportion may'r-tary.

ar-Em Inmakin'g the iron tlnhard'enerflia imilar procedure was 'followedbut'in this 'ca's th iron was usually "only *brought up te -about 1%, "the balance tin. Depending upon "the 'grade or hardener made, itmayor "may not be "necessary to "add "additional iron and/or manganese to obtain "the final alloy -desired.

As already stated the ingre dients employed in my novel alloy consist of lea'd, "tin, --ant1mony, manganese and iron. As will be understood by thoseskilled: in theart' thesemetals'often contain [minor impurities which "donot subsmmau aflect their use "andthe results obtamdmth them.

However, copper and nickel are "especially "detrimental "impurities "and should "both he less "than 202% ".to'ob'tain the best results with -my *bearingmetal alloy.

Theamounts of the various ingredients *employed in my novel :a'll'oy can be varied without deleteriously affeotingthe' properties of "the-"alloy, but "only within "certain ranges. "Thus, I have found that the desired'resiilt'sare'obtained when from 9 to 12.5 pereefit of tin, 8.5 to 10.5 per cent of "antimony, 0.01 -to 0.5 "per cent of manganese and the-same amount of iron are employed, the balance-being lead. When proportions differing from thosestated are employed, the resulting alloy loses some of its desirable properties, the ductility'of the alloy in particular .being adversely afiected when the proportions "of manganese or iron, or both, arefsubstantially outside thexrari'gs given. It was surprising to find that even the small amount of manganese or iron usedwou-l'd increase the hardness-substantially and otherwise cause .lpronounced changes .in thelmicrostructure of the alloyas seenunder--a.microseope, and would also re'fine the structure of the alloyias seen in the-fracture.

.The 1 important .and. .pronounced difierence in meohanical properties between the "two known classes of babbittsis in I regard toith'eir sductility, astthe lfollowing'table will i'show:

' luesreported are averagesora nuniber oit'ests, and iverefiiade The composition of the above typical tin base alloy was copper 3.5 per cent, antimony 7.5 per cent, and balance tin. The typical lead base alloy indicated above was composed of: tin per cent, antimony per cent, and balance lead.

The low elongation value and poor ductility that is characteristic of such known lead base babbitts is also an indication of their well known brittleness, as contrasted to such known tin base babbitts of the same general hardness. This low value is a further indication of poor resistance to impact stresses and pounding. Thus it be-- comes apparent that lead-base babbitts are subject to severe limitations of usefulness, particularly if the stresses are high, or reciprocating, or in the nature of an impact. It is primarily the very fact that tin base babbitts do show superior properties in the above mentioned regard, together with slightly better bonding properties, that has made them universally more desirable for bearings which are highly stressed or where the service conditions are severe.

On the other hand, as already noted, because of the high price of tin, compared to lead, tin base babbitts are much more expensive than lead base babbittsgenerally from three to five times the cost of the latter.- Nevertheless, this added cost has been fully justified in many installations because experience'has shown that a bearing failure will occur much sooner when lead base babbitt is substituted. Technically, the important physical property that makes the difference is the ductility of the alloy, and the higher price has been therefore justified to obtain this necessary property.

A preferred improved lead base alloy composed of 12 per cent of tin, 9.75 per cent of antimony, 0.1 per cent of iron and 0.1 per cent of manganese, balance lead, was prepared.

The following table shows a comparison in certain mechanical properties of. the improved lead base alloy with a typical tin base, and a typical lead base babbitt:

4 broken test bar, and converting it to the corresponding reduced area. By dividing the change in area by the original area of the bar, and again multiplying by 100, the percent reduction of area is obtained.

The following table indicates the comparative Brinell hardness values of the present alloy with those of typical lead base andtin base alloys. Hardness determinations were also made at elevated temperatures as shown:

In making the above determinations, specimens inch long were cut from the 1 inch diameter castings and were tested midway between center and edge of the cross-section. A minimum of six specimens was used for each value reported. The tests were made with a hydraulic hardness testing machine, using a 10 mm. ball, a 100 kg. load applied for 30 seconds, at 70 F., 150 F. and 300 F. The 150 F. and 300 F. specimens were preheated in an automatically controlled electric oven for 1'7 hours, at the temperature indicated, and then quickly transferred to an oil bath at the same temperature 5 minutes before testing, to facilitate making the impression for hardness determination.

It is evident from the above tables that the new improved lead base babbitt possesses an elongation, in tension, approaching that obtained in a typical tin base babbitt, and very much superior to a typical lead base babbitt. Furthermore, the yield strength, ultimate tensile strength, reduction of area, and Brinell hardness values are all superior to a typical lead base babbitt, and very similar to the properties exhibited by a typical Table I1 l Yield Ultimate Reduc- Elong. m Strength Strength, tlon of p. s. i. I p. s. i. 2 Inches Area Per Cent Per Cent Typical 'Iiu Ewe Babbitt 10. 0L0 12, 000 11.0 13.0 Typical Lead Base Babbitt. 8,000 10,000 2. 0 1.5 Im roved Lead Base Babbitt of t llS invention H 8. 500 11, 500 i 9. 5 9. 5

' I A vcragc values.

In making the above determinations, standard tin base babbitt. Also to be noted is th t th .505 inch diameter threaded tensile test bars were machined from solid castings 1 inch in diameter by 6 inches long. The'castings were poured at 800 F. into a cast iron mold at a temperature of 212 F. All determinations reported herein were made on castings poured as described. The tensile' test bars were tested at room temperature on a Tinius-Olsen hydraulic testing machine at a head speed of .05 inch per inch of specimen per minute. The yield strength determination was measured with B. C. Ames extensometer at an elongation of .01 inch per inch of gauge length, .under load.

The percentage of elongation is determined by dividing the increase in gage length, as measured on the broken test bar, by the original 2 inch gage length, and multiplying by 100. Similarly, the reduction of area is computed on the same specimen by using a micrometer caliper to measure the reduced diameter at the fracture of the loss of hardness at elevated temperatures is parallel to that of tin base alloys.

Test bars have been poured from a considerable number of widely varying tin base compositions, and lead base compositions, some of them proprietary, but all in common usage. In all cases, the present invention shows superior ductility (as measured by elongation) to that of lead base alloys. All other tensile values are either equal to, or slightly below those of tin base alloys. On the other hand, the hardness value of the present invention is either equal to, or superior to that of the lead base alloys, and about the same as that of tin base alloys.

In addition to use in hearings or for other anti-friction elements, my novel alloys can be used for other purposes. For example, type'for pattern dies when made from the novel alloys is able to withstand abrasion and rough foundry use. Such type also possesses the: desirable meters where a combination of hardness and ductility are essential. Other possible uses are for small castings made in permanent molds such as toys and similar objects. For this latter use, high lead alloys are used at the present time in order to obtain the necessary ductility with a cheap metal; however, these alloys do not possess hardness which the present alloy would add with similar ductility.

It will be understood by those skilled in the art that although the metals and proportions named herein, particularly with regard to iron and manganese, are essential to the proper practice of my invention, nevertheless minor changes may be made without departing from the spirit of my invention. All such modifications comin within the scope of the appended claim are intended to be secured herein.

I claim:

A lead base alloy composed of about 12 per cent of tin, about 9.75 per cent of antimony, about 0.1 per cent of manganese, about 0.1 per cent of iron, and the balance of lead.

JAMES F. EDNIE.

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

UNITED STATES PATENTS Number Name Date 1,502,391 Muller July 22, 1924 FOREIGN PATENTS Number Country Date 309,399 Great Britain Apr. 9, 1929 OTHER REFERENCES Metals and Alloys, 1941, fourth edition, pages 83, 147. Published by Louis Cassier Co., London, England.