US3234016A - Zinc base alloy - Google Patents

Description

Feb. 8, 1966 Filed April 30, 1963 Z INC BASE ALLOY 2 Sheets-Sheet 2 ftlbs. P,S.I. 40

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%BERYLL|UM BERYLLIUM HG. 7 Mbs. HG. 8 p.s.|. 40 n 45000 Aged 3o AS Cast X-x 35000 "-x zo As Cast N AJdf/MM,-

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Z LEAD Z LEAD FZ G. 9 Mbs. ETG. PISA. 40 43000 V1 l I A c D A B c D DESIGNATED ALLOYS DESIGNATED ALLOYS INVENTOR ATTORNEYJ United States Patent O 3,234,016 ZINC BASE ALLOY Leslie J. Larrieu, San Marino, Calif., assignor to Morris P. Kirk & Son, Inc., Los Angeles, Calif., a corporation of Nevada Filed Apr. 30, 1963, Ser. No. 285,169 4 Claims. (Cl. 75-178) This is a continuation-in-part of copending application S.N. 211,376 iiled July 20, 1962 and now abandoned, which, in turn, is a continuation-in-part of application S.N. 68,674, filed November 14, 1960, now Patent No. 3,083,096, granted March 26, 1963.

This invention relates to a high purity alloy of zinc base with improved mechanical and physical properties containing aluminum and copper as major alloy constituents'and beryllium and/or magnesium as a minor alloy constitutent present in small but highly critical amounts that are extremely determinative of the improved properties.

The most important mechanical properties that are essential for the best performance of a forming die are, tensile strength and impact strength. Brinel hardness also is important, as are the physical properties of grain refinement, dimensional stability upon ageing and castability. Adequate tensile strength insures commensurate adequacy of compressive strength because of the mutual proportional relations of these two strength properties.

Since the introduction of the basic 4% aluminum, 3% copper, .05% magnesium, balance zinc, sand casting alloy, in 1939, there has exi-sted .a need to improve the impact strength and tensile strength of this alloy. Today this need is even more urgent because of the expanding technologies of the aero-space industries, which pose even more exacting and more severe mental forming tasks. Research work directed toward such alloy improvement resulted in the alloy disclosed in Patent No. 2,940,846, granted to me on lune 14, 1960. The patent discloses that a radical reduction in the nominal .05% magnesium content of the prior art alloy to an amount less than .03%, and `preferably less than .02%, rennes grain size, increases tensile strength and impact strength and generally improves the basic 4% aluminum, 3% copper, balance zinc, lalloy in all mechanical and physical properties.

Additional research directed toward the improvement of this basic alloy type has resulted in the discovery that the addition of small, but highly critical amounts of beryllium to an alloy containing 4% aluminum, 3.25% copper, .01% magnesium, balance zinc, very substantially increases the tensile strength and impact strength of the alloy. Other improvements include a slight increase in Brinell hardness, a most substantial improvement in castability and a marked additional refinement of grain size. This discovery was unexpected in that it repre- Vsents complete departure from previous attempts to relne grain, `and obtain additional mechanical and physical property improvements, by the addition of potentially helpful agents, including the addition of beryllium in amounts approximating .05 The .05% beryllium addition, as will be revealed hereinbelow, detracts rather than helps in the .attainment of the desired improvements.

The use of beryllium as a minor alloy constituent in alloys of zinc base is known. Patent No. 3,037,859 granted to me on June 5, 1962, discloses the use of .05 to .110%

`beryllium in an alloy of zinc base containing substantial amounts of copper, such Vas 8%, lesser amounts of aluminum, such as 3%, and minor amounts of magnesium, such as .05%. This alloy possesses a very good tensile strength, compressive strength and Brinell hardnes and retains these properties in substantial amounts when sub- 3,234,016 Patented Feb. 8, 1966 ICC jected to operating temperatures up to 400 F. The impact strength of the alloy is about equivalent to that possessed by the 4% aluminum, 3% copper, .05% inagnesium, balance zinc alloy, or about 8 ft. lbs. Melting and casting temperatures are somewhat in excess of those required for the alloys containing 3% copper.

Accordingly, it is an important object of this invention to provide a zinc base alloy which, upon being sand cast, possesses maximized mechanical and physical properties.

Another object of this invention is to provide an improved zinc base alloy which readily can be melted in conventional melting equipment and which readily can be cast in sand, permanent molds and pressure die casting methods for producing sound forming dies, heavy duty tooling plate, exceptionally strong die castings having maximum high tensile strength, impact strength, and dimensionai stability.

Additional objects and advantages of the invention will become apparent from the following description.

Briefly stated, in general terms, the objects of this invention are attained by providing a zince base alloy of high purity containing from about 3.5% to about 4.5% aluminum, from about .5% to about 3.5% copper, from a trace to about .03% magnesium, from about .0002% to about .02% beryllium, and the remainder zinc. A preferred alloy contains from about 3.8% to about 4.2% aluminum, from about 1.5% to about 3.25% copper, from -about .005% to about .025% magnesium, from about .005% to about .012% beryllium and the remainder zinc. An especially preferred alloy contains about 4% aluminum, about 3.25% copper, about .01% magnesium, about .01% beryllium, and the balance zinc.

All of the above metals are substantially pure that is the aluminum, copper, magnesium, beryllium, and zinc are all substantially pure. However, some impurities do creep into the processing of the metals but these are kept to a very low maximum. In fact the soft metal contaminants consisting of lead, tin, cadmium, bismuth, and antimony are held to a collective maximum of .0066% with lead being held to a maximum of .004%. Iron is held to a maximum of .02% while silicon is held to a .003% maximum content. Other contaminants such as manganese, chromium and titanium are held to a collective maximum amount of .005%.

Applicant has used a commercial and ravailable special high grade zinc in which the Zinc content is 99.99796% pure. Included in the impurities is lead at .0008%, iron at .0005% and cadmium at .00004%. It does contain .0007% copper which is not considered an impurity because copper is used in this alloy. Applicant has used a commercial and available specially high grade aluminum which contains 99.85% aluminum with .07% silicon and .07% iron and .01% other metals. The copper used by applicant in the manufacture of the present alloy as set forth in the application, has been assayed to include .005 tin, .003% lead, leaving a copper content of 99.992% pure.

The beryllium copper master alloy used by applicant has been found to contain .005% lead, .005% tin, .06% silicon, .005% chromium, .01% nickel, .06% iron and .01% cobalt. This is the 4% beryllium copper master alloy which is used by applicant. However, as Will be explained later, applicant takes this beryllium copper master alloy and makes another master alloy with the same before putting this into the other constituents metals of the alloy. This beryllium copper alloy also contains some zinc, some aluminum and the balance copper.

A more detailed description of my invention is given below with reference to the attached drawings', wherein:

FIG. 1 is a graph showing the effect of copper on the 3 tensile strength o fa sand cast zinc base alloy containing 4% aluminum, .008% magnesium, and .01% beryllium solid line, and of the same alloy with beryllium broken line;

IFIG. 2 is a similiar graph showing the effect of copper on the impact strength of a sand cast zinc base alloy containing 4% aluminum, .008% magnesium, and .01% beryllium 'solid line, and of the same alloy with 0% berylliurn broken line;

FIG. 3'is .a graph 'showing the effect of magnesium on 'the ltensile strength of a sand cast Zinc base alloy containing4%"alur`ni'num, 3% copper, and .005% beryllium solid line, and of the same alloy With 0% beryllium broken line; 4 4 I a FIG. `4 is a similar graph showing the elect of magnesium 'on lthe impact strength 'of a sand cast zinc base alloy `containing 4% aluminum, 3% copper, andl.005% beryllium solid line, and of the same alloy with 0% beryllium broken line; a a

FIG. 5 'is a graph lshowing the etect y'of lberyllium on the tensile strength of a sand kcast zinc base alloy containinglft4% aluminum, 3.25% copper, .and .01% magnesium;

F1G. j6 is a similar `'graph showing the effect of beryllium on the impact 'strength Vof a sand cast zinc base alloy con-` taining 4% aluminum, 3.25% copper, and .0 l'ma gnesium;

FIG. 7 is Va graph showing the etect of lead on ythe tensile strength of l.a sand cast Zinc base alloy containing '4% aluminum, 3.25% copper, .'01%"`mag`nesium, .01% beryllium;

FIG, 8 i's a similar graphshowingthe eect of lead on the impact strength of a sand cast zinc base alloy containing the same alloy as described in connection with FIG. 7;

FIG. 9 is a bar graph showing the comparative ,tensile strengths of three 'sand cast zinc base alloys:

(a) Which contains 4%` aluminum, 3% copper and .05% magnesium;

a -(b) Containing 4% aluminum, 3.25% copper and ;005% magnesium; v

(c) Containing 3% aluminum, 8% copper and .05% magnesium 'and .05 beryllium;

(d) The alloy of this application, which contains 4% aluminum, 3.25% copper, .01% magnesium, and 0l% beryllium;

FIG. `1`0`is a similar bar graphshowing `the comparative impact strengthsof the four alloys (a), (b),"(c), and (d), defined above in'describing FIG. 9; Y l

(The basic'rnechanical vproperty, relationships and effects of the alloying elements comprising the alloy of this invention Will be better undenstood after consulting ythe graphs presented in FIGS. 1 through l0. y

presents the eiect of the addition of copper Y'v1/ith '.01% beryllium in the solid line of the graph,-and copper 'Without beryllium, in the broken line, `uponthe lsand cast tensile strength of they '4% aluminum, .008% magnesium, balance zinc, alloy. It is readily evident that increased 'copper content t produces increz'ised, tensile strength, and that the inclusion of .01% beryllium results in a gain of approximately 4000 p.s`.i. tensilefstrengthffor each copper percentage from A1.5% to 4.5%.

F'GZ presents 'the eliect of the additionofcoppe'r with .01% beryllium, in the solid line of the graph, and

copper Without beryllium, in the :broken line, upon sand cast impact strength of the 4%, aluminum, .008% magriesim, balance zinc, alloy ofFIG. l. This relationship:

is one of inverse proportionality in which the eect of beryllium is indicated to be one of retention of higher increments of impact strength for 'all levels of copper content from .5% to 4.5%.

Table 1l given ibelow contains the test data used to plot the broken lines ofthe graphs of FIGS. l and 2;

' Table 1 iect yof ycopper on the tensile strength, impact strength 'and Brinell hardnessv 'number of a sand cast zinc base 4 Y Y alloy containing 4% aluminum, .008% magnesium, and balance zinc.

Percent Tensile Impact Brinell Cu strength strength hardness added (psi.) (it. lbs.) (number) 5 29, 800 30.0 85. 7 1. 0 32, 600 30. 5 92. 6 1. 5 33, 300 31. 5 9216 2. O 35, '000 r32. 0 l 96. 3 2. 5 35, 900 33.0 100 3.0 36,900 31. 0 100 3. 25 37, 200 30. 0 104 3. 5 37, 500 27. 5 104 4. 0 38, 800 17. 5 109 4. 5 40, 000 14. 2 109 Table ,2

Effect of copper on `the tensile strengtlnr impact strength and Brinell hardness number, of a `sand cast Substantialimprovement` in melting/characteristics and castability as well as marked refinement of grain size'are obtained by the addition of small 'but critical 4amounts `of beryllium yalone to the alloy of this invention. Beryl'- lium addition alone` in critical amounts tothe alloy, also improves `tensile `strength and `impact strength.` However, maximum improvement'is obtained ffrom the addition of two elements namely, berylliumfand magnesium in the critical amounts or ranges specied. Theseaddil tions of small but critical amounts of beryllium'and-mag-z t Vnesiulnbeneit the alloy with regard `to tensile strength and impact strength in substantial mannenfor all increr Y ments of copper over the range :from about :5% to about 4.5% as caribe seen by 4examining FIGS. `1 and E2 `and Table 2.

However, the copper-contentfof the: alloyas set forth in FIGS. l and 2 must be limited to .amaximum of'3.`5%. This limitation on vnriaXinuLrn copper, must be observed in order topreventa substantial loss of impact strength. Attention is directed-to the graph of FIGJZ 'showing a considerable and fast drop olf of thewimpact strength when the copper content vis :over 3.5%, both with and 'Without beryllium. It has been coniirmed ,by multiple tests ythat a copper amount of 3.25%,l which :is AWithin the preferred range previously stated, gives the best cornbination of mechanical gproperties fWhen both impact. i

strength Eand tensile strength are considered.

FIG. 3 presents the eiect of the addition tofmagnesium with .005% beryllium, in `the vsolid *line of the graph,

and magnesium Without beryllium,- infthe'brokengline,

upon the sand cast tensile strength of the .4% aluminum, 3% copper, balance zinc, alloy .f A :critical `irange kforv magnesium `both with and without` the '.005% vberyllium addition is indicated. The optimum'r is indicated to Ybe v about .01% to about 025% magnesum. It is Vnote; worthy that the .005% beryllium addition accounts foi' f an increase `of overl3,000 p.s.i; tensile lstrength'for Yall levels of magnesiumcontentsthrough vIthe range from .01% to .04%.

FIG. "4 presents the effect of the'addfitionfof magnesiumv -with .005% beryllium, Vin the solid r.li'nef of thelgraph,.and

magnesium without beryllium, in the broken line, upon the sand cast impact strength of the 4% aluminum, 3% copper, balance zinc, alloy of FIG. 3. A critical range for magnesium is presented with an evident improvement from the beryllium addition over the range of from about"% magnesium to about .03% magnesium. The optimum from the magnesium addition resides within the range from about .005 to about .025% for both the magnesium alone and the magnesium with beryllium.

Table 3 given below contains the test data used to plot the broken lines of the graphs of FIG. 3 and 4:

Table 3 Effect of magnesium on the' tensile strength and impact strength of a sand cast zinc base alloy containing 4% aluminum, 3% copper and balance zinc.

Percent Mg Tensile Impact added strength strength (p.s.i.) (it. lbs.)

Zero 35, 000 2l. 0 005 36, 000 30.0 010 36, 700 31.8 015 37,000 32.0 020 37, 300 32. 0 025 3G, 600 30. 0 030 35, 400 28. 0 040 33, 600 22. 0

Table 4 given below contains the test data used to plot the solid lines of the graphs of FIGS. 3 and 4:

Table 4 Eect of magnesium on the tensile strength and impact strength of a sand cast zinc base alloy containing 4% aluminum, 3% copper, .055% beryllium and balance zinc.

- Percent Mg Tensile Impact added strength strength (p.s.i.) (it. lbs.)

Zero 36, 000 26. 5

It has been discovered that the presence of small amounts of magnesium in the zinc base alloy containing beryllium is not necessary to achieve the results. The small amounts of magnesium however, do improve the impact strength and the tensile strength over that of a beryllium containing alloy without the magnesium addition. The presence of beryllium in the alloy does enhance the d imensional stability thereof, produces reined grain, improves the castability and also improves the impact strength and the tensile strength. This is clearly shown in the graphs of FIGS. 3 and 4. The percentage of magnesium added, with beryllium of course, as shown by the solid line of the two graphs, does increase the impact and tensile strengths. However, it is to be noted from an examination of both FIG. 3 and FIG. 4 that a substantial improvement for tensile strength and a very substantial improvement for impact strength are obtained for the alloy containing 4% aluminum, 3% copper, .005% beryllium and essentially no magnesium over that obtained for the same magnesium free alloy without beryllium. Specifically the improvements are 1000 p.s.i. tensil strength and 5.5 ft. lbs. impact strength.

Thepresence of magnesium in relatively low amounts and speciiically in the preferred range of .005 to .025%

yproduces maximum mechanical properties for the alloy containing 4% aluminum, 3% copper, .005% beryllium,

6 balance Zinc of high purity both in the cast condition and after aging 1 year at room temperature.

In the absence of magnesium this same composition yields somewhat lower mechanical properties in the as cast condition, however, these properties improve upon aging and substantially exceed those obtainable from the same alloy composition without beryllium, but containing magnesium over the range .01% to .05% and higher, after aging l year at room temperature.

This property of beryllium that improves the magnesium free alloys in mechanical properties after aging at room temperature has been found to be maximum in amount for the desired alloy of 4% aluminum, 3.25% copper, .01% beryllium balance zinc and with the soft metal impurities present in a collective amount of less than .0066%.

FIG. 5 presents the eifect of the addition of beryllium, over the range of 0% to .04%, upon the sand cast tensile strength of the 4% aluminum, 3.25 copper, .01% magnesium, balance zinc, alloy. The critical amount of beryllium for maximum tensile strength is from about .008% to about .012%. It is to be noted that the .04% beryllium alloy has a tensile strength which is substantially equivalent to that possessed by the alloy without the beryllium addition inasmuch as both .0% and .04% are approximately at the 37,000 lb. level. It has been found from multiple test evaluation that additions of beryllium in excess of .04% to this alloy reduces both the tensile strength and the impact strength of the resulting alloy below that possessed by the beryllium free alloy.

FIG. 6 presents the effect of the addition of beryllium upon the sand cast impact strength of the 4% aluminum, 3.25% copper, .01% magnesium, balance zinc alloy of FIG. 5, over the range of 0% to .04% beryllium. It is evident that a high degree of criticality of the amount of added beryllium also applies to the property of impact strength. Beryllium in the amount of about .02% is the indicated absolute maximum addition. The desired optimum amount is indicated to be from about .008% to about .012% beryllium.

Although in the broad range the lower limit of beryllium has been placed at .0002% and that this amount has been found to have beneficial results as shown by the graphs of FIGS. 5 and 6, it has been found that the lower limit of beryllium may be placed at .0005%. With this increased amount of properties of the alloy are likewise increased as shown by the graphs.

Table 5 given below contains the test data used to plot the graphs of FIGS. 5 and 6:

Table 5 Effect of beryllium on the tensile strength and impact strength of a sand cast zinc base alloy containing 4% aluminum, 3.25 copper, .01% magnesium, and balance z1nc.

Percent Be Tensile Impact added strength strength (psi.) (ft. lbs.)

zero 27, 000 32. 0 005 29, 800 36. 0 008 41, 000 37. 8 010 41, 000 38. 0 015 40, 600 37. 0 020 39, 300 3l. 2 030 38,000 22. 2 040 37, 000 18. 0

when `sand cast forming dies, permanent mold east tooling plate and pressure die cast shapes. are subjected to maximum stresses.

F-IG. 7 vshows the effect ofleadon tensile strength in a zinc base alloy containing .4% aluminum, 3.25 copper,

.01% magnesium, V.01% beryllium, balance zinc, as cast inthe fsolid line, and -the broken ,line shows theteffeet of lead on thewtensile strength of the samealloy rwhen cast and after agingLfor 1 year.A It` will be notedthat in the' as cast line, the ytensile strength of the alloy drops voli considerably after .004% lead and also drops olf inthe line denoted for the aged alloy.

FIG. 8 is a char-t -showing the etfectof lead on `impact strength of an alloy containing 4% aluminum, 3.25%

copper, .01% magnesium. and .01% bery11ium, balance zinc as cast by Lthesolid line..-and after agnsfor 1 year:

in the broken line. Also in this -chart itis noted that both lines drop otlgafterg.()04% lead.

Therefore, it is to be noted that when the `lead content otanalloy is'rnore than .004470, such .percentage is detrimentalto the alloy, and-that, therefore, the'lead content ofY the alloy must be kept below/004% Table 6 :given below `Gontalis vrthe test data used vto i plot the graph of FIG. 7.

Table 6 Elect of lead on vthe tensile strength-and `impact strength of a sand cast zinc base alloy containing 4% aluminum, 3.25% Copper, .01 magnesium, .01% beryllium, balance zinc as cast.

Tensile Impact Percent Pb strength strength (psi.) (tt. lbs.)

Table 7 given below contains the test data used to plot the graph of FIG. 8;

Table 7 Effect of lead on the tensile strength and `impact strength of a sand lcast zinc base alloy containing y4% aluminum, 3.25 copper, .01% magnesium, .01%beryllium, balance Zinc when aged 1 year, at room temperature.

AGED

Tensile ,Impact Percent Pb strength strength (psi.) (tt. lbs.)

Asexplained above, other contaminants into the alloy such as tin',,cadmium,fbis1nuth, and an.

.timony which, together with lead, fform the soft metal contaminants. As explained above, ,leadisthe -most important contaminant anclmust not be over 004%.

may enter Tin vmust have -a maximum. of- 001%,Vv cadmium must havela maximum of ,001%, bismuth must have a maximum of .0005% and antimony musthave a maximum of .0001%. Thus the `soit metal contaminants must not have a collective maximum of more than 00,66%.

Iron can have a maximum of A.02% and silicon can have a maximum `of 003%. Other metals which include manganese,chromiumand titanium, cannot have arnaximnm of over .005%. Therefore all of the contaminants inthe alloy mustnot be over '.0346%.

Thus it can jbe seen that the alloy of the present invention is substantially pure and in fact is very close to pure.

FIGS. 9 and '10, present,:in;bar graph form, the ycomparativey sand cast tensilestrengthiand comparative sand cast impact. strength ,obtained 'fromxfour alloys designated A, B. C, and 1). Alloy A'is the equivalent of the A.S.T.M. Alloy XXI comprising 4% aluminum, 3% copper, .05% magnesium and balance'zinc of'high purity; Alloy B` is La preferred .composition of PatentV No. 2,940,846 and contains 4% aluminum; 3.25% copper,

.005% magnesium and Ibalance zinc of high purity; Alloy C isia preferred composition of Patent No. 3,037,859 and contains 3% aluminum, 8% copper, .05% magnesium, .05% .beryllium andfbalance zinc of yhigh purity, and

Alloy D 'is;the alloy of this invention having about the Alloy Tensile strength Impact strength (psi.) (it. lbs.)

An additional evaluation of lthe alloy of this invention is obtained by consulting FIGS. 1l, 12,13 and 14. These iigures are photo micrographs of alloys designated A, B; C, and D respectively.

It will be seen that the alloy of this invention-repre sentis an extension of the art with this class of alloy. The addition ofV a small, but highly critical amount of beryllium in the`V range of .005% to .012% to an. alloy of zinc base containing 4% aluminum, .01% magnesium and copper in the range from about .5% to about 3.5%, impartsv a remarkable improvementin vthe tensile ystrength and a lsubstantialimprovement in: the impact strength', this is particularly thevca-se with the preferred alloy of this invention containing abouty 4% aluminum, about 3.25% copper and about .01% magnesium.

i An example; of a specific manufacturing procedure for producing the alloy'of myrinvention is given below.

High purity copperin the form of wire or ingot` is added tothe correct amount of molten high purity `zinc at 900 F.A When all, ofther copper is in solution, the correct aamount of vhigh purity `aluminum V,is vadded to the molten1 alloy'. After solution and agitation, the molten alloy is skimmed. After skimming, Aa sufficient amountof copper-aluminum-beryllium Master .Alloy is added in order to introduce beryllium into the alloy. The LMaster Alloyv is prepared byl melting Ta suiiicient amount-of pure aluminum in a graphite l,Crucible Vat about 1300 F.V after which a predetermined amount of 96%` copper- 4% .beryllium alloy vis added. A Master Alloy of the following composition is obtained: Copper 57.8%, aluminum 39.75%, berylliumV 2.41% agitation at.900 F. readily introducesy this master alloy into the melt. Finally, the Vstick magnesium ot high purity is then addedin sufcient amount lto introduce .01%.

Intermittent slow Before adding the beryllium master alloy and the magnesium, it may be desirable to deoxidize the zincalurninum-copper melt. This is done while maintaining the temperature at approximately 900 F. by adding about .0005% of pure elemental lithium metal. After this addition of lithium, the resulting mixture is strongly agitated mechanically for about 45 minutes. Very thorough hand skimming of all dross and other nonmetallic residues concludes this deoxidation, desulphurization and oxide reduction operation. When excessive oxide, sulphur, or both are suspected in the metal, amounts of lithium greater than .0005% may be added. This excess lithium is removed preferentially by gassing the molten metal with nitrogen at from about 900 to about 950 F. The reaction is symbolized Iby the following chemical equation:

The desirability of removing excess lithium is based upon the adverse effect of lithium upon impact strength and an undesirable coloration imparted to sand cast shapes after aging.

It is to be understood that the foregoing description has been given only by way of illustration and example, and that changes and modifications in the present disclosure, which will be apparent to a person skilled in the art, 4are contemplated as being Within the scope of the present invention, which is limited. only by the claims which follow.

I claim:

1. A zinc base alloy of high purity consisting essentially of, by weight, aluminum 3.8% to 4.2%, copper 1.5% to 3.25%, magnesium .005% to .025%, beryllium .005% to .012%, and having as impurities soft metal contaminants 'not greater in collective amount than .0066%, iron not more than .02%, the balance zinc.

2. A zinc base alloy of high purity consisting essentially of, by weight, aluminum 4%, copper 3.25%, magnesium .01%, beryllium .01% with soft metal contaminants not 10 greater in collective amount than .0066%, iron not more than .02%, and the balance zinc.

3. A zinc base alloy of high purity consisting essentially of, by weight, about 3.5% to about 4.5% aluminum, labout .5% to about 3.5% copper, about .005% to about .025% magnesium, from about .0002% to about .02% beryllium, and impurities consisting of soft metal contaminants and iron, the soft metal contaminants being not greater in collective amount than .0066%, iron being not greater than .02% and the balance zinc.

4. A zinc base alloy of high purity consisting essentially of, by Weight, about 3.5% to about 4.5% aluminum, about .5% to about 3.5 copper, about .005% to about .025% magnesium, about .0002% to about .02% beryllium, and impurities consisting of soft metal contaminants and iron, the soft metal contaminants being tin not more than .001%, cadmium not more than .001%, lead not more than .004%, antimony not more than .0001% and bismuth not more than .0005 and iron not more than .02% and the balance zinc.

References Cited by the Examiner UNITED STATES PATENTS 2,385,497 9/ 1945 Bunn 75--178 2,467,956 4/ 1949 Bierman 75-178.2 2,631,936 3/1953 Kuhlmann 75--135 2,837,427 6/1958 Monaco 75-178 3,037,859 6/1962 Larrieu 75-178.2 3,083,096 3/1963 Larrieu 75--178.2 3,094,412 6/ 1963 Kaess et al. 75-135 FOREIGN PATENTS 1,110,429 7/ 1961 Germany.

638,733 6/ 1950 Great Britain.

111,444 2/ 1962 Pakistan.

DAVID L. RECK, Primary Examiner.

WINSTON A. DOUGLAS, Examiner.

Claims (1)

1. A ZINC BASE ALLOY OF HIGH PURITY CONSISTING ESSENTIALLY OF, BY WEIGHT, ALUMINUM 3.8% TO 4.2%, COPPER 1.5% TO 3.25%, MAGNESIUM .005% TO .025%, BERYLLIUM .005% TO .012%, AND HAVING A IMPURTIES SOFT METAL CONTAINMENTS NOT GREATER IN COLLECTIVE AMOUNT THAN .0066%, IRON NOT MORE THAN .02%, THE BALANCE ZINC.

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