US2479596A - High manganese brass alloys - Google Patents

Description

Aug. 23, 1949-. E. A. ANDERSON ET A1. 2,479,596

HIGH MANGANESE BRASS ALLoYs "iled Dec. 20, 1947 2 Sheets-Sheet 1 [mwa/v0 A, A I HAV/0 gyJ/Lso/v M, M @may Aug;I 23, 1949. E. A, ANDERSON ET Al. l 2,479,596

HIGH MANGANESE BRASS ALLOYS Filed Deo. 20, 1947 A 2 Sheets-Sheet 2 ATTORNEY5 manganeserbrasses,

` manganese: contents/:'.comn

Patented Aug. 23, 1949 dem; Y .t v. i.

HIGH MANGANESE BRASS ALLOYS mpany,

Liferea This invention relates to alloys anvdnior-"particularlylg to'higl'i. manganese brassL alloys ^oharacter-izedwby highductility .and excellent retention-of'cornpositionduring lelfiielting...l Manganesekbrassesnthates,'.copper-zinc-man- 5" yfganese alloys have `been knownioridecades. In

'- Y generaL-the.tensiletrength of-.these manganes f lorasses-increaseswithetheir.manganese content, i A rfand,=as inthecase `of..rnost.rnetals and alloys, an -'-increase.in:tensilestrength is. accompanied by Alo afdecrease:- in-I ductility.. The high .manganese content of these 'aloys hasa further disadvantage in that the-alloys exhibiteapronounce'd. tendency .A n

to form va scum loimanganese.oxide While the 1 alloy is in the molten state. l rapidly during'ithepouring oficastings and results in the formation .lof ocolusions `.of..rnanganese oxide Withinlfthe castingsThesencclusions, orw f `fla\vs, like loweredductilityftpneclude-theuse oi I such alloys-in ytheiialoricationsof Imany articlesgfol'These preferreda'lloys arecharacteriz-ed by tenvwherein .their exceptionalapropertiesvvould, otherwisebe advantageousf--lf Y In the copending application of John L; Rodda, i' l SerialNo.v-54l,900, iiled June 243.1944ynow. abanfdo'ned, l'thereT are ``described.` high..y manganesev 25` Lbrassescontainingeirom 15-toV 37.5% Zinc, from 4"2.5 to30% -rnanganesal irorn0.1eto.2.% aluminum,` 1" and the Y balance copper.`

As-1describedfin said application, the rpresence oigaluminur'n in! suchhigh manganesebrasses lservesto. inhibit oxida- 30 tionofthe manganese-whilethealloys a'reinftheI *l 'moltenstater LA'i'.he-ter-isile strength of thealloys` v varies fro'nir-'aboutlfliLOGO toabout 70,000 pounds 'per squareinoh', 'and-theten-sile elongation of the 'alloys varies-from about-20% to about 45%.'

' pointed-outin said application that the' alu'rninurnw 'improvesthetensileg-strength and hardness but decreases the tensile` elongation. Thus," the alum- Vinurntendstodecreasethe ductility ofthe alloys although-it serves# a particularly-usefull effect in 40 "its capacity as ananti-oxidantfor the manganese,i

'content oi--the alloyi i v "Wehavenow found that alniinuiiiis capable y,

of producing Aexceptionally high ductilityin highs this lcapability. 'depending 45 upon a definite relationshipybetween. the amount 'ofv aluminum used'and the -coppercontent of the.V ,l

alloys.

of aluminuml are thoseahaying..copper; zinc andY Ensor-)EA in ing. 1 of the drawings.

...elhisnscum forms l5 The aluminum -alsoserves 15o-.produce alloys of excellent tensilel-strngtnfand further: V servestofinhibitoxidationofmanganese when 50 Vthe alloy'isinthemoltenstata l y The manganese brasses Which'vve have found susceptible to-firnprovedductility. by theaddition Anderson and David C.. J iilson, Palmr etten .laaessisnvrs t0 New Quirk, v:iN

The New Jersey Zinc Y., a kcorporatrm of pplicitin Decernber 20, l31730427, :Serial of'7921967 @Claims (Crus-.1515) ,im

This figure comprises 4`a trilinear chart based on the pernwhich e'acl'i 'of 'the :elements'coppenfzinc and manganese bearstwthetotalamount of copper, Zinc and'manganese: As-aresultof-sextensive investigation, "Wehave found `that manganese brasses having'compositions vwithin the area ABCDEA are capable of' having-` their `tensile "elongation increased'jtoat-least about-.45% by the"addition of the properainount 4of aluminum as hereinafter"explained."Alloysolying outside of Y said area show marked reduction ofytensile-elongation Without facornrnensurate improvement in tensile strength.` WithintherareaABCDEA, We have found that vconipnsitions consisting'oiabout 68% copper, froni'iO to'25%-zinc,1irom7 to.22% rnanganese, and the "balanceaiurninumf in the optimum amount; are' characterized 'by maximum motility in additionto their high tensile strength.

f The manganese brasses inthe following table 'aref illustrative of those" Whichwe have found susceptible 'toimprovement in' ductility eby the copper-zinc-man'ganese Izontenifon the tensile elongation offthe'alloy.

Analygogfmgfuw d* Mechanical Properties Per Per Per Tensile Per cent' yRed. of Brinell cent cent cent Strength, Elong. Area, Hardness Cu Zn Mn p. s. i. in 2" Per cent Number 60:2 21:6 17. 7 59. 000V f 43; 433 8G 66.0 19.2 14.7 5o,ooo l61`l vr 38 6o 71.0 16.2 12.6 43,000 50 31" ,j: 54 70.2 20.5` 9.1 45,300.1 4Z. E8 63.5 25.0 171.1 ,000` 50" 34:5 i 68 V67.9 14:9 16.8 46,5005 6511, 40 j 59 63.4 17.0 19:2 50,000.- 60.. 35 1 u (i6 65.5 .13. 2 21,2 49, 000 58 "f 36 63 61. l 15.8 23.1 56,000 53.1.. 34.5 73

Although each of the alloys in the foregoing table is characteiid by'ahi'gh'tensile-elongation,

lit Will be understood "fromthe followingdiscus tent within the range of about 60% to about 74% g-awithin.. the areaz. 55 copper',l the 'diictility Vof the".l nove-.described mangrade metal containing 99.99%

3 ganese brasses increases to a maximum and then decreases as the aluminum content is progressively increased. The amount of aluminum which Will produce the maximum ductility varies with the copper content of the alloys. Based upon extensive investigation, the curve AB in Fig. 2 of the drawings shows the amount of aluminum plotted against copper content which will produce maximum ductility in these high manganese brasses. Commercially satisfactory alloys may have somewhat less, say 5% less, than the high maximum tensile elongation obtainable in accordance with the invention. cordingly, there are plotted two curves CD and EF which represent the upper and lower limits in the amount of aluminum which can be used with varying copper content to produce manganese brasses having a percentage tensile elongation not more than about 5 less than the maximum percentage tensile elongation obtainable in accordance with the invention. A minimum of 0.15% aluminum is required to impart to the alloys their characteristic ability to retain their composition in the molten state. Thus, aluminum to copper proportions defined by the area between lines CD and EF inFig. 2 represent particularly useful proportions capable of producing high ductility manganese brasses which are also characterized by excellent retention of composition during remelting.

The ability of aluminum to improve the ductili- 'ty of manganese brasses having compositions coming Within the area ABCDEA in Fig. 1 is exlhibited only in the substantial absence of silicon =or of iron plus silicon in the alloys. ample, we have found that as much as 0.05% silicon in such a manganese brass prevents the attainment of the characteristic ductility of the alloys of the invention even when using an amount of aluminum which produces the maximum improvement in ductility. Small amounts of iron alone may be tolerated but amounts of iron and silicon together totalling 0.25% or more of the alloy effect an embrittlement of the alloy which cannot be overcome by the presence of the aluminum. Accordingly, the high manganese brass alloys of the invention consist of copper, zinc, manganese and aluminum, the amount of copper, zinc and manganese coming within the area ABCDEA in Fig. 1 of the drawings, the amount of aluminum with respect to the copper being such as to come within the range of proportions defined by the area between lines CD and EF in Fig. 2 of the drawings, and the alloy being free of silicon in excess of 0.05% and being free of the common presence of iron and silicon totalling in excess of 0.25.

The limitation on the amount of silicon alone, or silicon plus iron, which can be tolerated in the alloys of the invention dictates the use of substantially pure manganese in making up the alloys. Commercial manganese of the highest quality available for the production of alloys generally contains at least 1.5% and usually several per cent of iron and silicon. Accordingly, the alloys of the present invention should be produced either with electrolytic manganese or aluminothermic manganese of substantially equivalent purity in practicing the invention. Electrolytic copper cathode sheet, or any other good commer- Y cial grade of copper, may be used in the manufacture of the alloys. The zinc is preferably high zinc. The alloys of the invention are preferably manufactured and handled in clay-silicon carbide and For ex- In Fig. 2, ac-

carbon-silicon carbide crucibles. Steel crucibles may be used for remelting purposes without excessive iron contamination provided the component elements of the alloys are substantially free of silicon. However, steel crucibles should be avoided entirely in the manufacture of the alloy. Crucibles made of refractory oxides, such as alumina and magnesia, may also be used with advantage.

In manufacturing the alloy, the copper is rst melted and brought to a sufciently high temperature so as not to freeze when the other alloying constituents are later added. The manganese is then added in small lots until all of the addition has dissolved in the copper. At this stage, it is expedient to add a small amount of borax to clear up the oxide on the surface of the melt. The amount of borax is preferably less than that required to form a continuous molten cover, the ideal condition being to have beads of molten borax which dissolve or flux the surface oxide and then gather near the Crucible wall leaving a clear center portion through which other additions may be made. After the borax has thus cleared up the oxide on the surface of the melt, the zinc is added and the entire melt is stirred to produce a uniform composition. Aluminum is next added in small pieces placed on the surface of the melt and allowed to dissolve quietly without stirring. This procedure gives a higher recovery of aluminum in the final melt than is otherwise obtained by plunging the aluminum below the melt surface. The nal operations are to stir thoroughly, allow the melt to stand for a few minutes to permit entrained oxides to reach the surface, and then skim and pour.

The alloys of the invention melt at temperatures between about 800 and 950 C., as shown by the dotted line contours of melting points appearing in Fig. 1, and can be cast without diiiculty. The molten metal should be superheated for casting, and the alloys of the invention are all characterized by the fact that they can be cast at temperatures not substantially in excess of 1000 C. This casting temperature is well below the temperature at which the aluminum tends to burn off and thus expose the manganese of the alloy to oxidation.

The alloys of the invention can be sand cast in the standard green sand mold common to the foundry industry, using casting and molding practices common in the industry. The alloys have a high shrinkage during solidication, as have many sand casting alloys, and means for handling such alloys are well understood and available in commercial foundry practice. A notable advantage of the alloys in sand casting is that the sand does not adhere to the casting and can be removed easily by shaking or by blowing as distinguished from most commercial foundry alloys which must be sand blasted to remove the sand burned into their surfaces during the casting operation. In addition to sand casting, the alloys of the invention may be chill cast or die cast.

The machinability of the manganese brasses of the invention may be improved by the common expedient of adding lead thereto. For this purpose, up to about 3% lead, and preferably about 2% lead, may be incorporated in the alloys.

We claim:

1. A high manganese brass alloy characterized by high ductility and by retention of composition during remelting consisting of copper, zinc, manganese and aluminum, the amount of copper,

zinc and manganese being such as to come within the area ABCDEA in Fig. 1 of the drawings, the aluminum being present in amount with respect to the copper such as to come within the ranges of proportions dened by the area between lines CD and EF' in Fig. 2 of the drawings, said alloy being free of silicon in excess of 0.05% and being free of the common presence of both silicon and iron totalling in excess of 0.25%.

2. A high manganese brass alloy characterized by high ductility and by retention of composition during remelting consisting of about 68% copper, 10-25% zinc, '1-22% manganese, and the balance aluminum, theV aluminum being present in amount with respect to the copper such as to come within the range of proportions defined by the area between lines CD and EF in Fig. 2 of the drawings, said alloy being free of silicon in excess of 0.05% and being free of the common presence of both silicon and iron totalling in excess of 0.25%.

3. A high manganese brass alloy characterized by high ductility and by retention of composition during remelting consisting of copper, zinc, manganese and aluminum, the amount of copper, zinc and manganese being such as to come within lthe area ABCDEA in Fig. 1 of the drawings, the ratio of aluminum to copper in said alloy being dened by the line AB in Fig. 2 of the drawings, said REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 24,815 Great Britain Sept. 28, 1895 722,597 Germany July 14, 1942 OTHER REFERENCES Engineering Alloys, by Woldman, 1936 ed., page 1'7'7.

Metallurgie du Cuivre et Alliages de Cuivre, by Altmeyer et Guillet, 1925, page 590.

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