US2023129A - Die casting alloy - Google Patents

Description

'20 of the 60-40 alloy gives a much better surface the fluidity of the alloy, reduces oxidation, pargo 25' sllicon'fgives a much better smoother surface to The improvement secured by the addition of 25 v 30 ings and permitting casting of more complicated 10; die casting are limited to those of relatively 30 40 a longer range of temperature. It also improves at the present time the die casting of the high cop- 40 I from-approximately 25% to 3%. W per cent '50, It is still further desirable to add a small copper 59 61 amount of aluminum for'the following reasons. Tin 5 1 5 Zinc has a relatively low melting point. That is, L ad ,5 1,5 I it has a high vapor tension at the melting tem- Aluminum .05- .15 perature of brass so it tends to vaporize and form Silicon .1 .2

Patented Dec- 3; I I e I 2 ,129 I ms cos-mic. annoy John B. Freeman, In, Cheshire, Gonn -assign! to The American Company, Waterbury, Conn, a corporation of Connecticut No Drawing. A'pplicaflon October 12,1934, D

Serial No. 748,113 a 4 Claims. (cue-1) v I This invention relates to a die casting alloy, and of the melted metal as it is ladled out. Aluminum has for an object to produce an alloy which gives has the characteristic. of forming a very tight a much better smoother surface on the casting aluminum oxide fllm over the top of the liquid that doesn't require machining, sand blasting and acts to prevent oxidation of the underlying 5- or other flnishing operations. 4 metal. The aluminum therefore reduces the 5 Another object is to provide an alloy which zinc flame and the loss of zinc. It prevents or flows readily into the recesses of the die so as reduces dressing in the holding pot, and reduces I to reduce to a minimum the casting of defective thezinc oxide and copper oxide which is likely castings, and also to permit satisfactory casting to be entrapped in the casting to make it unum'rso STATES PATENT orr cs 1-0 of more complicated castings. sound. The aluminum maybe from approxi- Other objects and improved results will bemately .05% to 1% and preferably about 0.1%. come apparent as the description proceeds. e The general composition of copper approxi- The lowest meltingpoint brass is the alloy of mately 60% and zinc 40%. is of course well approximately 60% copper and 40% zinc.- If we known. A general composition of copper 60%, use alloys of much higher melting temperatures lead 1%, tin 1% and remainderzinc is also old, 15 we run into difliculties as higher temperatures but I have found that the addition of silicon from reduce the life of the dies. approximately .05% to 5% to these alloys gives I have discovered that the addition of a small [the improved characteristics as above described. amount of silicon to brasses in the neighborhood particularly for die castings, that is it increases condition to a die casting of this alloy. The 'ticularly of the zinc, and gives a much superior silicon may be in amount from approximately surface tothe resulting casting. As stated above .05% to ..5% and preferably from approximately the preferred silicon content is from approxiv 0.1% to 0.15%. The addition of this amount of mately 0.1% to 0.15%

the die casting, and'one that does not require zinc isnot confined to an alloy of approximately machining,-sand blasting or other finishi g .09- 60% copper and 40% zinc, but for die casting it erations. It also makesthe metal flow betterinto is desirable to keep the copper about 60%; say 7 the recesses of the die giving more perfect castfrom about 59% to about 61%, as alloys today castings. In short silicon materially improves low melting points because of the limitations of the surface condition beyond that obtained by die steels at present commercially available. the use of tin. It increases the fluidity ,of the However, my tests have shown that a similar use brass somewhat and tendstoreduce drossing,that of silicon in brasses of higher copper content 35 it tends to reduce deposit of zinc oxide orf'the gives similar results. With increasing copper a5 'die surfaces. the silicon content may be increased if desired in It is desirable to'add a small amount of lead proportion of the'coefllcientof equivalents of silto these alloys when used for die casting as the icon to zinc. Brasses with a copper content of I leadkeeps it plastic and suitable for casting over approximately 55% to 75% can be die cast but its machinability. The lead used is generally per brassesisnot commercially practical because about 1% of the alloy, but mayvary from apof their relatively high melting points and conproximately 25% to 3%. It is also desirable to w sequent shortened life of metallic dies, generally add a small amount of tin as it inhibits or resteel dies, used in the die casting process. It

duces the tendency of the. lead to segregate in the would not be'advisable to go above about 13% 45 pot and to give better. fluidity to the alloy. It zinc figured by equivalents. also increases corrosion resistance. The tin is An alloy range I have found very satisfactory generally about 1% of the alloy but may vary in die casting is approximately the following;

clouds of zinc oxide, and to form dross on top Zinc j Balance A specific die casting alloy which is very sat- 1 I fluidity and superior surface finish in the as cast isfactory is approximately the following:

Per cent C ppe 60.00

- Zinc r 37.75 e 1.00 Tin 1.00 Silicon r 0.15 Aluminum 0.10

Having thus set forth the nature of my invention,-what I claim is:

1. A diecasting alloy characterized by superior fluidity and superior surface finish in the as cast condition comprising approximately 55% to 75% copper, lead from .25% to 3%, tin from .25% to 3%, aluminum from .05% to 1%. silicon from .05% to .5%, and balance zinc.

2. A die casting alloy characterized by superior condition comprising approximately 59% to 61% copper, .5% to 1.5% tin, .5% to 1.5% lead, .05% to .15% aluminum, .1% to 2% silicon, and bal- 3. A die casting alloy characterized by superior fluidity and superior surface finish in the as cast condition comprising approximately 60% copper, 1% lead, 1% tin, .1% aluminum, .05% to .5% silicon, and balance zinc.

4. A die casting alloy characterized by superior fluidityand superior surface finish in the as cast condition comprising approximately 60% copper,

37.75% zinc, 1% lead, 1% tin, 0.15% silicon; and 15 0.10% aluminum.

' JOHN R. FREEMAN, JR.