USRE19915E - Die casting alloy - Google Patents

Description

Reissued Apr. 7, 1936 10.015 nn: css'rmo ALLOY John B. Freeman, In, Cheshire, 04mm, amignor to The American Brass Company, Waterbury, Com, a corporation of Connecticut No Drawing. Ol'lg'llIl-I N0. 323,129, dated December 3, 1.85, Serial- No. 748,113, October 13,

This invention relates to a die casting alloy. and has for an object to produce an alloy which gives a much better smoother surface on the casting that doesn't require machining, sand blasting or other finishing operations.

Another object is to provide an alloy which flows readily into the recesses of the die so as to reduce to'a minimum the casting of defective castings, and also to permit satisfactory casting of more complicated castings.

Other objects and improved results will become apparent as the description proceeds.

The lowestmelting point brass is the alloy of approximately 60% copper and 40% zinc. If we use alloys of much higher melting temperatures we run into difllculties as higher temperatures reduce the life of the dies.

I have discovered that the addition of a small amount of silicon to lxasses in'the neighborhood of the 60-40 alloy gives a much better surface condition to a die casting of this alloy. The silicon may be in amount from approximately .05% to .5% and preferably from approximately 0.1% to 0.15%. The addition of this amount of silicon gives a much better smoother surface to the die casting, and one that does not require machining, sand blasting or other finishing operations. It also makes the metal flow better into the recesses of the die giving more perfect castings and permitting casting of more complicated castings. In short silicon materially improves the surface condition beyond that obtained by the use of tin. It increases the fluidity of the brass somewhat and tends to reduce drossing, that is tends to reduce deposit of zinc oxide on the die surfaces.

It is desirable to add asmall amoimt oi lead to these alloys when used for die casting as the lead keeps it plastic and suitable for casting over a longer range of temperature. It also improves its machinability. The lead used is generally about 1% of the alloy, but may vary from approximately .25% to 3%. It is also desirable to duces the tendency of the lead to segre ate in the pot and to give better fluidity to the alloy. It also increases corrosion resistance. The tinis generally about 1% ofthe alloy but may vary from approximately 25% to 3%.

of aluminum for the following reasons. Zinc has a relatively low melting point. "That is, it has a high vapor tension at the melting temperature of brass so it tends to vaporize and form clouds ofsincoxidaandtoformdrcesontopofthe melted metal as it is ladled out. the characteristic of forming a very fll t aluactl to prevmt oxidation of the underlying metal. Thealuminumthereforereducesthennc add a small amount of tin as it inhibits or re- It is still further desirable to add a small amount Aluminumbasminumoxidefllm'overthetopoftheliguidand Application for rei-ue February 14,. 1980. Serial No. 08,088

drosslng in the holding pot, and reduces the zinc oxide and copper oxide which is likely to be entrapped inthecasting tomake itunsound. The aluminum may be from approximately .05% to 5 1% and preferably about 0.1%. a

The general composition of copper approximately 60% and zinc 40% is of course well known.

A general composition of copper 60%, lead 1%, tin 1% and remainder zinc is also old, but I have found that the addition 0! silicon from approximately .05% to 5% to these alloys gives the improved characteristics as above described, particularly fo'r die-castings, that is it increases the fluidity of the alloy, reduces oxidation, particul6 larly of the zinc, and gives a much superior sur- I face to the resulting casting. As stated above the preferred'silicon content is from approximately 0.1% to 0.15%.

The improvementsecured by the addition of silicon is not confined to an alloy of approximately 60% copper and 40% zinc, but for die casting it is desirable to keep the copper about 60%, say from about 59% to about 61%, as alloys today for die casting are limited to those of relatively low melting points because of the limitations of die steels at present commercially available. However, my, tests have shown that a similar use of silicon in brasses of higher copper content gives similar results. With increasing copper content the silicon content may be increased if desired in proportion of the coeflicient of equivalents of silicon to zinc. Brasses with a copper content of approximately 55% to 75% can be die cast but at the present time the die casting of the high copper brasses is not commercially practical because of their relatively high melting points and consequent shortened life of metallic dies, generally steel dies, used in the die casting process. It would not be advisable to go 40 above about 43% zinc figured by equivalents.

An alloy range I have found very satisfactory in die casting is approximately the following:

A specific die casting alloy which is very satistactory is approximately the following:

Per cent Copper 60.00 zinc- 37.75 Lead 1.00 Tin 1.00 Silicon 0.15 Aluminum 0,10 00 Having thus set forth the nature of my invention, what I claim is:

1. A die casting 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 castingv alloy characterized by superiorfluidity and superior surface finish in the as cast 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 balance zinc. p

3. A die casting alloy characterised by' superior fluidity and superior surface flnish in the as cast condition comprising approximately 60% copper, 1% lead, 1% tin, .1% aluminum, .05% to .5% silicon, and balance zinc. p

4. A die casting alloy characterized by superior fluidity and superior surface flnish in the as cast condition comprising approximately 60% copper, 37.75% zinc, 1% lead, 1% tin, 0.15% silicon, and 0.10% aluminum. A V

e JOHN R. Jr.