US1731210A - Gold alloy - Google Patents

Description

Patented oa s, .1929

UNITED STATES PATENT OFFICE VICTOR 1). nA'vrenon, ATTLnnono, MASSACHUSETTS, ASSIGNOR To GENERAL PLATE COMPANY, or ATTLEBORO, MASSACHUSETTS, A' CORPORATION on nnonn ISLAND GOLD ALLoY Ho Drawing. Application filed June 10,

The invention relates to alloys of precious metals, and particularly to alloys of gold con taining metals of lowspecific gravity, and to the process ofmaking the same.

The gold alloy now commonly used in the. arts has as its characteristic constituents gold and copper or gold and silver with approprireducingof the specific gravity .ate base metals other than copper or silver to impart requisite hardness, color, and other desired properties. This alloy, although malleable and ductile to a degree permitting working by usual mill processes of rolling and drawing, has the disadvantage of possessing a relatively high specific gravity, present invention has among itsob ects the of such alloys by incorporating therein a sufficient quantity of low specific'gravity metal or metals such as calcium, lithium, -magnesium, sil1- con, titanium, and aluminum for materially reducing the specific gravity of the alloy.

It will be understood that small percentages of metals of low specific gravities in the order of the specific gravities of the metals mentioned above will materially reducethe specific gravity of the gold alloy, which can be appreciated from an observation'that in a 14: carat gold alloy containing by weight 1 .part magnesium out of 24parts alloy the magnesium will have a volume about 80% that of the gold. v

I have found that magnesium, calcium, lithium, and other metals of similar characteristics cannot be alloyed with gold by usual processes, and that the mixture of raw metals to be compounded to make the alloy, particularly when magnesium is-present, is explosive upon application of heat sufficient to raise the temperature of the mixture to a value necessary to melt the old. These effects I explain are due to the act that'such 7 low specific gravity metals are highly volatile at temperatures much below that at which gold melts, and consequently will be destroyed the destruction being aided by the strong aiiinity of the metals for oxygen;

According'to the practice of the improved process the low specific gravity metal is first alloyed with a metal or metals with which it and the 1926. Serial a. 115,114.

will combine without being destroyed, the resulting alloy then being alloyed with the gold or with a gold alloy. Preferably, but not necessarily, the low specific gravity metal is alloyed with a metal which has a melting point lessthan that of the low specific gravity metal, so that the latter will be combmed at of the melting point of the low specificgravity metal and that of the gold, with the result that the final alloy maybe produced without at any time subjecting the raw low specific gravity metal or the alloy containing it to an unnecessarily high temperature.

As an example of the practice of the invention, but without limitation thereto, apreliminary alloy consisting of by weight about 2 magnesium, 30% zinc, and 50% silver may be made byplacing the raw metals in a crucible and raising their temperature to about 1400 degrees Fahrenheit, with use of suitable fluxes as hereinafter described. I have found that the zinc melts first and aparently causes the magnesium to melt into it at a temperature lower than that of the melting point of raw magnesium, and the silver to melt into the liquid. zinc and magnesium at a temperature lower than that of the melting point of silver, the zinc therefore acting to reduce the melting point of the silver and magnesium. The silver makes the alloyv more homogeneous and raises its meltalloys, of which examples are given above,

are in the nature of chemical combinations, being brittle as glass, the silver alloys meltlng at about 1400 degrees F ahrenhelt. These alloys have the property of causing gold when metal. For example, if the alloy to be pro-- mixed with the alloy to melt at a temperature of about 1600 degrees Fahrenheit, which is lower than the melting point of gold.

In making the preliminaryv alloy the metals may be placed in the crucible inlump, shot, bar, or sheet form in the inverse order of their specific gravities, that is to say the low specific gravity metal in the bottom of the crucible and the metals of higher specific gravity above it, so that the low specific gravity metal upon melting tends to rise through the metals of high specific gravity.

I have found as suitable for flux in preparing the preliminary alloy potassium bifluoride or calcium chloride, or a mixture of the two in the proportion of 1 part calcium chloride and 2 parts potassium bifluoride, cryolite, potassium chloride, sodium chloride, and sodium fluoride. The flux preferably is placed in the cruciblein crystalline or pow- 'dered form ontop of the metals before heat is applied, sufficient flux being employed to maintain upon the molten metals a layer about A inch thick. The contents of the crucible together with'the flux and slag are poured simultaneously in a thin stream into the mold so at all times to protect the molten metal from the action of the air. I have found that this flux eflectively will eliminate all oxides of the metals entering into the alloy, which oxides if present in the final alloy will render it unhomogeneous. It will be understood that the invention is not limited to use of the'fiuxes given, but that other fluxes, which will eliminate the oxides of the low specific gravity metal and form a liquid seal preventing access of air to the molten metal, may be employed.

The gold preferably is alloyed with the remaining constituents of the final alloy prior to being allo ed with the preliminary alloy containing t e volatile low specific v gravity 'duced is'to contain gold, copper, silver and magnesium, the gold may be first alloyed with the copper and some'of the silver, and the magnesium isfirst alloyed withthe zinc and balance of the silver, both of these alloys as heretofore explained having ,a melting" point less than that ofgolde'. These two alloys are then placed in a crucible andlmelted.

remainder copper, or if ium up to 1%, Thespecific gravltyof the alloy to be pro-= duced may be further reduced by incorporating other low specific gravity metals, as for example aluminum which is not particularly volatile, in which case the aluminum will be preliminarily alloyed with the gold and copper, as for example by practice of the method described in United States Patent 1,557,431 granted to me October 13, 1925.

In making the final alloy the preliminary alloy containing the volatile low specific gravity metal may be placed at the bottom of the crucible and'the alloy containing the gold on top of it, the two alloys being in relatively small pieces. with a layer about inch thick of suitable flux and the crucible is placed in a furnace and raised to 1600 degrees Fahrenheit, at which temperature the metals become liquid. More flux is then placed in the crucible, say

"about 1 ounce for each hundred troy ounces of metal, and the temperature is raised to about 1700 degrees, at which temperature the crucible is removed from the furnace and the contents thereof are poured in a thin stream into the mold, which mold may have an elongated vertically inclined mold chamber of the type'dcscribed in-my aforesaid atent.

As suitable fluxes for making the nal alloy I may use those described above in connection with the preliminary alloy. In addition I have also found as suitable for use granular sodium chloride, window glass, green bottle glass, mercury bichloride, and potassium cyanide, all of which. will dissolve or otherwise eliminate the oxides of the low specific gravity metals. I have found that a mixture of sodium chloride, 12%% potassium flu- -metalssuch as silicon and titanium if desired also may be alloyed with gold'by the above described metho As an example of a desirable 14; carat com mercial green gold alloy the "same may con sist of about 58% .gold, 25% silver, 3% magnesium, 5% zinc, with the remainder copper, or if desired somejof the copper may be substituted by aluminum, for example to make the alloy contain 3% aluminum. As an example of a desirable commercial 14 carat yellow gold alloy the'alloy may consist of about 58%gold, 3% magnesium, 5% zinc, with the desired some of the copper may be replaced by aluminum, for ex ample enough to make the alloy contain 3% aluminum. 5

I have found that by practice of'the above method calcium-in amounts up to 0.5%, lithand magnesium up to 3% readily maybe incorporated into the alloy.

The metals are then covered By exercise of care it is possible to raise the calcium content up to 2%, the lithium up to 3%, and the magnesium up to 5%.

My improved alloy is distinguished from h prior alloys in that it contains 10W specific gravity metals, particularly highly volatile earthy metals in amount-sufficient materially to'reduce its specific gravity, While at the same time it is sufiiciently malleable and ductile to permit working thereof by the usual mill processes of alternate attenuation and an-v nealing, the ingot being sufficiently homogeneous and free from checks and blisters to permit economic utilization thereof. 1

Although I have described several examples of alloys and metals for use therein, one example of the improved method and several examples of fluxes for use therewith, it is, to be understood that within the scope of my invention Wide deviations may be made without departing from its spirit.

Claims 1. A substantially homogeneous, malleable i and ductile gold alloy containing by Weight about 58% gold, 8% copper, 3% magnesium,

5% zinc, and the remainder silver.

2. A substantially homogeneous, malleable and ductile gold alloy containing by Weight about 58% gold, 3% magnesium, 5% zinc, and

the rel'i'iainder consisting of a metal of the group comprising silver and copper.

3. A substantially homogenous malleable and ductile gold alloy containing by Weight about 58% gold, 8% copper, 3% aluminum, 3% magnesium, 5% zinc, and the remainder silver.

4. A substantially homogeneous malleable and ductile gold alloy containing by Weight about 58% gold, 3% magnesium, 3% aluminum, zinc, and the remainder consisting of metal of the group comprising silver and copper.

5. A substantially homogeneous, malleable and ductile gold alloy having by Weight from 25 to 85% gold, from 1 to 5% magnesium, the remainder predominately metal of the group comprising silver and copper.

(5; A substantially homogeneous, malleable an ductile gold alloy having by weight from 25 to 85% gold, from 1 to 5% mag-- nesium, a small but substantial amount of zinc, the remainder predominately metal of the group comprising silver and copper.

.7. A substantially homogeneous,malleable' and ductile gold alloy having by Weight from 25 to 85% gold, to 5% metal of the group comprising magnesium, calcium and lithium, the remainder predominately metal of the group comprising silver and copper.

8. A substantially homogeneous, malleable and ductile gold alloy having by Weight from 25 to 85% gold, to metal of the group comprising magnesium, calcium and lithium, a small but substantial amount of zinc, the

remainder predominately metal of the group comprising silver and copper.

9. A substantially homogeneous, malleable and ductile gold alloy having by Weight from 25 to 85% gold, from 1 to 5% magnesium, a

substantial amount of aluminum up to 3%, a small but substantial amount of zinc, the remainder predominately metal of the group comprising silver and copper.

In testimony whereof, I have signed my name to this specification.

VICTOR D. DAVIGNON.