Salt flux for addition to molten metal adapted for removing constituents therefrom and methods of using

BACKGROUND OF THE INVENTION 
This invention relates to salt fluxes and more particularly, this invention 
relates to a salt flux suitable for use in fluxing or purifying molten 
aluminum. 
In the prior references, there is disclosed the use of salt fluxes that are 
added to molten metal such as molten aluminum to remove inclusions such as 
oxides from the melt in order to provide an improved metal having superior 
properties. For example, U.S. Pat. No. 1,841,599 discloses the use of BaO, 
BaCO.sub.3, NaF, KClO.sub.3 and carbon. The patent discloses that oxides 
and oxy-salts of barium are particularly effective in reacting with 
non-metallic impurities in non-ferrous metals such as aluminum. U.S. Pat. 
No. 3,041,413 discloses the use of carbides of the alkali metals and the 
carbides of alkaline earth metals, the carbides being dissolved in molten 
solvents. The patent discloses the use of a fluxing agent such as sodium 
and potassium halides to aid in the dissolution of the carbides. 
U.S. Pat. No. 1,718,917 discloses a composition or flux suitable for 
welding, brazing or tempering compound, the compound suitable for use upon 
oily or greasy metallic surfaces without the necessity of cleaning. The 
flux has the following ingredients: borax, sol-ammerriac, Venetian red, 
bicarbonate of soda, salt and powdered coke. According to the patent, the 
coke is used as a reducing agent to prevent oxidation of the metals. 
U.S. Pat. No. 1,882,601 discloses a flux for coating welding rods for 
welding stainless steels. The flux contains 60% calcium fluoride or 
carbonate, 20% sodium fluoride and 20% carbon, and the ingredients may be 
varied according to the following: 40 to 80% alkaline earth salt, 15 to 
40% alkaline halide flux and 15 to 40% carbonaceous material. 
U.S. Pat. No. 1,975,084 discloses a flux composition for use with 
non-ferrous metals such as aluminum. The flux composition contains equal 
parts of an alkali metal chlorate, manganese dioxide, a boron compound, 
calcium fluoride, zinc, manganese, hematite, dolomite and a carbonaceous 
substance. 
U.S. Pat. No. 2,262,105 discloses a flux for use in melting light metals 
such as magnesium and aluminum. The flux composition has the following 
ranges: 20 to 50% magnesium chloride, 25 to 40% calcium chloride, up to 
30% sodium chloride and potassium chloride and 0 to 5% magnesium oxide. 
U.S. Pat. No. 2,479,798 discloses a welding flux for welding ferrous 
metals. The flux contains parts by weight, 30 to 50 parts sodium carbonate 
monohydrate, 10 to 30 parts alkali metal pentaborate, 20 to 40 parts 
alkali metal nitrate, 5 to 20 parts silica, 1 to 10 parts graphite, and 1 
to 10 parts oxide of iron or manganese. 
U.S. Pat. No. 2,499,827 discloses a welding electrode for cast iron having 
a flux coating containing 25-50 parts calcium carbonate, 20 to 35 parts 
calcium fluoride, 0 to 30 parts iron powder, 10 to 30 parts carbon, 1 to 
10 parts ferro-25 titanium and 3 to 6 parts bentonite. A binder may be 
added to this composition. 
U.S. Pat. No. 2,626,339 discloses a welding rod for welding copper alloys. 
The rod is coated with a flux composition composed of 5 to 15 wt. % 
carbonaceous material, 15 to 45 wt. % metal carbonate, 20 to 60 wt. % 
metal fluoride, and from 12.5 to 28 wt. % of a binder of sodium and/or 
potassium silicate. 
U.S. Pat. No. 2,900,490 discloses a flux-coated electrode for welding cast 
iron. The flux is composed of (parts by weight) 25 to 40 parts alkaline 
earth metal carbonate, 15 to 30 parts alkaline earth metal fluoride, 15 to 
30 parts carbon, 3 to 6 parts silicon as ferro-silicon and 2 to 10 parts 
rare earth metal and/or rare earth metal oxide. 
U.S. Pat. No. 4,761,207 discloses a slat-based melting process for melting 
aluminum scrap. The salt contains chlorides and fluorides of sodium, 
potassium, magnesium, aluminum, calcium and lithium. According to the 
patent, carbon or carbon monoxide is used to control oxide concentration. 
U.S. Pat. No. 4,983,216 discloses the use of halide salts such as alkaline 
earth metal halides or alkali metal halides such as Li, Na, K, Mg and Cu 
chloride or fluorides in melting aluminum scrap. 
U.S. Pat. No. 4,030,914 discloses that aluminum drosses are treated under a 
cover flux of sodium chloride or potassium chloride or mixtures thereof in 
combination with calcium chloride, the calcium chloride comprising about 1 
to 50% of the flux composition. 
U.S. Pat. No. 4,365,993 discloses treating lacquer-coated aluminum scrap 
with a solution of a mixture of halide salts. The mixture is applied to 
the scrap before the lacquer coating is pyrolyzed, leaving a metal 
relatively free from oxide inclusions. The preferred flux is a 50:50 
mixture of sodium chloride and potassium chloride, with an optional 
addition of up to 3% of an alkali metal fluoride. 
However, in spite of these fluxes and processes, there is still a great 
need for an economic, low melting point flux that is free from the use of 
fluorides. It will be appreciated that fluorides are generally 
ecologically and hygienically unacceptable. It will be noted that certain 
fluxes are suggested that do not employ fluorides; however, often these 
types of fluxes are not as effective in separating molten aluminum from 
dross or in minimizing oxidation of aluminum scrap during or after the 
melting process. Consequently, such fluxes can result in increased 
oxidation and greater losses of molten aluminum to dross or skim, 
seriously affecting the economics of the scrap recovery process. 
The subject flux has the advantage that it does not require or contain 
fluorides and thus is ecologically acceptable. In addition, the flux can 
be added in-line to sequestor oxides floating to the surface and to 
minimize skim. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved flux 
suitable for non-ferrous metals. 
It is a further object of the present invention to provide an improved flux 
suitable for use with aluminum. 
It is another object of the present invention to provide an improved flux 
salt free from the use of fluorides. 
It is still another object of the present invention to provide an improved 
flux that is effective in reducing oxidation of aluminum scrap during 
melting. 
Yet, it is still another object of the invention to add the flux in-line to 
improve effectiveness of continuous or batch metal treatment using rotary 
impeller device. 
These and other objects will become apparent from a reading of the 
specification and claims appended hereto. 
In accordance with these objects, there is provided an improved flux 
comprising 32 to 61 wt. % sodium chloride, 2 to 15 wt. % magnesium 
chloride, 2 to 12 wt. % carbon, the remainder potassium chloride. The 
ranges herein are inclusive of all the numbers within the range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the invention, there is provided a flux composition 
comprised of sodium chloride, potassium chloride, magnesium chloride and 
carbon. The flux composition can contain 32 to 61 wt. % sodium chloride, 
32 to 61 wt. % potassium chloride, 2 to 15 wt. % magnesium chloride, and 2 
to 12 wt. % carbon. Preferably, the composition contains 43 to 50 wt. % 
sodium chloride, 4 to 7 wt. % magnesium chloride, 3 to 8 wt. % carbon, the 
remainder potassium chloride. Typically, the flux composition comprises 46 
to 48 wt. % sodium chloride, 46 to 48 wt. % potassium chloride, 5 to 7 wt. 
% magnesium chloride, and 5 to 7 wt. % carbon. By "carbon" as referred to 
herein is meant to include all types of carbon such as graphite, carbon, 
coke and any other source of carbon that may be suitably incorporated into 
the melt or scrap which enables fluxing in accordance with the invention. 
When the source of carbon is graphite, carbon or coke, etc., for purposes 
of the present invention, it is important that the carbon be ground to a 
small particle size in order to mix homogeneously with the salts and to 
disperse thoroughly in the melt. Thus, in accordance with the invention, 
the carbon can have a particle size in the range of -3 to +24 preferably a 
particle size in the range of -16 to +20 mesh U.S. Sieve series. The 
carbon is important in the flux composition because it can operate to 
minimize oxidation of molten metal such as molten aluminum. Thus, in this 
sense, the carbon is important in that it is operational in minimizing 
dross or skim formation. The flux of the invention minimizes skim 
generation by minimizing skim fires on the top of the melt. This flux 
composition is superior to previous fluxes by enabling less expensive and 
high recoveries of aluminum without the level of dross and skim 
generation. Further, the present flux enables superior separation of 
aluminum from dross or skim. This permits higher recovery levels of metal 
without inclusions of materials such as oxides and nitrides. 
Operating within the ranges provided for the flux provides a low 
temperature melting range. For example, the flux composition of the 
invention provides for a melting point of less than 1320.degree. F. This 
permits efficient use of the flux at lower melt temperatures, thus 
minimizing the tendency of the melt, e.g., molten aluminum, to form 
oxides, nitrides, etc. Further, the flux composition can be adjusted to 
operate at the melting point of the aluminum alloy being treated, thus 
avoiding excessive temperatures. Thus, the flux composition of the 
invention is more economical too use. The flux composition is efficient in 
its ability to capture inclusions. 
The flux composition of the invention can be used as a cover flux, thereby 
reducing the available surface subject to oxidation. The cover flux has 
the ability to maintain higher temperatures in the melt without oxide 
formation. Thus, the cover flux has application to any stationary furnace 
or stationary well which is difficult to heat. Because of its high 
penetration ability, the flux composition is particularly suitable in 
aiding the separation of molten aluminum occluded in skim. The flux 
composition may be used with any suitable mechanical device used to stir 
skim layers for the separation of aluminum from the skim layer and permit 
the aluminum contained therein to return to the melt. 
The flux composition of the invention can be used in rotary furnaces for 
the melting of aluminum scrap, for example. When used in a rotary furnace, 
the flux composition is very efficient in maintaining low levels of dross 
to provide for high levels of aluminum recovery free of inclusions such as 
oxides and nitrides. Thus, it will be appreciated that these recoveries 
can be achieved without the use of fluoride salts such as cryolite which 
were commonly used. 
The flux composition of the invention can be injected or ingested into 
molten metal bodies, e.g., aluminum, for purposes of fluxing said bodies 
to remove or capture inclusions and carry such inclusions to the surface 
of the bodies. That is, the flux composition can be added to the surface 
of a body of molten aluminum and ingested and distributed by an impeller 
rotating in the body. The impeller can create a vortex that pulls the flux 
composition into the body and distributes the composition throughout the 
body. After the body has been thoroughly contacted by flux composition, 
the impeller may be stopped to permit the flux composition to float to the 
molten aluminum surface. In floating to the surface, the flux composition 
carries with it captured inclusions. Further, the flux composition may be 
injected into the body of molten aluminum by any means that enables 
introduction of the flux composition to the melt. The flux composition can 
be injected in powder or in molten form. Thus, it will be appreciated that 
the subject flux composition is particularly suitable because of its 
ability in reducing melting point. 
The flux composition of the invention has the advantage that it can be used 
along with gaseous fluxing media such as argon, helium, neon, krypton, 
xenon, along with nitrogen, carbon dioxide and mixtures of these gases 
along with mixtures of these gases and chlorinaceous gas such as chlorine. 
The gaseous media is particularly suitable in removing impurities such as 
entrapped gases, e.g., hydrogen, or oxide particles. The fluxing gas can 
be used in conjunction with the flux composition. That is, while the flux 
composition is being ingested by an impeller and distributed throughout 
the molten metal body, the fluxing gas can be introduced down a hollow 
shaft and out through radial holes in the impeller. The fluxing gas aids 
in floating impurities to the surface of the melt where it can be further 
treated to remove occluded aluminum. 
The amount of flux used for aluminum is the amount sufficient to remove 
inclusions. The amount can range from 5 to 20 ounces of flux to about 800 
lbs. of aluminum, with typical amounts being 8 to 14 oz. Fluxing 
temperatures can range from the melting point to 1450.degree. to 
1525.degree. F. When using the flux composition in conjunction with a 
fluxing glass that is introduced through an impeller, it is preferred that 
the fluxing gas flow rate be reduced or stopped until the flux composition 
is ingested and thoroughly dispersed in the melt by the impeller. 
Typically, this can be accomplished in one or two minutes. Thereafter, the 
flow rate of fluxing gas can be increased to the desired rate. 
While the invention has been described in terms of preferred embodiments, 
the claims appended hereto are intended to encompass other embodiments 
which fall within the spirit of the invention.