Improvements relating to the Production of Aluminium and Alloys thereof.
Year: 1886

page_text: Date of Application, 22nd July, 1886.
Complete Left, 21st Apr., 1887.
Complete Accepted, 24th May, 1887.
PROVISIONAL SPECIFICATION.
Improvements relating to the Production of Aluminium and
Alloys thereof.
I, LUDWIG GRABAU, of 15ª Höltystr, Hanover, Germany, Civil Engineer, do
hereby declare the nature of this invention to be as follows:-
This invention relates to the production of aluminium and alluminium alloys.
In the production of aluminium and aluminium alloys, by reducing compounds of
aluminium and fluorine, chlorine, bromine, iodine, or sulphur, by means of potassium
or sodium at red-heat, the said metals volatilize in such a manner that losses occur,
and the reduction of the aluminium compounds remains incomplete.
According to the present invention, I obviate this defect by using hermetically
closed reducing vessels of metal, so that the reaction can take place under pressure,
which, as experiments have shown, materially promotes the reduction of aluminium
compounds. To prevent the contamination of the aluminium by the metal of the
reducing vessel, the internal walls of the latter are provided with a fire-proof lining
incapable of being reduced, a carbon lining being most suitable. For this purpose a
crucible made of artificial carbon can, when the vessels are comparatively small, be
placed in the reducing vessel, and the intermediate space left can be filled up with
fire-proof material or carbon powder. When the vessels are comparatively large, the
lining may consist of single carbon bricks luted by tar. The protecting lining can
also be composed of a coating of tar or lac which during the reduction is transformed
into a solid lining of carbon, adhering closely to the walls of the vessel.
The cover of the vessels must in the same manner be lined with carbon on its
internal surface, and can be connected with the vessel by means of screws, a hermetic
joint being produced by a fire-proof packing material which cannot be reduced by
potassium or sodium at red-heat, for instance magnesia-cement.
To effect the reduction, the vessel is completely filled with the aluminium compound
and with a corresponding quantity of potassium or sodium. The vessel is then closed
tightly, and heated to a red heat in a furnace or in a coal-fire. The reduction
commences when a dark red heat is obtained, which can be recognized by the vessel

page_text: suddenly becoming bright red in consequence of the heat generated by the chemical
reaction which occurs. At the same time, owing to the potassium and sodium vapours
generated, a high pressure is produced in the vessel, promoting the reduction in the
briskest manner. After the termination of the reduction, which, according to
the size of the vessel and the degree of heat to which it is subjected lasts from 1 to 3
hours, the vessel can be opened by taking off the cover and the contents removed.
The utilization of the potassium or sodium is complete in this process, if the vessel
.is heated for a sufficient time, and if the aluminium compounds to be reduced are
present in excess. In the latter respect it has been found suitable to employ one
third more of the aluminium compounds than would correspond with the potassium
and sodium according to their equivalents.
The aluminium formed by the reduction is finely distributed throughout the entire
mass and can be united in various manners to form a regulus.
For example, the aluminium compounds to be reduced can be mixed with a flux
such as, for instance, potassium-chloride in such proportions that the mixture is
capable of melting at red heat. The aluminium then collects at the bottom of the
reducing-vessel.
Another method consists in using the reducing vessels only for carrying out the
reduction, and effecting the melting of the product obtained with the addition of a
flux, for instance potassium chloride, in a special crucible. made of carbon. All the
aluminium collects at the bottom of the crucible if the latter is kept for several hours
at a violent heat.
This process can be used with special advantage for the direct production of
aluminium alloys. To this end the aluminium compounds to be reduced, beside
potassium or sodium, are mixed with a suitable quantity of the metal, for instance
copper, if copper alloys are to be produced, in the reducing vessel, the copper being
preferably in a granulated state. All the alluminium then combines in the reduction
with the metal.
The union of the alloy, divided in the mixture to form a regulus can be effected by
melting the whole mass in a carbon crucible, the metals uniting at the bottom of the
crucible.
By comminuting and washing the mixture the metal can be separated and then
united in the crucible, using a flux.
A further method consists in melting the reduced mixture, containing the aluminium,
in a carbon crucible and stirring the same with a rod composed of the metal, with
which the aluminium is to be alloyed, for instance of copper. The aluminium finely
distributed in the molten mass then collects on the metal rod and mixes with the
melting metal of the rod.
In some cases the reduced mixture is placed in a carbon crucible in the comminuted
condition and molten metal, for instance copper, is poured thereon. The specifically
lighter substance then rises gradually during the melting, the ascending aluminium
alloying with the copper.
The alloy can be obtained by making the reducing vessel of the metal (for instance
copper), with which the aluminium is to be alloyed, and then, after the termination of
the reduction, causing the reducing vessels with their contents to melt in a larger
carbon crucible. In this case the lining of the reducing vessel with carbon is not
required.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: 1 LUDWIG GRABAU, of 15 Höltystr, Hanover, in the Empire of Germany, Civil
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
This invention relates to the production of aluminium and aluminium alloys.
In the process heretofore used of producing aluminium by reducing aluminium
fluoride compounds by means of potassium or sodium at a red heat, the aluminium,
when the ordinary fire-proof crucibles of clay, porcelain, iron, or the like, are used, is
contaminated to a considerable extent by the material of the crucible, because potassium
and sodium destroy these materials at red heat. Moreover the yield is very small,
because the potassium and sodium vapours volatilize for the most part, and this waste
cannot be prevented even by covering the crucible.
According to the present invention these defects are completely obviated, the
reduction being effected in such a manner that no contamination of the aluminium
occurs, and a yield of aluminium is obtained that is equivalent to the quantity of
potassium and sodium employed for the reduction.
The reduction of the aluminium fluoride compounds is, according to the said
invention, effected in hermetically closed metal vessels which do not permit the
potassium or sodium vapours generated at red heat to escape.
The pressure of the vapours produced has an advantageous effect upon the complete
reduction of the aluminium fluoride compounds, inasmuch as the vapours can penetrate
the entire space of the vessel, the heating at the commencement of the operation not
being raised to such a degree that the aluminium fluoride melts, but only say to gentle
red heat, so that the aluminium fluoride experiences only a certain loosening, and the
potassium or sodium vapours can come in intimate contact with the particles of
aluminium fluoride.
To prevent the contamination of the aluminium by the metal of the reducing vessel,
the internal walls of the latter are provided with an unreducible fire-proof lining, a
carbon lining being most suitable. For this purpose a crucible made of artificial
carbon can, when the vessel is small, be placed in the reducing vessel and the inter-
mediate space left can be filled up with fire-proof material or carbon powder.
When the vessel is comparatively large, the lining may consist of single carbon
bricks luted by tar. The protecting lining can also be composed of a coating of tar
or lac which during the reduction is transformed into a solid lining of carbon, adhering
closely to the walls of the vessel.
The cover of the vessel must in the same manner be lined with carbon on its internal
surface, and can be connected with the vessel by means of screws, a hermetic joint

page_text: being produced by magnesia cement, as this material cannot be reduced by potassium
or sodium at red-heat."
To effect the reduction, the vessel is completely filled with the aluminium fluoride
compound and with a corresponding quantity of potassium or sodium. The vessel
is then closed tightly and heated to a gentle red heat in a furnace or in a coal-fire.
The aluminium fluoride is not fusible at this temperature, but experiences only a
loosening of its particles so that the potassium or sodium vapours already extensively
generated at this heat can enter into the most intimate contact with the several particles
of the aluminium fluoride. As a matter of fact the reduction commences when a dark
red heat is obtained, which can be recognized by the vessel suddenly becoming bright
red, in consequence of the heat generated by the chemical reaction which occurs.
the same time, owing to the potassium or sodium vapours generated, a high pressure
is produced in the vessel, which pressure materially promotes the reduction. The
melting of the mass takes place only after the termination of the reduction. The
latter, according to the size of the vessel and the degree to which it is heated, lasts
from 1 to 3 hours; the vessel can then be opened by taking off the cover and the
contents removed.
At
The utilization of the potassium or sodium is complete in this process, if the vessel
is heated for a sufficient time and if the aluminium fluoride compounds to be reduced
are present in excess. In the latter respect it has been found suitable to employ one
third more of the aluminium fluoride compounds than would correspond with the
potassium and sodium according to their equivalents.
The following quantitative proportions have been found to be especially suitable.
For 100 parts by weight of aluminium fluoride 61.5 parts by weight of sodium, about
24 parts by weight of aluminium being obtained. The quantity of sodium necessary
according to theory would be 81-6 parts by weight for 100 parts by weight of
aluminium fluoride. For the reduction of cryolite (aluminium fluoride-sodium fluoride
Al 2 F1 6 (Na Fl) 6) use is suitably made, for 100 parts by weight of cryolite, of
26.3 parts by weight of sodium, from 10 to 10-5 parts by weight of aluminium being
obtained.
The aluminium formed by the reduction is finely distributed throughout the entire
mass and can be united in various manners to form a regulus. Although this addi-
tional treatment of the aluminium is not the immediate object of the invention the
following statement may be made.
The aluminium fluoride compounds to be reduced can be mixed with a flux, such, as,
for instance, potassium-chloride in such proportions that the mixture is fusible at red
heat.
The aluminium then collects at the bottom of the reducing vessel, if it is heated to
a bright red heat after the termination of the reduction.
Another method consists in using the reducing vessels only for carrying out the
reduction, and effecting the melting of the product obtained by the addition of a flux,
for instance potassium chloride or sodium chloride in a special crucible made of carbon.
All the aluminium collects at the bottom of the crucible, if the latter is kept for several
hours at a violent heat. This process can be used with special advantage for the direct
production of aluminium alloys. To this end the aluminium fluoride compounds to be
reduced, beside potassium or sodium are mixed preferably in a granulated state with
a suitable quantity of the metal, for instance copper, if copper alloys are to be
produced, and put in the reducing vessel. All the aluminium then combines in the
reduction with the metal.
The union of the alloy, distributed in the mixture to form a regulus can be effected
by melting the whole mass in a carbon crucible, the metals uniting at the bottom of
the crucible. By comminuting and washing the mixture, the metal can also be
separated and then united in the crucible, using a flux.
A further method consists in melting the reduced mixture in a carbon crucible and
stirring the same with a rod composed of the metal, with which the aluminium is to
be alloyed, for instance of copper. The aluminium finely distributed in the molten
mass then collects on the metal rod and mixes with the melting metal of the rod....

page_text: In some cases the reduced mixture is placed in a carbon crucible in the com-
minuted condition, and molten metal, for instance copper, is poured thereon. The
specifically lighter substance then rises gradually during the melting, the ascending
aluminium alloying with the copper.
A modification of the reducing process in order to produce aluminium alloys,
consists in making the reducing vessel of the metal (for instance copper) with which
the aluminium is to be alloyed effecting the reduction in the manner above fully
described and then, after the termination of the reduction causing the reducing vessels
with their contents to melt in a larger carbon crucible.
The vessel, which has previously served for the reception of the aluminium com-
pounds to be reduced, then combines with the aluminium obtained during the reduc-
tion to form the desired alloy.
In this case the lining of the reducing vessel with carbon is not required.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is ;-
First. The production of aluminium and aluminium alloys by reducing aluminium
fluoride compounds, or mixtures of the same with the metals with which the aluminium
is to be alloyed, by means of potassium or sodium in hermetically closed vessels lined
with carbon, and then heating such compound to a gentle red heat, in such a manner
that the aluminium fluoride mass does not become liquid but experiences only a
loosening of its particles, whereby the potassium or sodium vapours under pressure
enter into the most intimate contact with all the particles of the aluminium fluoride.
Second. The production of aluminium alloys by reducing the aluminium fluoride
compounds in hermetically closed vessels composed of the metal with which the alloy
is to be formed, and subsequently melting such metal vessels with the reduced
mixture.
1 1007
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.