Improvements in the Electric Reduction of Aluminium and other Metals, and in the Production of Alloys thereof.
Year: 1891

page_text: Date of Application, 17th Mar., 1891
Complete Specification Left, 11th Dec., 1891-Accepted, 16th Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Electric Reduction of Aluminium and other
Metals, and in the Production of Alloys thereof.
I, THOMAS LEOPOLD WILLSON residing at No. 163 Joralemon Street, in the
City of Brooklyn, in the County of Kings and State of New York, United States
of America, Electrical Engineer, do hereby declare the nature of this invention to
be as follows:-
This invention relates to the reduction of aluminium and other metals from
oxides or other refractory ores thereof by means of heat generated electrically.
The invention is characterized by subjecting the ore or metal to be reduced to the
action of an electric current passing from an anode of molten metal or ore beneath
upwardly to a cathode of any suitable material placed above, the operation being
conducted in the presence of finely comminuted carbon as a reducing agent. In
the making of an alloy, such as aluminium bronze, the base metal to be alloyed
with the reduced metal constitutes the molten bath. In other instances the fusing
of the ore by the action of the current or by externally applied heat may provide
the molten bath constituting the anode.
In practising my invention, I place the metal or ore to be reduced in a crucible,
preferably of carbon, and connect the crucible with the positive terminal of a
dynamo generating a suitable current. The crucible is covered over with a
refractory cover having a hole through it, and through this hole is inserted a carbon
rod or pencil which is connected to the negative terminal of the dynamo. On the
current being established, it passes upwardly through the crucible and the metal or
ore to the carbon cathode, which is separated so as to form an arc, the heat of
which fuses the metal or ore. The oxygen eliminated by the reduction of the
ore would be freed and would rapidly waste away the carbon pencil but for the
provision of a reducing agent to combine with the liberated oxygen. This reducing
agent consists of finely powdered carbon, such as lamp black or coal dust, which is
introduced into the crucible either by being previously ground up and thoroughly
mixed with the ore, or by being introduced into the crucible from time to time or
in a continuous stream during the reducing operation. The comminuted carbon
thus introduced serves solely the chemical function of combining with the liberated
oxygen and converting the latter into carbon dioxide so that it shall be powerless
to corrode and consume the negative carbon pencil. The introduction of pulverized
carbon also serves to protect the upper part of the crucible from the corrosive
action of the liberated oxygen. By thus protecting the carbon pencil and crucible
from being eaten away, the reducing process is rendered much more economical
than heretofore.
In the making of alloys such as aluminium bronze, the base metal to be alloyed
with the reduced metal is placed in the crucible and is reduced to a molten state
either by electric heat or by externally applied heat as from a furnace. The ore
to be reduced may be introduced at the same time or subsequently, and the
powdered carbon may be introduced with the ore by being mixed therewith, or may
be subsequently introduced. In making aluminium bronze, I place pieces of copper
in the crucible and use preferably an alumina as the ore to be reduced, such for
example as corundum.
a
The figure in the accompanying drawings is a vertical transverse section of the
furnace. The bench A of brick-work is constructed with a chamber a having
floor or hearth-plate C, preferably of carbon or other refractory electric conductor,
and which is in electric connection with the metallic bar & connected to the positive
terminal of the dynamo. The carbon crucible B is set into the chamber with its
bottom resting on the carbon plate in good electrical contact therewith, so that the

page_text: electric current may flow from the bar b through the plate C and carbon crucible B
into the charge of metal therein. d is the bath, and e is the granular or powdered
ore being reduced. The chamber a and crucible are covered with a lid F of
refractory insulating material such as fire-brick, preferably luted at c to prevent
the escape of gases. The carbon pencil E constituting the cathode is inserted
through a hole in this lid, in which it may fit with sufficient friction to hold it in
place. This pencil is suitably connected with the negative terminal of the dynamo.
The lid F may be formed with a passage f extending through it, which may serve
the double purpose of a vent hole for permitting any excess of gases to escape from
the crucible, and of affording a channel through which to pour the powdered
carbon from time to time, if it be preferred to introduce it separately during the
reducing process. In operation, the arc causes a hollow or crater g to form in the
molten surface of the ore undergoing reduction, and across this crater is projected
a stream of gases and particles of carbon and molten or vaporized metals, as
indicated by the dotted lines and arrows.
The improved process provided by my invention is not limited in its application
to the reduction of aluminium, but may be employed for reducing and alloying other
highly refractory ores or metals of analogous character, such as boron, silicon,
calcium, chromium, titanium, etc. By the partial melting down of the fireclay used
for the cover F, I have produced a bronze of aluminium and copper with silicon.
Dated this 16th day of March 1891
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.
COMPLETE SPECIFICATION.
Improvements in the Electric Reduction of Aluminium and other
Metals, and in the Production of Alloys thereof.
1, THOMAS LEOPOLD WILLSON, residing at No. 163 Joralemon Street, in the
City of Brooklyn, in the County of Kings and State of New York, United States
of America, Electrical 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 reduction of aluminium and other metals from
oxides or other refractory ores or metallic compounds by means of heat generated
electrically. The invention is characterized by subjecting the ore or compound to
be reduced to the heat of an electric arc formed by passing an electric current
through a gaseous space intervening between a bath of molten metal or ore beneath
and an electrode of any suitable material placed above, the operation being con-
ducted in the presence of finely comminuted carbon as a reducing agent. In the
making of an alloy, such as aluminium bronze, the base metal to be alloyed with
the reduced metal constitutes the molten bath. In other instances the fusing of the
ore by the action of the current or by externally applied heat may provide the
bath constituting the anode.
In practicing my invention, I place the ore or metallic compound to be reduced
in a crucible, preferably of carbon, and connect the crucible with the positive
terminal of a dynamo generating a suitable current.
The crucible is covered over
with a refractory cover having a hole through it, and through this hole is inserted
a carbon rod or pencil which is connected to the negative terminal of the dynamo.
On the current being established, it passes upwardly through the crucible and the
metal or ore to the carbon cathode, which is separated so as to form an arc, the heat
of which fuses the metal or ore. The oxygen eliminated by the reduction of the
ore would be freed and would rapidly waste away the carbon pencil but for the
provision of a reducing agent to combine with the liberated oxygen. This reducing
agent consists of finely powdered carbon, such as lamp black or powdered coke or
coal dust, which is introduced into the crucible either by being previously ground

page_text: up and thoroughly mixed with the ore, or by being charged into the crucible from
time to time or in a continuous stream during the reducing operation. The com-
minuted carbon thus introduced serves solely the chemical function of combining
with the liberated oxygen and converting the latter into carbon dioxide so that it
shall be powerless to corrode and consume the negative carbon pencil. The intro-
duction of pulverized carbon also serves to protect the upper part of the crucible
from the corrosive action of the liberated oxygen. By thus protecting the carbon
pencil and crucible from being eaten away, the reducing process is rendered much
more economical than heretofore.
In the making of alloys such as aluminium bronze, the base metal to be alloyed
with the reduced metal is placed in the crucible and is reduced to a molten state
either by electric heat or by externally applied heat as from a furnace. The ore
to be reduced may be introduced at the same time or subsequently, and the
powdered carbon may be introduced with the ore by being mixed therewith, or may
be subsequently introduced.
In making aluminium alloys by this process I prefer to use a pure alumina,
such as commercial precipitated alumina. Or an ore which is as nearly as possible
the pure oxide of aluminium may be used, such as corundum. I place in the
bottom of the crucible a layer of fragments of the metal, or an ore of the metal,
to be alloyed with aluminium, preferably copper. On this layer I place a layer of
the alumina. The electric connections being made the carbon cathode is pressed
down through the alumina until it touches the copper, whereupon the circuit is
completed and the current passes. On lifting the cathode an arc is formed between
the copper and the cathode, which quickly fuses the copper so that a bath of
molten copper is provided beneath the alumina. The cathode is gradually raised
until the arc is fully developed and the zone of fusion is extended in all directions
in the form of a hemisphere around the tip of the cathode, whereby the alumina
is caused to assume the form of a hollow crater. The intense heat causes the
copper bath to boil by the vaporization of the copper, and the copper vapors
circulate within the crucible, becoming condensed against the comparatively cool
sides thereof and falling down as liquid copper through the mass of alumina,
whereby a circulation is created through the latter and as rapidly as the alumina
is fused and its oxygen driven off the copper is caused to combine with the
aluminium. When the alumina has been wholly fused and melted down and its
oxygen eliminated, there remains in the crucible a bath of molten aluminium
bronze. The operation is then discontinued and the molten metal is poured or
tapped out of the crucible.
The oxygen eliminated from the alumina immediately combines with any incan-
descent carbon which it encounters, and is liable to attack the carbon electrodes,
the cathode, which is exposed, being attacked to the greatest extent, while the
cup-shaped electrode or crucible, which is protected by the copper bath, is eaten
away but very little.
In
In the practice of my invention I aim to prevent as far as possible the wasting
away of the carbon electrodes, since carbon in this form is an expensive fuel.
fact it is the aim of my invention to avoid as far as possible all heating by com-
bustion, the furnace being operated as nearly as possible by electric heat alone.
To this end, and because some oxidizable material is necessary in order to combine
with the oxygen set free by the reduction of the ore, I introduce into the crucible
some cheaper form of carbon than that of which the electrodes are made. I have
found the use of carbon in the form of lamp black or of crushed coke, or the ground
up waste fragments of retort carbon advantageous. Or, coal dust or slack may be
used. By thus supplying carbon in this form the wasting away of the carbon
pencil or cathode is reduced to almost nothing. The particles of carbon thus
introduced are oxidized in preference to the carbon pencil by reason of the fact
that they circulate with the molten metals and are thereby drawn into the most
intense part of the arc.
The figure in the drawing left with the Provisional Specification is a vertical.

page_text: transverse section of the furnace. The bench A of brick-work is constructed with
a chamber a having a floor or hearth-plate C, preferably of carbon or other
refractory electric conductor, and which is in electric connection with the metallic
bar connected to the positive terminal of the dynamo. The carbon crucible B is
set into the chamber with its bottom resting on the carbon plate in good electrical
contact therewith, so that the electric current may flow from the bar b through the
plate C and carbon crucible B into the charge of metal therein. is the bath,
and e is the granular or powdered ore being reduced. The chamber a and crucible
are covered with a lid F of refractory insulating material such as fire-brick,
preferably luted at e to prevent the escape of gases.
The carbon pencil E con-
stituting the cathode is inserted through a hole in this lid, in which it may fit with
sufficient friction to hold it in place. This pencil is suitably connected with the
negative terminal of the dynamo. The lid F may be formed with a passage f
extending through it, which may serve the double purpose of a vent hole for
permitting any excess of gases to escape from the crucible, and of affording a
channel through which to pour the powdered carbon from time to time, if it be
preferred to introduce it separately during the reducing process. In operation, the
are causes a hollow or crater g to form in the molten surface of the ore undergoing
reduction, and across this crater is projected a stream of gases and particles of
carbon and molten or vaporized metals, as indicated by the dotted lines and arrows.
This furnace may be operated for the reduction of aluminium and to produce
aluminium bronze in the following manner, which is that by which I have
obtained the most satisfactory results.
I place in the bottom of the crucible a suitable quantity of copper suitably
broken up, or of copper wire twisted or compacted into a mass of convenient
shape, and on top of this a layer of a suitable quantity of alumina in the form
of precipitated alumina or nearly pure corundum. I have found the best
proportions to be two parts by weight of copper to one part by weight of
alumina. The cover F is then placed over the crucible and luted down and the
carbon pencil E thrust through it and pressed down through the layer of
alumina until its tip touches the copper. The circuit connections being com-
pleted an electric current is passed through the electrodes. The carbon pencil E
is then lifted slightly to strike the arc and as the copper fuses it is lifted still
higher until the maximum arc is formed. The arc is then to be maintained
stationary. In a crucible containing about four or five pounds of materials 1
have used a current of 200 amperes under a difference of potential of 50 volts
at opposite terminals of the furnace. Comminuted carbon is introduced either
by mixing it with the ore before the latter is placed in the crucible, or by
introducing it from time to time into the crucible through a suitable opening.
The operation of reducing the alumina to aluminium bronze consumes from
fifteen minutes to two hours, depending upon the character of the alumina, the
proportions of the ingredients and the strength of current. When the aluminium
is completely reduced the current is discontinued, the carbon pencil lifted out,
the cover F pushed off, the crucible lifted out and the molten bronze poured
into a mould to form an ingot. The alloys I have made in this manner have
varied between three per cent. and eighteen per cent. of aluminium.
I have made numerous experiments with different quantities and proportions
of ingredients and different ores of aluminium, the best results having been
obtained by the use of pure alumina with copper in the proportions stated and
with a current of the character named.
I have also used iron ore (oxide of iron) in connection with corundum and by
smelting the two together have produced an aluminium steel of fine quality.
have also smelted iron ore or fragments of iron with a very small quantity of
aluminium ore added thereto, and have made a fine quality of steel by passing the
current through the furnace for a period of five minutes.
In my experiments I have used both the molten bath in the crucible as an anode
and the carbon pencil as a cathode, and the molten bath as a cathode and the

page_text: carbon pencil as an anode. I have found the reducing effect to be the same in
either case, there being ordinarily no perceptible difference in the rapidity of
operation or in the product. I find, however, a considerable difference in the
rapidity with which the electrodes are consumed, since when a current is passed
downwardly the upper electrode or carbon pencil is consumed more rapidly than
when the current is passed upwardly. Another advantage of passing the current
from the crucible and molten bath as an anode to the carbon pencil as a cathode is
that the most intense heat, which as is well known is generated at the point of
separation in the electric arc of the particles disrupted from the anode, is brought
to the position where it is made most useful, namely, in contact with the molten
metallic bath. It thus causes an ebullition and vaporization of this bath, and an
energetic circulation of the vaporized and liquefied metal within the crucible, while
the heat is utilized to the best possible advantage.
The improved process provided by my invention is not limited in its application
solely to the reduction of aluminium, but is applicable to the reduction and alloying
of other highly refractory metals of analogous character, such as boron, silicon,
calcium, chromium, titanium, etc. By the partial melting down of the fire-clay
used for the cover F, I have produced a bronze of aluminium and copper with
silicon. I contemplate employing instead of a cup-shaped crucible removable from
the refractory brick-work or bench of the furnace, a crucible or vessel of different
shape built permanently into the brick-work, with an outlet passage from its lower
side for running out the metal or alloy at the close of the smelting operation after
the manner of an ordinary cupola furnace.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The herein described process of reducing refractory oxides which consists in
subjecting them to the action of an electric arc passing upwardly from an anode
consisting of a molten bath of a base metal beneath to a cathode above the said
bath and out of contact therewith and with the fused oxide, in the presence of
comminuted carbon as a reducing agent, whereby the said comminuted carbon
combines with the liberated oxygen and protects the cathode from oxidation.
2. The herein described process of reducing refractory oxides which consists in
subjecting them in the presence of a base metal to be alloyed therewith, to the
heat of an electric arc passing between the molten bath of the said base metal and
a carbon electrode above the said bath and out of contact therewith and with the
fused oxide, in the presence of comminuted carbon as a reducing agent.
3. The herein described process of producing aluminium alloys which consists in
subjecting an alumina in the presence of comminuted carbon as a reducing agent to
the heat of an electric arc passing between a molten bath of base metal and a
carbon electrode above the said bath and out of contact therewith and with the
fused alumina, whereby the oxygen freed by the decomposition of the alumina
combines with the said comminuted carbon and its corrosion of the carbon electrode
is prevented.
4. The herein described process of producing aluminium alloys which consists in
subjecting an alumina to the action of an electric arc passing upwardly from an
anode consisting of a molten bath of base metal beneath to a cathode above, and in
the presence of comminuted carbon as a reducing agent, whereby the oxygen freed
by the decomposition of the alumina combines with the said carbon so that its
corrosion of the cathode and the crucible is avoided, and the liberated aluminium is
dissolved in the bath of base metal, forming an alloy therewith.
This 10th
DL 1001
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent.