Improvements in Electric Reduction of Metals and in Apparatus therefor.
Year: 1890

page_text: Date of Application, 17th June, 1890
Complete Specification Left, 17th Mar., 1891—Accepted, 18th Apr., 1891
PROVISIONAL SPECIFICATION.
Improvements in Electric Reduction of Metals and in Apparatus
therefor.
1, THOMAS LEOPOLD WILLSON, of 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 smelting or reduction by the agency of heat derived
from the passage of an electric current, for producing aluminium or its alloys, or
other metals or alloys of more or less refractory character, such as boron, silicon,
calcium, chromium, titanium, etc., as well as iron or steel. In such electric smelting
of refractory ores, usually oxides, the ore is fused and decomposed by the heat
generated, and the oxygen thus liberated attacks the vessel or crucible enclosing
the material acted upon and the electrodes through which the electric current is
introduced, which are usually of carbon, and which are thus rapidly wasted away.
The material of the electrodes and crucible thus is made to serve as a reducing or
deoxidizing agent, and as such electrodes or crucibles are of somewhat expensive
material, and are more costly than other equally effective deoxidizing substances,
their consumption is attended with loss, and the process of electric smelting or
reduction is rendered expensive and uneconomical.
It is the object of my present invention to economize expense in electric smelting
by the avoidance of the loss referred to. To this end my invention contemplates
the introduction of a deoxidizing or otherwise reducing agent in gaseous form, and
in such manner that it shall be interposed between the liberated oxygen or other
agent requiring elimination and the surfaces of the crucible and electrodes, which
would otherwise be exposed to the destructive action of the oxygen, so that the
oxygen is caused to unite with the gaseous agent thus introduced before it can gain
access to the surfaces of the electrodes and crucible, so that the latter are protected
from oxidation, and their wasting away is almost entirely prevented.
In the preferred practice of my invention I employ an electric furnace consisting
of a crucible holding the material to be reduced, an electrode or electric connection
with such crucible for the passage of the current to its contents, and a second
electrode in the form of a tubular carbon rod thrust into the crucible and connected to
the opposite terminal of the electric circuit, and a source of gas connected through
a suitable pipe or duct with the said tubular electrode. When the current passes,
the upper electrode is lifted sufficiently to form an electric are between it and the
surface of the metal or ore in the crucible, and the gas is injected through
the tubular electrode into the electric arc, and hence into the hottest portion of the
molten or vaporized mass. In the case of reduction of a metal from an oxide the
gas is hydrogen gas or a hydrocarbon, preferably the latter, ordinary illuminating
gas being suitable. The oxygen liberated by the decomposition of the ore unites
with the carbon and hydrogen of the gas, producing water, carbonic acid and carbonic
oxide, which escape from the furnace through a suitable vent.
My invention is applicable to the reduction of other ores than oxides, it being
only necessary in such case to inject a gas of different character, that is to say, one
having an affinity for the substance that is liberated by the decomposition of the ore
in order that this substance may enter into a new combination with the gas and be
carried away from the furnace, or reduced to such form as to be readily separable
from the reduced metal

page_text: My invention comprehends also the construction of the furnace or apparatus for
carrying my improved method into effect. This furnace is constructed with a
suitable hearth or bench of brickwork having an opening or recess within which to
set the crucible. A carbon plate forms the bottom or floor of this opening, and to
this plate is connected one terminal of the electric circuit. The crucible is covered
by placing over its top a cover consisting of a plate of refractory material having
an opening through its centre through which to pass the carbon rod or pencil, the
opening being preferably of such size as to hold the pencil with sufficient friction to
retain it at any height at which it may be placed. The cover has also a vent
opening, which is preferably distinct from this hole. A luting of fire-clay should be
interposed between the crucible and cover.
The tubular carbon rod or pencil is preferably fastened at its upper end to an iron
or other suitable pipe which extends upward in line with the carbon rod, being
suitably guided, and to the upper end of this pipe is connected a flexible tube leading
to a fixed pipe through which the gas is conducted, a valve being provided to
regulate the flow.
The gas will ordinarily be the usual hydrocarbon illuminating or heating gas
served in city nains. Usually, however, the pressure in such mains is insufficient
for the purpose, and I therefore provide a pump driven by suitable power which draws
the gas from the main and forces it into the pipes leading to the furnace. The
action of such a pump being somewhat irregular preferably provide a gas-holder
of any usual construction between the pump and furnace, into which gas is delivered
from the pump and from which it flows out at a uniform pressure to the furnace.
The pressure at the furnace may be reduced or regulated by the valve before-
mentioned.
Since according to my invention there is very little wasting away of the carbon
pencil there is no necessity for providing means for feeding it downwardly to
maintain the are at uniform length. The pencil may be adjusted from time to time
by an attendant. Preferably the carbon pencil will be counterpoised by arranging
a counterweight so that it just counterbalances the weight of the carbon pencil and
its accessories, so that the latter will stand at any height at which the attendant
may set it.
The operation may now be understood. I will describe the operation in furnaces
used for the reduction of aluminium from its ore, and the production of aluminium
bronze, that being the principal use to which my invention has thus far been
applied.
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 suitable quantity of alumina in the form of a nearly
pure corundum. I have found the best proportions to be two parts by weight of
copper to one part by weight of corundum. The cover is then placed over the
crucible and luted down, and the carbon pencil thrust through it and pressed down
through the layer of corundum until its tip touches the copper. The circuit
connections being completed the current is turned on. The carbon pencil is then
lifted slightly to strike the arc, and as the copper fuses it is lifted still higher until
the maximum are is formed. This arc is then to be maintained stationary. At the
same time the gas is turned on.
The heat of the are first fuses the copper and sets it into ebullition, partially
vaporizing it. As the heat becomes more intense the alumina is also fused and is
decomposed, its oxygen being set free and immediately combining with the hydro-
carbon gas and forming carbonic acid, carbonic oxide and steam, which escape
through the vent. The aluminium which is freed from its combination with oxygen
at once combines with the copper, forming an aluminium bronze. Throughout the
operation the copper is vaporized by the intense heat and the copper vapours
circulate within the crucible, becoming condensed against the comparatively cool
sides thereof, and streaming down as liquid copper through the mass of corundum,

page_text: whereby a circulation is created through the latter, and as rapidly as the corundum
is fused and its oxygen driven off, the copper combines with the aluminium. When
the corundum 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 by stopping the current and shutting off the stream of gas, and
the molten metal is poured or tapped out of the crucible.
In my experiments I have used both the crucible as an anode and the carbon
pencil as a cathode by passing the current upwardly, and the crucible as a cathode
and the carbon pencil as an anode by passing the current downwardly through the
furnace. I have found the reducing effect to be the same in either case, but I prefer
in practice to pass the current upwardly, making the carbon pencil the cathode or
negative electrode.
The gas by being injected through the carbon pencil is introduced directly into
the are, and is caused to flow around and cover the exposed and incandescent tip of
the pencil. The injected gas thus interposes itself between the liberated oxygen
and the portion of the carbon pencil which is most exposed to oxidation, while at
the same time the gas is heated to incandescence, and is thus in condition to afford
the utmost possible affinity for the oxygen, so that the oxygen is caused to unite
with it in preference to passing through the stream of hydrocarbon gas and attacking
the incandescent carbon. Thus the wasting away of the carbon pencil by oxidation
is almost or quite entirely prevented.
By the partial melting down of the fire-clay used for the cover I have produced
a bronze of aluminium and copper with silicon.
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. I have
also smelted iron ore or fragments of iron with a very small quantity of aluminium
ore used as a flux, and have made a fine quality of steel by passing the current
through the furnace for a period of five minutes.
In practising my invention on a large scale it is desirable to provide electrodes
which present a large surface in order that the zone of fusion may be as extended
as possible, thereby rendering the process rapid and subjecting the entire mass
under treatment to as nearly as possible simultaneous action. This increase of
surface in the lower electrode or crucible results as a matter of course from the
employment of larger crucibles. To secure this increased surface in the case of the
upper electrode or carbon pencil I build it up of separate sections or plates suitably
united together. I employ by preference four plates united so as to leave an enclosed
space or duct between them, each plate being set with its edge against the face of
the next plate. Preferably the plates are rabetted or shouldered to prevent their
collapsing. At the upper part of the pencil they are held together through the
medium of metal clamps. The lower portion of the pencil, which is destined
eventually to enter the crucible where it is exposed to heat that would melt any
known metal, is necessarily secured together by other means.
For this purpose
I prefer to use dowel-pins of carbon driven tightly into holes in the respective
plates.
Instead of introducing the gas through a tubular electrode it may be introduced
through a separate tube of refractory material, provided this tube is so arranged
within the furnace as to discharge the gas into, or closely adjacent to, the arc, that
is to say, into the crater formed by the are.
I contemplate by a further development of my invention the utilization of
the electric furnace simultaneously for the reduction of metals, etc., from their
ores, or for the melting or other metallurgical treatment of metals, and for the
production of various chemical substances requiring a high degree of heat.
Dated the 12th day of June 1890.
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Reduction of Metals and in Apparatus
therefor.
I, THOMAS LEOPOLD WILLSON, of 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 smelting or reduction by the agency of heat derived
from the passage of an electric current, for producing aluminium or its alloys, or
other metals or alloys of more or less refractory character, such as boron, silicon,
calcium, chromium, titanium, etc., as well as iron or steel. In such electric smelting
of refractory ores, usually oxides, the ore is fused and decomposed by the heat
generated, and the oxygen thus liberated attacks the vessel or crucible enclosing
the material acted upon and the electrodes through which the electric current is
introduced, which are usually of carbon, and which are thus rapidly wasted away.
The material of the electrodes and crucible thus is made to serve as a reducing or
deoxidizing agent, and as such electrodes or crucibles are of somewhat expensive
material, and are more costly than other equally effective deoxidizing substances,
their consumption is attended with loss, and the process of electric smelting or
reduction is rendered expensive and uneconomical.
It is the object of my present invention to economize expense in electric smelting
by the avoidance of the loss referred to. To this end my invention contemplates
the introduction of a deoxidizing or otherwise reducing agent in gascous form, and
in such manner that it shall be interposed between the liberated oxygen or other
agent requiring elimination and the surfaces of the crucibles and electrodes, which
would otherwise be exposed to the destructive action of the oxygen, so that the
oxygen is caused to unite with the gaseous agent thus introduced before it can gain
access to the surfaces of the electrodes and crucible, so that the latter are protected
from oxidation, and their wasting away is almost entirely prevented.
In the preferred practice of my invention I employ an electric furnace consisting
of a crucible holding the material to be reduced, an electrode or electric connection
with such crucible for the passage of the current to its contents, and a second
electrode in the form of a tubular carbon rod thrust into the crucible and connected
to the opposite terminal of the electric circuit, and a source of gas connected
through a suitable pipe or duct with the said tubular electrode. When the current
passes, the upper electrode is lifted sufficiently to form an electric are between it
and the surface of the metal or ore in the crucible, and the gas is injected through
the tubular electrode into the electric are, and hence into the hottest portion of the
molten or vaporized mass. In the case of reduction of a metal from an oxide the
gas is hydrogen gas or a hydrocarbon, preferably the latter, ordinary illuminating
gas being suitable. The oxygen liberated by the decomposition of the ore unites
with the carbon and hydrogen of the gas, producing water, carbonic acid and
carbonic oxide, which escape from the furnace through a suitable vent..
My invention is applicable to the reduction of other ores than oxides, it being
only necessary in such case to inject a gas of different character, that is to say, one
having an affinity for the substance that is liberated by the decomposition of the
ore in order that this substance may enter into a new combination with the gas and
be carried away from the furnace, or reduced to such form as to be readily
separable from the reduced metal.
My invention comprehends also the construction of the furnace or apparatus for
carrying my improved method into effect. This furnace is constructed with a
suitable hearth or bench of brickwork having an opening or recess within which to
set the crucible. A carbon plate forms the bottom or floor of this opening, and to

page_text: this plate is connected one terminal of the electric circuit.
The crucible is covered
by placing over the top a cover consisting of a plate of refractory material having
an opening through its centre through which to pass the carbon rod or pencil, the
opening being preferably of such size as to hold the pencil with sufficient friction
to retain it at any height at which it may be placed. The cover has also a vent
opening, which is preferably distinct from this hole. A luting of fire-clay should
be interposed between the crucible and cover.
The tubular carbon rod or pencil is preferably fastened at its upper end to an iron
or other suitable pipe which extends upward in line with the carbon rod, being
suitably guided, and to the upper end of this pipe is connected a flexible tube
leading to a fixed pipe through which the gas is conducted, a valve being provided
to regulate the flow.
This apparatus is shown in the accompanying drawings, wherein,
Fig. is a sectional elevation showing in general the preferred apparatus for the
practice of my invention.
Fig. 2 is a sectional elevation on a larger scale, showing the furnace and electrodes
more in detail.
Fig. 3 is an enlarged fragmentary view of one form of the upper or tubular
electrode and its connections.
Fig. 4 is a transverse section thereof.
Fig. 5 is a similar view to Fig. 3, showing another and preferable construction of
the electrodes.
Fig. 6 is a transverse section of Fig. 5.
Fig. 7 is a transverse section, showing a different construction.
Fig. 8 is a plan view, showing the means for making electrical connection with
the upper electrode, the latter being shown in transverse section.
Fig. 9 is a vertical longitudinal section of a modified form of furnace.
I will first describe the construction shown in Figs. 1 to 8 of the drawings.
Let A designate a suitable hearth or bench of brickwork constructed with an
opening or recess a of suitable size and shape, within which is set a crucible B.
A carbon plate C is built into the bench A and forms the bottom or floor of the
opening u, so that the crucible rests on this plate. The brick-work immediately
surrounding the opening a should be constructed of fire-brick or other highly
refractory material.
D designates the dynamo, which of course may be of any suitable type adapted
to generate a current of the requisite volume under suitable electro-motive force,
and the positive and negative terminals of which are connected respectively with the
carbon plate C and with a carbon pencil or electrode E. The connection with the
carbon plate is made preferably through the medium of a bar of metal fastened
by bolts to one edge of the carbon plate, and its end projecting beyond the brick-
work is provided with a socket and set-screw constituting it a binding-post into which
the positive terminal of the wire is fastened. The connection of the carbon
pencil E may be made by a clamp c fastened on it at its upper portion, and formed
with a binding-post into which the end of the other wire is fastened.
The crucible B having been placed into the opening a it is covered by placing
over it a cover F, which may rest either on top of the crucible or on top of the
brick-work A. A luting of fire-clay, d, should be placed under this cover in order
to prevent access of air to the crucible. A suitable hole g is formed vertically
through the middle of the cover F, and also a vent-opening which is preferably
distinct from the hole g. The hole y is made of such size as to admit the passage
of the carbon pencil E through it with just sufficient friction to hold the carbon
pencil at any height at which it may be placed.
The carbon pencil or electrode E is made tubular, as clearly shown in Figs. 3
and 4, the duct through it constituting a gas-passage. The upper end of the
carbon-rod has united to it preferably an iron or other suitable metallic pipe G,
which extends upward in line with the carbon-rod, being preferably guided by
passing through a hole e in a guiding or supporting-arm H, as shown in Fig. 2.

page_text: The joint between the pipe G and carbon-rod E may be made, as shown in Fig. 3,
by fitting a short piece of tube k over the upper end of the carbon and filling in
plaster of paris or other cement, i, into this tube and around the pipe G, the latter
being preferably flanged at its lower end. Thus a sufficiently strong joint is
made, which is not liable to be affected by any heat which can reach it in
practice. The upper end of the pipe G is connected by a flexible tube 1 with
a fixed pipe through which the gas is conducted, a valve being provided to
regulate the flow.
The gas, which will ordinarily be the usual hydro-carbon illuminating or heating
gas served in the city mains, or which may be natural gas, will be drawn usually
from a main designated at K, in Fig. 1, passing through a pipe J controlled by a
valve. Ordinarily, however, in the use of common illuminating gas the pressure
will be insufficient for the purpose, and I therefore provide a pump P driven by
suitable power, which draws the gas from the pipe and forces it through a
pipe J, whence it enters the pipe J and flows to the furnace. The action of such
pumps, however, being somewhat irregular, and it being desirable to introduce the
gas at a uniform pressure and free from any puffing or pulsating, I provide a gas-
holder or reservoir L between the pump P and furnace, into which the gas is
delivered from the pump, and from which it flows out through the pipe J to the
furnace. This gas-holder is of usual construction, consisting of an inverted box or
tank with its lower edge submerged in water or other liquid, and with its weight so
nearly counterbalanced that the gas under suitable pressure will raise it, and it will
rise and fall as the volume of gas varies and thereby largely compensate for any
variations of pressure occasioned by the irregular operation of the pump. The
pressure at the furnace may be still further reduced or regulated by the valve j.
The operation may now be understood. I will describe the operation in furnaces
used for the reduction of aluminium from its ore, and the production of aluminium
bronze, that being the principal use to which my invention has thus far been
applied.
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 the top of this a layer of suitable quantity of alumina in the form of a
nearly pure corundum. I have found the best proportions to be two parts by
weight of copper to one part by weight of corundum. 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 corundum until its tip touches the copper. The
circuit connections being completed an electric current is passed through the
electrodes Band E, which in a crucible containing about four or five pounds of
materials have used at 200 amperes under an electro-motive force of 50 volts.
The carbon pencil E is then lifted slightly to strike the are and as the copper fuses
it is lifted still higher until the maximum are is formed. This arc is then to be
maintained stationary. At the same time the gas is turned on by opening the
valve, the gas-holder having been previously supplied with a charge of gas,
and during the operation the pump P is kept running at sufficient speed to supply
the desired quantity of gas at the proper pressure. This pressure should be
sufficient to overcome any pressure existing in the furnace and to cause a slight
blowing out of the gaseous products of combustion through the blow-hole or vent h.
If inflammable gases are blown out through this vent it may be known that the
pressure is in excess and it should be reduced by slowing down the pump or partly
closing the valvej or the valve j'.
The heat of the arc first fuses the copper and sets it into ebullition, partially
vaporizing it. As the heat becomes more intense the alumina is also fused and is
decomposed, its oxygen being set free and immediately combining with the hydro-
carbon gas and forming carbonic acid, carbonic oxide and steam, which escape
through the vent. The aluminium which is freed from its combustion with oxygen,
at once combines with the copper, forming an aluminium bronze. Throughout the
operation the copper is vaporized by the intense heat and the copper vapours

page_text: circulate within the crucible, becoming condensed against the comparatively cool
sides thereof, and streaming down as liquid copper through the mass of corundum,
whereby a circulation is created through the latter, and as rapidly as the corundum
is fused and its oxygen driven off, the copper combines with the aluminium. The
operation consumes from fifteen minutes to two hours, depending upon the character
of the corundum, the proportions of the ingredients and the strength of the current.
When the corundum 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 by stopping the current and shutting off the stream
of gas, and the molten metal is poured or tapped out of the crucible. With the
construction of furnace shown in Figs. 1 and 2, the furnace is discharged by first.
lifting out the carbon pencil, then pushing off the cover, and then lifting out the
crucible and pouring the molten bronze from it, preferably into a mould to form an
ingot. The aluminium alloys I have made in this manner have varied between
three per cent. and eighteen per cent. of aluminium.
In my experiments I have used both the crucible as an anode and the carbon
pencil as a cathode by passing the current upwardly, and the crucible as a cathode
and the carbon pencil as an anode by passing the current downwardly through the
furnace. I have found the reducing effect to be the same in either case, there
being ordinarily no perceptible difference in the rapidity of operation, and little or
no difference in the product. There is, 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. I therefore prefer in practice to pass the
current upwardly, making the carbon pencil the cathode or negative electrode.
In either case an extended are is formed between the upper electrode or pencil
and the surface of the molten metal, and the latter assumes the form of a deep
hollow or crater partly surrounding the end of the carbon pencil. It is within this
crater that the most violent action and the most intense heat exist, and hence it is.
within this crater that the greater portion of the oxygen is liberated from the ore.
This circunstance is availed of in my invention in order to effect a union between
the liberated oxygen and the injected reducing or deoxidizing gas before the
oxygen can gain access to the exposed surfaces of the electrodes, that is, the
carbon pencil and the crucible. This union is effected according to the best means
of applying my present invention by the use of the tubular carbon pencil G as a
duct through which to inject the gas, as described, whereby the gas is introduced
into the crater above referred to, and hence into the arc itself, in such manner that
it flows around the exposed and incandescent tip of the carbon pencil. The injected
gas thus interposes itself between the liberated oxygen and the portion of the
carbon pencil which is most exposed to oxidation, while at the same time the gas is
heated to incandescence and is thus in such condition as to afford the utmost
possible affinity for the oxygen, so that the oxygen is caused to unite with it in
preference to passing through the stream of hydro-carbon gas and attacking the
incandescent carbon. Thus the wasting away of the carbon pencil by oxidation is
almost or quite entirely prevented.
The copper fumes or vapours circulate from the crater upwardly within the
crucible and are condensed against the comparatively cool sides thereof, and by
streaming down the latter, protect it from oxidation. There is also, but to a less
degree, a condensation of liquid copper against the upper portion of the carbon
pencil, whereby it also is shielded from the action of any uncombined oxygen that
may be circulating within the crucible. In practice, however, when the reducing
gas is introduced into the crater, as described, there is, as I believe, little or no
uncombined oxygen that can escape beyond the crater, and hence little or no
liability of a wasting away of the crucible or the upper portion of the carbon pencil
by oxidation,
When the current is passed upwardly the surface of the crucible from which the
current passes, being entirely covered by the bath of molten metal, is protected

page_text: thereby from the action of the electric are in tearing off particles from the positive
electrode and projecting them against the negative electrode, this action being
confined to the surface of the molten bath which hence becomes essentially the
positive electrode, and this projecting action thus assists the ebullition and
vaporization of the copper and promotes its circulation. By passing the current
in this direction, in connection with the introduction of gas around the tip of the
carbon pencil I, the wasting away of the latter is almost entirely provided against,
being reduced to the slow disintegration occasioned by the intense heat. Hence
there is little or no necessity for feeding the pencil E downwardly as the operation
proceeds in order to maintain the are of uniform length, the very gradual increase
in the length of the are being easily corrected from time to time by the attendant,
who will very slightly lower the pencil whenever he observes that the are is
becoming too long. For this purpose an am-meter or volt-meter may be advan-
tageously introduced in the circuit by which from time to time the resistance of the
are may be ascertained. Thus it is one advantage of my invention, in addition to
the economy which it effects, that all complication of automatic feeding or
regulating mechanism for moving the carbon pencil is eliminated.
If desired, the carbon pencil may be counterpoised in the manner shown in
Fig. 2, that is, by hanging a weight W from one end of a chain which passes over
pulleys EE, and the other end of which is connected to the carbon pencil. By
altering the weight W, so that it just counterbalances the weight of the carbon
pencil and its accessories, the latter may be made to stand at any height at which
the attendant may set it. Even this refinement, however, is not necessary, since
the hole may be made so close a fit for the carbon pencil that the latter will be
held frictionally in any position in which it may be placed.
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 corundum with copper in the proportions stated, and with a
current of the character named.
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 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. I
have also smelted iron ore or fragments of iron with a very small quantity of
aluminium ore used as a flux, and have made a fine quality of steel by passing the
current through the furnace for a period of five minutes.
In practising my invention on a large scale it is desirable to provide electrodes
which present a large surface in order that the zone of fusion may be as
extended as possible, thereby rendering the process rapid and subjecting the
entire mass under treatment to as nearly as possible simultaneous action. This
increase of surface in the lower electrode or crucible results as a matter of course
from the employment of larger crucibles. To secure this increased surface in
the case of the upper electrode or carbon pencil my invention provides the con-
struction shown in Figs. 5 to 7. In the present state of the art it is impracticable
or unduly expensive to construct tubular carbon pencils, such as shown in Figs. 3
and 4, of sufficiently large diameter for the purpose. I therefore build up the
carbon pencil of separate sections or plates suitably united together. I employ
by preference four plates united in the manner best shown in Fig. 6, so as to
leave an enclosed space or duct between them, each plate being set with its
edge against the face of the next plate. Preferably the plates are rabbetted or
shouldered, as shown in Fig. 6, to prevent their collapsing. At the upper part
of the pencil they are held together through the medium of metal clamps, one of
which is shown at min Figs. 5 and 6. The lower portion of the pencil, which is
destined eventually to enter the crucible, where it is exposed to heat that would
melt any known metal, is necessarily secured together by other means. For this
purpose prefer to use dowel-pins n n of carbon driven tightly into holes in the
respective plates, as clearly shown in Fig. 6. The joints between the plates may

page_text: be made tight by luting them during the operation of fitting the plates together
with a paste of carbon-dust and molasses, or other carbonaceous cement. Fig. 7
shows a modified construction of the pencil, wherein instead of four like plates
being employed, two opposite wide plates and two intervening narrow plates are
fastened together by pins nn passing through from side to side.
Since currents of great volume will be used with these large electrodes it is
necessary to provide electrical connections which shall afford at once very great
conductivity with perfect flexibility in order to conduct the current to the
electrode without danger of melting the connections, and to admit of the free
up
and down movement of the carbon pencil. To this end the wire or conductor w',
Fig. 1, is made adjacent to the carbon pencil in the form of a cable consisting of
a great many fine wires of sufficient number to provide ample conductivity, and
this cable is opened or spread out near the carbon pencil in the manner shown in
the plan view, Fig. 6, its separate wires or groups or strands of wire w³ being
passed through holes in a horizontal bar L, which is fixed in place at a suitable
distance from the electrode, and fastened in said holes by screws, and extending
thence in the form of freely suspended or pendant loops w³ to another bar M into
holes in which their ends are thrust and fastened by set-screws constituting binding
connections. This bar M is fastened to the carbon pencil E by means of a
clamping-jaw c and clamping screws in such manner as to secure an extended
surface of contact with the carbon pencil. The numerous parallel wires or
strands are hung between the bars L and M with sufficient slack to permit of
any desired movement of the pencil E in up and down direction, both to permit the
new pencil of greatest length to be lifted entirely out of the furnace, and to permit
the pencil as it becomes shorter in the course of time to be fed downwardly
into the furnace and until it is consumed to the shortest length that may
be used.
My invention is susceptible of considerable modification without departing from
its essential features. The constructions and operation hereinbefore described
are those which I consider preferable, but they are not in all respects essential.
arc,
Instead of introducing the gas through a tubular electrode it may be introduced
through a separate tube of refractory material provided this tube is so arranged
within the furnace as to discharge the gas into, or closely adjacent to, the that
is to say, into the crater formed by the arc. One such construction is shown in
Fig. 9, where Q is a tube of refractory carbon passing through the cover F,
receiving gas from a pipe G, and terminating at its lower end in the crater.
My invention is by no means confined to the introduction of gas in the nature
of hydrogen or hydrocarbon, since any other deoxidizing gas may be substituted
in cases where the metal or other substance to be reduced contains oxygen to be
eliminated. In case the metal or ore contains other materials than oxygen the
reducing gas should be of such character as to present a chemical affinity with
such other materials. In such cases the particular constitution of the gas will be
determined in accordance with the known components of the ore or other material
which are to be eliminated. For example, in making aluminium bronze, an alumina
and an ore of copper in combination with sulphur (as redruthite or other cuprous
sulphide) may be put in the crucible, and the eliminated oxygen and sulphur, both
of which are corrosive of the carbon electrode, may be combined with an introduced
gas, such as a hydrocarbon gas, which has an affinity for both, thereby protecting
the electrode. The gas may also be of such a character as to present some
constituent having an affinity for the reduced metal or other material which is
derived from the ore in order to produce special alloys. This characteristic will
be especially useful in the treatment of iron or steel.
I contemplate, also, by a further development of my invention, the utilization of
the electric furnace simultaneously for the reduction of metals, etc., from their ores,
or- for the melting or other metallurgical treatment of metal, and for the pro-
duction of various chemical substances requiring a high degree of heat.
B

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The advantages of my invention may be in part availed of by introducing into the
crucible a reducing agent in other form than that of a gas, provided only that it be
of such character and be so introduced that it will serve to protect the electrode
from being decomposed and consumed. Thus a spray of liquid hydro-carbon might
be employed, being introduced in such manner as to envelop the tip of the carbon
cathode and protect it from the action of the oxygen evolved from the alumina.
Or, carbon or other suitable reducing agent night be introduced in the form of an
impalpable powder, preferably through the hollow carbon pencil, (or through an
auxiliary pencil as shown in Fig. 9) so as to enter the crater formed by the arc and
thereby interpose itself between the place of liberation of oxygen and the exposed
incandescent tip of the carbon cathode, so that the oxygen must pass through or
into contact with this carbon dust or powder before it can reach the carbon pencil,
and hence will combine with the undivided particles of powder in preference to the
solid carbon pencil, so that by the time it reaches the latter it will be reduced to
the condition of carbon dioxide, and be powerless to corrode the pencil. This
method of protecting the pencil is, however, much less perfect and less convenient
than by the use of a gaseous reagent, as is preferred.
Having thus particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that which I
claim is
1. The herein described process of reducing metals or orcs, which consists in
heating them to fusion by means of an electric are between the metal or ore and
an electrode and introducing a reducing agent between the point of liberation of
oxygen or other corrosive agent and the exposed incandescent surface of the
electrode to protect the latter from corrosion, in substantially the manner
set forth.
2. The herein described process of reducing metals or ores, which consists in
heating them to fusion by means of an electric are between the metal or ore and
an electrode above it, and introducing a reducing gas downwardly into the arc
and between the point of liberation of oxygen or other corrosive agent and the
exposed incandescent surface of the electrode, to protect the latter from corrosion,
in substantially the manner set forth.
3. The herein described process of reducing metals or ores, which consists in
heating them to fusion by means of an electric are between the metal or ore and
an electrode above it, and introducing a reducing gas downwardly into the arc
through the said electrode, whereby the gas is delivered uniformly around the
incandescent tip thereof and ascends in a protecting stream around all sides of the
electrode, in substantially the manner and to the effect specified.
4. The herein-described process of reducing metals or ores, which consists in
subjecting them to the heat of an electric are passing between a positive electrode
beneath the metal or ore and a negative electrode above it and introducing a
reducing-gas into the arc through said negative electrode, whereby the gas is
caused to pass across the current of gases projected toward the negative electrode
from the positive bath beneath and thereby protects the electrode from corrosion,
substantially as specified.
5. The herein-described process of reducing aluminium or other metals from
refractory ores and making alloys of such metals, consisting in heating the ore to
fusion by means of an electric arc in the presence of a molten bath of base metal
to be alloyed with the reduced metal, the electric current passing from said bath
as the anode, to a carbon cathode above said bath, and in the presence of a reducing
agent to combine with the liberated oxygen or other agent evolved from the decom-
posed ore, in substantially the manner and to the effect set forth.
6. The improved electric furnace for reduction of refractory ores, consisting of
a crucible in connection with a circuit conductor for conducting an electric current
to its contents, a tubular electrode projecting downwardly into said crucible, and a

page_text: source of reducing gas connected to the electrode and discharging gas through the
latter into the crucible to envelop and protect the incandescent tip of the electrode,
substantially in the manner set forth.
7. In an electric furnace of the character herein described, a tubular electrode
through which to admit a stream of reducing gas into the furnace, consisting of
plates of carbon relatively arranged to form an enclosed central space within
them, and fastened together by pegs or rods of carbon, substantially in the manner
and for the purposes set forth.
Dated this 16th day of March 1891.
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.