IMPROVE- MENTS IN PROCESSES FOR THE PRODUCTION OF IRON AND STEEL AND IN THE CONSTRUCTION OF FURNACES FOR THAT PURPOSE
Year: 1876

page_text: LETTERS PATENT to Charles William Siemens, of No. 12, Queen Anne's Gate,
Westminster, in the County of Middlesex, for the Invention of "IMPROVE-
MENTS IN PROCESSES FOR THE PRODUCTION OF IRON AND STEEL AND IN THE
CONSTRUCTION OF FURNACES FOR THAT PURPOSE."
Sealed the 17th November 1876, and dated the 22nd September 1876.
PROVISIONAL SPECIFICATION left by the said Charles William Siemens at
the Office of the Commissioners of Patents on the 22nd September 1876.
CHARLES WILLIAM SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in the
County of Middlesex. "IMPROVEMENTS IN PROCESSES FOR THE PRODUCTION of
IRON AND STEEL AND IN THE CONSTRUCTION OF FURNACES FOR THAT PURPOSE."
In reducing iron ores in rotative furnaces of the nature described in my former
Patents, such as Nos. 3077 of 1871, 3642 of 1872, 4075 of 1873, and 43 of 1875, it
is important that the flame should circulate freely within the chamber in order to
produce a uniform degree of heat throughout the same, and to effect the complete
combustion of the gases, which mostly consist of carbonic oxide, part of which is
supplied from without the rest, being generated by the mass of ore and reducing
agents under treatinent.
It is also important that the regenerators employed in these furnaces should be so
constructed that they are not easily choked with dust arising from the ore, and that
they may be easily cleared of any dust which may accumulate from time to time
without letting down the heat of the furnace.
The first of these objects I realise according to my present Invention by increasing
the diameter of the rotative chamber relatively to its length so as to make these
dimensions nearly equal, and also by increasing the thickness of the midfeather or
the division wall between the incoming and outgoing currents to not less than
14 inches, whereby a quick return of the incoming gaseous current is prevented, or.
at least greatly diminished. This quick return of the incoming current causes
amongst other prejudicial effects an excessive degree of heat at the neck of the
furnace, and rapid wear by fusion of the lining of the back and throat of the
furnace. To obviate this latter defect I construct the back end of the rotative
chamber of stout wrought iron or steel plates, with a neck-like extension of a ring
Price Qd77

page_text: of channel iron with flanges standing outward, one of the flanges being rivetted
securely against the back end of the rotative chamber, on the stationary neck-like
extension of the regenerators a similar piece of channel iron is rivetted; these two
rings of channel iron form the neck of the furnace on which sprays of water from a
perforated pipe are directed against the back end and neck of the rotating chamber
and against the neck-like extension of the regenerators, and this serves to maintain
the brick and oxide lining of those parts.
Instead of constructing the regenerators of brick chequer work in the usual
manner I form multitudinous horizontal or nearly horizontal channels of brickwork
terminating in brick chambers furnished with doors for cleaning out accumulations
of dust; from these the products of combustion pass through another set of multi-
tudinous brick passages and so downwards in a zig-zag fashion until the chimney is
reached. The currents are directed alternately upward through one set of zig-zag
passages and downwards through the adjoining set by means of reversing valves, as
described in my previous Patents relating to regenerative furnaces.
Instead of constructing the whole of each regenerator in zig-zag multitudinous
passages I sometimes construct only the upper portion in this manner, that is,
where the dust from the rotative chamber will be mostly deposited, and the
remainder I build of ordinary chequer-work.
In order to simplify the apparatus I sometimes suppress the gas regenerators and
introduce the gas into the rotative chamber in a continuous stream through a
channel formed of refractory materials between the two sets of multitudinous
channels forming the pair of air regenerators, which in this case are mado of
increased area and heating surface.
The gas producer or producers may be constructed in close proximity to the
furnace in order to prevent loss of heat, and slide valves formed of fire-brick may be
used for regulating the supply.
The furnace is worked in the following manner for the production of wrought
iron The oxide lining having been formed in the manner described in my Patent
of 1873, No. 4075, a charge of ore or mixture of ores together with fluxing materials
and coal or other reducing agents is introduced, to which I prefer to add a certain
per-centage of granulated or broken pig metal. When after about two hours of
heating and rotation the reduction of the metal is completed, the earthly con-
stituents of the ore and fluxing materials begin to melt and a slag comparatively
poor in iron is formed; this is discharged through a tapping hole in front of the
furnace. Both the heat and speed of rotation are then increased with the view of
welding the iron until a ball or balls are produced, which may be removed and
shingled in the usual manner. Or if the balls are not hot enough for shingling I
pass them through a reheating furnace with a cinder bottom which has the
advantage of depriving the iron more thoroughly of earthy slag and improving its
physical qualities.
The effect of adding pig metal is to set up an active obullition amongst the mass
of reduced iron whilst forming into balls, whereby the expulsion of foreign matter
is promoted, and the farther advantage is obtained of adding to the iron so made
some combined carbon, of which iron produced directly from the ore stands in need.
The cinder remaining in the furnace, after the ball or balls have been removed, is
comparatively rich in iron; this is mixed with some roll scale or other rich oxide,
and allowed to consolidate in the furnace, either while rotating slowly under the
influence of an external spray of water or while standing, if it is intended to produce
a flat sido for preventing the sliding of the succeeding charge. Such sliding action
is further prevented by introducing into the stationary bath of cinder, while still
liquid, lumps of iron ore or other refractory material.
If it is intended to produce spongy iron only, I prefer to provide the rotative
furnace with a fire-brick lining of considerable thickness to prevent loss of heat by
radiation.
If fluid metal is to be produced from ore a carbon lining is the most-suitable,
which may be made with retort carbon, coke, or anthracite, ground up and mixed

page_text: with either clay or pitch to bind it together, and then rammed into its place and
heated.
Another part of my Invention has reference to the processes and furnaces employed
in converting such materials as are produced in the rotative furnace, pig metal
and raw ore with or without the use of scrap, into cast steel. The melting furnace
I employ for this object differs from that described by me in previous Specifications
(notably in those of 1867, 1870, 1871, and 1875) by an arrangement of gas and air
ports, in which each air port rises from its regenerator behind the corresponding
gas port, and is made to project into the furnace over such gas port, it being
important that the air port should overlap the gas port on both sides, great solidity
of brick work and perfect combustion is thereby attained.
Another point of difference in the improved melting furnace consists in providing
below the centre of the furnace an open cave, through which air freely circulates,
and rises through openings into the air space below the melting chamber and
behind the bridges, whereby the perfect cooling of the sides of the melting chamber
is effected. This cave serves moreover as a receptacle for any metal which may
break through the sides or bottom of the melting chamber, whence it can bo
removed at leisure without meanwhile encumbering the ventilating spaces around
the melting chamber.
Another modified arrangement in connection with the improved melting furnace
consists in providing one or more doors or openings at such an elevation that the
scoria floating on the metallic bath may be run off continuously or from time to
time during the process of decarburization without discharging the metal itself, and
for this purpose these doors or openings should be made low enough to suit the
lowest possible surface level of the metallic bath, and rendered capable of being
banked up readily by means of sand or other refractory material to the height required.
By thus removing the slag from the metal, either continuously or at certain intervals
during the decarburization of the pig metal forming the metallic bath, two consider-
able advantages are obtained, viz., the process of decarburization is accelerated in
consequence of the more direct access of the flame to the surface of the metal, and
the quality of the metal is improved, because the slag, which, at comparatively low
temperatures, takes up a considerable proportion of the sulphur and phosphorus
originally contained in the materials employed, yields back these impurities to the
metal as the higher temperatures of mild steel are approached, so that it is
very important to get rid of it as soon as possible. By these means a comparatively
pure metal may be obtained from impure materials, and the time necessary for
completing a charge is materially lessened.
When the metal is sufficiently decarburised, as may be ascertained by chemical
tests and by the appearance of a chilled and fractured sample, the charge is tapped
into a moveable ladle lined with fire-clay, and heated internally by means of a gas
flame or otherwise to low redness, but half an hour or so previous to tapping rich
spiegeleisen or ferro-manganese is broken up into small pieces and distributed over
the bottom of the ladle where it becomes heated, and so is afterwards readily melted
by the stream of liquid metal from the furnace. The quantity of ferro-manganeso
required depends upon the per-centage desired in the metal, and one of the principal
advantages realised by this mode of working consists in not allowing the manganese
any opportunity of oxidising, and thus a definite proportion of manganese is ensured
in the metal produced. At the same time a saving of ferro-manganese is effected
and the process of manufacture is simplified.
If it is intended to convert old iron, or steel rails, or other scrap metal into cast
steel I prefer to charge into a furnace, as above described, about three tons of scrap
intermixed with two tons of comparatively pure pig metal and to continue firing
until the whole charge has become a fluid mass. A sample of this is taken and
examined, and more scrap metal, or metallic oxide, or ore is added until the samples
shew the requisite per-centage of carbon, when the whole is discharged into a heated
ladle containing pieces of ferro-manganese, as before described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles William Siemens in the Great Seal Patent Office on the
22nd March 1877.
CHARLES WILLIAM SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in the
County of Middlesex. "IMPROVEMENTS IN PROCESSES FOR THE PRODUCTION OF
IRON AND STEEL AND IN THE CONSTRUCTION OF FURNACES FOR THAT PURPOSE."
In reducing iron ores in rotative furnaces of the nature described in my former
Patents, such as Nos. 3077, of 1871; 3642, of 1872; 4075, of 1873; and 43, of
1875, it is important that the flame should circulate freely within the chamber in
order to produce a uniform degree of heat throughout the same, and to effect the
complete combustion of the gases, which mostly consist of carbonic oxide, part of
which is supplied from without, the rest being generated by the mass of ore and
reducing agents under treatment.
It is also important that the regenerators employed in these furnaces should be
so constructed that they are not easily choked with dust arising from the ore, and
that they may be easily cleared of any dust which may accumulate from time to
tine without letting down the heat of the furnace.
The first of these objects I realise according to my Invention by increasing the
diameter of the rotative chamber relatively to its length so as to make these
dimensions nearly equal, and also by increasing the thickness of the midfeather or
the division wall between the incoming and outgoing gaseous currents to not less
than fourteen inches, whereby a quick return of the incoming gaseous current is
prevented or at least greatly diminished. This quick return of the incoming current
causes amongst other prejudicial effects an excessive degree of heat at the neck of
the furnace, and rapid wear by fusion of the lining of the back and throat of the
furnace. To obviate this latter defect I construct the back end of the rotative
chamber of stout wrought-iron or steel plates, with a neck-like extension of a ring
of channel iron with flanges standing outward, one of the flanges being rivetted
securely against the back end of the rotative chamber. On the stationary neck-
ike extension of the regenerators a similar piece of channel iron is rivetted; these
two rings of channel iron form the neck of the furnace, on which sprays of water
from a perforated pipe are directed against the back end and neck of the rotating
chamber, and against the neck-like extension of the regenerators, and this serves to
maintain the brick and oxide lining of those parts, or in place of this arrangement
one somewhat modified in detail, herein-after described, may be employed, whereby
the same effect is produced.
Instead of constructing the regenerators of brick chequer work in the usual
manner I form multitudinous horizontal or nearly horizontal channels of brickwork,
terminating in brick chambers, with doors for cleaning out accumulations of dust.
From these the products of combustion pass through another set of multitudinous
brick passages, and so downwards in a zig-zag fashion until the chimney is reached.
The currents are directed alternately upward through one set of zig-zag passages,
and downwards through the adjoining set by means of reversing valves, as described
in my previous Patents relating to regenerative furnaces.
Instead of constructing the whole of each regenerator of zig-zag multitudinous
passages I sometimes construct only the upper portion in this manner, that is,
where the dust from the rotative chamber will be mostly deposited, and the
remainder I build of ordinary chequerwork, or I employ modified chequerwork
arrangement, as shewn in Figs. 7 to 9 of the Drawing, whereby the advantage of
the zig-zag arrangement is combined with an unimpeded passage for the dust to fall
through.
In order to simplify the apparatus I sometimes suppress the gas regenerators, and
introduce the gas into the rotative chamber in a continuous stream through a
channel formed of refractory materials between the two sets of multitudinous

page_text: channels forming the pair of air regenerators, which in this case are made of increased
area and heating surface.
The gas producer or producers may be constructed in close proximity to the
furnace, in order to prevent loss of heat, and valves formed of fire-brick may be
used for regulating the supply.
Figs. 1 to 6 of the Drawings shew the arrangement of my before-described rotative
furnace and the regenerators and gas producers in combination therewith, which I
prefer to employ. Fig. 1 shews a longitudinal section on line A, B, C, D, E, Fig. 3;
Fig. 2 shews a part sectional plan on line F, G, H, I, Fig. 3; Fig. 3 shows a part
transverse section on line K, L, Fig. 1; Fig. 4 shews partly a section on line M, N,
Fig. 1, and partly an end elevation of the gas producer; Fig. 5 shows a section on
line O, P, Fig. 1; and Fig. 6 shews an enlarged view of one of the valves to the
water chamber f.
The rotative chamber a is made of large diameter in proportion to its length, so
that these dimensions are nearly equal, and the mid-feather b dividing the passages
c, c¹, for the incoming and outgoing currents is of considerable thickness, being
widened at the bottom for the passage through it of the gas flue d, through which
the combustible gas enters continuously into the furnace through the projecting
nozzle d', which has the effect of throwing the gas well forward into the furnace
and of preventing the gas escaping at the joint between the rotator and the
stationary part of the furnace. The heated air enters alternately through the one
or the other of the passages c, cl, leading to the regenerators e, e¹, while the products
of combustion escape through the other. Against the back surface of the furnace,
and round the throat a¹ thereof, is formed an annular wrought-iron trough or closed
chamber f, into which water is introduced through a pipe f¹. The circumferenco
of the chamber is for this purpose provided with a number of openings that are
closed by valves f kept up to their seats by springs, as shewn at Fig. 6.
The projecting stems f³ of these valves have small rollers, which as they arrive
at the top by the rotation of the chamber are brought under the fixed rail f',
which presses them down, and thus keeps the valves open so that a certain portion
of the water contained in the chamber can escape and flow down into the receptacle
f5, while fresh cold water enters from the pipe fl as the holes pass beneath it;
thus a sufficient circulation is maintained in the chamber f to keep it cool.
In place of the spring valves f2 might be employed weighted flap valves, which
as they arrive at top would fall open of themselves, being kept closed by the
pressure of the water at the other parts of the circumference or any other suitable
form of valve may be used. The regenerators e, e¹, for heating the air are
constructed with multitudinous horizontal channels e², e³, c, and are formed by
upright fire-brick walls or slabs, with spaces between them separated by horizontal
partitions e, each channel communicating with those above and below it at opposite
ends by vertical passages e³, e, so as to form continuous zig-zag passages for the
alternate upward current of the air and downward current of the products of
combustion. Openings g, g, closed by doors g¹, are formed in the brickwork casing
opening into the vertical chambers or passages e, through which doors access is
gained to the horizontal passages for the purpose of clearing them of deposit, other.
larger doors g closed by brickwork and sand in the manner usual with regenerative
gas furnaces are provided at the opposite side. The top passages being made of
greater height than the lower ones are stayed across by transverse bonding of fire-
brick e¹o. The air enters the zig-zag passages at bottom through the reversing
valve h and passage h¹. h is the flue through which the products of combustion
are led away from the reversing valve to the chimney.
The gas flue d leading direct from the rising flue of the gas producer i is
formed in the division wall b¹ separating the two regenerators, so that the gas in
passing through the fluo becomes somewhat heated before issuing through the
projecting nozzle d into the rotative furnace. The quantity of combustible gases
is regulated hither by means of a slide, or by preference by a valve, such as shown

page_text: at at the top of the flue ¹. The gas producer i, which is of the usual con-
struction, is supplied with fuel through the hopper ³, in which are two feed
regulators, which may consist of cylindrical receptacles, as shewn at 4, fitted in an
outer casing, and having a large opening at one point of their circumference, so
that rotary motion being imparted to the cylinders by gearing they are
alternately filled with fuel from the hopper and their contents discharged into the
producer, which is thus supplied at regular intervals with uniform quantities of
fuel.
The rotative furnace is worked in the following manner for the production of
wrought iron-The oxide lining having been formed in the manner described in
my Patent of 1873, No. 4075, a charge of ore or mixture of ores, together with
fluxing materials and coal, or other reducing agents, is introduced, to which I
sometimes add a certain per-centage of granulated or broken pig metal. When
after about two hours of heating and rotation the reduction of the metal is
completed the earthy constituents of the ore and fluxing materials begin to melt,
and a slag comparatively poor in iron is formed. This is discharged through a
tapping hole in front of the furnace. Both the heat and speed of rotation are then
increased with the view of welding the iron, until a ball or balls are produced,
which may be removed and shingled in the usual manner; or if the balls are not
hot enough for shingling I pass them through a reheating furnace with a cinder
bottom, which has the advantage of depriving the iron more thoroughly of earthy
slag and improving its physical qualities.
The effect of adding pig metal is to set up an active ebullition amongst the mass
of reduced iron whilst forming into balls, whereby the expulsion of foreign matters
is promoted and a farther advantage is obtained of adding to the iron so made
some combined carbon, of which iron produced directly from the ore stands in
need.
The cinder remaining in the furnace after the ball or balls have been removed is
comparatively rich in iron; this is mixed with some roll scale or other rich oxide
and allowed to consolidate in the furnace either while rotating slowly under the
influence of an external spray of water, or while standing if it is intended to produce
a flat side for preventing the sliding of the succeeding charge. Such sliding action
is farther prevented by introducing into the stationary bath of cinder while still
liquid lumps of iron ore or other refractory material.
If it is intended to produce spongy iron only, I prefer to provide the rotative
furnace with a fire-brick lining of considerable thickness to prevent loss of heat by
radiation.
If fluid metal is to be produced from ore a carbon lining is the most suitable,
which may be made with retort carbon, coke, or anthracite ground up and mixed
with either clay or pitch, to bind it together, and then rammed into its place and
heated.
Another part of my Invention has reference to the processes and furnaces
employed in converting such materials as are produced by the above-described or
other process, pig metal and raw ore with or without the use of scrap into cast steel:
The melting furnace I employ for this object differs from that described by me in
previous Specifications (notably in those of 1867, 1870, 1871, and 1875), by an
arrangement of gas and air ports, in which each air port rises from its regenerator
behind the corresponding gas port, and is made to project into the furnace over
such gas port, it being important that the air port should overlap the gas port on
two opposite sides; great solidity of brickwork and perfect combustion is thereby
attained.
Another point of difference in the improved melting furnace consists in providing
below the centre of the furnace an open cave through which air freely circulates and
rises through openings into the air space below the melting chamber and behind the
bridges, whereby a perfect cooling of the sides of the melting chamber is effected.
This cave serves moreover as a receptacle for any metal which may break through.

page_text: the sides or bottom of the melting chamber, whence it can be removed at leisure
without meanwhile encumbering the ventilating spaces around the melting
chamber.
Another modified arrangement in connection with the improved melting furnace
consists in providing one or more doors or openings at such an elevation that the
scoria floating on the metallic bath may be run off continuously or from time to
time during the process of decarburization without discharging the metal itself, and
for this purpose these doors or openings should be made low enough to suit the
lowest possible surface level of the metallic bath, and rendered capable of being
banked up readily by means of sand or other refractory material to the height
required.
When the metal is sufficiently decarburized, as may be ascertained by chemical
tests and by the appearance of a chilled and fractured sample, the charge is tapped
into a moveable ladle lined with fire-clay and heated internally by means of a gas
flame or otherwise to low redness, but half an hour or so previous to tapping a
moderate amount of rich spiegel eisen or ferro-silicon-manganese is broken up into
small pieces and distributed over the bottom of the ladle, where it becomes heated, and
so is afterwards readily melted by the stream of liquid metal from the furnace. The
remaining spiegel eisen is put into the furnace, by preference in a heated condition,
just before tapping; the quantity of ferro-silicon-manganese required depends upon
the per-centage desired in the metal, and one of the principal advantages realised by
this mode of working consists in not allowing the manganese or silicon any oppor-
tunity of oxidising, and thus a definite proportion of manganese and silicon are
ensured in the metal produced.
If it is intended to convert old iron or steel rails or other scrap metal into cast
steel, a certain proportion thereof may be introduced together with the pig metal
into the furnace, and the remaining portion up to the limits of three parts of wrought
metal, to about one part of pig, being afterwards introduced into the furnace;
the bath is thereupon adjusted by the introduction of wrought metal ore, or before
spiegel eisen or ferro-silicon-manganese is added, as before described.
Fig. 7 of the accompanying Drawings shows a longitudinal section of the before
described improved steel melting furnace taken on line Q, R, Fig. 8, which shews a
sectional plan on line S, T, U, V, Fig. 7; Fig. 9 shews a cross section through one
of the regenerators on line W, X, Fig. 7; and Fig. 10 shews a side elevation of the
furnace.
The air passages & leading from the air regenerators k₁ are arranged directly
behind the gas passages 7 leading from the gas regenerators, the upper ends of the
air passages being projected horizontally at a higher level than the gas passages, as
shewn, so that the currents of combustible gas in issuing from their passages impinge
upon and mix intimately with the horizontal currents of air passing over them.
The air passages being of greater width than the gas passages, as shewn in plan in
Fig. 8, the air currents are made to overlap the currents of gas on either side; by
this means perfect combustion and great solidity of the brickwork is attained.
the back of the air passages are sight holes m closed by plugs.
At
The filling in of the gas regenerators is in this arrangement built up of vertical
fire-brick walls 12, 12, with narrow spaces between them, and bonded together by
transverse blocks of firo-brick arranged, as shewn in Fig. 9, so that the gaseous
currents passing up or down through the spaces between the walls are repeatedly
split up, so as to insure the contact of all particles thereof with the surfaces of the
walls for taking up the heat therefrom or giving off heat thereto. By this con-
struction of the filling-in the regenerators clear themselves more readily of deposit
than the old construction with chequer work filling. The air regenerators k¹ inay
be constructed in the same manner, but as they are less liable to receive dust from
the furnace they may be filled with chequer work arranged in the usual mauner.
Between the two sets of regenerators a cave n is formed communicating with
the spaces o beneath the bed p and sides of the furnace, air being allowed to cir-

page_text: culate freely through these spaces, so as effectually to cool the sides and bottom of
the furnace bed. Any molten metal that may leak through the bed will drop into
the cave
non to a bed of sand prepared for that purpose, whence it can be
readily removed without interfering with the regenerators.
Doors or openings q, q, are provided at the sides of the melting chamber at such
a level that the scoria floating on the metallic bath can be run off through thein,
either continuously or at intervals, without discharging the metal itself, as herein-
before mentioned, the openings at the bottom of the doors being formed of gradually
decreasing width, as shewn, so as to facilitate their being banked up to any.
required height corresponding to the level at which the liquid slag stands on the
metallic bath.
Having thus described the nature of my Invention and in what manner the
the same is to be performed, I claim,-
First. Providing at the back end and neck of a rotative furnace for the pro-
duction of malleable or spongy iron an annular trough or receptacle into which a
stream of water is made to flow for the purpose of cooling those parts, substantially
as herein described.
Second. So arranging regenerators for furnaces in which dust is carried away
with the products of combustion that the dust cannot fill up the chequer work, but
either falls between the checks to the bottom of the regenerator or is readily
removed through doors at intermediate points, such arrangements being shewn
respectively at Figs. 7 and 9 and at Figs. 1 to 3 of the accompanying Drawings.
Third. The arrangement of gas producer in close connection with the rotative
furnace in such a manner that the gas passes in a heated condition from the gas
producer through a hot passage between the two air regenerators, and issues through
a contracted passage or nozzle into the rotative chamber, substantially as herein
described with reference to Figs. 1 to 3 of the Drawings.
Fourth. The combination of the rotative furnace a with the regenerators e, e¹,
formed of multitudinous zig-zag passages, the gas flue d, and gas producer 2,
arranged and operating as herein described with reference to Figs. 1 to 6 of the
Drawings.
Fifth. The method of producing wrought iron from the ore in a rotative furnace
by charging together with the ore and fluxing and reducing agents a quantity of
granulated or broken pig metal, and after reduction of the ore running off the slag
and balling, substantially as herein set forth.
Sixth. In rotative furnaces for the production of iron directly from the ore,
forming the lining of the liquid cinder remaining after the balling of the iron mixed
with roll scale or rich oxide, and allowed to solidify with or without the introduction
of lumps of refractory material, substantially as herein described.
Seventh. In regenerative reverberatory furnaces for the melting or heating of iron
and steel, arranging a number of air passages to rise directly behind the corre-
sponding gas passages, the air passages having their upper ends projected horizontally
above the gas passages, and being made of such a width that the air currents overlap
the gas currents on either side, substantially as herein described with reference to
Figs. 7 to 9 of the Drawings.
Eighth. Providing below the steel melting furnace a cave or chamber through
which the air is allowed to circulate freely, and which communicates with the air
spaces at the sides and bottom of the furnace bed, in order to receive any molten
slag or metal that may break out from the furnace, substantially as herein described
with reference to Figs. 7 to 9 of the Drawings.
Ninth. In the manufacture of cast steel on the open hearth furnace the method
of running off the slag or scoria continuously or at intervals through doors or holes,
so constructed and arranged at a suitable height above the furnace bed that the
overflow admits of being regulated according to the height of metal in the furnace,
substantially as herein described.
Tenth. The method of insuring a given per-centage of manganese in the metal

page_text: by placing a proportion of rich ferro-silicon-manganese in a broken condition into
the heated ladle before running in the charge of liquid metal from the furnace,
substantially as herein described.
In witness whereof, I, the said Charles William Siemens, have hereunto set
my hand and seal, this Twenty-second day of March, in the year of our
Lord One thouand eight hundred and seventy-seven.
Witness,
E. F. BAMBER,
12, Queen Anne's Gate,
S.W.
C. WILLIAM SIEMENS. (L.S.)