IMPROVEMENTS IN THE MANUFACTURE OF CAST STEEL, AND IN FURNACES AND APPARATUS EMPLOYED FOR THAT PURPOSE."
Year: 1868

page_text: LETTERS PATENT to Charles William Siemens, of No. 3, Great George
Street, Westminster, in the County of Middlesex, for the Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF CAST STEEL, AND IN FURNACES
AND APPARATUS EMPLOYED FOR THAT PURPOSE."
PROVISIONAL SPECIFICATION left by the said Charles William
Siemens at the Office of the Commissioners of Patents, with his
Petition, on the 10th June 1868.
I, CHARLES WILLIAM SIEMENS, of No. 3, Great George Street, West-
minster, in the County of Middlesex, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF CAST STEEL,
AND IN FURNACES AND APPARATUS EMPLOYED FOR THAT PURPOSE," to be as
follows:-
My Invention has reference to the process of and apparatus for
making steel, described in the Specification to certain Letters Patent
granted to me, and bearing date the 21st August 1867, No. 2395.
Instead of reducing the ore in vertical hoppers descending into the
metallic bath, as described in the Specification to the said Patent, I
'
A

page_text: effect its reduction in a revolving cylinder of cast iron or other suitable
material, which is placed horizontally or nearly so above the furnace
within an outer casing, through which flame is made to circulate. The
ore to be reduced is fed in at the one extremity of the rotating cylinder,
and is worked gradually forward by its rotation (the charging end being
slightly tipped upwards), the cylinder, being at the same time heated to
redness by the external heat. Reducing gas previously purified and
heated is made to enter the same cylinder at the charging end through
an opening in its axis, which gas in being brought extensively into
contact with the heated and moving ore effects its entire and uniform
reduction into spongy or pulverized malleable iron, which latter falls in
due course through an aperture in the further extremity of the rotating
cylinder or drum, and through a vertical hopper or channel into the
metallic bath of the melting furnace, where it is readily dissolved and
incorporated with the bath, with the exception of its earthy constituents,
which will form a slag upon the surface of the metal. The reducing
gases employed also escape from the further end of the rotating cylinder
into the surrounding casing, where atmospheric air is admitted to burn
them; the products of combustion being made to escape from the
casing near the feeding end towards a chimney, and the draft being
regulated by dampers. The air employed for burning these gases-should
be made to enter the casing under a certain pressure in order to prevent
the hot flame of the melting furnace from rising into the casing in such
quantities as to injure the rotating cylinder by excessive heat, for which
purpose a fan or steam jet may be employed. The air should also be
heated moderately before entering the casing, which can be easily
effected by conducting it under the bed or over the roof of the melting
furnace.
2
time the reduction of the ore within the rotating

page_text: at which the reduced ore is fed into the metallic bath. When the bath
is complete the rotation of the drum is stopped until after the bath has
been tapped and another bath of cast metal has been formed. In the
meantime the communication between the casing surrounding the drum
and the melting furnace may be entirely stopped by introducing a solid
piece of fire-clay into the communicating channel or hopper, but the
work of reducing the ore may be nevertheless carried on by the supply
of reducing and heating gas.
Instead of the rotating cylinder above described, any mechanical
equivalent may be employed for causing the heated ore to be fed
gradually forward towards the furnace. The bottom of the melting
furnace may be formed of white sand, as described in my before-
mentioned Patent, but I prefer to use oxide of magnesia, which has
been previously highly calcined, powdered, and mixed with a certain
proportion of the same oxide which has been calcined to a less degree,
in order to retain the property of binding the highly calcined material
into a solid mass. Or lime or silica may be mixed with the calcined
maguesia.
Another part of my Invention consists in the addition of certain
materials to the bath of liquid metal in the furnace with the view of
removing from the steel impurities such as silicon and sulphur.
The material which I chiefly intend to use for this purpose consists of
a mixture of oxide of lead (litharge) and of nitrate of soda prepared by
first fusing, say, ten pounds avoirdupoids of the nitrate, and dropping
into it from 20 to 30 pounds of litharge; this is cast into a cylinder or
cannister of lead or iron, and to this compound peroxide of manganese
or other metallic oxide or acid may be added in small proportions. In
throwing such cannisters into the liquid bath near the end of the
operation of melting a powerful ebullition is set up, and while the
oxygen set free attacks the carbon and silicon the metallic lead and soda
will combine, the one with the sulphur and the other with the silica
produced, which bodies will appear on the surface in the form of slag..
The metallic bath may thereupon receive an admixture of ferro-
nanganese, or be treated in any other suitable known manner. When
he cannisters are thrown in I open a communication from the furnace
or heated chamber to a condenser communicating with the chimney,
losing at the same time the ordinary communication to the chimney
hrough the regenerators of the furnace; the object being to condense

page_text: the surplus litharge and alkaline vapours which would otherwise attack
the brickwork composing the regenerators. The condensed litharge
may, moreover, be used again and again.
Instead of placing the substances into cannisters, they may also be
used in the form of cakes or other compact forms.
Instead of using nitrate of soda, other salts or oxides of soda, potash,
or lime may also be used.
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 10th December 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
WILLIAM SIEMENS, of No. 3, Great George Street, Westminster, in the
County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of June, in the year of
our Lord One thousand eight hundred and sixty-eight, in the thirty-
first year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Charles William Siemens, Her special
licence that I, the said Charles William Siemens, my executors, adminis-
trators, and assigns, or such others as I, the said Charles William
Siemens, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IM-
PROVEMENTS IN THE MANUFACTURE OF CAST STEEL, AND IN FURNACES AND
APPARATUS EMPLOYED FOR THAT PURPOSE," upon the condition (amongst
others) that I, the said Charles William Siemens, my executors or
administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the
said Letters Patent.

page_text: NOW KNOW YE, that I, the said Charles William Siemens, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, reference being had to the accom
panying Drawings, and to the figures and letters marked thereon, that is
to say :-
My Invention has reference to the process of and apparatus for
making steel, described in the Specification to certain Letters Patent
granted to me and bearing date the 21st August 1867, No. 2395.
Instead of reducing the ore in vertical hoppers. descending into the
metallic bath, as described. in the Specification to the said Patent, I
effect its reduction in a revolving cylinder, drum,. or muffle of refractory
material, which is placed horizontally, or nearly so, above the furnace
within an outer casing, forming part of the rotating drum or cylinder,
through which flame is made to circulate. The ore to be reduced,
which is mixed by preference with a certain proportion of solid carbona-
ceous material and with fluxing materials, is fed in.at the one extremity
of the rotating cylinder, and is worked gradually forward by its rotation,
the interior cylinder being at the same time heated to redness. by the
external heat.. Reducing gas previously purified and heated is made to
enter the same cylinder at the charging end through an opening in or
near its axis, which gas in being brought extensively into contact with
the heated, and, moving ore effects its entire and uniform reduction into
spongy or pulverulent, malleable iron, which latter falls in due course.
through a vertical hopper or channel into the metallic bath of the
melting furnace,, where it is readily dissolved and incorporated with the.
bath of fluid cast iron previously prepared, or with an excess of solid
carbon charged upon the hearth of the furnace to form the commence-.
ment of a liquid bath, while the earthy constituents of the reduced ore.
form a slag upon the surface of the metal.. The reducing gases employed
also escape from the further end of the rotating cylinder into the
surrounding casing, where atmospheric air is admitted to burn them,
the products of combustion being made to escape from the casing near
the feeding end towards a chimney, and the draught being regulated
by dampers. The air employed for burning these gases should be made
to enter the casing under a certain pressure in order to. prevent the hot
flames of the melting furnace from rising into the casing in large.
quantities to the exclusion of the air necessary for burning the reducing;

page_text: gases emanating from the interior of the drum; for this purpose a fan
or other means of propelling the air may be employed; or the same
effect may be obtained by creating a relative vacuum by virtue of the
chimney in throttling the exit passages leading from the interior of the
cylinder into the outer casing or combustion channels, and thus causing
atmospheric air to enter by its natural pressure to effect the combustion.
The air should also be heated moderately before entering the casing,
which can be effected by conducting it under the bed or over the roof
of the melting furnace, or by leading it through channels in the rotating
cylinder exterior to the combustion casing or channels.
Instead of effecting the reduction of the ore within the rotating
cylinder entirely, or even partially, by means of reducing gases solid
reducing agents, such as anthracite, coke, charcoal, sawdust, or peat
may be employed, with or or without the addition of pitch, tar, oil, or
resinous substances. Oxides of manganese may be charged with
advantage with the iron ore, to be likewise reduced, and lime or other
fluxing material may be added to combine in the melting furnace with
the silica or gangue contained in the ore; or ores containing silica may
be mixed in due proportion with others containing lime, alumina,
magnesia, or other basic constituents. The rotation of the drum may
be conveniently effected by imparting motion to antifriction rollers, upon
which the drum is made to rest, and its rotating velocity should be
capable of being regulated at will, as upon it depends the rate at which
the reduced ore is fed into the metallic bath. When the bath is
complete the rotation of the drum is stopped until after the bath has
been tapped, and another bath of cast metal has been formed. In the
meantime the communication between the casing surrounding the drum
and the melting furnace may be entirely stopped by introducing a solid
lump of fire-clay into the communicating channel or hopper, but the
work of reducing the ore may be nevertheless carried on by maintaining
the supply of reducing and heating gas.
Instead of the rotating cylinder above described, any mechanical
equivalent may be employed for causing the heated and reduced ore
to be fed gradually forward towards the furnace. Thus the reducing
chamber may be made stationary, having heating channels provided
within its lining, and the reducing gases may be forced through the orc
in the manner described in my Patent No. 2413 of 1866, the ore being

page_text: fed down the inclined surface of the reducing chamber by a piston or
pistons at the feeding end.
Instead of using only one reducing drum or chamber several may be
employed in connection with one furnace, and a different kind of ore
may be treated in each, in order to vary at will the composition of the
metallic bath in adding reduced metal from the one or other drum; thus
one drum may contain an ordinary description of ore and a second one
ore rich in manganese, which latter may be worked at such an increased
temperature as may be necessary for the reduction of that metal, and
may be made to feed the bath towards the end of each operation in lieú
of adding spiegel eisen. The bottom of the melting furnace may be
formed of white sand, as described in my before-mentioned Patent,
or sand mixed intimately, with magnesia, or fire-clay may be used
with advantage..
Another part of my Invention consists in the addition of certain
materials to the bath of liquid metal in the furnace with the view of
removing from the steel impurities such as silicon and sulphur. The
material which I chiefly intend to use for this purpose consists of a
mixture of oxide of lead (litharge) or oxides of other metals with nitrate
of soda, prepared by first fusing, say, ten pounds avoirdupoids of the
nitrate, and dropping into it from 20 to 30 pounds of the oxide; this
is cast into a cylinder or cannister of lead, or lead and iron combined.
In throwing such cannisters into the liquid bath near the end of the
operation of melting a powerful ebullition is set up, because the
cannisters, owing to their superior specific gravity, sink to the bottom
of the bath, and the salts which they contain are there decomposed
by the heat, and while the oxygen set free attacks the carbon and
silicon the soda and lead combine, the one with the silica produced
(by the oxidation of the silicon) and the other with the sulphur, and
partly also with the phosphorus contained in the metal; and form
compounds which appear on the surface in the form of slag. The
metallic bath may thereupon receive an admixture of spiegel eisen or
ferro-manganese, or be treated in any other suitable known manner.
When the cannisters are thrown in I open a communication from the
furnace or heated chamber to a condenser communicating with the.
chimney, and close at the same time the ordinary communication with
the chimney through the regenerators of the furnace, the object being
to condense the surplus litharge and alkaline vapours which would

page_text: otherwise attack the brickwork composing the regenerators. The con-
densed litharge may moreover be used again and again. Instead of
placing the substances into cannisters they may also be used in the
form of cakes, or in other compact forms, and may be forced below the
surface by pressing upon them with rods of iron. Instead of using only
nitrate of soda other salts of soda, potash, or lime (among which the
chlorates and manganates deserve the foremost place) may also be used,
either separately or mixed in any proportions, the object being to set up
an active commotion of the liquid bath by the generation of gaseous
oxidizing agents, introducing at the same time strong bases for the
purification of the metal.
Having thus set forth the nature of my Invention I will now proceed
more particularly to describe the arrangements of furnaces and apparatus
which I prefer to employ in carrying the same into effect.
Figures 1 to 11 on Sheets I. and II. of the accompanying Drawings
show the two principal arrangements of reducing apparatus herein-before
mentioned.
Figures 1 to 5 on Sheet I. show one arrangement of furnace and
reducing muffle for the production of cast steel directly from the ore.
Figure 1 shows a longitudinal section of the melting furnace and
regenerators, and a transverse section through the discharging end of
the revolving muffle or drum on line 1, 1, Figure 2; Figure 2 shows
a transverse section through the melting furnace, and a longitudinal
section through the reducing muffle on line 2, 2, Figure 1; Figures 3
and 4 shew transverse sections through the reducing drum on lines 3, 3,
and 4, 4, Figure 2; Figure 5 is a sectional plan through the melting
furnace at 5, 5, Figure 1. Similar letters of reference indicate similar
parts in each of the Figures.
The melting furnace itself is similar in construction to that described
in the Specification to my previous Patent bearing date the 21st August
1867, No. 2395, to which I have before referred.
In the arrangement of furnace which is described in the Specification
just named the reduction of the ore was effected in two vertical shoots
or hoppers placed above the bath of liquid metal in the melting
chamber, into which the ore gradually sank down by gravity as it was
reduced.

page_text: According to my present improved arrangement the ore is reduced in
a rotating cylinder or drum A, A, which rests in a horizontal position
above the melting furnace on four rollers, as shown in Figures 1 to 4
of the accompanying Drawings. The outer casing of the drum A, A,
is divided into three sections, the middle portion being made of strong
wrought-iron plates, and the ends of cast iron, as shown on Figure 2 of
the Drawing. This outer shell of the reducing cylinder A, A, is lined
throughout its length with two courses of hollow fire-bricks B, C, which
are so arranged as to leave a double series of small flues or passages in
the substance of the lining, extending from the one extremity of the
cylinder to the other, as shown in Figures 2, 3, and 4. The opening
of the cylinder is diminished at each end by the addition of inner rings
of lining bricks D, E. The ore is introduced at the one extremity of the
revolving drum through a cast-iron shoot F attached to the fixed sheet-
iron casing G. The shoot F is kept always filled with ore, which is fed
gradually forward into the reducing muffle through the circular opening H,
the thickness of the bed of ore in the muffle being regulated by the
plate I, which closes more or less the upper part of the charging
opening H. The other extremity of the reducing cylinder opens into
a second shect-iron casing K, which is lined with fire-brick, and com-
municates directly by the small opening L with the bath of the melting
furnace below. The two casings G and K at the ends of the revolving
cylinder A, A, bear closely against it by means of accurately turned
faces at M, M, M, and are kept in contact with it by screw clips N, N,
Figure 2, the casings G, K, being both so supported that they are free
to adjust themselves closely to the ends of the revolving cylinder A, A.
The cylinder is carried by two pairs of rollers R, R, and S, S, Figures 2,
3, and 4, and is put in motion by the driving arrangement shown in
Figures 2 and 4. A pulley O driven by a band or in any other
convenient manner communicates motion through two endless screws
P, P, and two worm wheels Q, Q, to the rollers R, R, already mentioned,
which support the greater part of the weight of the cylinder A, A, (when
it is filled with ore), and which drive it by friction. By the slow
rotation of the reducing cylinder or muffle, the ore introduced through
the shoot F from the charging floor above is continually turned over,
and each portion of it is exposed in succession to the action of the
reducing gas which is introduced through the tube T, Figure 2.
To prevent the slipping round of the ore in one mass inside the muffle,
in which case the surface only would be exposed to the action of the gas,

page_text: rows of projecting bricks are built into the lining at intervals, as shown
at U, U, Figures 2, 3, and 4, between the bricks B, C. These projecting
bricks carry the mass of ore round with them, preventing any slipping
and forcing the ore to roll over and over, exposing every part equally
to the reducing action of the gas. The excess of reducing gas is drawn
away at the end D of the muffle into the series of small flues V, V, in the
brick lining. Air is drawn in at the same time through a series of
openings W, W, (Figure 2) near the other end of the muffle, which
conmunicate with an annular air channel W', into which the air passes
from the pipe W2, as shown. In traversing the whole length of the
outer series of flues X, X, the air drawn in at W, W, becomes more or
less heated before it meets with the gas at the apertures Y, Y, and burns
with it along the inner flues V, V, heating the muffle to bright redness,
and escaping at length into the casing g, and thence through the tube Z
(Figure 2), which is furnished with a valve for regulating the draught
into the main chimney fluc. Instead of admitting the air into the
passages X through the annular passage W', it may pass in directly from
the atmosphere through separate openings into each passage X, and its
entrance be governed by separate slides or regulators.
The mode of working this furnace is as follows:-The reducing
cylinder is in the first instance heated to redness, and the melting
furnace below is raised to a full steel melting heat. The cylinder is
then put into slow rotation round its axis, and the ore, which I suppose
to be hæmatite mixed with from 10 to 15 per cent. of its weight of solid
reducing agents, such as anthracite, coke, charcoal, or with a somewhat
larger proportion of sawdust or peat, and about 3 per cent. of lime is
filled in at the one extremity through the shoot F from the charging
floor above, a supply of reducing gas being introduced at the same time
through the tube T, Figure 2. The reducing gas as it passes through
the box T, and the ore descending in the curved shoot F, are heated
by the waste gases on their passage towards the chimney flue. The
reducing gas employed is ordinary produce gas, consisting principally of
carbonic oxide and nitrogen. It should be washed thoroughly before
it is introduced through the box T, Figure 2, and the tube T into the
reducing muffle, in order to condense and remove as completely as
possible the water vapor that it may contain, and to purify it from
sulphurous acid and other injurious compounds. Although I mix with
the ore (as already mentioned) from 10 to 15 per cent. of solid carbon

page_text: in any form or combination which does not contain sulphur, phosphorus,
or other deleterious substance (among which forms wood and peat
deserve especial mention) I depend mainly upon the carbonic oxide
introduced into the muffle for effecting the reduction of the ore. The
gas entering at I is brought by the rotation of the drum into extensive
contact with the heated ore, but inasmuch as its reducing action
would cease as soon as a considerable proportion of the carbonic oxide
contained in it had been converted into carbonic acid (as shown by
Le Play and others) the presence of solid and heated carbon is necessary
in order to bring the carbonic acid back again to the state of carbonic
oxide, unless indeed a vastly excessive quantity of gas were passed
through the reducing drum, which would be attended by waste. If
such solid reducing agents are employed as wood or peat, these
should be dried completely before they are charged in with the ore,
and inasmuch as reducing gases will be evolved from them by
heat, the admission of gas at I may be greatly diminished when
they are employed instead of pure solid carbons; but on the other
hand they must be added in an increased proportion to bring up the
solid carbon to from 10 to 15 per cent. according to the nature and
richness of the ore. Nevertheless the use of gases cannot be wholly
dispensed with except at a risk of irregular and insufficient action in
the reducing cylinder. The temperature within the reducing cylinder
should be maintained during the process at a full red heat, or from
700° C. to 1000° C. (according to the nature of the ore) towards the end
where the discharge takes place, but diminishing towards the charging
end. By the slow rotation of the cylinder a portion of the reduced
pulverulent metal is discharged through the opening L into the bath of
liquid cast iron (which is maintained in the melting furnace below)
at each revolution of the drum, when the notch D', Figures 1 and 2, in
the brick ring D at the end of the mufile comes into the lowest position,
as shown in the Drawings. The rate at which the reduced metal is fed
into the furnace depends on the one hand upon the velocity of rotation
of the muffle (which should be under perfect control) and on the other
upon the inclination of the upper surface of the bed of ore; this last is
regulated by closing to a greater or less extent the upper part of the
charging opening H, Figure 2, by means of the plate I, which can be
readily changed for either a deeper or a shallower plate. By suitably
regulating the speed of rotation of the muffle the successive charges of
reduced spongy iron are dropped into the bath of liquid metal in the

page_text: melting furnace in proportion as each previous charge is dissolved. The
metal in the bath is stirred occasionally and small samples are taken
out at intervals in the manner described in my previous Specification,
dated 21st August 1867; additional charges of pig iron are intro-
duced if the metal is found to become decarburetted too rapidly, and
the slag accumulating on the surface may be skimmed off from time to
time, or it may be allowed to run off over the fore plate of the centre
furnace door over the tap hole, which is for this purpose several inches
lower than the doors near the ends of the furnace. When a sufficient
amount of reduced spongy iron has been added to bring the metal into
the condition of liquid soft iron containing not more than 1 to 2 per
cent. of carbon, the rotation of the drum is stopped and from 5 to 8
per cent. of spiegel eisen is then charged upon the bridge of the furnace
and allowed to melt down into the bath, or the spiegel eisen may be
melted in a separate furnace either in crucibles or on an open bed and
charged into the principal furnace in a liquid state. The proportion of
spiegel eisen to be added depends upon the "temper" or per-centage of
carbon required in the finished steel. If the ore and the pig iron
employed are very pure no spiegel eisen may be required; samples may
be taken out at intervals, and when the desired temper has been reached
the steel may be tapped at once into the ladle. But in most cases
when the ore is not exceptionally pure and the steel obtained from it is
contaminated with a sensible amount of sulphur, phosphorus, or other
impurities, it will be found that the ingots cast from the steel without
the addition of spiegel eisen, ferro-manganese, or other re-agents at the
end of the process are "red short," or cannot be forged, and the greater
the impurity of the steel the larger is the amount of spiegel eisen that
will generally be required. To admit of adding a sufficient proportion
of manganese in the form of spiegel eisen without at the same time
introducing so much carbon as to make the steel too hard for many
purposes, it is advisable in most cases to decarburet the metal almost
entirely before the spiegel eisen is added as has been already described.
This plan of reducing the proportion of carbon in the first instance to a
definite point and then adding a fixed per centage of spiegel cisen
(depending on the hardness required) has the further advantage of
facilitating very much the production of a uniform temper of steel. By
a little practice the point at which the metal is sufficiently decarburized
may be judged of very accurately by the fracture of the sample taken
out. The addition of spiegel cisen at the end of the process. may also

page_text: be dispensed with if the orc is rich in managanese, or a second reducing
muffle may be added charged with ore rich in manganese to be used last
in each operation. The addition of spiegel eisen or manganese in other
forms may also be dispensed with in the production of steel for castings
which are not to be hammered, and need not therefore be so thoroughly
purified as forge ingots. If hardness and tensile strength is the principal
object rather than ductility and elasticity, the carbon may be maintained
with advantage in such castings at from 1 to 2 per cent. by an abundant
use of the reducing agents. A comparatively low furnace temperature
will suffice for such metal. After adding the spiegel eisen or otherwise
treating the metal it is well stirred over and is then retained in the
furnace under a covering of neutral or basic slag for between half an
hour and an hour before it is tapped out and cast into ingots in the
usual manner. The reducing muffle remains stationary until the charge
of steel has been tapped out of the melting furnace and a fresh bath of
liquid pig iron has been formed, but the reduction of the ore is still
continuously carried on it it by maintaining the supply of reducing and
heating gas. If the ore employed is in the state of fine powder it may
be desirable to turn it over occasionally during this period in order to
expose it more thoroughly to the action of the gas. In this case the
muffle may still be rotated a little at intervals, the reduced metal being
kept from falling into the melting furnace below by pushing it back from
the end of the muffle by a rake put in through the door K'. The muffle
may be entirely shut off if required from the melting furnace by inserting
a slab of fire-clay into the connecting channel L at L'. A furnace of
the dimensions represented in the Drawings is capable of producing
three charges of cast steel per 24 hours of from 3 to 4 tons cach charge,
but the dimensions of these furnaces may be varied considerably. Thus
in producing steel of high quality and rich in carbon, such as tool steel,
it will be found convenient to employ furnaces of less capacity, whereas
in making large castings of steel, such as guns, bells, and armour plates,
or. ingots for engine shafts, furnaces of a capacity exceeding 5, 6, or
even 10 tons may be employed. The contents of several furnaces
may be poured into the same mould either by running them directly
from the tapping holes, or by running the metal first into ladles
and then into the mould or moulds. I heat these moulds or ladles
beforehand by passing a flame of producer gas through them.

page_text: be as pure as possible. The ore should be by preference a pure oxide
of iron containing but little gangue or carthy matter and as free as may
be from compounds of sulphur, phosphorus, or arsenic, magnetic ores,
hæmatite ores, or rich calcined spathic ores are particularly suitable.
The ore may be in the form of powder, sand, or dust, and on this account
many ores are suitable for this process which notwithstanding their
purity cannot be employed in blast furnaces, amongst which the
magnetic sands of Canada, Spain, and New Zealand, the micaceous ores,
and the refuse ore produced in treating pyrites for copper and sulphur
may be specially mentioned. If the ore employed is in the state of
powder and therefore not pervious to the reducing gas, I prefer to mix
it with loose and pervious reducing agents such as wood, in small pieces,
sawdust, dried peat, or charcoal, or with pitch, asphalte, or oils as already
described. The nature and amount of the fluxing material to be added
depend on that of the foreign substances contained in the ore.
In some
cases such a mixture of ores may be adopted as contains both silica
and fluxing material such as lime, magnesia, or manganese in suitable
proportions, thus avoiding the necessity for adding any separate flux.
Hæmatite or magnetic ores containing silica may for example be mixed
with advantage with spathic ores containing lime, magnesia, or manganese,
or with clay ironstones. If nearly pure oxides of iron such as some
hæmatites or magnetic ores or calcined spathic ores are treated I some-
times employ no fluxing materal except a small per-centage of oxide
or carbonate of manganese, which forms with the small proportion of
earthy matter invariably associated with the ore sufficient slag for the
protection of the molten metal. The ores should always be crushed
before use into powder or into pieces not exceeding the size of peas
or beans in order to facilitate their reduction into pulverulent or
spongy iron, and they should be mixed intimately with the fluxing
material that is added. If they contain volatile constituents, such as
carbonic acid, water of hydration, arsenic or sulphur, they should also
be calcined in the usual manner. Ores containing sulphur in the form
of sulphide of iron should be calcined carefully at a very low heat and
subsequently washed, in order to remove as large a proportion as possible
of the sulphur as soluble sulphate of iron. The pig iron employed
should also be as pure as possible, by preference charcoal pig iron
(containing manganese) or the purest qualities of coke, pig iron made
from hæmatite, magnetic, or spathic ores, though inferior pig irons
may also be employed to a greater or less extent in making the lower

page_text: qualities of steel (the metal being purified before tapping it out of the
melting furnace in the manner described below). The proportion
between the cast iron and the ore employed in the production of cast steel
by the above process may be varied between very wide limits. In case
rich ores not containing sulphur or phosphorus in any notable quantity
can be obtained at a moderate price, it is advantageous to reduce the
ore to metallic iron as completely as possible by employing a large
reducing muffle heated in the interior nearly to whiteness, and by
mixing the ore with an abundant proportion of reducing agents. It
is sufficient then to commence the operation with no more than from
10 to 15 per cent. of cast iron in the bath of the melting furnace.
The use of pig iron for the purpose of dissolving the reduced spongy
metal may even be dispensed with altogether by throwing on the bed
of the melting furnace a considerable quantity of charcoal or of pure
coke or anthracite before commencing the introduction of the reduced
ore from the muffle. Or the extra proportion of solid carbon may
be advantageously charged either wholly or partly into the reducing
muffle itself through the door K¹ before the commencement of each
operation, in order that it may be mixed intimately with the reduced
metal before this reaches the melting heat of the furnace. The effect
of this excess of carbon is to carburet very highly the spongy iron
first charged in from the muffle, thus forming a bath of liquid pig
iron on the bed of the furnace in which the remainder of the reduced
metal is subsequently dissolved in the usual manner. Charcoal, coke,
or anthracite may also be thrown upon the surface of the bath from
time to time during the process if the liquid metal is found to become
decarburetted too rapidly. On the other hand, in those localities in
which the price of rich and pure ores is high, and in which a sufficiently
pure quality of pig iron may be obtained at a price comparatively
moderate, it is preferable to employ a smaller reducing muffle (through
which the ore will pass more rapidly) and to maintain it at a lower
working heat in order that the reduction of the ore may be effected
in part only. A much larger proportion of cast iron may in this case
be charged into the bath, even up to 80 or 90 per cent. of the weight
of steel produced. Instead of producing liquid cast steel by the use
of ores and pig metal only as herein-before described, the bath may
be increased by charging into the same furnace waste ingots of
previous operations, scrap iron or steel, or balls or blooms of puddled
or otherwise refined iron or steel by whatever process it may have been,

page_text: produced. Or the spongy or pulverulent iron may be produced in an
independent reducing muffle and may be charged into the melting
furnace, if the muffle or muffles attached to the furnace are not in order
or do not by themselves furnish to it a sufficient supply of reduced metal.
The pulverulent iron is in this case made to fall from such separate
reducing drum into a closed casing, where it is cooled before removal
to the steel melting furnace. In working up such spongy iron or light
scrap, as for instance steel or iron turnings or punchings or clippings
of sheet iron or steel, it is advantageous to heat the metal before
introducing it into the bath by charging it through the reducing muffle,
which in the above described process is employed for effecting the
reduction of the ore. If the metal in the bath of the melting furnace
contains silicon, sulphur, or phosphorus it is improved in quality by the
introduction into it (before charging the spiegel eisen) of oxidizing agents
and powerful bases. The re-agents which I prefer to employ for this
purpose are nitrate of soda and other nitrates, chlorates and manganates,
oxides of lead, iron and managense and metallic lead; I prefer to
introduce these re-agents into the liquid metal in the forms shown in
Figures 6 and 6A on Sheet I. of the accompanying Drawings. The block
or cylinder a, d, e, shown in Figure 6 consists first of a cast-iron
plate a, say 6 ins. in diameter, pierced in the centre with a hole b and
furnished with three feet c, c, c; second, of a plate of nitrate of soda d
which may be mixed with oxide of iron or manganese or with litharge
(oxide of lead), and third, of a plate of lead e. The cylinders are cast
in a mould f in which the cast-iron plate is first set and the melted
lead and nitrate then poured in through the hole b. The cylinders are
easily introduced into the furnace by a bar or hook put through the
ring at the top. Figure 64 shows another form of cylinder consisting
simply of a lead tube / open at the ends and filled with nitrate of soda
i either alone or mixed with oxide of iron or other metallic oxides. On
dropping these cylinders into the bath, after first warming them for a
few seconds in the flame of the furnace, a powerful ebullition is set
up, and while the oxygen set free attacks the carbon and silicon, the
soda and metallic lead combine, the one with the silica produced and
the other with the sulphur, and to some extent with the phosphorus, and
form compounds which appear on the surface in the form of slag.
When these cylinders are introduced into the bath I open a communi-
cation from the furnace or melting chamber to a condenser communi-
cating with the same or another chimney or other exhausting apparatus,

page_text: or directly with the atmosphere, and close at the same time the ordinary
communication to the chimney through the regenerators and reversing
valves, the object being to condense the surplus litharge and alkalinė
vapours which would otherwise attack the brickwork composing the
regenerators. The condensed litharge may also be used again and
again in the melting furnace..
The arrangement of condenser which I prefer to employ is shown
in Figures 9, 10, and 11 on Sheet II. of the Drawings. Figure 9 is a
longitudinal' section through the condenser on the line 9, 9, in Figures
10 and 11. Figure 10 is a transverse section on line 10, 10, Figures 9
and 11. Figure 11 is a sectional plan, on the line 11, 11, Figure 9. The
condenser communicates with the melting furnace X through the flue
A, A, leading out from the back of the furnace immediately above
the level of the bath of liquid metal. The condenser consists of a
brick chamber B, B, into the top of which the flue A from the furnace
opens, while from one side a flue C leads off above to the main
chimney flue, and a drain flue D communicating with the bottom of
the chamber leads through a syphon trap into a drain. The opening
of the flue C is regulated by a damper as shown at E in Figure 9, and
the opening into the drain flue D is closed at F by a grating (which
is covered with felt or canvas so as to form a filter). When the
refining cylinders are introduced into the bath of metal in the melting
furnace, the ordinary chimney damper of the furnace leading off from
the reversing valves is closed, and the damper E in the flue leading
from the condenser is opened. The products of combustion and the-
fumes from the lead and the nitrate of soda are thus drawn. off to
the main chimney fluc, entirely through the condensing chamber B: A
small jet of water under considerable pressure is turned on at the same
time at G (Figures 9 and 10) in the flue leading to the condenser, and
in striking against the small plate H fixed immediately above the orifice
through which it escapes the jet of water is broken up into fine spray
which mixes intimately with the waste gases from the melting furnace
their passage towards the condenser, cooling them thoroughly, and
condensing, and carrying down the lead fumes that they contain while
he purified gases pass off to the chimney through the flue Ċ as already
mentioned. The water flows off from the condenser through the filter.
into the drain fluc D, leaving the condensed lead fume behind in-
he bottom of the condensing chamber A, from which it may be

page_text: removed from time to time. The presence of silicon in the metal is
advantageous if it is to be used for making castings of steel which
are not to be hammered. In this case no lead cylinders containing
nitrates or other salts are employed; but silicon may be on the contrary
introduced into the metal by throwing carbon and sand on its surface
before tapping. Instead of reducing the ore in one or more revolving
cylinders or drums in the manner above described, I sometimes effect
its reduction in a fixed reducing muffle inclined at an angle of about
25° through which the ore is forced inwards towards the melting
furnace by any convenient mechanism. This arrangement is shown in
Figures 7 and 8 on Sheet II. of the Drawings.
Figure 7 shews a longitudinal section through the melting furnace and
the reducing muffle on the line 7, 7, of Figure 8, and Figure 8 shows a
transverse section on the line 8, 8, Figure 7. Similar letters of reference
indicate similar parts in the two Figures.
The melting furnace employed is identical in all respects with that
already described. In the roof of the furnace there is a circular opening L
which communicates with the reducing muffle above. In the arrange-
ment shewn on the Drawing two reducing muffles are provided, or more
properly speaking a double muffle, into which the ore is charged at each
end. The muffle A, A, is supported above the furnace on the upper ends
of the cast-iron binding plates or "brickstaves" of the latter. It consists
of a wrought-iron shell lined with fire-brick or other suitable refractory
material. The ore, either alone or mixed as .already explained with
solid reducing agents and with fluxes, is charged into the muffle through
the hoppers I (which are kept always filled with ore), and it falls in a
sloping heap on the bed. It is there heated to redness in part by the
flame or heat from the melting furnace below acting on its upper surface
and in part by heating flues J, J, passing below the bed. At the
same time currents of reducing gas are passed through the mass of ore
from one or more openings K, K, by preference transverse slits, the gas
being heated to some extent before it is introduced into the ore by the
flues J, J, below the bed. By the united action of the reducing gases
and the intermixed solid reducing agents before mentioned on the ore at
a red heat it is rapidly reduced to the state of spongy or pulverulent
metallic iron, while at the same time it is kept continually in move-
ment and is gradually worked forward towards the lower end of the
muffle by the alternate backward and forward motion of the slide N and

page_text: the hinged flap O which are worked from the shaft P in the manner
shewn in Figure 7 of the Drawing. This stirring or pushing motion is
so regulated that the spongy or pulverulent metal is worked gradually
forward to the lower end of the muffle and drops through the shoot L
into the bath of pig metal in the melting furnace below in proportion
as it is reduced and as the bath is ready to receive it. Doors Q, Q, are
provided at each side of the muffle immediately opposite to the shoot L,
through which it may be cleared of any obstruction and any mass
of ore that may have become caked together through excessive heat
or otherwise may be broken up. The excess of reducing gas rising
from the surface of the ore is drawn away at the points R, R, into the
heating flues J, J, below the bed, and air sufficient to effect the complete
combustion of the gas is admitted into each heating flue at the points
8, S, as shewn in Figure 7, the admission of air to the whole series of
heating flues below each muffle being regulated by the motion of a
notched or perforated sliding bar which is indicated in section at S. The
heating flues J, J, open at each end of the double muffle into the wrought-
iron boxes T, T, which communicate with a chimney or other exhausting
apparatus and the lower ends R, R, of the flues are throttled more or
less, as is shewn in Figure 7, to admit of drawing in a sufficient pro-
portion of air at S, S, to effect the complete combustion of the gas.
When a sufficient amount of the reduced ore has been gradually added to
the metal in the bath the pushing forward of the ore is stopped until the
steel has been tapped out as already described and a fresh charge has
been commenced. The work of reducing the orc may nevertheless be
carried on in the muffle by maintaining the supply of reducing and
heating gas, and if it is found desirable to keep the ore in occasional
motion, the communication between the reducing muffle and the melting
furnace may
in the meantime be entirely stopped by introducing a lump
of fire-clay into the communicating channel L.
Having now described the nature of my Invention and the best mode
I am acquainted with of performing the same, I wish it to be distinctly
understood that I do not confine myself to the details of apparatus
herein-before described, as these may be variously modified without
departing from the nature of my Invention, nor do I claim the arrange-
ments of regenerative gas furnaces apart from their combination with the
reducing apparatus, as they are similar to those described by me in my
former Patents, nor do I claim the manufacture of cast steel in large

page_text: masses directly from the ore, this being likewise the subject of former
Patents, but what I claim is,―
First. Producing cast steel in effecting the total or partial reduction
of iron ores or oxides into pulverulent or spongy iron by causing them
to pass along the interior of a horizontal or nearly horizontal revolving
cylinder or equivalent apparatus for feeding the ore gradually forward-
by mechanical means, while it is at the same time acted upon by
reducing agents in the presence of considerable heat, and from which
apparatus the resulting wholly or partially reduced ore descends on to
the open bed of a regenerative gas furnace, with practically perfect
exclusion of the atmospheric air, substantially as herein-before described.
Second. Effecting the partial or total reduction of iron ores within a
rotating drum (or any modification of such apparatus in which the ore'
is moved about by mechanical agency) by the conjoint action of carbonic
oxide or other reducing gas, and of solid carbonaceous substances mixed
with the ore in order to maintain the reducing character of the gas, as
herein-before set forth.
Third. Connecting one or more rotative reducing cylinders or their
equivalents with a regenerative gas furnace for melting steel upon the
open furnace hearth in such a manner that the reduced ore is supplied
in a heated condition, and with a practically perfect exclusion of the
atmospheric air, and by mechanical agency strictly under control of the
operator, substantially as herein-before described with reference to the
accompanying Drawings.
Fourth. Constructing apparatus for the reduction of iron ore in
connection with the production of cast steel, consisting of a horizontal
or nearly horizontal revolving cylinder or drum having an outer casing,
through which the gases resulting from the reduction of the ores within
the drum pass with or without the addition of other heated gases, and
are consumed by the simultaneous introduction into the said casing of
heated atmospheric air, the object being to heat the interior of the
rotating drum without exposing the external metallic casing to the
destructive action of heat.
Fifth. The combination of the reducing apparatus, herein-before
described, with a bath of highly-heated pig metal previously prepared
on the bed of a regenerative gas steel melting furnace to promote a
practically instantaneous dissolution of the reduced or partially reduced
metal to avoid its reoxidation in the furnace.

page_text: Sixth. Effecting the purification of the steel by the introduction into
the liquid. bath of cannisters or receptacles of lead or lead and iron filled
with powerful oxidizing agents accompanied by strong bases, which
cannisters or receptacles by virtue of their great specific gravity sink to
the bottom of the bath, and cause its violent agitation and a chemical
reaction upon the metal through the ensuing decomposition, substan-
tially as described.
Seventh. Diverting, condensing, and recovering the lead and other
basic materials which are volatilized in the furnace during the chemical
reaction last referred to by lowering the ordinary chimney damper, and
connecting the interior of the furnace during such interval with the
same or a separate chimney or other exhausting apparatus, or with the
atmosphere through a condensing apparatus or special channel, sub-
stantially as described.
In witness whereof, I, the said Charles William Siemens, have here-
unto set my hand and seal, this Tenth day of December, in the
year of our Lord One thousand eight hundred and sixty-eight.
Witness,
THO. TAYLOR,
20, Southampton Bldgs.,
Chancery Lane.
C. W. SIEMENS. (L.S.)