IMPROVEMENTS IN THE MANUFACTURE OF CAST STEEL
Year: 1857

page_text: LETTERS PATENT to Sir Francis Charles Knowles, of Lovell Hill, in the
County of Berks, Baronet, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF CAST STEEL."
Sealed the 11th September 1857, and dated the 17th March 1857.
PROVISIONAL SPECIFICATION left by the said Sir Francis Charles
Knowles at the Office of the Commissioners of Patents, with his.
Petition, on the 17th March 1857.
1, SIR FRANCIS CHARLES KNOWLES, of Lovell Hill, in the County of Berks,
Baronet, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE MANUFACTURE OF CAST STEEL," to be as follows:-
The first part of my Invention is the construction of furnaces, either air
or blast, whereby the manufacture of cast steel from the ore becomes a
continuous operation.
This furnace, whether an air or a blast furnace, consists of two essential
-parts, the outer part or the heating furnace, and the inner part, called the
reducing, cementing, and fluxing, or the "smelting" furnace.
The complete separation of these two parts allows of the employment of
coke, even the sulphurous, for the purpose of heating, and of charcoal for that
of reducing the oxide of iron in the ore, and carbonizing the metal into the
state of steel before it is smelted and separated from the cinder or scoria.
These furnaces are open at the top, so as to allow of their being fed conti-

page_text: nuously, the ore with coke, the other with the appropriate materials for making
steel from the ore by reducing, cementing, and fluxing. They admit of being
closed by fire-brick lids or stoppers after charging, but apertures must be left
for the escape of the gases, which must be carried away from the heating fur-
nace by a flue or chimney stack in the ordinary way. In the other form, the
furnace is reverberatory, and the cementing and reducing and smelting cham-
bers are erected within it, and are fed through the top of the heating furnace,
where they are furnished with stoppers or lids. The heating furnace in this
case is fed as usual with coal, and in all cases the air furnaces are provided
with dampers for regulating the draught and the heat.
I do not recommend the use of this reverberatory furnace for making steel,
except where an accumulation of metal is required for a large casting; in all
ordinary operations I prefer one of the two first forms, but I give this as one
mode of construction in which my essential principle, namely, the separation
of the heating from the fluxing furnace, is applied.
In my non-reverberatory furnaces there is an annular chamber surrounding
fire-brick cylinders, which chamber is for the reception of the coke for heating;
the coke rests on fire bars at bottom, and extends to nearly the top of the
chamber just below the aperture into the flue, in which a damper is fitted.
The fire-brick cylinders are formed with flanges and rest on one another; they
are cedented together with fire clay. The bottom cylinder opens into the
crucible. The cylinders are fed at top with the ores, fluxes, &c., after which
the upper cylinder is closed by means of a lid or cover.
The whole rests upon a firm column of masonry in the midst of an ash-pit.
There is a dam, over which, as it rises, the cinder flows away.
The fore part of
the crucible and dam are accessible by an arched oven of fire brick, with aper-
tures to let in the heated air (like an ordinary muffle for cupelling), which
oven is closed by a door at pleasure.. Where a mere draught is used the ash-
pitis open in the usual mode, but where a blast is used it is closed air-tight by
a door, which can be opened to keep the bars clean and to clean the ash-pit.
The tap hole is at the side of the furnace, and is accessible by an appropriate
aperture and fire-brick gutter for casting. The furnace may be from 6 to 8
feet, more or less, from the fire bars, and the sides must be furnished with
holes closed by glasses (as in some cupolas), through which the workman can
watch and estimate the heat. Where a blast is used 1 prefer hollow fire bars,
through which a current of water passes to keep them cool.
In the reverberatory heating furnace thesmelting cylinders have no crucible,
but each has a tap hole accessible by a door in the outer furnace; and when
the fusion is complete they are all tapped at once, and the metal and cinder

page_text: let into a common crucible, as in an ordinary air foundry cupola; this form
also is applicable to the re-melting of steel ingots for heavy castings.
In putting the furnaces first described into blast, great care must be taken
not to let the steel "set" in the hearth, which it will be apt to do, until the
furnace is at its proper heat. The best mode will be to fill the crucible with
scrap steel, which will keep the materials out of it, and will melt and get
possession of the crucible, and then, as it fills from above by the accession of
fresh steel from the ore, it can be tapped and continued in action.
The second part of my Invention relates to the making in pots, or in one of
the afore-described or other furnaces, of steel directly from those richer ores of
iron which are free as can be from sulphur and phosphorus.
For this I employ several kinds of fluxes, viz.,-
1. Cyanide of potassium or of sodium;
2. Cryolite or fluoride of sodium and aluminium;
3. Pure alumina or kaolin combined with quicklime, or quicklime and
caustic magnesia derived from magnesian limestone.
The second flux, obtained from Greenland, is costly, I therefore use it only
where the earthy matter in the ore is very small, and wholly silica or nearly
so. In this application the silica is acted on by the fluorides, and a glass or
qaasi glass is formed, while the oxide is left to the reaction of the reducing
charcoal employed. The quantity used is to be such as to form a fluoride of
silicon.
When I employ the cyanides in (1), I prefer to do so in cases in which
silica is largely present, and is the only earth, or almost the only earth, present.
in the ore, because, in point of economy, the resulting glass or silicate of
potash or soda is the more valuable in reduction of the cost of the fluxes. I
use such a proportion of the cyaride (one or other) as shall wholly reduce the
oxide of iron, which proportion, when the state of oxidation and the per-centage
of oxide in the ore is known, may be readily computed by.the known rules of
chemical equivalents. I add a small quantity of charcoal to insure the ade-
quate carbonization of the steel, in case the carbon of the cyanide should not
suffice for it. When I use pure alumina and lime (such lime being quick
lime, derived either from common limestone or from magnesian limestone, free
as far as may be from silica), I adjust the several earths to each other in the
aggregate of the ore and fluxes, according to the method laid down in my
former Patent Specifications, namely, so that the silica shall be as 3, the lime
as 2, and the alumina as 1, and reckoning every 5 parts of magnesia as
equivalent to 7 parts of lime (nearly), according to the law of isomorphous
combinations.

page_text: Where I do not employ the cyanides, I use charcoal for the reducing and
the cementing agent, in the well-known usual mode of mettalurgical assays
in iron.
Great attention must be paid to the heat and the draught, or the blast
regulated accordingly, but the experienced steel melter can easily effect this,
whether the work be carried on in pots or in the furnaces described above.
If the ores contain water or carbonic acid, they must be carefully calcined, so
as not to be allowed to vitrify on any account. In all cases the materials must
be ground fine, and if the ores be deficient in manganese the peroxide of man-
ganese must be added in such a quantity as to confer the welding property.
All the materials besides being ground fine must be well mixed together
in large quantities, so as to insure as faras possible uniformity in the aggregate
combination.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Sir Francis Charles Knowles in the Great Seal Patent
Office on the 17th September 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, SIR FRANCIS
CHARLES KNOWLES, of Lovell Elill, in the County of Berks, Baronet, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of March, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twentieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Sir Francis Charles Knowles, Her special licence that I, the said Sir
Francis Charles Knowles, my executors, administrators, and assigns, or such
others as I, the said Sir Francis Charles Knowles, my executors, administra-
tors, 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 IMPROVEMENTS IN THE MANUFACTURE OF CAST STEEL,"
upon the
condition (amongst others) that 1, the said Sir Francis Charles Knowles, 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 he
performed, and cause the same to be filed in the Great Seal Patent Office

page_text: Letters Patent.
NOW KNOW YE, that I, the said Sir Francis Charles Knowles, do hereby
declare the nature of my 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 Drawings hereunto annexed, that
is to say:
The first part of my Invention is the construction of furnaces, either air or
blast, whereby the manufacture of cast steel from the ore becomes a continuous
operation.
This furnace, whether an air or a blast furnace, consists of two essential
parts, the outer part or the heating furnace, and the inner part, called the
reducing, cementing, and fluxing," or the "smelting" furnace.
The complete separation of these two parts allows of the employment of
coke, even the sulphurous, for the purpose of heating, and of charcoal for that
of reincing the oxide of iron in the ore, and carburizing the metal into the
state of steel before it is smelted and separated from the cinder or scoria.
These fornaces are open at the top, so as to allow of their being fed con-
tinuously, the one with coke, the other with the appropriate materials for
making steel from the ore by reducing, cementing, and fluxing. They admit of
being closed by fire-brick lids or stoppers after charging, but apertures must
be left for the escape of the gases, which must be carried away from the
heating furnace by a flue or chimney stack in the ordinary way. In another
form the furnace is reverberatory, and the cementing, and reducing, and
smelting chambers are erected within it, and are fed through the top of the
heating furnace, where they are furnished with stoppers or lids. The heating
furnace in this case is fed as usual with coal, and in all cases the air furnaces
are provided with dampers for regulating the draught and the heat.
I do not recommend the use of this reverberatory furnace for making steel,
except where an accumulation of metal is required for a large casting; in all
ordinary operations I prefer one of the two first forms, but I give this as one
mode of construction in which my essential principle, namely, the separation
of the heating froin the fluxing furnace, is applied.
In
my non-reverberatory furnaces there is an annular chamber surrounding
fire-brick cylinders, which chamber is for the reception of the coke for heat-
ing; the coke rests on fire bars at bottom, and extends to nearly the top of
the chamber just below the aperture into the flue, in which a damper is fitted.
The fire-brick cylinders are formed with flanges and rest on one another;
they are cemented together with fire clay. The bottom cylinder opens into

page_text: The whole
There is a
the crucible. The cylinders are fed at top with the ores, fluxes, &c., after
which the upper cylinder is closed by means of a lid or cover.
rests upon a firm column of masonry in the midst of an ash-pit.
dam, over which, as it rises, the cinder flows away. The fore part of the
crucible and dam are accessible by an arched oven of fire brick, with apertures
to let in the heated air (like an ordinary muffle for cupelling), which oven is
closed by a door at pleasure. Where a mere draught is used the ash-pit is
open in the usual mode, but where a blast is used it is closed air-tight by a
door, which can be opened to keep the bars clean and to clean the ash-pit.
The tap hole is at the side of the furnace, and is accessible by an appropriate
aperture and fire-brick gutter for casting. The furnace may be from 6 to 8
feet, more or less, from the fire bars, and the sides must be furnished with
holes closed by glasses (as in some cupolas), through which the workmen can
watch and estimate the heat by the usual indications known in present
practice. Where a blast is used I prefer hollow fire bars, through which a
current of water passes to keep them cool.
In the reverberatory heating furnace the smelting cylinders have no crucible,
but each has a tap hole accessible by a door in the outer furnace; and when
the fusion is complete they are all tapped at once, and the metal and cinder
let into a common crucible, as in an ordinary air foundry cupola; this form
also is applicable to the re-melting of steel ingots for heavy castings.
In putting the furnaces first described into blast, great care must be taken
not to let the steel "set" in the hearth, which it will be apt to do, until the
furnace is at its proper heat The best mode will be to fill the crucible with
scrap steel with a little glassy cinder, which will keep the materials out of it,
and will melt and get possession of the crucible, and then, as it fills from
above by the accession of fresh steel from the ore, it can be tapped and
continued in action.
The next part of my Invention relates to the making in pots, or in one of
the afore-described or other furnaces, of steel directly from those richerores of
iron which are free as can be from sulphur and phosphorus. For this I
employ several kinds of fluxes, videlicet,―
1. Cyanide of potassium or of sodium;
2. Cryolite or fluoride of sodium and aluminium;
3. Pure alumina or kaolin combined with quicklime, or with or without
quicklime or caustic magnesian lime derived from magnesian limestone.
The second flux, obtained from Greenland, is costly, I therefore use it only
where the earthy matter in the ore is very small, and wholly silica or nearly
In this application the silica is acted on by the fluorides, and a glass or
So,

page_text: quasi glass is formed, while the oxide is left to the reaction of the reducing
charcoal employed. The quantity used is to be such as to form a fluoride of
silicon.
When I employ the cyanides in (1), I prefer to do so in cases in which
silica is more largely present and is the only earth, or almost the only earth,
present in the ore, because, in point of economy, the resulting glass or silicate
of potash or soda is the more valuable in reduction of the cost of the fluxes.
But I claim in all cases the use of the said cyanides in reducing and cementing
iron ores for steel. I use such a proportion of the cyanide (one or other) as
shall wholly reduce the oxide of iron, which proportion, when the state of
oxidation and the per-centage of oxide in the ore is known, may be readily
computed by the known rules of chemical equivalents. I add a small quantity
of charcoal to insure the adequate carburization of the steel in case the
carbon of the cyanide should not suffice for it. When I use pure alumina or
kaolin and lime (such lime being quicklime, derived either from common
limestone or from magnesian limestone, free as far as may be from silica), 1
adjust the several earths to cach other in the aggregate of the ore and fluxes,
according to the method laid down in my former Patent Specifications,
namely, so that the silica shall be as 3, the lime as 2, and the alumina as 1,
and reckoning every 5 parts of magnesia as equivalent to 7 parts of lime
(nearly), according to the law of isomorphous combinations.
Where I do not employ the cyanides, I use charcoal for the reducing and
the cementing agent, in the well-known usual mode of metallurgical assays in
iron, taking care to calculate according to the nature and quantity of oxide
and the temper of the steel required.
Great attention must be paid to the heat, and for that purpose the draught
or the blast regulated accordingly, but the experienced steel melter can easily
effect this, whether the work be carried on in pots or in the furnaces described
above. If the ores contain water or carbonic acid, they must be carefully
calcined, so as not to be allowed to vitrify on any account. In all cases the
materials must be ground fine, and if the ores be deficient in manganese the
peroxide of manganese must be added in such usual quantity as to confer
the welding property. All the materials, besides being ground fine, must be
well mixed together in large quantities, so as to insure as far as possible
uniformity in the aggregate combination.
The Drawings hereunto annexed illustrate the manner in which my improved
furnaces are constructed.
Figure 1 represents a vertical section of the furnace, with its central pipe A
for reducing, cementing, and fluxing the ore charcoal and fluxes. P, P, are

page_text: the blast pipes; D is the dam. The crucible C is shewn adjoining the dam.
E is the cinder; F is the steel, filling up the crucible; above the steel are
the steel-producing materials. At the top are seen the apertures G, G, G, for
charging the furnace B, B, with coke and materials; they are covered by
stoppers.H, H, H. The arched muffle I is seen sideways in action, perforated by
holes J, J, to admit heat Under the crucible are seen the flues K, K³, which
distribute the heat at the bottom of it; L is the ash-pit; the fire bars M
are indicated by dotted lines. A door at D' closes the muffle when the work-
man does not require to inspect the interior of the fore hearth.
Figure 2 represents the side of the furnace in which the dam is placed.
The arched muffle A, A, is opened to shew the fore hearth or crucible, the
shaded horizontal lines of which represent the cinder or scoria derived from
the earthy matter and the finxes. The vertical lines A, A, represent the
. position of the central pipes forming the reducing, cementing, and fluxing
furnace or retort. The door of the hearth is shewn by the dotted lines D', D';
it can be raised or lowered at pleasure by the usual application of a lever and
chain. The stoppers EL, H, are seen at the top of the building, as in Figure 1.
The Drawing is made to shew both forms of the furnace; the one in which the
air is supplied by a draught, as in an ordinary wind furnace, the other in which
the air is delivered by blast pipes P, P. In the former case the ash-pit Lis
open as usual; in the latter it is air-tight, but accessible by manholes, as
shewn at Q, Q, in Figure 3. The products of combustion pass off by the
flue R into the chimney S.
Figure 3 represents the side of the furnace, in which is the táp hole N and
the gutter N (indicated by dotted lines) for running out the steel. O is the
brickwork or masonry, which supports the crucible and interior pipe; the
fire bars are seen in dotted lines M, M ; Q, Q, are the manholes.
And having now described the nature of the said Invention, and in what
manner the same is to be performed, I declare that I claim,-
First, the construction and arrangement of furnaces in which the heating
and the chemical or reducing and smelting parts are separate, as herein-
before described.
Second, theconstructionandarrangement of furnacesherein-beforedescribed,
and represented in the Drawings hereunto annexed.
Third, the employment of the cyanides of sodium and potassium in making
steel from the ores, as herein-before described, with or without charcoal.
Fourth, the employment of cryolite of pure alumina or of kaolin in the
making of steel from ores of iron, the two latter being combined with lime,
common or maguesian, as herein-before described.

page_text: Fifth, the employment of kaolin in conjunction with lime for the manu-
facture of steel in ordinary blast furnaces, the lime being either common or
derived from magnesian limestone, and the earths being in the aggregate
adjusted as herein-before described.
Sixth, the employment of the cyanides before mentioned in conjunction with
the other fluxes, viz., kaoliu or alumina and lime or cryolite, and of cryolite
kaolin, or alumina and lime.
In witness whereof, 1, the said Sir Francis Charles Knowles, have
hereunto set my hand and seal, this Sixteenth day of September, in
the year of our Lord One thousand eight hundred and fifty-seven.
FRANCIS CHARLES KNOWLES. (L.s.)