A NEW OR IMPROVED METHOD OF PURIFYING AND CONVERTING CAST IRON INTO MALLEABLE IRON OR INTO STEEL, AND FOR THE MAKING AND USE OF MATERIALS AND APPLIANCES FOR THE SAME
Year: 1869

page_text: LETTERS PATENT to Francis Charles Knowles, of Lovell Hill, in the
County of Berks, Baronet, for the Invention of "A NEW OR IMPROVED
METHOD OF PURIFYING AND CONVERTING CAST IRON INTO MALLEABLE IRON OR
INTO STEEL, AND FOR THE MAKING AND USE OF MATERIALS AND APPLIANCES
FOR THE SAME."
Sealed the 6th July 1869, and dated the 8th May 1869.
PROVISIONAL SPECIFICATION left by the said Francis Charles Knowles
at the Office of the Commissioners of Patents, with his Petition,
on the 8th May 1869.
I, FRANCIS CHARLES KNOWLES, of Lovell Hill, in the County of
Berks, Baronet, do hereby declare the nature of the said Invention for
"A NEW OR IMPROVED METHOD OF PURIFYING AND CONVERTING CAST IRON INTO
MALLEABLE IRON OR INTO STEEL, AND FOR THE MAKING AND USE OF MATERIALS
AND APPLIANCES FOR THE SAME," to be as follows:-
The first part of my Invention consists of a method whereby I retain
below a bath of molten cast iron the chemical substances employed in
A

page_text: the purification or conversion thereof, in order to prevent such substances
from rising to the surface by reason of their less specific gravity before
their reactions upon the metal have taken place. I pour any suitable
cast iron in a thin stream into a cistern of water. By means of this the
metal is separated into small hollow grains or spherical particles, which
fall to the bottom of the cistern. It is called "shotting" the metal, and
is well known. These small shot of cast metal I collect, and I spread
at the bottom of my crucible, ladle, or other converting vessel a thin
layer thereof above the chemical substances employed. This layer must
not be so thick but that it may in a short time be melted up by the
great mass of molten iron above it and diffused therein, but thick enough
to bring the chemical substances into action by degrees. The thickness
of the layer will depend partly upon the weight of metal treated, partly
upon the fusibility of the shot, and partly upon the rapidity with which
the chemical substances used come into full action. This thickness in
given cases is to be ascertained only by actual trial.
I do not claim the process itself of shotting the metal, but I claim
only the peculiar use of the shot so formed in keeping down under the
charge of molten cast iron the chemical substances used in its purifi-
cation and conversion.*
The second part of my Invention is the use of caustic soda as it comes
from the alkali works to mix with pulverised ores of the oxides of iron
or of manganese, or both of these, or to mix with other oxiding sub-
stances, for the purpose of affording a base to take up the phosphoric
acid formed from the phosphorous of the cast iron, and the silicic acid
or silicie formed from the silicon of the same in the processes of purifying
or converting such cast iron into malleable iron or into steel, and also
for the purpose of obtaining more fluid scoria or cinders.
I claim the use of the said caustic soda however mixed in such use.
The third part of my said Invention is the use of the permanganate of
soda, which I employ as an ozidizer to purify cast iron or cast steel,
especially the finer qualities of cast steel, from silicum, sulphur, and
phosphorous, to furnish an alkaline base for the acids formed therefrom,
and to render the scoria more liquid and lighter in the casting of
the metal.
I claim the use of permanganate of soda for the above purposes. The
proportions of the two last-mentioned substancies used depend on the
amount per cent. of the metal, of the carbon, and of the impurities to be

page_text: removed; they must be at least such as to afford oxygen in due chemical
proportions to the elements which are to be oxydised, so as to form
therefrom carbonic oxide, silicic acid or silica, sulphurous acid, and
phosphoric acid, as the case may be, and to afford an alkaline base
respectively.
The fourth part of my said Invention is the making or preparation of
a gas of great heating power to be used in the purification and conversion
of cast iron into malleable iron or into steel. I herein call it "lime
gas," and I obtain it as follows:-I grind up or reduce to a fine powder
any kind of limestone or chalk, and I mix therewith powdered charcoal,
coke, or anthracite coal, the two last as free from sulphur as possible.
I use for ordinary or magnésian limestone or chalk from about 18 to 25
per cent. for pure carbon as the standard according to the richness of the
fuel in carbon. This mixture I submit to a very strong heat in close
retorts, and, to insure as far as may be the absence of carbonic acid gas,
I place a layer of the carbonaceous matter used over the surface of the
mixture between it and the exit pipe of the gas leading to the gasometer,
or if preferred directly to the converting furnace, or other converting or
refining apparatus; or, which is in effect the same thing, I calcine small
fragments of the limestone or of chalk in close retorts, and having
collected the gas thence evolved I pass it through highly-heated closed
retorts containing small lumps of charcoal, coke, or anthracite coal, the
lumps not being so small as to much impede the flow of the gas to the
exit pipes leading from the retort to the gasometer, to the furnace, or
to the converting or refining apparatus. The calcined lime after tho
operation may be economically used as a flux in the blast furnace.
I claim the above methods of preparing the said gas as one species of
gaseous fuel which I use in my said method of purifying or converting
cast metal into iron or into steel. I use also two other kinds of gaseous
fuel in my said method, as described herein-after; but I do not claim any
mode of preparing the latter gases, I claim only the peculiar mode of using
them in common with the first above-mentioned gas. The first of the last-
mentioned gases are the gases evolved from the blast furnaces or cupolas,
or generators in which nearly the same gases are produced. The second
of these is what may be termed "water gas." This gas is prepared by a
method (described by John Samuel Dawes, under his Patent, 1835,
December 9, No. 6948, and by William Henry Dawes, under his Patent,
1859, July 8, No. 1620), which method consists essentially in passing

page_text: jets of superheated steam through carbonaceous matters in closed retorts
externally heated. These three kinds of gas, separately or mixed
together, I make use of in the manner herein-after described, the only
precaution taken being to free them by any of the known methods
from dust and from carbonic acid gas. I use with them air, cold air,
or highly heated air, though the last is most efficient. I use them in
the purifying, refining, and converting of cast iron into malleable iron
or into steel (as the case may be) by means of chemical substances or
re-agents, namely, by mixing the said gases with common air or air
highly heated, and in the exact proportion due to a perfect combustion,
and no more, in order by such combustion to furnish an external and
independent source of heat for the purpose of retaining in the fluid
state or of otherwise more highly heating the molten metal while the
chemical reactions are going on, and until they are fully completed.
The essence of this part of my Invention is the passing of the said
mixture of air, or of heated air and gases, in such said proportions
upwards or downwards through the body- of the metal, so that the
combustion of the gases may take place thercin and impart its heat
thereto.
I have two methods of applying this source of heat, both alike in
effect but differing slightly in the application.
The first is that of purifying and refining cast iron and converting it
into malleable iron or into steel, which may be run out into moulds or
into ingots. This I effect in a common ladle or other converting vessel,
as follows:-I fix up in a convenient situation a water tuyere, and below
it I place a moveable table or platform, on which the ladle or other
converting vessel can be firmly fixed, and admitting of adjustment in
any position by appropriate mechanism. I then so adjust the position
of the ladle as that the nozzle of the water tuyere may dip vertically
nearly to the bottom of the vessel. This tuyere must be long enough to
admit of the application to it of a blast pipe much above the lip of the
vessel in order to protect the pipe against the intense heat evolved. The
blast pipe must be fixed and luted quite air-tight into the tuyere. In
order to still farther protect the pipe and tuyere, they should be sur-
rounded with a jacket made of highly refractory materials, such as
best fire-clay beaten up with plumbago, pulverized stone, coal, or other
matter, and well baked..
The chemical substances to he used may be placed as a "fettling" in

page_text: the ladle, or thrown in in pellets (as by David Mushet, under his
Patent, 1835, October 22, No. 6908), or injected with the blast (as by
John Samuel Dawes, under his Patent of 1831, December 22, No. 6207,
and by Samuel Marlow Banks, under his Patent of 1840, April 6,
No. 8479). I claim no special mode of doing this. Things being so
ordered as above, I pour into the ladle or other converting vessel the
desired charge of molten cast iron from a cupola, and I then convey the
ladle to its place upon the above-described platform, and there fix and
adjust it to the tuyere. At the same moment I let on the blast of the
gases above named mixed with the air or with the heated air in the
proportion due to complete combustion as aforesaid; and I continue
the blast until the required reactions of the chemical substance, the
purification and refinement of the cast metal, and its conversion into
malleable iron or into steel are completed. The ladle is then removed
for pouring the metal into moulds or ingots, or otherwise treating it.
The second method is a method of treating cast iron for the production
of iron or of steel preparatory to the puddling thereof whereby the
puddler is relieved from almost of all that severe labour and exposure to
heat which precede the collecting of the balls of malleable iron or puddled
steel for the hammer or the squeezer in order to roll the metal into bars.
Previously to the use of the common puddling furnace I employ a
furnace or hearth somewhat resembling the common finery both in
appearance and in construction, but differing therefrom in this respect
that in the cast-iron troughs or water blocks which form the sides
of the finery furnace are placed in my present method permanent water
tuyeres, which are kept cool by the same current of cold water which
cools the troughs or blocks themselves. These tuyeres are continued
down to the surface of the hearth itself; they are cast in one solid
pięce with the troughs, and are bored out when cold. They communicate
by means of apertures countersunk to meet the bore at the lowest point
directly with the metal bath itself, so that the blast of the above-described
gascous mixture with air may be driven through the body of that metal.
The tuyeres and their apertures are not exactly opposite to each other.
It is advisable to line both the sides of this hearth and the bottom with
5 slabs of the most refractory material. The blast pipes which enter the
tuyeres must be firmly fixed and luted in so that there may be no
escape of the gaseous mixture. The bottom or sole of the hearth is best
formed of a hollow cast-iron piece, through which a current of cold air

page_text: must be made to pass in order to keep the sole cool. This apparatus 1
call a "converting finery," and I claim as my Invention the above con-
struction of the troughs and tuyeres. It may be made either a separate
structure, or it may be placed under the same vaulted cavity as the
puddling furnace, and lead to a common chimney; but in either case it
must be so placed as to admit of the charges of refined or nearly con
.verted metal being run into the puddling furnace. The metal to be
purified and refined must be melted in a cupola at hand, and the charges
as required must be poured into the converting finery by an opening
therein for the purpose from the orucible of the cupula, which should be
somewhat elevated above the level of the finery. Before the hot charge
is thus let in the fettling of the hearth must be made with the materials
preferred, taking care not to obstruct the blast holes. The chemicals
to be used may be applied by any of the methods referred to above to
the bath of molten cast iron. The hearth being thus prepared I let on
the blast (under the pressure depending on the depth of the metal) of
one or other of the above gases combined with cold air or with highly
heated atmospheric air in the exact proportion required for perfect
combustion and no more. The gas in burning heats intensely the metal
and the chemical substances in contact with it, while the carbonic acid
gas, the principal product of the combustion, and the nitrogen of the air
do the work of the puddler in agitating, stirring, and mixing the contents
of the finery while subjected to the chemical reactions. The quantity
per minute of time of the gaseous mixture to be used cannot be numeri-
cally defined, as it varies with the nature and degree of fusibility of the
metal itself; but it may be generally described to be such as may suffice
to keep the metal bath somewhat above the original temperature. It
should also be increased as the operation advances in order to meet the
diminished fusibility of the metal due to the abstraction of its carbon
and of its impurities, also in case it may be desired to add carbon to the
use of spiegeleisen or otherwise, and to reduce the oxide of iron present,
The operation must be watched so as to learn the exact moment when
the carbon is almost all oxidized or burned away. The time will vary
with the richness of the metal in carbon and in impurities, but the
moment may be readily known by cutting off the gas and blowing in for
a moment a small jet of pure air. If this does not give out a blue flame
at the surface the operation is completed, and the refined metal is ready
for the puddler. The finery then being run out into the puddling furnace
the blast is turned off, the hearth is cleaned and refettled, the tuyeres are

page_text: carefully examined, and all needful preparations are made for the intro-
duction of a fresh charge.
I claim as my Invention, the construction of the above finery and
the use therein of the said gaseous mixture with cold or with heated air
as described, and that even where there may be a slight excess of air,
provided that there be used therewith such a quantity of the gaseous
mixture as would develope considerable heat, such being the end and
object and means of my process. It may be an object to thus accelerate
the operation even at a small loss of metal, but this is no. part of my
design, which is to sacrifice as little metal as possible; and further,
no carbon must on any account be consumed by excess of air therein.
And now in order to define more clearly that I herein claim I
must explain that I do not claim the use of the two last-mentioned
gases or similarly generated gases in puddling in the ordinary way;
but what I do claim is, the passing through the body of the metal
by such means as the above or by the like means a mixture of air
and of one or other or all of such gases above described in the proportion
due to a perfect or nearly perfect combustion, and that whether the
air be heated or not, though it is more efficient to use it highly heated
for the purpose of sustaining an adequate heat, and for mechanically
stirring and mixing the metal by the action of the gaseous products
of that combustion, which products have no chemical action, while the
chemical reactions are purifying and converting the cast metal; whereas
in puddling with such gases in the ordinary way they are directed on
the surface of the metal, and have a very large excess of air mingled
with them, without which no conversion of the metal into iron or
into steel by puddling could possibly take place.
Again, in order that there may be no misunderstanding of the object,
nature, and application of this and of the former part of my Invention
and no confusion of them with other methods which they may seem
to resemble in part though totally different from them in object, in
principle, and in fact, I enjoin the following precautions:-Great care
must be taken so to adjust the quantities or proportions of the said
gases to the atmospheric air mixed therewith as that the oxygen of
the air may be exactly sufficient for the complete combustion thereof,
and no more, so in fact that there may be no great amount of un-
consumed or free oxygen left after the combustion, as this would only

page_text: harm and waste the metal, which it is my purpose to prevent. All
the oxygenation of the carbon and of the impurities of the metal to
be treated must in my method be effected by the nascent oxygen
in the chemical substances employed. I do not therefore herein propose
or claim the use of streams of oxygen contained in air or otherwise
to heat the metal by burning its carbon or any part of the metal itself,
the essential object of my Invention being to exclude such streams and
to heat the metal or to preserve or to renew its heat by independent
and external means and not by the combustion thereof, or of any
element therein contained. I separate rigidly, both in the converting
ladle and in the converting finery, the heating operation from the
chemical operations, except so far as that the latter may from their
very nature unavoidably evolve heat during the reactions which take
place.
Lastly. I recommend that the puddling which is to succeed the
latter process described should be performed with gas and excess of
air in order to prevent its contamination by dust and sulphur derived
from the coals. I also where possible reserve the carbon of the cast
iron in the preliminary process for the purpose of reducing oxide of
iron and thereby increasing the yield of iron or of steel.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Francis Charles Knowles in the Great Seal Patent
Office on the 8th November 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FRANCIS
CHARLES KNOWLES, of Lovell Hill, in the County of Berks, Baronet,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of May, in the year of
our Lord One thousand eight hundred and sixty-nine, in the thirty-second
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Francis Charles Knowles, Her special licence that
I, the said Francis Charles Knowles, my executors, administrators, and
assigns, or such others as I, the said Francis Charles Knowles, 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

page_text: 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 "A NEW OR IMPROVED
METHOD OF PURIFYING AND CONVERTING CAST IRON INTO MALLEABLE IRON OR INTO
STEEL, AND FOR THE MAKING AND USE OF MATERIALS AND APPLIANCES FOR THE
SAME," upon the condition (amongst others) that I, the said 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 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.
NOW KNOW YE, that I, the said 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 Drawing
hereunto annexed, that is to say: -
The first part of my Invention consists of a method whereby I retain
below a bath of molten cast iron the chemical substances employed
in the purification or conversion thereof, in order to prevent such
substances from rising to the surface by reason of their less specific
gravity before their reactions upon the metal have taken place. I pour
any suitable cast iron in a thin stream into a cistern of water. By
means of this the metal is separated into small hollow grains or
spherical particles, which fall to the bottom of the cistern. It is called
"shotting" the metal, and is well known. These small shot of cast
metal I collect, and I spread at the bottom of my crucible, ladel, or
other converting vessel a thin layer thereof above the chemical sub-
stances employed. This layer must not be so thick but that it may in
a short time be melted up by the great mass of molten iron above it
and diffused therein, but thick enough to bring the chemical substances
into action by degrees. The thickness of the layer will depend partly
upon the weight of metal treated, partly upon the fusibility of the shot,
and partly upon the rapidity with which the chemical substances used
come into full action. This thickness in given cases is to be ascertained
only by actual trial.
I do not claim the process itself of "shotting" the metal, but I claim
only the peculiar use of the shot so formed in keeping down under

page_text: the charge of molten cast iron the chemical substances used in its
purification and conversion.
The second part of my Invention is the use of caustic soda as it
comes from the alkali works to mix with pulverized ores of the oxides of
iron or of manganese, or of both of these, or to.mix with other oxidizing
substances, for the purpose of affording a base to take up the phosphoric
acid formed from the phosphorous of the cast iron and the silicic acid
or silica formed from the silicon of the same in the processes of
purifying or converting such cast iron into malleable iron or into steel,
and also for the purpose of obtaining more fluid scoriae or cinders.
I claim the use of the said caustic soda however mixed in such usc.
The third part of my said Invention is the use of the permanganate
of soda, which I employ as an oxidizer to purify cast iron or cast steel,
especially the finer qualities of cast steel, from silicium, sulphur, and
phosphorous to furnish an alkaline base for the acids formed therefrom,
and to render the scoriæ more liquid and lighter in the casting of the
metal.
I claim the use of permanganate of soda for the above purposes. The
proportions of the two last-mentioned substances used depend on the.
amount per cent. of the metal, of the carbon, and of the impurities to
be removed; they must be at least such as to afford oxygen in duc
chemical proportions to the clements which are to be oxidized, so as to
form therefrom carbonic oxide, silicic acid, or silica, sulphurous acid, and
phosphoric acid, as the case may be, and to afford an alkaline base re-
spectively, but at the same time in the case of cast steel such as to leave
in it the carbon due to its required temper.
The fourth part of my said Invention is the making or preparation
of a gas of great heating power to be used in the purification and
conversion of cast iron into malleable iron or into steel. I herein call it
"lime gas," and I obtain it as follows:-I grind up or reduce to a fine
powder any kind of limestone or chalk, and I mix the earth, powdered
charcoal, coke, or anthracite coal, the two last as free from sulphur as
possible. I use for ordinary or magnesian limestone or chalk from
about 13 to 25 per cent. of the weight of the same, taking about 13 per
cent. for pure carbon as the standard according to the richness of the
fuel in carbon. This mixture I submit to a very strong heat in close
retorts, and to insure as far as may be the absence of carbonic acid
gas, I place a layer of the carbonaceous matter used over the surface of

page_text: converting or refining apparatus; or, which is in effect the same thing,
I calcine small fragments of the limestone or of chalk in close retorts,
and having collected the gas thence evolved I pass it through highly
heated closed retorts containing small lumps of charcoal, coke, or
anthracite coal, the lumps not being so small as to much impede the
flow of the gas to the exit pipe leading from the retort to the gasometer,
to the furnace, or to the converting or refining apparatus. The calcined
lime after the operation may be economically used as a flux in the blast
furnace.
I claim the above methods of preparing the said gas as one species of
gaseous fuel which I use in my said method of purifying and converting
cast metal into iron or into steel. I also use two other kinds of gascous
fuel in my said method, as herein-after described; but I do not claim any
mode of preparing the latter gases, I claim only the peculiar mode of
using them in common with the first above-mentioned gas. The first
of the last-mentioned gases are the gases evolved from blast furnaces or
cupolas, or generators in which nearly the same gases are produced.
The second of these is what may be called "water gas." This gas is
prepared by a method (described by John Samuel Dawes, under his
Patent, A.D. 1835, December 9, No. 6948, and by William Henry
Dawes, under his Patent, A.D. 1859, July 8, No. 1620), which method
consists essentially in passing jets of superheated steam through
carbonaceous matters in closed retorts externally heated. These three
kinds of gas, separately or mixed together, I make use of in the manner
herein-after described, the only precaution taken being to free them by any
of the known methods from dust and from carbonic acid gas. I use with
them air, cold air, or highly heated air, though the last is most efficient.
I use them in the purifying, refining, and converting of cast iron into
malleable iron or into steel (as the case may be), by means of chemical
substances or reagents, namely, by mixing the said gases with common
air or air highly heated, and in the exact proportion due to a perfect
combustion and no more, in order by such combustion to furnish an
external and independent source of heat for the purpose of retaining in
the fluid state or of otherwise more highly heating the molten metal
while the chemical reactions are going on, and until they are fulled
completed.

page_text: The essence of this part of my Invention is the passing of the said
mixture of air, or of heated air and gases, in such said proportions
upwards or downwards or otherwise through the body of the metal,
so that the combustion of the gases may take place therein and impart
its heat thereto.
I have two methods of applying this source of heat, both alike in
effect but differing slightly in the application.
The first is that of purifying and refining cast iron and converting
it into malleable iron or into steel, which may be run out into moulds
or into ingots. This I effect in a common ladle or other converting
vessel, as follows:-I fix up in a convenient situation a water tuyere,
and below it I place a movable table or platform, on which the ladle or
other converting vessel can be firmly fixed and admitting of adjustment
in any position by appropriate mechanism. I then so adjust the position
of the ladle as that the nozzle of the water tuyere may dip vertically
nearly to the bottom of the vessel. This tuyere must be long enough to
admit of the application to it of a blast pipe much above the lip of the
vessel in order to protect the pipe against the intense heat evolved.
The blast pipe must be fixed and luted quite air-tight into the tuyere.
In order to still farther protect the pipe and tuyere they should be
surrounded with a jacket made of highly refractory materials, such as
best fire clay or china clay beaten up with plumbago, pulverized stone,
or coal, and well baked.
The chemical substances to be used may be placed as a "fettling"
in the ladle or thrown in pellets (as by David Mushet under his
Patent, A.D. 1835, October 22nd, No. 6908) or injected with the blast
(as by John Samuel Dawes under his Patent of A.D. 1831, December
22nd, No. 6207, and by Samuel Marlow Banks under his Patent of
A.D. 1840, April 6th, No. 8479. I claim no special mode of doing this.
Things being so ordered as above, I pour into the ladle or other con-
verting vessel the desired charge of molten cast iron from a cupola,
and I then convey the ladle to its place upon the above-described
At the same
platform, and there fix and adjust it to the tuyere.
moment I let on the blast of the gases above named mixed with the air
or with the heated air in the proportion due to complete combustion
as aforesaid; and I continue the blast until the required reactions of
the chemical substances, the purification and refinement of the cast
metal, and its conversion into malleable iron or into steel are completed.

page_text: The ladle is then removed for pouring the metal into moulds or into
ingots, or otherwise treating it.
The second method is a method of treating cast iron for the pro-
duction of iron or of steel preparatory to the puddling thereof whereby
the puddler is relieved from almost all of that severe labour and exposure
to heat which precede the collecting of the balls of malleable iron or
puddled steel for the hammer or the squeezer, in order to rolling the
metal or hammering it into bars.
Previously to the use of the common puddling furnace, I employ a
furnace or hearth somewhat resembling the common finery both in
appearance and in construction, but differing therefrom in this respect,
that in the cast-iron troughs or water blocks which form the sides of
the finery furnace are placed in my present method permanent water
tuyeres, which are kept cool by the same current of cold water which
cools the troughs or blocks themselves. These tuyeres are continued
down to the surface of the hearth itself, or to any point below the
surface of the metal; they are cast or otherwise formed in one solid
piece with the troughs, and if cast are bored out when cold. They
communicate by means of apertures countersunk to meet the bore at
the lowest point, or at some point below the surface of the metal,
directly with the metal bath itself, so that the blast of the above-
described gaseous mixture with air may be driven through the body
of that metal. The tuyeres and their apertures are not exactly
opposite to each other. It is advisable to line both the sides of this
hearth and the bottom with slabs of the most refractory material. The
blast pipes which enter the tuyeres must be firmly fixed and luted in,
so that there may be no escape of the gaseous mixture. The bottom
or sole of the hearth is best formed of a hollow cast-iron piece, through
which a current of cold air or of cold water must be made to pass in
order to keep the sole cool. This apparatus I call a "converting finery,"
and I claim as my Invention the above construction of the troughs and
tuyeres. It may be made either a separate structure, or it may be
placed under the same vaulted cavity as the puddling furnace, and lead
to a common chimney, but in either case it must be so placed as to
admit of the charges of refined or nearly converted metal being run
into the puddling furnaces. It may be made, moreover, either a fixed
structure or one movable from place to place by appropriate mechanism,
and made so as to admit of casting the metal into moulds or other

page_text: receptacles. The metal to be purified and refined must be melted in
a cupola at hand, and the charges as required must be poured into the
converting finery by an opening therein for the purpose from the
crucible of the cupola, which should be somewhat elevated above the
level of the finery. Before the hot charge is thus let in the fettling
of the hearth must be made with the materials preferred, taking care
not to obstruct the blast holes. The chemicals to be used may. be
applied by any of the methods referred to above to the bath of molten
cast iron. The hearth being thus prepared I let on the blast (under
pressure, depending on the depth of the metal) of one or other of the
above gases combined with cold air or with highly heated atmospheric
air in the exact proportion required for perfect combustion and no more.
The gas in burning heats intensely the metal and the chemical sub-
stances in contact with it, while the carbonic acid gas, the principal
product of combustion, and the nitrogen of the air do the work of the
puddler in agitating, stirring, and mixing the contents of the finery
while subjected to the chemical reactions.
In the Drawing annexed I illustrate in an isometrical perspective view
a portion of one of the water blocks as above referred to with the water
supply pipe A leading to the top of the block; T, T, are the entrances
of the tuyeres, these entrances are bored out of the solid wall of the
water block, which is of greater thickness at that part for that purpose;
S, S, are the countersunk holes at the level of the sole or hearth. The
arrow indicates the axis of the tuyere in the opposite side of the
finery. The blast enters the furnace at the lower part at S, S, and is
instantly ignited in a column of intense flame. The dimensions depend
on the weight or height of the charge; when it is deep other tuyeres
at the places 8, 8, may be employed in conjunction with the others.
The quantity per minute of time of the gaseous mixture to be used
cannot be numerically defined as it varies with the nature and degree
of fusibility of the metal itself, but it may be generally described to
be such as may suffice to keep the metal bath somewhat above its
original temperature. It should also be increased as the operation
advances, in order to meet the diminished fusibility of the metal due
to the abstraction of its carbon and of its impurities, also in case it be
desired to add carbon by the use of "spiegeleisen" or otherwise, and to
reduce the oxide of iron present the operation must be watched so as to
learn the exact moment when the carbon is almost all oxidized or burnt
away. The time will vary with the richness of the metal in carbon and

page_text: in impuritics, but the moment may be readily known by cutting off the
gas and blowing in for a moment a small jet of pure air; if this does not
give out a bluish flame at the surface the operation is completed and, the
refined metal is ready for. the puddler. The finery then being run out
into the puddling furnace the blast is turned off, the hearth is cleaned
and refettled, tuyeres are carefully examined, and all needful prepara-
tions are made for the introduction of a fresh charge.
I claim as my Invention the construction of the above finery and the
use therein of the said gaseous mixture with cold or with heated air as
described, and that even where there may be a slight excess of air,
provided that there be used therewith such a quantity of the gaseous
mixture as would develope considerable heat, such being the end and
object and means of my process. It may be an object to thus accelerate
the operation even at a small loss of metal, but this is no part of my
design, which is to sacrifice as little metal as possible; and further, no
carbon must on any account be consumed by excess of air therein in the
general management and conduct of the process.
And now in order to define more clearly what I herein claim I must
explain that I do not claim the use of the two last-mentioned gases or
similarly generated gases in puddling in the ordinary way; but what I do
claim is, the passing through the body of the metal bath by such means
as the above or by like means a mixture of air and of one or other or all
of such gases above described in the proportion due to a perfect or a
nearly perfect combustion, and that whether the air be heated or not,
though it is more efficient to use it highly heated for the purpose of
sustaining an adequate heat, and for mechanically stirring and mixing
the metal by the action of the gaseous products of that combustion,
which products have no injurious chemical action, while the chemical
reactions are purifying and converting the cast metal; whereas in
puddling with such gases in the ordinary way they are directed on the
surface of the metal, and have a very large excess of air mingled with
them, without which no conversion of the metal into iron or into steel
by puddling could possibly take place.
Again, in order that there may be no misunderstanding of the object,
naturé, and application of this and of the former part of my Invention,
and no confusion of them with other methods which they may seem
to resemble in part, though totally different from them in object, in
principle, and in fact, I enjoin the following precautions:- Great

page_text: care must be taken so to adjust the quantities or proportions of the
said gases to the atmospheric air mixed therewith as that the oxygen
of the air may be exactly sufficient for the complete combustion thereof
and no more, so in fact that there may be no great amount of uncon-
sumed or free oxygen left after the combustion, as this would only burn
and waste the metal, which it is my purpose to prevent. All the
oxygenation of the carbon and of the impurities of the metal to be
heated must in my method be effected by the nascent oxygen in the
chemical substances employed. I do not therefore herein propose or
claim the use of streams of oxygen contained in air or otherwise to heat
the metal by burning its carbon or any part of the metal itself, the
essential object of my Invention being to exclude such streams and to
heat the metal, or to preserve or to renew its heat by independent and
external means, and not by the combustion thereof or of any element
therein contained. I separate rigorously, both in the converting ladle
and in the converting finery, the heating operation from the chemical
operations, except so far as that the latter may from their very nature
unavoidably evolve heat during the reactions which take place.
Lastly. I recommend that the puddling which is to succeed the latter
process described should be performed with gas and an excess of air in
order to prevent its contamination hy dust and sulphur derived from the
coals. I also, where possible, reserve the carbon of the cast iron in the
preliminary process for the purpose of reducing oxide of iron and thereby
increasing the yield of iron or of steel.
And having now described the nature of my said Invention, and
in what manner the same is to be performed, I-declare that I claim,-
Firstly. The use of a layer of iron shot for the purpose of retaining
below the bath of molten cast iron the chemical substances employed to
purify and convert it, as herein-before described.
Secondly. The use of caustic soda to furnish an alkaline base for the
various acids (silicic, phosphoric, &c.) generated by oxidizing reagents
during the process of purification of cast iron and its conversion, and to
give more fluid scoriæ, as herein-before described.
Thirdly. The use of permanganate of soda to oxidize the impurities
(silicium, phosphorous, sulphur, &c.) of melted cast iron or of steel,
and to afford to the acids formed thereby an alkaline base as well as to
render the scoriæ mere fluid and lighter, as herein-before described.

page_text: Fourthly. The preparation of a gaseous fuel from limestone or chalk
heated in contact with pure carbonaceous substances or by the passing
through such substances highly heated in separate retorts the gas
previously evolved by heat from limestone or chalk, as described.
Fifthly. The burning within the body or mass of a bath of molten
cast iron or other iron or steel, however contained, a mixture of the gases
from blast furnaces or from generators of similar gases, or of lime gas
the subject of the last claim, or of water gas, as described above, with
atmospheric air, either cold or heated, such mixture being in the exact
proportions as near as may be due to a perfect combustion, and being
driven in a blast upwards or downwards or otherwise, so as to pass
through the interior of the metallic bath, and so as to develope its
heat of combustion and to impart it to the metal in its course through
the same, as herein-before described.
Sixthly. The construction and employment of a finery composed of
hollow iron castings called "water blocks," wherein tuyeres are so cast
or otherwise so formed within the interior of the said castings as to form
one piece therewith, and so as to admit of cooling by one and the same
current of cold water during its passage through the blocks, as herein-
before described and represented in the accompanying Drawing. The
above gaseous mixture with air is to be used in such finery for heating
the bath of molten iron therein during its treatment with chemical
substances.
Lastly. I claim the employment of this finery, whether it be so
constructed as to be a fixed structure or so as to be one capable of
movement and transfer from place to place by some appropriate me.
chanism, and so as to admit of its contents being poured into moulds or
otherwise poured out into other vessels.
In witness whereof, I, the said Francis Charles Knowles, have
in
hereunto set my hand and seal, this Third day of November,.
the year of our Lord One thousand eight hundred and sixty-nine.
ATT
KNOW TO
FRANCIS CHARLES KNOWLES (L.C.)
of Lovell Hill, Berks, Baronet.