IMPROVE- MENTS IN THE MANUFACTURE OF CAST STEEL
Year: 1855

page_text: LETTERS PATENT to Henry Bessemer, of Queen Street Place, New
Cannon Street, in the City of London, for the Invention of "IMPROVE-
MENTS IN THE MANUFACTURE OF CAST STEEL."
Sealed the 11th April 1856, and dated the 17th October. 1855.
PROVISIONAL SPECIFICATION left by the said Henry Bessemer at the
Office of the Commissioners of Patents, with his Petition, on the 17th
October 1855..
I, HENRY BESSEMER, of Queen Street Place, New Cannon Street, in the
City of London, do hereby declare the nature of the Invention for "IMPROVE-
MENTS IN THE MANUFACTURE OF CAST STEEL" to be as follows:-
In order to carry this Invention into practical operation, I construct a furnace
having a long rectangular chambér, the mouth of which is on a level with the
floor of the foundry; the sides and ends of the chamber are vertical and parallel
to each other, and the bottom of it is formed into an elevated ridge, which
extends the whole length of the chamber. This ridge is formed by the apex
of a pointed arch, which is made below it, and is called the "cave." Along each
side of the furnace there are arranged fire bars, which extend from the lower-
parts of the ridge for some distance up the vertical sides of the chamber, tliere
being no fire bars at the bottom of the chamber; the central part of the ridge
is flattened, and there are formed in it at equal distances several holes, over or
into which the lower end of the pots or pot-stands are placed; so as to ensure

page_text: the proper position of the pots. The top of the chamber is covered with large
fire tiles, or with an iron frame in which fire bricks are fixed, several openings
being left to afford access to the pots. Along one side of the furnace there is
a row of square holes leading into a chimney of sufficient height to insure a
powerful draught. The pots I prefer to be of the form known as skittle pots,
with a lid to each, and a tapping hole made in the bottom of them. The pots
should be placed on a stand some four or five inches in height; or the lower
part of the pots may be elongated,.so, as, to form a stand, and be of such a size
as to fit the holes in the top of the ridge, so that access may be had to the
under side of the pots from the cave below. The fuel used should be hard oven
coke, which is supplied from the openings on the upper side of the furnace,
the fuel filling up the spaces round about the pots, and rising as far as the top
of them. The fire bars are placed below the foundry floor, and the air for com-
bustion is supplied from the caves below the furnace, which, when the draught
of the chimney is alone depended on, must have a free communication with the
outer air; but in order to obtain a powerful combustion in the furnace, I prefer
to close up the cave below, and. to employ a blowing fan, by means of which
I force air into the cave, and thus assist the draught of the furnace. In order
to obtain access to the caves, I construct a revolving door, which is made to
act as a valve, and will allow a workman to walk through it on one side of the
axis (which is vertical), wliile at the other side a small portion only of the
compressed air will make its escape, the revolving door being in part enclosed
in a cylindrical casing.
Before commencing to use the furnace it will be necessary to gradually
bring up the pots to a red heat in a suitable oven, and also to make a small
fire inside the furnace, and bring it up to about the same temperature as the
pots, which are then to be quickly placed, therein and the fire, increased;..an
iron support is then, passed upwards against the under side of each pot, which
should have a hole from one to two inches in diameter made on the bottom of it,
and against the under side of which holes,the iron supports rest; the workmen
will then throw into, the pots a small handful of coarse, dry sand, which will
fill up the hole in the bottom, and prevent the pot from leaking; or, in lieu of
this, I put a spherical-ball of burned fire clay into each pot; the ball being too
large to fall through the hole, below; a little broken glass is then, thrown into
the pot, which will lute up the joint and retain the metal. On the floor of the
cave beneath the pots I fix a line of rails,, on which, an in
iron carriage can.be
moved. This carriage..contains the moulds, into which the molten steel is. to
be run, the moulds, being so arranged as each to receive a charge of metal
from the pots. When the iron supports are removed, a rod is introduced from

page_text: above to displace the ball or the stopping of sand, which will have become
concreted into a mass, but sufficiently friable to be easily removed. When a cast-
ing has taken place, the moulds are wheeled away with their contents, but may
bé again wheeled under the furnace when required; sometimes; however, the
contents of all the pots may be required for one casting, in which case a gutter
lined with Joam is extended below the line of pots, which receives their several
contents, and conducts them into the mould in like manner. The contents of
two or more furnaces? may be conveyed into one mould; the furnaces being so
arranged as to come as near as convenient to each other.
Having now described the peculiar form of furnace, and the mode of dis-
charging the metal therefrom, I will proceed to describe in what way I use
the same for the conversion of crude or refined pig iron-into steel. Ata
convenient distance from the said furnace I construct a finery furnace, or a
common cupola blast furnace, in either of which I melt the pig iron intended
for conversion into steel. From time to time the finery or cupola furnace is
tapped, and the molten iron run into a ladle; the metal is poured from thence
into the pots before described, where its high temperature will be still further
increased. Above the furnace I fix up an iron pipe, covered with'.brickwork,
or otherwise protected by a bad conductor of heat; into this pipe highly heated
atmospheric air alone, or air and steam mixed; or steam alone, also highly
heated, is forced under a pressure exceeding that of a column of metal equal
to the depth of fluid metal in the pots; the flow of air or steam into this pipe
is to be regulated by a valve under the control of the workmen who attend the
furnace; a small moveable pipe is placed vertically over the centre of each pot,
and passes freely through a hole into a branch of the air pipe above, and is
capable of sliding downward as far as the bottom of the pot, or nearly so; the
apparatus being thus, arranged, the operation will be as follows:-The pots
having been charged with molten iron in the manner described, the workmen
will lower the small vertical pipe, which passes through a small hole in the
cover), down nearly to the bottom of the fluid metal, through which the air.or
steam will force its way to the surface, producing considerable, agitation of the
melted metal, and thus in,turn exposing every part of it to the chemical action
of the gaseous products passing through it, the oxygen of the air or decomposed
steam absorbing rapidly the carbon of the iron and carrying it off, as also the
sulphur or other volatile matters. As soon as the iron becomes somewhat pasty,
or exhibits other signs of sufficient decarbonization, the pipes are lifted up and
some additional heat given to the metal, which may now be considered-steel,
in order, to render it sufficiently fluid to run into, moulds. During this last
heating the pot lids must be put on to prevent too great a loss, of carbon. The

page_text: state of the metal may be tested by dipping out a sample with a small ladle,.
as practised in refining, copper; if too much carbon is retained, the pipe may
be again introduced for a short time, or a small quantity of scrap iron may be
put into it; but if too much carbon has been driven off, an addition may be
made of some melted iron from the finery or cupola furnace..
Although I have herein-before shewn how the pots may be supplied with
melted metal from a finery or cupola furnace erected for that purpose; it will
be obvious that the molten metal may be run direct from the blast furnace
in which it has been obtained from the ore, the choice of which modes of
operating will depend much on local circumstances, and on the quality of steel
required; so, likewise, it will be understood that the particular kind of furnace
with pots, herein-before described, may be used for the melting and casting
of steel prepared otherwise than in the manner herein-before described.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry Bessemer in the Great Seal Patent Office on the
17th April 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
BESSEMER, of Queen Street Place, New Cannon Street, in the City of London,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of October, in the year of our Lord
One thousand eight hundred and fifty-five, in the nineteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Henry Bessemer, Her special licence that I, the said Henry Bessemer, my
executors; administrators, and assigns, or such others as I, the said Henry
Bessemer, 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 "IMPROVEMENTS IN THE MANU-
FACTURE OF CAST STEEL," upon the condition (amongst others) that I,' the said
Henry Bessemer, 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 mouth's next and immediately after the date of the
said Letters Patent:

page_text: NOW KNOW YE, that I, the said Henry Bessemer, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
In order to carry this Invention into practical operation, I construct a
furnace having a long rectangular chamber, the mouth of which is on a level:
with the floor of the foundry; the sides and ends of the chamber. are vertical
and parallel to each other, and the bottom of it is formed into an elevated ridge,
which extends the whole length of the chamber. This ridge is formed by the
apex of a pointed arch, which is made below it, and is called the cave. .Along.
each side of the furnace there are arranged fire bars, which extend from the:
lower parts of the ridge for some distance up the vertical sides of.the chamber,
there being no fire bars at the bottom of the chamber; the central part of the
ridge is flattened, and there are formed in it at equal distances. several holes,.
over or into which the lower end of the pots or pot stands are placed, so as to:
insure the proper position of the pots. The top of the chamber is covered
with large fire tiles, or with an iron frame in which fire bricks are fixed,
several openings being left to afford access to the pots. Along one side of the
furnace there is a row of square holes leading. into a chimney of sufficient
height to insure a powerful draught. The pots I prefer to be of the form
known as skittle pots, with a lid to each, and a tapping hole made in the bottom:
of them. The pots should be placed on a stand some four or five inches: in
height; or the lower part of the pots may be elongated, so as to form a stand,.
and be of such a size as to fit the holes in the top of the ridge, so that access
may be had to the under side of the pots from the cave below. The fuel used
should be hard oven coke, which is supplied from the opening on the upper side.
of the furnace, the fuel filling up the spaces round about the pots, and rising as.
far as the top of them. The fire bars are placed below the foundry floor, and
the air for combustion is supplied from the cave below the furnace, which, when
the draught of the chimney is alone depended on, must have a free communi-.
cation with the outer air; but in order to obtain a powerful combustion in the
furnace, I prefer to close up the cave below, and to employ a blowing fan, by
means of which I force air into the cave, and thus assist the draught of the:
furnace. In order to obtain access to the caves, I construct a revolving door,
which is made to act as a valve, and will allow a workman to walk through it.
on one side of the axis (which is vertical), while at the other. side a small
portion only of the compressed air will make its escape, the revolving door:
being in part enclosed in a cylindrical casing.
In order that this construction of furnace may be fully understood, I have.

page_text: hereunto annexed a Sheet of Drawings; in which, Figure 1 represents a vertical
cross section, taken on the line A, B, of Figure 2; Figure 2 is a sectional plan;
and Figure 3, a'longitudinal section, on the line C, D; of Figure. 2. a,ta, are
the outer walls of the furnace, which have openings in them at a', where the
fire: bars b are arranged so as to form a line with the vertical sides of the,fur-
nace. The fire bars are divided lengthwise into three sets by the intermediate
piers of brickwork a²; these piers rest on or form part of the parallel walls c, c,
which support the arch c*; the upper side of this arch is flat along the central
part of it, and has several circular holes d made therein, into which the pot
stands e are placed on each side of the central flat part. The upper part of the
arch is made to slope downwards, so that it forms, an inclined solid bottom
to the furnace. At a³ there is formed an arch, which extends across the top of
the furnace; and has openings.f made therein for the purpose of putting in the
crucibles or-pots; and for the supply of fuel, from time to time., These openings
are covered with a tile or stopper g, which may be moved aside when required.
At there are other openings or flues; which terminate in a chimney i, part of
which is shown as broken-off. j, j, is the cave or chamber, in the central part
of which the furnace is erected. This chamber should be provided with an
open passage to admit the external air freely, when the draught of the chimney.
is alone 'depended on; but when it is intended to use a pressure of, air to urge
the furnace, I close up the communication with the external, air by means of a
revolving door, which may be formed of thin iron or, other suitable material,
and which consists of four plates or leaves k, one side of each of them being
inserted in a vertical axis m, and made to fit closely to the curved plates 1, 1,
so that as little air as possible may escape past them from the cave or
chamber j. When the workmen require to go in or out, they will pass into
one of the recesses: or segmental spaces between the plates k, and by pushing
round the door may pass through without much loss of air. A blowing fan or
other blast apparatus, not shown. in the, Drawings, is made to force air into the
cave j; and thus a most powerful combustion will be maintained in the furnace,
the air entering it at all the spaces between the fire bars. It will be seen that
the position of the fire bars, will prevent their. becoming choked by the melted
refuse matter of the fuel, which; instead of accumulating on them and becoming
solidified by the entering air, will be received upon and flow down the inclined
bed of the furnace; and escape beneath the bottom lines of fire bars...
Before commencing to use the furnace it will be necessary. to gradually. bring
up the pots to a red heat in a suitable oven, and also to make a small fire inside
the furnace, and bring it up to about the same temperature as the pots, which
are then to be quickly placed therein and the fire increased. An iron support

page_text: is then passed upwards against the under side of each pot, which should have a
hole from one to two inches in diameter made in the bottom of it, and against
the under side of which holes the iron supports rest. The workmen will then
throw into the pots a small handful of coarse dry sand, which will fill up the
hole in the bottom, and prevent the pot from leaking; or in lieu of this I put
a spherical ball of burned fire clay into each pot, the ball being too large to
fall through the hole below. "A little broken glass is then thrown into the pot,
which will lute up the joint and retain the metal. On the floor of the cave
beneath the pots: I' fix á line of rails, on which an iron carriage can be moved.
This carriage contains the moulds' into which the molten steel is to be run, the
moulds being so arranged as each to receive à charge of metal from the pots.
When the iron supports are removed, a rod is introduced from above to displace
the ball or the stopping of sand, which will have become concreted into a 'mass,
but sufficiently friable to be easily removed. When a casting has taken place
the moulds are wheeled away with their contents, but may be again wheeled
under the furnace when required; sometimes, however, the contents of all the
pots may be required for one casting, in which case a gutter lined with loam
is extended below the line of pots, which receives their several contents, and
conducts them into the mould in like manner. The contents of two or more
furnaces may be conveyed into one mould, the furnaces being so arranged as
to come as near as convenient to each other, and whereby any massive castings
may be produced by the combined charges of steel from the several pots con-
tained in the different furnaces. In Figure 1 of the annexed Sheet of Draw-
ings, the ingot mould in, as shown in 'section; is placed within its carriage p;
the two halves of the mould being held together by wedges', driven in between
it and the sides of the carriage. In Figure 3 the carriage is shown with 'two
moulds only in it'; they occupy their proper place for receiving 'the contents of
the pots or crucible's 's beneath the pots's. The supporting rods t are repre-
sented as still in the position they occupy previous to their removal for the
discharge of -the metal; they rest on the central part of the horizontal bar u,
the ends of which are supported by projections.v, formed on the walls c, c, the
elasticity of the bars u serving to keep the upper enlarged ends of the rods t
firmly pressed against the bottom of the pots...
"Having now described the peculiar form of furnace, and the mode of
discharging tlie metal therefrom; "I will proceed to describe in what way I use
the same.
for the conversion of crude or refined pig iron into steel. At a
convenient distance from the said furnace I construct a finery furnace, or a
common cupola blast furnace, in either of which I melt the pig iron intended
for conversion into steel. From time to time the finery or cupola furnace is.

page_text: tapped, and the molten iron run into a ladle; the metal is poured from thence
into the pots before, described, where its high temperature will be still further
increased. Above the furnace I fix up an iron pipe, covered with brickwork,
or otherwise protected by a bad conductor of heat. Into this pipe highly heated
atmospheric air alone, or air and steam mixed, or steam alone, also highly
heated, is forced under a pressure exceeding that of a column of metal equal to
the depth of fluid metal in the pots. Although the action of highly heated air
or steam produces a more rapid change in the quality of the metal than cold
air or steam of low pressure, and for that reason is to be preferred for the
purposes of my Invention, it will, nevertheless, be understood that air less
heated, or of the ordinary temperature of the atmosphere and steam of the
temperature due to a low pressure, may be used in all cases where it is desired
to do so. The flow of air or steam into the pipe A is to be regulated by a
valve, under the control of the workmen who attend the furnace. A small
moveable pipe is placed vertically over the centre of each pot, and passes freely
through a hole into a branch of the air pipe above, and is capable of sliding
downward as far as the bottom of the pot, or nearly so. In order that the
pipes. when they are withdrawn from the pots may be moved on one side, and
thus afford free access to the furnace mouth, I construct them in the following
manner: The main steam or air pipe A is placed horizontally over the furnace,
and is kept in position by rods or stays attached to the roof or other part of the
building. This pipe has fitted to it several jointed branches B, so made that
the upper part of the pipe B embraces the lower half of the pipe A, and is
provided with lugs, by means of which a curved clip C is fastened to it, and
made to embrace the upper side of the main pipe, so that the pipe B, which is
pendant, may be moved backwards and forwards when desired, as represented
at B, Figure 1. The under side of the main pipe has holes made at the parts
where the pipes B are fitted to it, so that the air or steam may have free access
to the pipes B, the lower part of which are bored out and fitted accurately to
the sliding piece of pipe D, at the upper end of which there is an enlargement
or collar to prevent it from falling out of the pipe B. It is also provided with
a socket E at its lower end, which is fitted on to a short length of stout pipe,G,
made of malleable iron, platina, or other metal, which descends nearly to the
bottom of the pots, but if prevented from quite reaching the bottom.in con-
sequence of the raised collar or projection formed at the upper end of them,'
and by which they are supported on the top of the covers H of the pots s
during the time they are immersed the metal, from which they should be
withdrawn from time to time in order that they may be cooled down. This
movement into.or out of the metal under operation is also of great importance,

page_text: as it allows the apertures from which the jets of air or stean issue into the
molten metal to be lifted above the surface of it, or be entirely removed, and
thus the tendency which such apertures have to become clogged up is in a
great measure avoided. The lower ends of the pipes-G may have a single
orifice made therein, or there may be several smaller holes, which I prefer, as it
divides more completely the air or steam into small portions. The apparatus
being thus arranged, the operation will be as follows:-The pots having been
charged with molten iron in the manner described, the workmen will lower the
small vertical pipe D on to the pipe G, which passes through a small hole in
the cover, down nearly to the bottom of the fluid metal, through which the
air or steam will force its way to the surface, producing. considerable agitation
of the melted metal, and thus in turn exposing every part of it to the chemical
action of the gaseous products passing through it, the oxygen of the air or
décomposed steam absorbing rapidly the carbon of the iron, and carrying it off,
as also the sulphur or other volatile matters. As soon as the iron becomes
somewhat pasty (as it is liable to do when steam is being used and the heat is
not fully maintained), or exhibits other signs of sufficient decarbonization, as
herein explained, the pipes are lifted up and some additional heat given to the
metal (which may now be considered steel), in order to render it sufficiently
fluid to run into moulds. During this last heating the pot lids must be put on
to prevent too great a loss of carbon. By reference to the Sheet of Drawings
hereunto annexed, it will be seen that the crucibles s are provided with covers
I, in which several holes N are made, and means of which the gaseous
products arising from the combustion of the carbon of the iron and other volatile
matters are allowed to escape into the furnace. Although the steel 'may be
retained in the furnace, as before described, for the purpose of being further
heated after the process of forcing air or steam therein has ceased, it will,
nevertheless, be found that by proper attention to the furnace fire the workmen
will be enabled to maintain the metal in such a state of fluidity through the
decarbonizing process when using steam as to avoid the necessity of applying
any further heat thereto, and whereby the fluid steel so produced from crude
or refined iron may be at once formed into any desired article by the process
of casting in iron moulds, or founding the same in loam or sand moulds, such
as are cominonly used by ironfounders; or the fluid steel may be run into ingot
moulds for the purpose of forming ingots or masses of malleable cast steel
suitable for being tilted, hammered, or rolled into bars, plates, or rods by the
processes already known and practised for that purpose. During the decar-
bonizing process, the state of the metal may be tested by dipping out a sample
with a small ladle, as practised in refining copper; if too much carbon is

page_text: retained, the pipe G may be again introduced, for a short time, or a small
quantity of scrap iron may be put into it; but if too much carbon has been
driven off; an addition may be made of some melted. iron: from the finery or
cupola furnace; a little experience will, however, enable 'the workmen to regu-
late; his process so as to produce the different.qualities of steel which. he may
require, for which purpose he must note the time that a given weight of iron
requires with an ascertained pressure of air or steam to produce steel of a
certain standard of hardness; he will then apply the air. or steam for a less
length of time if he require a harder steel than the standard, or he will
continue the process for a longer period if steel of a very soft or mild quality is
required. In all cases, however, the process; must be continued until the metal
is rendered ductile and malleable, and, acquires other properties: common to
cast steel.
.
Although I have herein-before. shewn how the pot may be supplied with
melted metal from a finery or cupola furnace erected for that purpose, it will
be obvious that molten metal may be run direct from the blast furnace in
which it has been obtained from the ore, the choice of which modes of
operating, will depend much on local circumstances and on the quality of steel
required. In order that the nature and extent of. my said Invention may be
correctly ascertained, and in what manner the same differs from some other
methods that have been heretofore used or proposed to be used for making
iron and steel, I will, in the first place, state that I do not use either the
juddling furnace or the manipulation called puddling, nor is the iron solidified
or made into balls, or removed from the vessels in which it is treated for the
purpose of remelting the same, but is retained therein in a fluid state until
the completion of the process, and is allowed to flow from thence into suitable
moulds. In the second place, I would state that both air and steam have
before been employed in the manufacture of iron in different ways, and it has
recently been proposed to dispense with the finery or running out furnace in
the manufacture of iron by causing jets of air or steam or water to pass up
through the melted crude iron as it flows along a gutter from the blast
furnace, or after it has run into the pig beds,, or after it leaves a finery
furnace (if one should be used), but in either case it is proposed to use such
process only as a preparatory process to puddling in a reverberatory or
puddling furnace in the ordinary manner. And, thirdly,. I am aware that the
blowing or forcing of steam into and below the surface of fluid iron contained
in a reverberatory or puddling furnace has before been proposed, and may
have been practised, such introduction of, steam forming part of. and assisting
in the process of puddling iron, in which case the fluidity of the metal

page_text: would not, as in the process of manufacture herein described, be maintained
throughout the process.
' :
I have mentioned these different known processes in order to state that I
make no claim thereto, and also to show more clearly the distinctive character
of my Invention, which consists in the production of malleable metal direct
from crude or refined iron by means of air or steam, or both; whilst retaining
it in the fluid state, and without the use of the puddling furnace, or of any
manipulation or process analagus to the puddling process, at the same time
admitting of the fluid metal after the completion of the process being.run.or
poured into moulds, or formed into ingots suitable for the further process of:
hammering or rolling..:
In the above description, in order that the, mode which I consider best
adapted to the successful and economic working of my said Invention may be
fully understood, I..have shewn and, described a peculiar, construction of
furnace in which pots are used, and wherein, the pots are so arranged as to
discharge their contents through the bottoms. I nevertheless desire it to be
understood that the main or primary object of; my. Invention may be success-
fully accomplished in the furnaces and crucibles at present in use for manu-.
facturing cast steel, and also by many other, modifications' and forms of
apparatus, provided that such apparatus is so arranged that currents of air or
steam, or a mixture of air and steam, may be forced into and, among the.
particles of fluid metal until the separation of so much of its carbon and other
impurities has been effected as will render the metal so treated malleable and
ductile whilst it still retains a fluid state, and, like cast steel produced by other.
means of manufacture, capable of being run into moulds to form ingots or
other articles of cast steel.
The workman may always judge, more or less accurately, of the state of
the metal as the process proceeds, by observing, the color and size of the
sparks, and the quantity and color of the flame issuing from the metal under
operation.
The tendency of the metal to become less fluid towards the close of the.
process, although it may indicate the lessened quantity of carbon in the metal,
may also be caused by the use of too much steam, or from a cooling down of
the metal, consequent on the withdrawal of the blow.pipe for too long a period
of time, or it may arise from other causes, and, therefore, taken alone, should
not be relied on as an indication of the state of the metal, more especially as
such a condition of the metal should and may be entirely avoided. The use
of steam has always a tendency to cool down and lessen the fluidity of the
metal when used alone towards the close of the process. I have, therefore,
.

page_text: found, in carrying my Invention into practical operation, that it is preferable
to use steam at the early stages of the process, and to use air for its com-
pletion. I have also found that the employment of steam is very serviceable
when the crude iron contains sulphur, because the steam becomes decomposed
on passing into the fluid metal and yields hydrogen gas, which readily com-
bines with the sulphur and carries it off'; but steam is not so well adapted as
atmospheric air to maintain the necessary heat and fluidity of the metal. I
therefore prefer to use steam only in the early stage of the process, when the
iron contains a comparatively large quantity of carbon, and is consequently
easily maintained in a fluid state, notwithstanding the cooling effect of the
steam, which I generally employ for about one-third of the time that is
required to bring the metal to the proper quality. No precise rule can be
laid down as to the time required by the process, which must in every case
depend both on the quality of metal used and on the quantity of steam or air
passed through it, but I may state generally that from twenty to forty
minutes will be required. The steam having been used as long as the work-
man considers necessary, he will shut the steam passage and open a communi-
cation with the blast pipe, and allow the air to force its way into the metal.
The change will soon become apparent; the metal, which may have lost much
of its heat during the steaming process, will quickly brighten up, an increase
of flame will be observed, and a rapid increase in the temperature of the
metal will take place, the metal passing from a red or yellow heat to an
intense white; a violent ebullition of the metal will also be observed during
any intervals in the blowing operation, in consequence of the disengagement
of gaseous carbon or other volatile matters in the act of separating from the
metal; a similar effect will be obtained by using a small quantity of steam
mixed with the air throughout the process, but I prefer to use them
separately, as before stated; and here I would observe that the workman
should take care that the hole in the top of the furnace, and in the cover of
the pot through which the blowing pipe passes, should be sufficiently large to
allow him to see through it what is going on.
Having pointed out certain other known processes or inventions that have
been proposed or used in the manufacture of iron, and shewn in what respect
such processes or inventions differ from my own Invention as herein-before
described, both in their professed objects and also in the manner in which
they are proposed to be carried into effect, I desire it to be distinctly under-
stood that I lay no claim thereto, nor do I, on the other hand, confine myself
to the precise details herein given of my own Invention, so long as the
peculiar character thereof is retained; but what I do claim is, the forcing of

page_text: currents of air or of steam, or of air and steam, into and among the particles
of molten crude iron, or of remelted pig or refined iron, until the metal so
treated is thereby rendered malleable, and has acquired other properties.
common to cast steel, and still retaining the fluid state of such metal, and
pouring or running the same into suitable moulds.
In witness whereof, I, the said Henry Bessemer, have hereunto set my
hand and seal, this Seventeenth day of April, in the year of our Lord
One thousand eight hundred and fifty-six.
o Witness,
B. GOBEY,
4, Old Square, Lincoln's Inn.
HENRY BESSEMER. (L.S.)