IMPROVEMENTS IN THE TREATMENT OF CRUDE OR CAST IRON AND IN THE MANUFACTURE OF MALLEABLE IRON AND STEEL
Year: 1867

page_text: LETTERS PATENT to Henry Bessemer, of Queen Street Place, Cannon
Street, in the City of London, for the Invention of "IMPROVEMENTS IN
THE TREATMENT OF CRUDE OR CAST IRON AND IN THE MANUFACTURE OF
MALLEABLE IRON AND STEEL."
Sealed the 9th June 1868, and dated the 31st December 1867.
PROVISIONAL SPECIFICATION left by the said Henry Bessemer at the
Office of the Commissioners of Patents, with his Petition, on the 31st
December 1867.
I, HENRY BESSEMER, of Queen Street Place, Cannon Street, in the City
of London, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE TREATMENT OF CRUDE OR CAST IRON, AND IN THE MANUFACTURE OF
MALLEABLE IRON AND STEEL," to be as follows:-
In the Specification of a Patent granted to me, and dated the 12th day of
February 1856 (No. 356), there is described the conversion of molten crude
iron or of remelted pig or finery iron into steel or into malleable iron without
the use of fuel for re-heating or continuing to heat the molten iron, such
conversion being effected by forcing into and among the particles of a mass of
molten iron currents of air or gaseous matter containing or capable of evolving
sufficient oxygen to keep up the combustion of the carbon contained in the
iron till the conversion is accomplished. This process is now well known as

page_text: the Bessemer process. One method of conducting it is to place beneath the
molten iron a perforated case capable of bearing a high heat and containing
a solid matter, such as nitrate of soda, which gives off oxygen on being heated.
The heat of the molten iron causes the nitrate or other matter to liberate
oxygen, which forces its way through the perforations in the case, and it
issues into and amongst the particles of the molten iron as when air is forced
in through tuyere pipes in the ordinary way of conducting the Bessemer
process. When solid matters are used to generate the oxygen as above stated it
is advantageous to use a converting vessel like that which is usually employed
in conducting the Bessemer process, that is to say, a vessel mounted on
trunnions and with a mouth or opening to receive and discharge the metal and
give exit to the gasses passing away during the conversion and also with
an aperture at the bottom; this aperture usually receives the tuyere box,
which closes it when the vessel is at work. When solid substances are to be used
I replace the tuyere box by a case lined with refractory material; this case is
filled with the nitrate of soda or other material, and is closed at the top with a
perforated fire-tile or it may be with a slab of refractory stone. I make the case
of such dimensions that the area of the surface of the nitrate or material is but
small as compared with the area of the principal horizontal section of the metal
in the converting vessel. In this way I both modify the intensity of the action
and also prevent the rapid scoring action which would result from the passages
of the gas between the metal and the sides of the vessel. Also in order to
render the action more regular than it otherwise would be I fuse the nitrate
of soda or other material and cast it into the case in which it is to be used and
there allow it to solidify. The melted metal is then effectually prevented from
acting on more than the upper surface of the cast block of nitrate or material,
or the fused nitrate or material may be cast into separate moulds and after-
wards placed in the cases; or in some cases I mould the nitrate or material
into blocks under heavy pressure before inserting it into the case, and the
violence of the action of the nitrate or material on the iron may be reduced
to any desired extent by mixing dry clay or other inert matter with the nitrate
or material.
Also according to my Invention when I employ either nitrate of soda
or nitrate of potash or other easily fusible matter which yields oxygen on
coming in contact with fluid iron and purifying or decarbonizing the same I
bring the nitrates or other matters into a fluid state in a suitable vessel before
such matters are brought in contact with the molten iron, and I introduce
such fused matters in jets or currents which are forced through small openings
or tuyeres into the fluid metal, the force with which they are injected being

page_text: such as will prevent the fluid iron from entering the tuyeres or the chamber
containing the aforesaid fluid nitrates or other matters.. I prefer to fuse these
matters in an iron vessel provided with a jacket for the circulation of super-
heated steam or hot air. I insert one or more fire-clay tuyeres in the lower part
of the converting vessel, which tuyere or tuyeres I connect by a short pipe
with the vessel containing the fluid matters before named. The passages leading
into and through the tuyeres may be beated by passing superheated steam or
hot air through them previous to admitting thereto the fluid. nitrates or other
matters. The emission of the superheated or hot air will serve to exclude the
fluid metal from the tuyere openings until it is desired to introduce the fluid.
matters into the vessel,, and also after the whole of the fluid nitrate or other
matters have been injected the steam or air will again pass and thus prevent
the iron from entering the tuyeres or passages. In order to force these jets
of fluid into the molten iron I also employ superheated steam or hot air
under sufficient pressure to act on the surface of the said fluids, the mouth of
the vessel containing them being closed by a valve for that purpose.
I would observe that when I so employ fluid matters to refine, purify, or de-
carbonize any molten iron that I prefer that the vessel containing the iron should'
be of such formas will admit of a much greater depth of fluid metal in proportion.
to its diameter than vessels usually employed in the Bessemer process, such
vessels either being moveable on trunnions or they may be fixed cylindrical or
other shaped vessels. Usually I employ such a proportion of nitrate or material
in relation to the quantity of crude or cast iron operated on as to convert the
metal at once into malleable iron or steel. In some cases however it may be
convenient to employ a smaller proportion of nitrate or material and to leave
the metal in the form of a readily fusible cast iron but of improved quality, and
this cast iron may be afterwards converted by the ordinary Bessemer process
or otherwise employed. Nitrate of soda, or nitrate of potash, or chlorate of
soda, or chlorate of potash may be carried into and amongst the molten iron
by means of a current or currents of air introduced below the surface of the
metal, as is suggested in general terms in the Specification of iny said former
Patent, as also in that of another Patent granted to nie and dated 31st May
1856, No. 1292; or in place of converting the metal in part by means of jets.
of air the conversion may be similarly effected entirely by means of the nitrate,
or chlorate, a current or currents of an inert gas, such as carbonic acid gas, or
stean or vapour being employed to carry the powdered nitrate or chlorate
into the converting. vessel amongst the molten: metal.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry Bessemer in the Great Seal Patent Office on the
30th June 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, J, HENRY
BESSEMER, of Queen Street Place, Cannon Street, in the City of London,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of December, in the year of our
Lord One thousand eight hundred and sixty-seven, in the thirty-first 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 inight 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 CRUDE OR CAST IRON, AND IN THE MANUFACTURE OF MALLRABLE IRON AND
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 months next and immediately after the date of the said
Letters Patent.
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 performed,
to be particularly described and ascertained in and by the following statement
thereof, that is to say:-
In the Specification of a Patent granted to me, and dated the 12th day of
February 1856, No. 356, there is described the conversion of molten crude
iron or of remelted pig or finery iron into steel or into malleable iron without
the use of fuel for re-heating or continuing to heat the molten iron, such
conversion being effected by forcing into and among the particles of a mass of
molten iron currents of air or gaseous matter containing or capable of evolving
sufficient oxygen to keep up the combustion of the carbon contained in the
iron till the conversion is accomplished. This process is now well known as
the Bessemer process. One method of conducting it is to place beneath the

page_text: molten iron a perforated case capable of bearing a high heat and containing
a solid matter such as nitrate of soda which gives off oxygen on being heated.
The heat of the molten iron causes the nitrate or other matter to liberate
oxygen which forces its way through the perforations in the case, and it issues
into and amongst the particles of the molten iron as when air is forced
through the tuyere pipes in the ordinary way of conducting the Bessemer process.
When solid matters are used, to generate the oxygen as above stated it is
advantageous to use a converting vessel like that which is usually employed in
conducting the Bessemer process, that is to say, a vessel mounted on trunnions
and with a mouth or opening to receive and discharge the metal and give exit
to the gases passing away during the conversion, and also with an aperture at
the bottom; this aperture usually receives the tuyere box, which closes it
when the vessel is at work and air is blown through the tuyeres, but when
solid substances are to be used I replace the tuyere box by a case or chamber
lined with refractory material; this case or chamber is filled with the nitrate
of soda or other material capable of evolving oxygen, and is closed at the top
with a perforated fire-tile or it may be with a slab of refractory stone.
make the case of such dimensions that the area of the surface of the nitrate or
material is but small as compared with the area of the principal horizontal section
of the metal in the converting vessel. In this way I both modify the intensity of
the action and also prevent the rapid scoring action which would result from
Also in
the passage of the gas between the metal and the sides of the vessel.
order to render the action more regular than it otherwise would be I fuse the
nitrate of soda or other material and cast it into the case or chamber in which
it is to be used and there allow it to solidify. The melted metal is then
effectually prevented from acting on more than the upper surface of the cast
block of nitrate or material, or the fused nitrate or. material may be cast
into separate moulds and afterwards placed in the cases or chambers; or in
some cases I mould the nitrate or material into blocks, under heavy pressure
before inserting it into the case or chamber, and the violence of the action of
the nitrate or material on the iron may be reduced to any desired extent by
mixing dry clay, or other inert matter with the nitrate or material; but I lay
no claim .to.. the moulding of such blocks by pressure nor to the mixture of
inert matters with the nitrates or other material, nor do I lay any general
claim to the use of nitrates or materials. yielding oxygen gas except when
used according to my present Invention.
In order that the way in. which the case or chamber containing the nitrates
or other material capable of yielding oxygen gas, is applied to converting
vessels such as are generally employed in the Bessemer process may be fully.

page_text: understood I have shown a vertical section of an apparatus so arranged at
Figure 1 on the Sheet of Drawings hereunto annexed. At the lower part of
the vessel a, which is similar to the vessels usually employed in conducting
the Bessemer process, a ring or hoop of iron b is fixed to the plates a* which
form the lower part of the vessel. The case or chamber d for holding the
nitrates or other material is provided with a flange at its upper edge, which
is secured to the vessel by a series of slotted studs and cotters, one of which
studs is shewn at e. The case or chamber is lined with fire-brick, fire-clay,
ganister, or other suitable refractory material, as shown at c. When the
nitrate or other material shown at g is put into the case the perforated cover or
tuyere plate h composed of fire-brick or Ransom's concrete stone is put on,
and the case will then be in a condition ready for use. When however
the nitrate or other material is fused and cast into the case or chamber d
and has become solidified therein the use of the tuyere plate may be dispensed
with, as the metal will act on the upper surface of the nitrate or other
material and fuse it gradually and not float it upwards in the way that loose
crystals of the nitrates would be carried up if tuyere plates were omitted.
Before operating on the crude iron I prefer to beat the vessel, which may be
effected by securing an iron grating to the bottom of the converting vessel by
means of the slotted studs e; on this grating a fire can be made, the products
of combustion escaping by the mouth i of the vessel. When the vessel has
been heated sufficiently. the grating may be removed, and the case or
chamber d may be secured in place, as shewn in Figure 1.
A little "slip"
or mixture of clay and fine sand in a creamy state is put around the edges of
the tuyere plate h, so as to secure a good joint; after which the vessel may
be turned on its axes (one of which is shewn by dots at j) into a position to re-
ceive the molten crude iron to be operated upon, so that the whole of the metal
from the melting furnace may be run or poured into the vessel before any action
of the nitrates takes place; the movement upward of the vessel thus brings the
whole of the metal simultaneously into a position to be operated on. The fluid
iron enters the tuyere holes, and coming in contact with the nitrate or other
material rapidly generates oxygen gas, which passes upwards from the tuyere
plate in numerous streams through the fluid metal in the same manner as air
passes upwards from the tuyere holes in the ordinary Bessemer process. The
oxygen will decarbonize the crude iron and convert it into malleable iron or
steel, after which the products may be discharged from the mouth i. of the
vessel by turning the vessel on its axes as usually practised.
Also according to my Invention when I employ either nitrate of soda or
nitrate of potasb or other easily fusible matter which yields oxygen in coming

page_text: .
in contact with fluid iron and purifies or decarbonizes the same I bring the
nitrates or other matters into a fluid state in a suitable vessel before such
matters are brought in contact with the molten iron, and I introduce such fused
nitrates or other matters in jets or currents which are forced through sinall
openings or tuyeres into the fluid metal, the force with which they are injected
being such as will prevent the fluid iron from entering the tuyeres or the
chamber containing the aforesaid fluid nitrates or other matters. I prefer to
fuse these matters in an iron vessel provided with a jacket for the circulation
of superheated steam or hot air. I insert one or more fire-clay tuyeres in
the lower part of the converting vessel, which tuyere or tuyeres I connect by a
short pipe with the vessel containing the fluid matters before named. The
passages leading into and through the tuyeres may be heated by passing super-
heated steam or hot air through them previous to admitting thereto the fluid
nitrates or other matters. The emission of the superheated steam or hot air
will serve to exclude the fluid metal from the tuyere openings until it is
desired to introduce the fluid matters into the vessel, and also after the whole
of the fluid nitrate or other matters have been injected the steam or air will
again pass and thus prevent the iron from entering the tnyeres or passages.
In order to force these jets of fluid into the molten iron I also employ super-
heated steam or hot air under sufficient pressure to act on the surface of the
said fluids, the mouth of the vessel containing them being closed by a valve for
that purpose.
I would observe that when I so employ fluid matters to refine, purify, or
decarbonize any molten iron that I prefer that the vessel containing the iron
should be of such form as will admit of a much greater depth of fluid metal
in proportion to its diameter than vessels usually employed in the Bessemer
process, but this increased depth of metal is not essential to the success of the
process but is to be preferred in constructing new apparatus. Such vessels may
either be moveable on trunnions or they may be fixed cylindrical or other
shaped vessels, but I prefer to employ vessels mounted on trunnions usually
called tipping vessels, such as are generally employed in the Bessemer process.
Vessels that are now in use for that process may be readily adapted to the use
of fluid nitrates in lieu of atmospheric air, as will be readily understood on
reference to the Sheet of Drawings hereunto annexed, where Figures 2 and 3
represent vertical sections of a Bessemer converting vessel in different
positions with the apparatus necessary for using fluid nitrates attached thereto.
The converting vessel A is constructed of plate iron and has a lining of ganister
B at the lower part of the vessel. There is a hoop of iron C from which slotted
studs project and by means of which the tuyere plate E is secure:

page_text: to the vessel; this plate has a tubular part F and an inclined ring G
projecting from its upper surface. A block or tuyere of burned fire-clay H is
fitted into the inclined ring G, and rendered air-tight by running in some
Portland cement or plaster. The central part of the tuyere H is made hollow
and several small openings I converge from it, as shewn, for the purpose of
'distributing the fluid nitrates or other materials in small streams through the
fluid metal. At the back of the converting vessel the chamber J is fixed; it
is surrounded by a jacket L, which also encloses the four-way cock M, the
handle of which is external to the jacket and therefore not seen in the
Drawing. K, K, are brackets by which the jacket L is connected with the
casing of the converting vessel. Before the apparatus is employed to convert
the crude metal a fire may be made in the vessel, a blast of hot air being pro-
pelled through the tuyere block G for the purpose of keeping up the combustion
of the fuel. Meanwhile the nitrate of soda or other material yielding oxygen
gas is put into the chamber J through the funnel aud cock N which is then
closed, highly beated air is passed by or through the axis of the vessel (shewn
by dots at P), and the air is conveyed by the pipe Q into the jacket and
allowed to blow off through the cock R. This air is heated to a temperature
sufficiently high to melt or fuse the nitrates or other materials contained in
the chamber J, or their fusion may be effected in other vessels before they
are supplied to the chamber J, where they are then retained in a fluid state
by the hot air passing through the jacket.
Figure 3 shews the position the apparatus is put into for the purpose of
receiving the crude molten iron to be operated on, which is run in through
the open mouth o of the vessel. Whilst the metal is running in a current of
hot air is employed to heat the pipes and tuyere block through which the
fluid nitrates are to pass, the air also serving to prevent any of the molten iron
from entering the tuyeres. The air for this purpose is conveyed from the
axis of the vessel by the pipe S, passes through the four-way cock M and
pipes T and T* into the tuyere block, from which it escapes by several small
passages. As the mouth of the vessel is turned upwards the tuyere block H
descends, and just as it is about to be immersed beneath the surface of the
molten iron the four-way cock M is reversed; the vessel is then turned up
into the position shewn in Figure 2. By the reversal of the four-way cock
the air under pressure no longer passes through the pipes T and Tx into the
tuyere block but finds its way through the pipe U into the upper part of the
chamber J, and there pressing on the surface of the molten nitrate or other
material forces it through the four-way cock and pipes T and T* and through
the several tuyere openings into the fluid metal. When the whole of the

page_text: fluid has been discharged the air under pressure will follow through the same
passages and exclude the metal from the tuyeré block until the vessel is turned
down and its contents discharged. If the nitrate or other material yielding
oxygen gas be used in such quantity as only. to partially decarburize the
crude iron the passage of air through the metal after all the fluid nitrate has
been discharged will not only complete the decarburization to the desired
extent but it will increase the temperature of the metal; this increase of
temperature will be still more readily effected if some fluid spiegeleisen or
other carburet of iron be added at the time, that is to say, after all the nitrate
or material has been injected. In order that the removal of an old tuyere block
and the supply of a new one may be effected readily a joint is made in the pipe T*.
át W; this joint is shewn on a larger scale at Figure 4. The elbow pipe T has
a dovetailed ring X bolted to it, and the pipe Tx has a corresponding dovetailed
flange fitted into the ring X and capable of moving within the dovetailed ring,
so that whenever the flange of the pipe Tx is unbolted from the tuyere plate E
it may be moved on the joint W out of the way, and thus admit of the removal
of the tuyere plate from the vessel. Such vessels may either be moveable on
trunnions or they may be fixed cylindrical or other shaped vessels. Usually:
I employ such a proportion of nitrate or material in relation to the quantity
of crude or cast iron operated on as to convert the metal at once into
malleable iron or steel. In some cases however it may be convenient to
employ a smaller proportion of nitrate or material, and to leave the metal in'
the form of a readily fusible cast iron but of improved quality, and this cast
iron may be afterwards converted by the ordinary Bessemer process or other-
wise employed.
It is well known that there are many gradations of quality
or degrees of decarburization between what is usually called mild steel and
that quality of metal which is usually termed cast iron; and it will be obvious
that the decarburization of the metal may have any range between these limits
depending on the quantity of oxygen producing material employed and the
quantity of carbon originally contained in the crude iron, and therefore that
the metal may be discharged from the vessel after treatment with the nitrates
or other material in such a state of decarburization as may best adapt it to
the uses or after processes for which it may be required. Nitrate of soda or
nitrate of potash, or chlorate of soda or chlorate of potash may be carried
into and amongst the molten iron by means of a current or currents of air
introduced below the surface of the metal, as is suggested in general terms
in the Specification of my said former Patent, as also in that of another
Patent granted to me, and dated 31st May 1856, No. 1292. In some cases
however it is desired in place of converting the metal in part by the air intro-

page_text: duced and in part by the nitrate or chlorate which it carries with it to effect
the conversion entirely by the nitrate of chlorate. I then employ a current or
currents of an inert gas, such as carbonic acid gas, or steam, or vapour to carry
the powdered nitrate or chlorate into the converting vessel amongst the molten
metal. For this purpose I prefer to reduce the nitrates or other materials
capable of yielding oxygen gas of a fine powder, having first baked them so
as to deprive them as far as possible of water. The powder may be admitted
to the pipes which convey the gas into the metal by a feeding screw or other
known contrivance for regulating the supply of powdered or granulated
materials. The gaseous matters employed for conveying these powdered
materials into the molten metal may be obtained by passing air or steam
under sufficient pressure through a close vessel lined with fire-brick and
containing coke or other fuel in an incandescent state, as is well under-
stood, or the gases may be generated by any other known and efficient
means.
I do not claim under my present Invention the use of atmospheric air or
steam in their natural state for the purpose of carrying nitrates or other
matters into molten iron.
Having thus described the nature of my said Invention, and the manner
of performing the same, I would have it understood that I do not confine
myself to the exact details described; but what I claim is, the treating molten
crude or cast iron with nitrate of soda or other solid oxygen yielding sub-
stance in a vessel mounted on trunnions, such vessel being provided at one end
with a chamber or case to contain the nitrate or other substance and at the
other end with a mouth serving to receive and deliver the iron and also as an
exit for the gases passing away during the conversion, the arrangement being
also such that the vessel may have the metal poured into it at the mouth
without coming in contact with the nitrate or other substance, and may then
be tipped so as to carry the nitrate or substance below the molten metal, and
finally when the conversion is complete may be again tipped to pour out the
metal at the mouth.
I also claim in treating molten crude or cast iron the pouring the nitrato
of soda or other fusible oxygen yielding substance in a melted state into the
case or chamber in which it is used, allowing it to become solid in the said
case or chamber and form a mass the surface only of which can be attached
by the molten iron.
I also claim in treating molten crude or cast iron the closing the top of the
case or chamber in which the nitrate or other substance is contained beneath
the molten iron with a perforated fire-tile or a slab of refractory stone.

page_text: I also claim the treating molten crude or cast iron with nitrate of soda or
other fusible oxygen yielding substance by forcing the liquid nitrate or sub-
stance in jets into and amongst the molten metal.
I also claim the forcing heated air or steam through the same tuyeres or
orifices by which the liquid nitrate or other substance is forced into the metal
so as (before the nitrate is supplied) to heat the said tuyeres or orifices, and to
exclude the metal from them both before and after the application of the
liquid nitrate or substance.
I also claim in the treatment of molten crude or cast iron and in the
manufacture of malleable iron and steel the use of apparatus arranged as is
represented in Figures 2 and 3 of the Drawings.
I also claim the treating molten crude or cast iron by carrying nitrate of
soda or other oxygen yielding substance in a powdered state into and amongst
the said metal by means of a jet or jets of carbonic acid gas or other gas
incapable of yielding oxygen to the molten metal.
In witness whereof, I, the said Henry Bessemer, have hereunto set my
hand and seal, this Thirtieth day of June, in the year of our Lord
One thousand eight hundred and sixty-eight.
HENRY BESSEMER. (L.S.)