IMPROVEMENTS IN THE MANUFACTURE OF IRON AND STEEL, AND APPARATUS THEREFOR
Year: 1872

page_text: LETTERS PATENT to John Imray, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, for the Invention o
"IMPROVEMENTS IN THE MANUFACTURE OF IRON AND STEEL, AND APPARATUS
THEREFOR.
-A communication from abroad by Thomas Schoenberger
Blair, of Pittsburg, Pennsylvania, in the United States of America.
PROVISIONAL SPECIFICATION left by the said John Imray at the
Office of the Commissioners of Patents, with his Petition, on the
14th June 1872.
I, JOHN IMRAY, of No. 20, Southampton Buildings, Chancery Lane,
in the County of Middlesex, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN the ManufactURE OF IRON AND Steel, and
APPARATUS THEREFOR," to be as follows:-
In reducing oxides of iron sometimes iron in a spongy condition has
been produced, but on so small a scale and so imperfectly that it has not
constituted an article of manufacture or commerce. My Invention
relates to the production of such iron sponge in a complete and
A

page_text: economical manner, and on such a scale that it can be treated as an
article of manufacture, to the conversion of of such sponge with cast or
wrought iron and steel, and to the construction and working of apparatus
for this purpose.
In producing the iron sponge I mix iron oxides with carbonaceous
matter, and heat the mixture in channels so formed and arranged that
all parts of the mixture are near the heating surfaces. I then pass the
heated matter through retorts, which are in parts heated and in parts
cooled, so that the matter has to pass through zoues of heating and
cooling. In passing through the heated channels and zones the oxygen
is separated from the iron, and the latter forms a sponge, which after its
formation is cooled as it passes through the cooling zones, and is finally
discharged from the retorts. As it is essential to the success of this
operation that air should be excluded from the matter under treatment,
I so arrange the retorts that the mixture supplied to them forms a packing
or stopper to exclude air, and I arrange the discharge from the retorts
so that a quantity of the sponge can be removed without admitting air
to act on the contents of the retorts.
A. convenient mode of constructing the apparatus is as follows:-The
retorts are placed in an upright position, surmounted by tubes of small
diameter, through which the mixture is fed, and which are heated.
Owing to the small diameter of these tubes the mixture fed into them
forms a packing or stopper which excludes air from the retorts, and all
parts of the contents of those tubes are near their heated surfaces, so that
the mixture is thoroughly and evenly heated in passing through them.
The upper parts of the retorts are heated, and constitute the heating zones
through which the mixture supplied by the tubes slowly descends. The
lower parts of the retorts are kept cool, either by the application of
water to them externally or by the insertion into them of water casings,
and constitute the cooling zones, in passing through which the sponge is
cooled before it is taken from the retorts. The discharge apertures at
the bottoms of the retorts may be made with slides, so that a portion
of the contents can be removed without admission of air. The slides
may be made to work transversely to the retorts in the manner of tables
having receptacles in them which can be presented alternatcly to the
mouths of the retorts, so that while one receptacle is withdrawn when
filled another is brought under the retort to be charged and withdrawn
in its turn. Or the slides may be in the form of sleeves, which can be

page_text: slid longitudinally along the retorts so as to present lateral openings
through which a portion of the sponge can be withdrawn.
In employing retorts arranged as above described the contents descend
by gravity. It may be readily understood however that the retorts could
be arranged horizontally or in other attitudes, the contents being forced
along them or having their passage along then assisted by mechanical
means.
The carbonaceous matter, instead of being mixed with the oxide in a
solid form may be supplied by gas flames rich in carbon being made to
act for a sufficient time on the oxide.
The iron sponge produced as above described may be employed in the
production of cast iron, steel, or wrought iron in the following
manner:-
For producing cast iron the sponge is charged with carbonaceous
matter in a cupola, wherein it is carburized and melted, and whence it
can be tapped off in the ordinary way.
For producing steel the sponge, either cold or hot, and either with or
without compression, is charged into a bath of melted pig iron in an
open hearth furnace; or for producing crucible steel the sponge may be
first compressed and then melted in a crucible with a suitable admixture
of carbon.
For producing wrought iron the sponge may first be charged into a
bath of melted pig, and the mixture puddled in the ordinary way, or the
sponge may be heated to a welding heat and balled. In this case, in
order to protect the sponge from oxydation, it should be heated with
fluxes such as will, with the mineral matter mingled with the sponge,
produce under heat a slag which serves to shield the metallic iron from
the action of oxygen.
0
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Imray in the Great Seal Patent Office on the
13th December 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
IMRAY, of No. 20, Southampton Buildings, Chancery Lane, in the
County of Middlesex, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourteenth day of June, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-fifth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said John Imray, Her special license that I, the said
John Imray, my executors, administrators, and assigns, or such others as
I, the said John Imray, 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 MANUFACTURE OF IRON AND STEEL, AND APPARATUS
THEREFOR," a communication to me from abroad by Thomas Schoenberger
Blair, of Pittsburg, Pennsylvania, in the United States of America, upon
the condition (amongst others) that I, the said John Imray, 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 John Imray, do hereby declare the
nature of the said Invention, and in what manner the same is to he
performed, to be particularly described and ascertained in and by the
following statement thereof, reference being had to the accompanying
Sheet of Drawings, and to the figures and letters marked thercon, that
is to say:
In reducing oxides of iron sometimes iron in a spongy condition has
been produced, but on so small a scale and so imperfectly that it has not
been constituted an article of manufacture or commerce. This Invention
relates to the production of such iron sponge in a complete and
economical manner and on such a scale that it can be treated as an
article of manufacture, to the conversion of such sponge into cast or
wrought iron and steel, and to the construction and working of apparatus
for this purpose.
In producing the iron sponge iron oxides are mixed with carbonaceous
matter, and the mixture is heated in channels so formed and arranged

page_text: that all parts of the mixture are near the heating surfaces. The heated
matter is then passed through retorts which are in parts heated and in
parts cooled, so that the matter has to pass through zones of heating and
cooling. In passing through the heating channels and zones the oxygen
is separated from the iron, and the latter forms a sponge, which after its
formation is cooled as it passes through the cooling zones and is finally
discharged from the retorts. As it is essential to the success of this
operation that air should be excluded from the matter under treatment
the retorts are so arranged that the mixture supplied to them forms a
packing or stopper to exclude air, and the discharge from the retorts is
so arranged that a quantity of the sponge can be removed without
admitting air to act on the contents of the retorts.
A convenient mode of constructing the apparatus is as follows:-The
retorts are placed in an upright position, surmounted by tubes of small
diameter, through which the mixture is fed, and which are heated.
Owing to the small diameter of these tubes the mixture fed into them
forms a packing or stopper which excludes air from the retorts, and all
parts of the contents of those tubes are near their heated surfaces, so that
the mixture is thoroughly and evenly heated in passing through them.
The upper parts of the retorts are heated and constitute the heating zones
through which the mixture supplied by the tubes slowly descends. The
lower parts of the retorts are kept cool either by the application of water
to them externally or by the insertion into them of water casings, and
constitute the cooling zones, in passing through which the sponge is
cooled before it is taken from the retorts. The discharge apertures at
the bottoms of the retorts may be made with slides, so that a portion of
the contents can be removed without admission of air. These slides may
be made to work transversely to the retorts in the manner of tables,
having receptacles in them which can be presented alternately to the
mouth of the retorts, so that while one receptacle is withdrawn when
filled another is brought under the retort to be charged and withdrawn
in its turn. Or the slides may be in the form of sleeves, which can be
slid longitudinally along the retorts so as to present lateral openings
through which a portion of the sponge can be withdrawn.
In employing retorts arranged as above described the contents descend
by gravity. It may be readily understood however that the retorts could
be arranged horizontally or in other attitudes, the contents being forced

page_text: of B.
Hence it is only necessary to arrange such a length for the
channel or feeder B as will ensure the equal or uniform heating of all
the material before passing into A.
It is plain that the feeding pipes or channels may be indefinitely
varied in number and form to suit circumstances. Figs. 2 and 3 shew
an arrangement which is found to answer the purpose.
Fig. 2 represents a longitudinal section, and Fig. 3 a sectional plan
of the upper portion of a circular reducing chamber, of which C represents
the cylindrical wall. A smaller cylinder D is inserted at the top of C,
so as to leave an annular passage a, which constitutes the feeding channel.
If now heat be applied to the exterior of the cylinder C and to the
interior of the cylinder D, it is obvious that the initial heating is per-
formed under the condition above mentioned. The details of the
manner of holding the cylinder D in place, and supplying the heat to
the same, are given below in the complete description of the apparatus.
Having thus provided for imparting the heat with uniformity, the
next step is to obtain the requisite isolation of the material while under
treatment, so that no intrusion of air shall disturb the absorption of the
oxygen by the carbon, or afterwards re-oxidize the sponge before it has
cooled to a safe temperature. In the numerous attempts hitherto made
for meeting these requirements dependance has been placed either
upon operating with vessels to be kept shut during the process and
until cold, or upon maintaining a pressure of gas within the reducing
chamber greater than the atmospheric pressure without, or upon special
mechanical arrangements for withdrawing the material when finished.
In the first of these cases the operation is too tedious and costly, neither
of the others has proved satisfactory in practical working.
The improved arrangement about to be described obviates in a simple
way all the difficulties heretofore encountered. It consists substantially
in so planning the apparatus that the material under treatment shall
itself constitute a packing," whereby the air is excluded from the
zones of reduction and of cooling.
"
Fig. 4 illustrates diagrammatically the apparatus in its simplest form.
It represents the vertical section of a pipe E open at both ends. Its
outer surface, between the planes 1 and 2, is understood to be in contact
with a red hot atmosphere, and between the planes 2 and 3 its outer

page_text: surface is in contact with cold water. Its lower end is far enough above
the floor 4 to allow its contents to be withdrawn.
It may be farther understood that x . x is the plane at which the
contents of the pipe have attained the degree of heat necessary for
reduction; that the length of pipe from x, x, to 2 is sufficient to give
to the material under treatment the duration of exposure of heat that is
required to perfect the operation; and that the length of pipe from 2 to
3 is sufficient to allow the contents of the pipe to cool to the tempe-
rature of the air by the time it reaches the plane 4. These data being
assumed, the several zones of the contents of the pipe may be classed as
Sallow

page_text: )
the axis of the reducing chambers.
Fig. 6 represents a section of plan on the line
-
x of Fig. 5.
Fig. 7 represents a sectional plan at the line y-y of Fig. 5.
Fig. 8 represents a transverse section of one of the reducing chambers.
Fig. 9 is a perspective representation of the discharging apparatus
shown in Fig. 8.
.
Fig. 10 represents a section of a modified form of the discharging
apparatus.
Fig. 11 represents a section of a cooling box applied to the lower end
of a retort.
The reducing furnace represented in section in Fig. 5 is an oblong
chamber of brickwork or masonry built upon a base plate F, which is
supported at a convenient height above the surface of the ground on a
sufficient number of pillars, so as to afford access to the discharging
apparatus at the lower extremity of the reducing furnace. The furnace
shewn in the Drawing is furnished with a single row of three retorts,
the number of which may be more or less, as may be desired. The
height of the furnace above the base plate F may be about 24 fect,
) although this and other dimensions which are herein given need not be
exactly observed, but are merely stated by way of illustration. The lower
portion G of the furnace for about one-fourth of the height above the
base plate F is built solid of brickwork around that portion of the retorts
which forms the lower (but not the lowest) zone. These retorts may be
3 about 36 inches in internal diameter, and are made either of fire-brick
material or of iron, which may be encased in fire-brick material, being
cylindrical pipes set in the masonry G. The outside walls H of the
reducing chamber are built on the masonry G about 18 inches in
thickness to the top of the chamber K, which is covered over with a
O cap 6 baving no opening at top to the external air, excepting a flue or
flues c, c, to allow of the escape of the waste heat and gases from the
furnace. At or near the lowest point of the chamber K are openings d
in the outer walls H for the entrance of heat from a gas furnace or
other furnace for heating the reducing chamber. Higher up in the
5 outer walls H are small apertures at different heights, which serve as
spy holes through which the degree of heat in the reducing chamber

page_text: may be observed from time to time by the workmen. These spy holes e
are closed when not being used by means of plugs or stoppers, as at e¹
in Fig. 5.
The retorts I are continuous cylindrical pipes extending to the top of
the chamber K, and communicating at top with the external air. The
retorts have no openings in their sides, there being no communication
between the chamber K and the interior of the retorts I.
J, J, J, represent cylinders of iron, protected by an interior lining of
fire-brick material, open at their lower extremities, and furnished with a
moveable cap g at their upper ends, through a pipe in the contre of each
of which gas escapes from the interior of the cylinder. Each of these
cylinders J is of smaller external diameter than the interior diameter of
the retorts I, so that when inserted into the cavity of the retort there is
an annular space of about 4 inches all around it. One such cylinder J
is introduced into each retort I at the top, being suspended or supported
by lugs h, as shewn in Figure 7, in such a manner as not to close the
top of the annular space around it, and it extends downwards about one-
third of the height of the chamber K. These cylinders J are heated by
means of a stream of gas introduced from the outside of the reducing
furnace through a suitable pipe or passage i in the outer wall H (see
Fig. 8), at the top of which it communicates with the pipe i, and then
passes down through the body of tho cylinder J, whence it emerges near
its lower end. The gas thus passing through the wall of the furnace
and cylinder receives additional heat on its passage to the point of exit.
Similar passages k on the opposite side of the reducing furnace conduct
atmospheric air to the interior of the cylinders J, which becomes heated
in its passage, and uniting with the heated gas causes vivid combustion
sufficient to heat the cylinder. The flues or passages i, k, instead of
passing up to the top of the wall H may be turned inwards (as shown in
dotted lines in Fig. 8), and be connected with pipes to lead the gas and
air into the cylinder J at the bottom. Below each retort I is an
iron pipe L of the same internal diameter, and forming an extension of
the retort below the base plate. The pipes L are open at their lower
extremities, and they are surrounded by a trough M, through which a
current of cold water is kept running. The trough is so connected with
the bottom of the pipes L that the water cannot enter them, the cavity
of the pipe extending through the bottom of the trough, as seen in
Figs. 5 and 8.

page_text: Attached to the bottom of the trough M or to the flange surrounding
the lower end of each pipe L are guides 7 (see Fig. 9) placed parallel
to each other, between which slides a table N, the upper surface of
which is in close contact with the under surface of the lower extremity
of the pipe L. This table has two circular openings in which are
inserted two pots m, having flanged rims flush with the upper
surface of the table N. The table N being slid between its guides
brings one or other of the pots m under the bottom of the pipe L, so
that a portion of its contents may be discharged into the pot, and when
the slide is drawn back again the pot with its contents may be
removed from the table N without exposing the interior of the retort to
access of the external air. If preferred, a single pot may be used, the
surface of the table serving to seal the lower end of the pipe N when-
ever the pot is withdrawn from its position under the pipe L.
As a substitute for this discharging apparatus the lower end of the
pipe L may be covered by a perforated platen (see Fig. 5), to the centre
of which is pivotted another similarly perforated plate p, so that when the
perforations in the two plates are made to coincide by turning the lower
plate p, any desired quantity of the contents of the retort may be
discharged, and then the opening can be closed by turning back the
plate p. As the contents of the lower portion of the retort (in the
pipe L) are cold (or nearly so) before being removed from the retort, no
damage will accrue by the opening of the perforated plate for the period
of time required for removing the desired quantity of the material.
As a further modification of the apparatus for discharging the finished
sponge from the reducing apparatus the table N, and pots m, as also the
perforated plates n, p may be dispensed with, and the pipe L extended
of uniform diameter below the trough M, to within a short distance of
the floor, as in Fig. 4.
This distance between the bottom of the pipe L and the floor beneath
is made variable at pleasure by means of a sleeve o, shewn in Fig. 10,
which can be slid upwards and downwards upon the pipe L by means of
projecting pins q sliding upon or in spiral ways r, so that by turning the
sleeve o to the right or to the left it is caused to ascend or descend as
the case may be, thus opening or closing the bottom of the retort.

page_text: When the diameter of the pipe is so great relatively to the length of
its cooling zone that the material would be discharged too hot, an extra
cooling arrangement is employed similar in principle to the plan of
initial heating before described. It is substantially as follows:-
Fig. 11 represents the lower end of the pipe into which is intro-
duced a water box P, which may be a hollow cone projecting up into
the mass of finished sponge. This box is furnished with a water pipe s,
by which cold water is introduced into the interior of the box, and water
escapes in a continuous stream at the waste pipe . By this means the
spongo at the lower extremity of the pipe L is cooled more rapidly and
effectually.
The operation of initial heating and of isolating by means of the
material itself may be applied to a horizontal instead of a vertical
chamber or retort by providing mechanical force to take the place of
gravitation in causing the materials to travel through the chamber, and
arranging so that a sufficient body of the material shall be packed both
before and behind the zone at which the heat is applied to accomplish
the object, substantially as above described. In this plan the arrange-
ments for heating could be of the simplest construction, and for working
on a small scale especially it would be decidedly less costly than the
apparatus above described.
Heretofore reference has been made exclusively to the employment of
the carbon in a solid condition. This is not absolutely necessary.
When the ore is of such size that a mass of it will, after being charged
into a chamber, remain pervious to gases it may be de-oxidized by
sufficient duration of exposure to those gases which are of a reducing
nature. When employing this method the isolation of the zones of
reduction and cooling is to be effected by employing the material as a
packing, as in the apparatus already described, so far as relates to the
lower portion. It is unnecessary above, as the upward flow of the;
injected gases sufficiently guards that portion against intrusion of air.
The operation of the apparatus is as follows:-The carbon and oxide are
first mixed together, then charged into the tops of the pipes so as to keep
them constantly full; the heat in the hot chamber is kept steadily at the
original temperature, and the water in the cooling tanks kept constantly

page_text: cool by a fresh supply; and finally, the withdrawal of the sponge is so
regulated as to give the material under treatment whatever duration of
exposure it may require. There are however several details learned in
practical working which are important. to be known and observed, and
which will now be specified.
In selecting and preparing the materials the quantity of carbon
theoretically necessary is three-fourths by weight of the quantity of
oxygen present in the oxide, but as perfect uniformity of distribution
and contact cannot be practically attained, an excess (say ten per cent.)
of carbon should be added. The carbon may be charcoal, coke,
or anthracite coal. If coke is used, the coal from which it is
made should be previously washed, unless of great purity. Bituminous
coals do not answer so well, both because they "cake" (and thus
disturb the downward flow of the material) and because the hydrogen
evolved tends to produce carburization of the iron sponge.
There is no marked difference in the action of the carbon, whether it
is fine powder or in pieces even so large as half an inch in diameter.
In the case of the oxide, very compact sorts, such as tap cinder from the
puddling furnace or some of the black magnetic ores, are best used fine
if used raw. They should however be roasted first, and then they may,
in common with the natural ores of looser texture, be employed of any
It does however
size, from dust up to, say, one inch in diameter.
require longer time for the reduction of the pieces in proportion to their
size; hence, to ensure uniformity, the ore should be classified according
to size by screening, and only one size of ore should be used at a time.
It facilitates the separation of the surplus carbon from the sponge if
coarse ore be used with fine carbon, or coarse carbon with fine ore, so
that most of the separation can be done by simply screening, and
care should be taken not to have all the material coarse, but rather to
have always enough of either ore or carbon small enough to ensure good
"packing."
The heat should be carefully kept at the required degree, which is a
fair red tending toward yellow. A higher heat makes the sponge sticky
and gives rise to trouble.
As to the withdrawal of the sponge, the intervals must be regulated by
observation of the product as withdrawn. The true iron sponge can be
7-7
..
יו
1
Tatning the

page_text: general contour or shape of the ore or cinder from which it is derived,
somewhat expanded in bulk and with a marked loss in weight. It has
a cellular or spongy structure, is readily pared with a knife or indented
by the finger nail, chews like lead between the teeth, and polishes quickly
to a silvery lustre. Its colour, unless influenced by some colouring
matter present in the orc, is grayish, varying from blackish to a clear
lead colour. When pulverized and burned in the open air it sparkles
brilliantly, as does iron burned in in an atmosphere of oxygen. As long
as the material withdrawn exhibits those features the operation is going
on properly.
As a general indication it will be enough for the workmen to observe
the feel and colour. If the sponge is so soft that it can be easily pressed
flat between the finger and thumb it has been under treatment longer
than necessary, and the intervals between drawings may be shortened
without detriment. If on the other hand it cannot be readily cut with a
knife and has a gritty feel between the teeth, the reduction is not perfect,
and the intervals between drawings should be increased. When working
steadily upon one kind of material the proper interval between drawings
can soon be ascertained, and the reduction casily kept at the right point.
There is no danger of carburization at the temperature required for
reduction, and no special harm in "overdoing" the sponge (other than
useless expenditure of time and fuel), hence the whole operation is an
exceedingly simple one to any workman who can control the heat.
If any portion of the sponge as withdrawn should show instead of its
characteristic colour a stcely-blue or straw colour tinge it indicates re-
oxidation by air getting into the chamber when the sponge is still hot.
Although these colours may show when there has been but a small
amount of re-oxidation, yet they prove the existence of a defect which
may become serious, and the cause should be at once sought out and
remedied.
If for any reason it is desirable to withdraw the sponge warm, even
at a red heat, it may be effected without much detriment if managed so
that it can be quickly covered in by fine dust of charcoal, coke, etc.
When the sponge is withdrawn, even when no such covering in is
employed, it of course is accompanied by the excess of carbonaceous
matter that had been charged with it. This can be separated roughly

page_text: by screening and winnowing, more thoroughly by magnetism, and best
by washing. It is found in practice that pure water does not oxidize
the iron sponge if it is used immediately after being taken out of the
water.
The iron sponge thus produced is almost entirely deoxidized, suf-
ficiently so at least for all practical purposes in the production therefrom
of cast iron, wrought or malleable iron, and steel, and when cold and
kept dry will oxidize very slowly by simple contact with atmospheric air.
.
The iron sponge produced as above described may be employed in the
production of cast iron, wrought iron, or steel in the following manner:―
For producing cast iron the cupola is employed as the apparatus, it
being simply modified in details of proportionate parts so as to secure
the carburization and fusion required. It is well known to those skilled
in the art that ordinary wrought iron, even in masses so large as the
crop ends of rails, can be converted into cast iron by treatment in the
cupola. The iron sponge being so much more sensitive to carburization,
the cupola can be readily adapted to its utilization as a material from
which to produce cast iron. But this element of sensitiveness and the
presence of foreign matter in the sponge require a special treatment as
to fluxing, which will be herein-after described in reference to the
manufacture of wrought iron from the sponge.
In the manufacture of wrought iron from the iron sponge either of
two methods may be employed; in the first of which melted pig metal
is used in connection with the iron sponge, while in the other method
the sponge is treated without pig metal.
The first method consists in charging iron sponge into pig metal melted
in the ordinary way in a puddling furnace. The iron sponge is introduced
into the pig metal as soon as the latter becomes liquid in such quantity
as máy may be desired, to be determined ingreat measure by the economic
consideration of the relative cost of production of the pig metal and
sponge, as it makes but little difference, so far as the success of the
operation is concerned, what may be the relative proportion of the
sponge and pig metal, provided there be a sufficient quantity of molten
pig metal to form a bath for or to mix with the sponge.
It is wasteful to introduce the iron sponge into the puddling furnace
before the pig metal has become liquid, but after the metal is melted the

page_text: sponge may be successfully introduced at any stage in the process of
bringing the iron to nature, and either at one time or in smaller quan-
titics from time to time, as may be preferred.
•
The effect of this method on the process of puddling is that the
introduction of the iron sponge facilitates and hastens the coming to
nature of the iron, and improves the quality of the product.
As the sponge is introduced into the puddling furnace it is stirred and
worked into the melted pig metal, and the work of gathering and balling
the iron is conducted in the same way as in ordinary puddling, regard
being had to the more rapid formation of the particles of wrought iron.
According to the second method the iron sponge is treated in a rever-
beratory furnace previously heated. The iron sponge is thrown in,
heated to a welding heat, and then balled, the operation and mode of
treatment being like that applied to fine borings or turnings of wrought
iron, with a single important exception, rendered necessary by the
extreme sensitiveness to oxygen of the iron sponge when heated, and to
the fact due to the conditions of its production, that it usually has in
intimate association a considerable quantity of mineral matter differing
in kind and degree according to the variety of ore from which it was
made.
In order to prevent excessive waste from oxidation, which would
result were the iron sponge treated as if it were finely divided particles
of ordinary wrought iron, and which is one of the practical difficulties of
treating iron sponge without a bath of melted pig metal, the sponge is
supplied (either by admixture before it is charged into the furnace or
during the operation) with a fluxing material adapted to combine with
the foreign matter present in the sponge at a sufficiently low heat to
form a cinder or glass which will furnish the desired protection to the
particles of metallic iron. What this flux shall be depends of course on
the character of the foreign matter. If it be silica, protoxide of iron
(hammer slag for example) or basic minerals, such as lime, alumina,
&c. should be used. If lime should be present in excess, alumina or
silica should be added.
When alar on thankoto

page_text: water, and add this paste to the iron sponge before charging it into the
furnace, mixing them thoroughly so as to coat the particles of iron with
the protecting flux.
The furnace used should be so arranged as to introduce as little free
oxygen as possible in the working chamber. Thus treated the sponge
can as soon as it comes to a welding heat be readily balled, and may
then be manipulated like puddle ball.
In the manufacture of steel from iron sponge either of two methods
may be employed, the first by the fusion of the sponge in the presence
of the requisite proportion of carbon in a crucible, and the second by
effecting such fusion upon the open hearth.
To render the crucible treatment economically successful it is essential
that the crucible shall contain a sufficient quantity of iron sponge to
yield a product as large as is usually obtained from a crucible charge of
solid wrought iron. This is difficult owing to the extremely loose
texture and light specific gravity of the sponge. For this purpose the
pulverization and subsequent compression of the sponge in a cold state
has been suggested, but without practical success, owing no doubt to the
fact that the so-called iron sponge heretofore experimented with has
been but partially deoxidized ore, the particles of which were incapable
of uniting so as to give the requisite density to the muss.
Iron sponge thoroughly and uniformly reduced by the process herein-
before described is however capable of the requisite compression and
cohesion of its particles. To effect this the sponge is reduced to a fine
powder, then heated to redness, and in this condition it is subjected to
powerful compression in order to protect the comminuted sponge from
oxidation, which would occur if it were exposed while hot to contact
with the atmosphere, the sponge is packed in a case made of iron,
fire-clay, or other suitable material which will bear the requisite heat
and afford the desired protection. These cases may be cylindrical or of
other shape having parallel sides, and closed at. top by a loose cap or
follower. They are charged with the pulverized iron sponge in a cold
state and the cap or follower being applied, each case is heated to
redness in a muffle, and when sufficiently hot is withdrawn and imme-
diately placed in a clamp or matrix which supports its sides and prevents
B

page_text: it from bursting, pressure is then applied by a nyaraune or other press
until the red hot mass is sufficiently condensed.
Instead of using a case as described, the comminuted sponge may be
first compressed while cold, which will cause the particles to cohere into
a solid mass or block, which is then coated with a plaster of clay or other
suitable adhesive substance capable of excluding the air and sufficiently
refractory to the heat, and after being heated to a fair red heat, pressure
is applied to secure the desired density.
Another difficulty in the use of iron sponge for making steel is due to
the fact that the process of reducing iron ore to form metallic sponge
docs not eliminate the foreign substances, such as silica, lime, &c.,
present in the ore, so that unless the ore used should happen to contain
the requisite balance of acids and bases to form a natural flux (which
seldom occurs), the steel made from the sponge would be greatly
deteriorated or perhaps rendered worthless by the combination with
these mineral impurities. To remedy this practical difficulty the com-
minuted iron sponge before compressing it, as just described, has mixed
with it some suitable substance which will unite with the impurity to be
removed, and form a glass which will thereafter remain neutral and prevent
the contamination of the steel. For example, if the iron sponge should
contain silica in excess, fincly powdered lime may be mixed with the
comminuted sponge in quantity dependant on the amount of silica to be
neutralized, the result being, that before the temperature of the crucible
has reached the point at which the reduction of the silica into silicon by
carbon would ensue, the lime and silica have united, forming a glass
which will not combine with the steel. If on the other hand lime in
excess should be present in the sponge, sand or clay is added to present
silica or alumina to the basic ingredients with the same result as before
stated. Iron sponge thus prepared by the judicious admixture of suitable
fluxing ingredients (as indicated by analysis of the sponge or ore before
reduction), and by red hot compression can then be employed in the
same manner as wrought iron is now used in making steel in crucibles.
The other method of making cast steel from iron sponge is by melting
it on an open hearth in a charge of molten pig metal, in the like manner
as steel is made with ordinary wrought iron by what is known as the
Siemens-Martin process. For this purpose a charge of pig metal is

page_text: melted in a reverberatory furnace, and when at a high white heat the
requisite quantity of iron sponge is added so as to leave in the mixture
the proper proportion of carbon to yield the desired grade of steel, adding
more or less as may be desired. The iron sponge may be supplied to
the melted pig metal from time to time in its natural condition, cold and
uncompressed or coated, as before described, with clay or other suitable
material, or it may be previously heated and compressed as before
described, or it may be previously brought to a plastic condition by
heating in a separate furnace. From its porous texture the iron sponge
in its natural condition will melt more rapidly than ordinary solid
wrought iron, thus shortening the process of making steel by this
method. This latter mode of making steel from iron sponges possesses
peculiar advantages, and owing to the fact that the iron sponge has
suffered none of the contaminations of the blast furnace the product is
a higher grade of steel than when wrought iron made from pig metal is
the stock employed.
Having now described the nature of the said Invention, and the
manner in which the same is to be performed, as communicated to me
by my foreign correspondent, I claim,―
First. The process substantially as herein described of reducing oxides
of iron to the metallic state by subjecting them to a red heat in contact
with carbonaceous matter, in a chamber so constructed that the material
under treatment shall supply the packing which excludes the air
therefrom.
Second. As a part of the process above described, the initial heating
of the materials to be treated by causing them to pass into the reducing
retort, through one or more conducting channels so shaped, transversely
to the direction of passage of the material, that every particle of the
material shall be within short reach of a heating surface, substantially as
herein described.
Third. The construction substantially as herein described of a reducing
retort without other aperture than those at the charging and discharging
extremities, and of such length above and below the zone of reduction
if vertical, or before and behind it if horizontal, that the material under
treatment shall itself secure the exclusion of air from the zone of
reduction, or from the zones of reduction and cooling.
B 2

page_text: Fourth. The use in combination with such reducing retort of the
cylinder J, or its equivalent, for the purpose of furnishing a conducting
channel of relatively small cross section, within which to effect the
uniform initial heating of the mixed ore and carbon before their intro-
duction into the reducing retort, substantially as and for the purpose
herein described.
Fifth. The use of a sliding table N with inserted pot or pots m, in
combination with the cooling pipe or section L of the reducing apparatus,
for the purpose of discharging its contents without the admission of the
external air, substantially as herein described.
Sixth. The combination of the double perforated gratings n and p with
the cooling pipe or section L of the reducing apparatus, for the purpose
of discharging its contents without admission of the external air, sub-
stantially as herein described.
]
Seventh. The combination of the sliding sleeve o with the cooling 1
pipe or section L of the reducing apparatus, for the purpose of dis-
charging its contents substantially as herein described.
Eighth. The combination with the cooling pipe or section L of the
reducing apparatus of an inserted water box P for the purpose of more
rapid cooling of the finished sponge, substantially as herein described.
Ninth. The use for the manufacture of cast iron, of iron sponge,
produced by apparatus constructed and operating substantially as herein
described, the said sponge being charged into a cupola and subjected
therein to carburization and fusion.
Tenth. The use for the manufacture of wrought iron, of the said iron
sponge added in a cold state to pig metal melted in a puddling chamber,
substantially as herein described.
Eleventh. The protecting of the particles of the said iron sponge from
oxidation during puddling by mixing it with a suitable flux, substantially
as herein described.
Twelfth. The use of the said iron sponge for the manufacture of steel,
by methods substantially as herein described.
Thirteenth. In the manufacture of crucible steel from iron sponge,
charging the sponge in a cold state into a protecting casing, and after
2
{

page_text: heating the same compressing the sponge, substantially as herein
described.
Fourteenth. In the manufacture of crucible steel from iron sponge,
compressing the sponge while cold so as to cause it to cohere, and after
coating the same with a refractory covering heating the sponge and sub-
jecting it to further compression, substantially as herein described.
In witness whereof, I, the said John Imray, have hereunto set my
hand and seal, this Twelfth day of December, in the year of our
Lord One thousand eight hundred and seventy-two.
JOHN IMRAY. (L.S.)