Improvements relating to the Production of Homogeneous Cast Iron or Steel, and to Apparatus therefor.
Year: 1894

page_text: Date of Application, 31st Dec., 1894-Accepted, 20th Apr., 1895
COMT DIE STEIFAHUN.
Improvements relating to the Production of Homogeneous Cast Iron
or Steel, and to Apparatus therefor.
I, ALEXANDRE LExCauchez, of 240 Rue de Rivoli, Paris, in the Republic of
France, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement
My invention relates to the treatment of cast on, old non or gelap iron to
refine the same for the production of a homogeneous cast metal of high quality and
weldable when it is required to give it this properly
In treating cast iron according to my said invention, the cast on, if it is new
metal, is cast in a refining furnace on the system hereafter mentioned, at as low
a temperature as possible. It is maintained in a very fluid condition without the
employment of an excessively high temperature for about twenty minutes, with
a neutial flame or as slightly oxydizing a flame as possible, that is to say, a flame
having a large excess of combustible gas. During this tune the manganese which
is contained in the metal reacts with the lime on the sulphur which is in the state
of sulphide of iron combined with the mass, under the action of the manganese and
the lime, the sulphur from the sulphide of non forms sulphide of manganese which
Hoats on the surface of the molten mass, and which need only be scummed off to
produce a metal free from sulphur.
In the event of the charge consisting of old iron, scrap iron or the like containing
sulphin, the furnace 15 charged with powdered coke, small coal or anthracite, and
fei ro-manganese and lime me added in such a manner as to bring the metal to
a molten state, the temperature is then allowed to fall to that at which ordinary
cast iron melts (about 1100°) and the desulphurization takes place in the manner
above mentioned.
When the desulphurization is complete, the temperature of the molten metal is
raised, without, however, reaching the point at which the oxidation of the carbon
commences, the oxidation of the phosphorus and silicon is then effected by blowing
on the surface of the molten metal, and employing a very strongly oxidizing flame
by admitting an excess of hot air, without raising the temperature. The iron oxide
this formed reacts on the phosphorus and forms phosphate of iron which floats on
the surface of the molten inetal and may be removed in the same manner as the
sulphun above mentioned. Lime is then added to thoroughly neutralize the last
traces of phosphoric acid and the surface of the metal again cleaned; by continuing
to oxidize the metal by the air-blast and by admitting an excess of hot air, silica is
formed by the oxidation of the silicon which combines with the lime which has
been added. Under these conditions, a double silicate of iron and lime is produced,
which is not fusible and floats on the sui face of the molten metal and can be easil
removed by raking and scumming.
It cheap oxide of iron be ready at hand, the successive oxidations of the molten
metal could be effected by successive additions of the said oxide (such as magnetic,
hæmatite or other non ore which should be as pure as possible and obtained from
exclusively calcareous strata). The oxidation by minerals (ore process) would
give the same result as oxidation by flame and blast, when the temperature of the
molten metal is not raised too high as mentioned above, the phosphorus as phosphate
of non, and lime and silicon in the form of various silicates being removed by
successive akings and scummings as above describedi

page_text: As may be seen, the elimination of sulphur, phosphorus and silicon is effected at
temperatures below that at which decarburization commences, or in other words
below that temperature at which bubbles of oxide of carbon begin to be given off.
At these low temperatures the basic walls of the furnace are not attacked, that is
to say, they are not vitrified, and can thus last almost indefinitely, when their life
19 compared with that of other apparatus of the same class, which require continual
repaire.
"
"
The metal thus produced is what is called a "fine metal," that is to say,
a "carburetted iron" freed from a portion of the manganese, sulphur, phosphorus
and silicon which it contained. The refining of the metal thus produced may be
completed in a soparate apparatus from that in which it was commenced, when
carrying out the well-known "epouring" or "transfer "process (tiansvasement),
but, whatever be the second apparatus employed, such as a rotating health furnace.
fixed hearth furnace, Bessemer, or the like, (if the " repouring 01 " transfer
process be effected by the Bessemer apparatus, it is necessary, before running the
metal, to bring it to the highest temperature that the furnace can give, so as to
produce a sufficiently high temperature to commence the blast), it is important to
note that the refining at a high temperature is effected without the production of
dross on slag, since it is now only necessary to remove the carbon in a gaseous state,
an operation which caunot give rise to any vitrification of the walls of the finishing
apparatus, oven at the highest temperatures used industrially.
But, if it be desired to avoid the "repouring" or "transfer" and complete the
refining of the metal m a single basic furnace, the said furnace should be 30
arranged that, after the production of the "fine metal" and the careful scumming
of the surface of the said metal, it is possible to raise it, in a few moments, to the
highest temperature that a furnace heated by a rich gas from a gas-producer can
produce, the heat being reinforced by powerful regenerators In working in this
innune, the refining is divided into six stages
13

page_text: Figue 2 is a detail view of the arrangement of i gas producer for use with coal.
Figure 3 is a sectional elevation of a turnace with regenerators and blowing
apparatus.
Figure 3 is a horizontal section on the line C-D, Figure 3.
Figure 4 is a transverse section of the furnace showing the arrangement of the
tuyères in the arcb.
Figure 5 is a plan showing the general arrangement of my apparatus, and a front
view of the furnace.
Figue 6 is a section on the line G-H, Figure 3, of the furnace and
regenerators, and
Figure 6 a section on the line 1-J, Figure 3
I have said above that in order to put my improved method of refining (with on
without repouring or transfer of the metal fiom one furnace to another) into
practice successfully, it is necessary to be able to raise the temperature of the
furnace very rapidly, that is to say, to have an apparatus possessing great elasticity
of action I fulfil this condition by employing a very rich gas, produced by the
gas generator shown in Figure 1, in which various kinds of diy fuel are burnt.
such as coke, coal dust, nou-bituminous coal, and anthracite.
The said gas
generator comprises a fire-bridge (A) which compels the gases and vaporis, which
are given off below the charging aperture to pass through the meandescent fuel
aud be decomposed into permanent combustible gases The ash-pit of this
apparatus is closed, and air is supplied under pressure to the interior of the said
gas gonerator by a pipe (B) Figure 1b, sprayed water being supplied thereto by
ineaus of a regulating arrangeuicut and a constant-level siphon provided with au
overflow pipe (C). In this arrangement, the ash chamber serves as a vaporizer
and a superheater for the an and steam, which arrangement permits the production
of 50% of water gas, that is to say, half the fixed cabou is burnt by the oxygen
from the water vapour in the gas generator, which thus finishes a gas containing
relatively small proportion of mitrogen.
I sometimes use the gas generator shown in Figme 2, which distils the coal; the
ash-pit is closed, and provided with blast and water pipes, an enters the ash-pit by
pipe (D) and passes into the fuel though the grate, the gases then pass below the
bridge though the incandescent fuel into the main (E). This gas generator com-
prises an inclined plane (F) for distilling and caking the mixture of powdered
bituminous and semi-bituminous, non-bituminous or hard coals, when the said
powdered coals are caked and distilled they behave on the grate of the gas-producer
Similarly to the non-bituminous coal and coke considered above; thus, the gases
produced by distillation are added to the gases from the water and the Lunaces
This gas generator is provided with two hoppers or charging boxes (G) and two
doos (11). The mixtures of coal are admitted by the changing boxes (G) and the
powdered coke o sinall coke by the doors (H) The filtration of the tairy and
other vapours through the incandescent coke produces the same effect as takes
place in the gas generator for coke, (Figure 1), and forms, at the same time, a
method of cleansing the gas from soot and smoke, which is thus prevented from
choking the gas mains.
As the gas leaving the gas generators is at a certain pressure, it is necessary
that the secondary air supply to the icfiamg hearth should be at the same pressure
in order that the two currents may not interfere with one another in the burning.
In order to effect the said combustion perfectly and at a high rate, so as to produce
the maximum temperature, employ return-tube regulators, I, J, Figure 5,
CODsisting of suitable valves controlled by the use and tall of the bells
of gas-holders, the enclosed space of which is in communication with the gas
and furnace-blast mains through return tubes M, L. These regulators receive the
blast from a single bifurcated conduit (2), one regulator, I, being placed on the
primary an-supply conduit D for the gas-generators, and the other, J, on
the secondary air-supply conduit 5.
I simultaneously blow the secondary air-supply and the gas, the flames are thus

page_text: concentrated in the burners in such a manner as to produce jets or blow-pipe flames
in the furnace up to the limit determined by the rate of removal of the products
of combustion by the chimney draught The jets of flame thus produced localize
the heat of combustion, and so to speak, throwing and breaking themselves on the
metal to be melted or refined, they render these operations more rapid and perfect
and thus effect an economy of time and of fuel.
In order to apply the flames in a still more perfect manner onto the metal under
trentment and to refine it more rapidly, an jets are employed at a pressure of
from 0 750 to 1000 mètre of water to the number of 5 7 and 9 Jets or blast-pipes R
on each side as shown in Figures 3, 3, and 4 These jets discharge the blast at a
ate corresponding to the charge, in the proportion of from 5 to 15 per cent. of the
quantity of an necessary to completely consume the gases which pass through the
tmnace It must be understood that this 5 to 15 per cent are reckoned by weight,
for as they do not enter the fun nace at the same temperature as the secondary air-
supply, they cannot be compared therewith by volume. The said air-jets produce
an intimate mixture of the hot air and gases leaving the binets at their entry to
the operative space of the fumace, so that the employment of an excess of
from 5 to 15 per cent. of secondary au, whilst only very slightly modifying the final
result of the combustion, will concentiate the flame and cause it to give practically
the maximum temperature at those parts to which the operator desires this maximum
to be directed.
To cleanse the metal and remove the dross of slag which forms a layer of
vitrified mattci over the surface and thus impedes oxidation, inclined tuyères o
blast-pipes (S) are employed, provided with small nozzles, 0006 to 0.010 mètres in
diameter (Figures 3 and,b) These tuyères, which have an independent supply-
pipe (s) from the supply (r) of the inclined jets on tnyeres R, Figure 5, project the
compressed air at a piessure equal to 3 kilos. per square centimetre or a head of
30 mètres of water, to a distance of 1500 mètre from the said nozzles, the jets
being sufficiently powerful to penetrate from 30 to 50 millimetres into the molten
metal. It will be easily seen that under these conditions the chung will take
place with very great rapidity. The secondary an-jets from the tuyères R and S
are controlled automatically by gates or valves coupled to the reversing valves or
bells of the flames, in a similar manner to the retin tubes of the regulators, to
deliver the blust in the same duections as the said flames
In basic refining, as is well-known, it is necessary to provide against the
accumulation of lime dust, the same as when employing the gases from high
furnaces, it is thus necessary to remove this powder from the gas in which it is
suspended The particles of Inne leave the working space of the rehning furnace,
and pass into the regenerators T, Figme 3, after having passed through suitable
catch pits U, Figures 3 and 3, at a very high temperature The said catch pits
are provided with double bends on windings V which retain the drossy matter, as
well as any deposits of dust, which may be removed from time to time by suitable
doors V, which are provided at the end of mehed taking floors V" at the bottom
of the said catch pits.
In order to further prevent the regenerators from being choked with useless lune
dust, they are arranged with straight channels tm such a manner as not to present
any projections on which the dust may be caught and deposited; further, to prevent
these deposits, the upper extremities of the regenerators are rounded so as to
entuely avoid flat sun faces.
Another characteristic feature of my improved regenerator consists in the
employment of refractory supporting blocks W, Figure 6, which enable the metallic
flooring to be dispensed with, the said metallic floor being often split, especially
when, by a lack of secondary air supply, the combustion continues in the passages
beneath. These specially formed refiactory blocks enable spacious cleaning and
dust depositing chambers to be provided.
The passages X connecting the regenerators to the furnace ate arched in such a

page_text: manner as not to be deformed in the houzontal plane of the body of the furnace
under the pressure exerted by the expansion of the same.
In furnaces under forced draught, the smallest leakages cause great waste of gas
and air, these mixtures igniting in the passages and filling the chimney with au
excess of an and smoke which diminishes the diaught. To prevent these leaks,
I employ hydraulic joints with a double water ring, maintained at a constant level by
the same arrangements as those employed to regulate the water-supply to the
furnace grates of the gas generators Figue 1, section -, and preventing back-
currents of an during the working
Figure 5 is a plan of the general arrangement of the apparatus; the gas from
the gas-producets arrives by the underground conduit 1 and passes through the
opening 2, which may be closed more or less by a door or damper 3, into the
evoising bell or valve Y and thence, according to the position of the valve, into
one of the regenerators by one of the conduits 4 and 41; the secondary air-blast
reaches the reversing-valve Y2 through the conduit 5 which may be more or less
closed by a stable damper; from the reversing bell or valve and according to the
position thereof, the air or blast passes into one of the regenerators by one of
the conduits 6 and 6', the products of combustion pass to the chimney 7 by the
conduits 8 and 8'
The refimng furnaces for weldable, homogeneous, cast iron should work at the
highest temperatures employed industially, and at these high temperatures many
of the most refractory materials fuse; silicious bricks alone, consisting of 99% of
silicic acid, strongly chilled, are able to resist, under the condition of very closely
controlling the operation of the furnace and preventing the least increase of
temperature.
Beyond the inconvenience resulting from the failure of the arch, which disables
the furnace for a week at the least, the partial falling in or the fusion of a portion
of the arch places the molten metal, slag consisting of silicic acid which
displaces the phosphonic acid from its combinations; the said phosphoric acid 18
cduced and the metal takes up the phosphorus, so that the dephosphorization has
to be repeated, this is a very serious matter which I have provided against by
employing arches constructed as follows
If the arch of the furnace be constructed of magnesin, it will resist much higher
tempeintures without even partial fusion, and that in cases where temperatures not
only of 1700° to 1800°, but of 2200° to 2400°, but in the event of a partial fusion
thereof magnesia alone would fall into the molten metal, and this, contrary to the
silicic acid, would assist the refining
Unfortunately magnesia bricks nie very expensive and expand badly owing to
their low conductivity for heat Employed according to the usual practice for the
building of aiches (cold externally and very hot internally) they are very brittle,
and fall piecemeal on to the hearth. In order to protect the said bricks against
sudden variations of temperature, I arrange the magnesia bricks in an arch 10,
Fig. 3, under another arch 11 constructed of good refractory bricks, leaving an ur
space between them. Under these conditions the two arches 10 and It may
expand freely without injury to themselves, and the air space, which separates
them, keeps the magnesia atch bucks at a constant temperature, and they may thus
be considered to have an unlimited h'e.
The above are the improvements which I have made in the "Martin" furnice
for refining economically at a very high temperature in the production of
homogeneous. weldable cast on.
Having now particularly described and ascertained the nature of my said inven-
Lion, and in what manner the same is to be performed, I declare that what [
claim is :-
First The herein before described method of refining cast on, characterized by
the elimination at a low temperature of the slag produced by desulphurization,
dephosphorization and the removal of the silicon, the metal thus obtained, termed

page_text: "carburetted iron," being then subjected to very high temperatures so as to entirely
decarburize it, the refining being carried out either in a single furnace, capable of
being worked at different temperatures, or in two furnaces working at different
temperatures, by effecting the transfer of the carburetted iron.
Second. The hereinbefore described improvements in the "Martin " furnace
whereby adapt the same for use in carrying out the method of refining
hereinbefore described.
Dated the 31st day of December 1894
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.