IMPROVEMENTS IN THE MANUFACTURE OF IRON AND STEEL
Year: 1880

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF IRON AND
STEEL." A communication from abroad by Monsieur Rollet, of St. Etienne,
in the Republic of France.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 17th December 1880.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
MANUFACTURE OF IRON AND STEEL." [A communication from abroad by Monsieur
Rollet, of St. Etienne, in the Republic of France.]
This Invention has for its object improvements in the manufacture of iron and
steel.
Sulphur is only sufficiently eliminated from iron and steel in metallurgical
operations, either by an oxidizing action in the presence of a basic slag at a
relatively low temperature, as in puddling, or by a reducing action of its oxygenized
compounds in the presence of a basic slag at a high temperature, as in a blast
furnace.
Hence the impossibility under practical conditions of obtaining steel in a
Bessemer convertor or in a melting furnace from sulphurous cast irons whether the
slag be basic or not. It happens, in fact, that the metal obtained is insufficient in
quality when hot, or at least requires a supplementary puddling before its trans-
formation into merchantable products.
By this process steel can be manufactured from sulphurous and phosphatic
cast irons, which by known processes would only yield worthless or inferior
products.
The process consists of, 1st, in submitting cast iron at a high temperature to a
reducing action to the oxygenized compounds of sulphur in the presence of a slag,
which will be more and more basic as the iron is more and more sulphurous; 2nd,
in finishing the refining of the cast iron so treated in a basic converter, or in a
furnace with a basic sole.

page_text: This result may be obtained in both ways. 1st method; the iron is melted in a
cupola lined internally at the parts liable to wear with a basic material, magnesia,
dolomite, lime, or bauxite, in preference to the ordinary argilo siliceous lining. The
iron and the coke are charged into it mixed with basic matters, lime, magnesia, and
the like, and fluor spar; the melting operation is carried on as usual, the tempe-
rature being more elevated according as a more energetic desulphurizing
action is desired. After melting the cast iron, which now contains only a very
small proportion of sulphur, a little less silicon than before melting, and all or
nearly all its phosphorus is transferred into a basic Bessemer convertor, where it is
completely refined by the Thomas Gilchrist process, or in place of performing the
refining in a basic converter it may be performed in a furnace with a basic sole.
2nd Method. The iron is melted in a melting furnace_fixed or moveable (pre-
férably the Pernot furnace), with a sole of basic materials as above; a slag of the
same composition as that employed for the cupola is charged in, before, or at the
same time as the iron; the reducing action is obtained by maintaining on the bath
a thin layer of combustible coal or coke. After a sufficiently prolonged contact of
the liquid iron with the slag it is deprived of the greater part of its sulphur, its
other impurities being little varied; it is then transferred to a basic Bessemer
convertor to refine it according to the Thomas-Gilchrist process; its complete
refining may as before be performed in a furnace with a basic sole, either in that
which was employed for the desulphurization or in another for the separation of
the slag.
This mode of making steel may be advantageously employed for iron run liquid
from the blast furnace, and finally treated in the Bessemer converter by the Thomas-
Gilchrist process.
The final composition of the desulphurizing slag of the slag of the desulphurizing
operation, that is to say, that which results from the matters added, and from the
oxidation of some impurities of the cast iron, especially silicon, and from the wear
of the lining of the apparatus, also from the ashes of the fuel, may vary within
somewhat wide limits. Those given below correspond to a very large elimination
of sulphur.
Silica, allumina, and phosphoric acid, 25 to 35 per cent.; lime, magnesia, oxide
of iron, manganese, &c., and fluoride of calcium, if there be any, 72 to 60 per cent. ;
sulphur, less rather than more, 4 to 5 per cent.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt' in the Great Seal Patent Office on the 17th June
1881.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
MANUFACTURE OF IRON AND STEEL." A communication from abroad by Monsieur
Rollet, of St. Etienne, in the Republic of France.
This Invention has for its object the elimination of sulphur and more or less of
other impurities from cast iron.
Sulphur is only sufficiently eliminated from iron and steel in metallurgical
operations either by an oxidizing action in the presence of a basic slag at a
relatively low temperature, as in puddling, or by a reducing action of its oxygenised
compounds in the presence of a basic slag at a high temperature, as in a blast
furnace.
Hence the impossibility under existing conditions of obtaining steel in a
Bessemer converter or in a melting furnace from sulphurous cast irons, whether the
slag be basic or not,
By this process steel can be manufactured from sulphurous and phosphatic irons
which by known processes would only yield worthless or inferior products.
The process consists, 1st, in submitting cast iron at a high temperature to a
reducing action to the oxygenized compounds of sulphur in the presence of a slag
which will be more and more basic as the iron is more and more sulphurous.
2nd, in finishing the refining of the cast iron so treated in a basic converter or in a
furnace with a basic sole.
The first method by which I obtain this result is to melt the cast iron in a
cupola lined internally with basic, not oxidizing substances, by any of the known
ways. Outside and around the parts exposed to rapid wear from overheating is a
surrounding jacket through which is passed a stream of water. Water tuyeres are
also used like those employed with blast furnaces.
This arrangement of apparatus ensures a minimum wear of the parts, so that
they have not to be frequently renewed. The pressure of blast employed is higher
than with ordinary cupolas, 30 centimetres of water at least, but preferably 50 or
more.
The charge is made up as follows:-In addition to the pig iron and coke, the
charge is made up of limestone, flux, or dolomite, and of fluor spar; or failing
this latter, or together with it, oxide of manganese, either in a slag or as a
mineral.
The coke should contain little ash, and the other matters little silica or clay.
The following composition gives good results when the object is to obtain the
greatest elimination of each impurity:
Pig iron
o
Limestone flux or dolomite with about 2% of clay
Fluor spar with 10% silica or clay
°
Coke with 8 or 10° ash
Pressure of blast 35 to 50.
Centimetres of water.
1000 kilo.
140 to 90
25 to 20
170 to 150
When it is desired to retain in the iron its silicon, as when it contains but little,
and its phosphorus, the temperature required is higher. This is obtained by
increasing the proportion of coke by from 4 to 5 per cent. of the weight of iron.
The quantity of fluor spar is reduced one third or one half; the quantity of the
other materials need not be varied.
The wind pressure should be reduced to about 25 to 40 centimetres of water.
With either one or other of these compositions account should be taken of the

page_text: •
oxide of manganese derived from the oxidation of the manganese in the iron, as it
tends to render the slag basic and more fusible, and its formation aids, as in puddling,
the extraction of the other impurities. A smaller proportion may consequently be
used if the other elements of the slag which are to render it more basic and more
fusible.
If a hot blast is used, the limestone flux and fluor spar will be reduced as well
as the fuel on account of the diminution of ash. The proportions of sulphur of
silicon and of phosphorus eliminated are greatest by employing a cold working
cast iron, the composition of the charge being as first indicated, and the tuyeres
placed at 3 or 4 heights, preferably at 2 or 1, to facilitate the oxidizing of the
silicon and phosphorus without decreasing the elimination of sulphur, which goes
off. for the most part as vapour, and the remainder as sulphurous acid, but the
iron so obtained is more especially applicable for the making of steel on a
hearth.
The charge composed as secondly described, and the arrangement of the tuyeres
at one or two heights, are used for treating pig irons, the refining of which is to be
completed in a basic lined Bessemer converter. The pig irons treated should then
be but little silicious.
For pig irons which are to be refined in a puddling furnace it will often be
advantageous for better puddling to retain in the iron a large percentage of carbon
and some silicon.
The composition of the first charge, the arrangement of the tuyeres mentioned
for the second, and a suitable choice of irons, will permit of the desired composition
being easily obtained.
The manner of working is as follows:-
The cupola lining having been dried, or the volatile matters contained in it
driven off, coke is fed into the cupola. For every 100 k of coke 4 k of flux and as
much fluor spar is added, for in spite of what has been above said of the composition
of the slag it should not be sought to be obtained for the first run, or a chokage
might arise; on the other hand it is necessary to add flux and fluor spar in the
proportions given to ensure purification of the first runs. Afterwards the charging
of the cupola is continued with the composition previously set forth.
The difficulties of running the slags, or their adhering to the tuyeres from
whatever cause they may arise, are obviated by increase of temperature or momentary
increase of the dose of fluor spar.
The temperature at which the purified irons are run off is governed by the
proportion of coke consumed and the temperature of the blast used; nevertheless
some causes may make it vary, and it is necessary to indicate it.
When employing the first charge for the elimination of sulphur and the greater
part of the other impurities it should be of about the same intensity as that of grey
iron run from a blast furnace; it can be regulated by controlling the proportion of
coke in the charge.
When employing the second charge for the elimination of sulphur only it should
be of the same intensity as required for the fusion of hard steel.
A second method is as follows:-
The apparatus, a reverberatory furnace, moveable preferably like the Pernot
furnace, is lined at the parts in contact with the iron and slags with dolomite
calcined at high temperature. The repairs to the hearth are to be made with
dolomite or with lime roasted to the temperature of ordinary lime kilns; these are
thrown on to the worn parts where they agglomerate, and are fixed by heating
them for a sufficient length of time to a very high temperature.
The operation is as follows:-
The temperature of the furnace having been raised to a glowing white the
purifying matters are introduced into it, lime or basic slag 5 to 6% of the weight
of the iron, and 1/2 to 1% of fluor spar. The employment of fluor spar is not
indispensable; less fluidity of the slag does not produce the same inconvenience, as
in a cupola; also it is not indispensable that the matters used for forming the
0

page_text: basic slag should be as free from silica or clay as those used in the cupola. After
some minutes, coal or coke in small fragments are introduced in to the furnace in
sufficient quantity to cover the bath to a depth of 2 or 3 centimetres. The iron
is then introduced.
The apparatus is kept in movement until the end of the operation, which last
about 16 minutes. The carbon or coke which covers the bath is replaced as it is
consumed.
°
The slag, the weight of which is from 6 to 10% of the iron, contains about
20 to 30% of silicon, taking into account to obtain it the ash from the carbon or
coke added to the bath, the reduction of the lining, and the slight refining of the
iron.
When running off, or during the operation, the temperature of the iron is of the
same intensity as that of a welding or re-heating furnace.
If the refining of the iron thus purified is to be completed in the same apparatus
by the known process, the sulphurous slag which covers the bath is first to be
drawn off as much as possible.
This mode of purification is especially suitable for iron run direct into the
apparatus from a blast furnace the refining of which should be finished in a basic
lined. Bessemer converter.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Sixteenth day of June, in the year of our Lord One thousand
eight hundred and eighty one.
SYDNEY PITT. (L.S.)