IMPROVEMENTS IN THE MANUFACTURE OF IRON AND STEEL
Year: 1884

page_text: I SYDNEY PITT of Sutton in the County of Surrey Gentleman do hereby declare
the nature of my invention for "IMPROVEMENTS IN THE MANUFACTURE OF IRON
AND STEEL a communication to me from abroad by Antoine Rollet of St Etienne
France to be as follows:-
"
This Invention has for its object improvements in the manufacture of iron and
steel.
The purified metal is obtained by the treatment at a high temperature in special
furnaces of cast iron, wrought iron, scrap and ore either together or separately,
with coke or other fuel under the action of a forced blast in the presence of a slag
containing lime and fluoride of calcium and it may be other bases or materials as
baryta, magnesia, oxide of manganese in proper proportions; the action of the
blast upon the melted materials being prolonged and the action of the coke and the
slag on the metal being limited; all of which results from the arrangement of the
apparatus and the method of conducting the process.
The furnace employed is double and resembles a pair of cupolas or small blast
furnaces connected by a siphon like channel; each division of the furnace has
several ranges of tuyeres one over the other and those on the lowest range are
directed upon the bath of melted matter to favour the action of the blast upon the
metal and the slag. The metal passes continuously from the first division of the
double furnace to the second by the siphon like channel whilst the slag is drawn
off at a higher level over a dam and does not pass to the second part. The melted
metal enters the second division of the furnace at a point above the tuyeres and
descends amongst the ignited contents to the bed; it is drawn off from time to
time by a tapping hole whilst the slag formed in the second division of the furnaco
is drawn off from a point above. The furnace may be formed of any refractory
material. Water cooling is applied to protect the metallic casing and the lining
from destruction by the heat.
The process is conducted as follows:-the fires being lighted as in cupolas the
first part of the furnace is charged with cast iron, with or without scrap and ore
flux, spath-fluor and coke; the second part is charged with flux spath-fluor and
coke with or without scrap and ore. The pressure of the blast should be 35 to 80

page_text: centimetres of water or more according to the size of the tuyeres. The quantity of
calcareous flux included in the charge of each division of the furnace is such that
the acid matters in the slag such as silica and phosphoric acid represent about
20 per cent of its weight less the fluoride of calcium which it contains; the quantity
of spath fluor is so calculated that the slag may contain from 15 to 30 per cent of
fluoride of calcium according as phosphoric acid and the metallic oxides pass into
it in larger or smaller quantities. Ore facilitates the oxidation of the cast iron and
consequently the elimination of its impurities, phosphorus and silicum; if the
object is only the oxidation of the cast iron, the quantity of ore may be 10 to 20
per cent of the weight of the cast iron.
The quantity of coke should be sufficient to melt and maintain at a high
temperature both the metal and the slag; when employing blast heated to 350 to
400° C this quantity will be in the first division of the furnace 12 to 15 per cent
of the weight of the metal and in the second division from 4 to 5 per cent according
to the proportion of flux and other materials to be melted.
The metal after passing out of the first division of the furnace into the second
experiences a second purification from the action of the blast and the matters added
with the coke; the conduct of the further operations, the tapping out of the metal
and the alag is as with a blast furnace.
The second division of the furnace may in some cases be replaced by a receiver
where it is retained in a melted state and where it may be further treated.
Or the purified metal may be further treated in a Bessemer converter with basic
lining preferably of magnesia.
The purification will have completely eliminated sulphur and silicum; if the cast
iron originally was very phosphatic after purification it should not retain more than
about a per cent of phosphorus.
For a cast iron containing a per cent of phosphorus the temperature necessary
to the success of the operation will be obtained; 1° by raising the temperature of
the metal to a higher point than is necessary for metal treated by the ordinary
Bessemer process, 2° by the employment of blast at 450° to 500° about. The
temperature of the blast and that of the metal as well as the contents as respects
phosphorus may however be varied so that the necessary temperature of the liquid
bath may be always obtained.
The Bessemer operation will be conducted as in the treatment of pure cast iron;
the addition of the manganiferous iron will be made at the commencement or the
end of the operation.
To obtain cast iron with the proportion of phosphorus indicated the slag will
have the composition given above or it will contain less lime but the proportion of
silica and phosphoric acid will not be higher than 20 per cent.
The first division of the furnace may be used alone or a receiver may be added 4
to the double furnace. Or the metal may be allowed to collect in the lower part
of the furnace,
The metal and slag together may be allowed to pass into a receiver but the
separation by means of the siphon like passage is usually preferable.

page_text: COMPLETE SPECIFICATION.
I SYDNEY PITT of Sutton in the County of Surrey Gentleman do hereby
declare the nature of my invention for "IMPROVEMENTS IN THE MANUFACTURE
OF IRON AND STEEL" (a communication to me from abroad by Antoine Rollet of
St Etienne France) and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
According to this invention cast iron purified from sulphur silicium and phos-
phorus is used in the manufacture of iron and steel and the invention relates
mainly to a process of purifying the cast iron.
The purification of the cast iron is effected by treating at a high temperature
preferably in a cupola furnace such as shown in the drawings hereunto annexed
ordinary cast iron or wrought iron scrap with coke, flux, spath-fluor and oxide of
iron in sufficient quantity to form with the oxidized clements of the cast iron a
basic slag but little ferruginous.
The cupola furnace cooled by water is at first lined at the parts exposed to rapid
wear with a thin coating of any suitable refractory material but after 20 or
30 hours work these parts become covered with metallic iron.
The tuyeres are more dispersed than usual as the weight of lime and spath-fluor
per ton of cast iron is increased-the object is as much as possible to bring into
contact and to fuse all the matters which ought to react one on another.
The part E is put into communication with the front hearth a by a syphon c
taking the metal at a level as near as practicable to the lower row of tuyeres.
The slag is drawn off at a higher level over a dam and does not pass to the froat
hearth the object of this is to separate the cast iron from the slag and coke so
as to avoid the re-absorption into the iron of the phosphorus previously separated.
Such reabsorption would otherwise take place by the partial reduction of the
phosphate of lime in the slag on contact of the iron with coke. The downward
inclination of the lowest row of tuyeres has for its object to prolong the action of
the blast on the iron, slag and coko so as to maintain and increase the elimination
of phosphorus from the iron.
These last arrangements also enable too high a carburation of the iron to be
avoided which would result from the temperature at which the operation is carried
on and from the basic and little ferruginous nature of the slag.
The front hearth e is made of refractory material and can be heated by a grate
as shown or otherwise.
The pressure of the blast used is from 40 to 60 centimetres of water at least and
its temperature raised as much as possible say to 350° or more.
According to the proportions of phosphorus and silicium in the iron or scrap the
charge should consist for every
1000 10 L

page_text: To obtain a better result so far as the elimination of phosphorus is concerned
the composition of the slag should approximate to the following—
Silica and phosphoric acid-the least possible
Alumina arising from the coke and purifying matters 2- 8
Lime as much as possible
Fluoride of calcium as little as possible -
Oxide of iron
Sulphur
-
12-16%
-
50-60
20-28
-
2- 4
1-2
In the calculation of the composition of the charge it is assumed which is only
approximately true that all the silicium and phosphorus eliminated from the iron 1
enters into the slag forming silicates and phosphates-As to the sulphur whatever
quantity of it is contained in the cast iron to be purified the slag will only retain
from 1 to 2% or thereabouts. The rest often more than the half will be driven
off with the furnace gases by the action of the outer furnace and the blast in the
cupola furnace.
The proportion of oxide of iron which enters into the charge is made less for
white irons containing sulphur than for grey or white irons which contain but
little sulphur.
1
Sulphurous irons more oxidizable than those which are less sulphurous produce
by themselves in the upper parts of the furnace oxide of iron which augments the 2
amount in the charge which has to be reduced in the lower parts of the furnace.
The cast iron obtained is white and fibrous or grey and crystalline generally it
is more carburated and contains less manganese than before purification.
The slag is white or slightly yellowish or grey white.
It will be understood that the purified cast iron instead of being collected in the 2
front hearth e might be received into another apparatus arranged similarly to the
cupola furnace where it would be subjected to a second purifying operation in
contact with fresh purifying matters.
The purification could also be effected in other forms of apparatus with tuyeres
at the sides either disposed horizontally or inclined to act on the cast iron or other 3
matters in the charge the charge being composed of the same elements as the
charge for the cupola furnace. This last arrangement would be more especially
suitable for irons in first fusion.
In the cupola furnace apparatus first described the front hearth might serve
either partially or completely as a refining furnace in this case the product might 3
either be decarbonized iron or steel. When the object is to obtain a complete
refining for iron or cast steel the channel forming a continuation of the siphon
might be so arranged as to conduct the cast iron alternatively into two furnaces
of the Siemens-Martin type or into furnaces of other kind. But generally it will
be preferable to draw off the purified iron from the front hearth of the apparatus 4
described into the apparatus where the refining is to be completed. It will be seen
that the invention is characterized principally
1. By the treatment of cast iron or wrought iron scrap at a high temperature
with coke flux spath-fluor and oxide of iron in proportions determined by the
quality of the cast iron or scrap to obtain taking into account the oxidized elements 4
in the cast iron or scrap an extra basic slag little ferruginous in a medium but
little reducing or oxidizing so as to favor the elimination of the impurities in the
iron by the maximum formation of metallic sulphates silicates and phosphates
entering into the slag without the amount of carbon in the cast iron being too
much diminished by the purification properly so called.
50
2. By the means described for realizing the purifying operation of the cast iron.
Whilst the entire elimination of sulphur and silicium is effected during the
traverse of the cast iron from top to bottom of the furnace-the elimination of
the phosphorus which to a great extent takes place conjointly with the sulphur
and silicium is maintained and increased by the prolonged action of the blast on 5!
the iron and slag in presence of coke so that there may not be too great an
oxidation of the metal or carbon of the cast iron,

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The process substantially as herein before described for purifying cast iron
or wrought iron scrap.
2. The arrangement of the apparatus for carrying out this process substantially
as herein before described.