IMPROVE- MENTS IN THE MANUFACTURE OF STEEL, AND IN THE LINING OF BESSEMER CONVERTERS
Year: 1877

page_text: "
LETTERS PATENT to Sidney Gilchrist Thoinas, of 3, Queen's Road Villas, Queen's
Road, Battersea, in the County of Surrey, for the Invention of IMPROVE-
MENTS IN THE MANUFACTURE OF STEEL, AND IN THE LINING OF BESSEMER
CONVERTERS."
Sealed the 8th February 1878, and dated the 23rd November 1877.
PROVISIONAL SPECIFICATION left by the said Sidney Gilchrist Thomas at
the Office of the Commissioners of Patents on the 23rd November 1877.
SIDNEY GILCHRIST THOMAS, of 3, Queen's Road Villas, Queen's Road, Battersea,
in the County of Surrey. "IMPROVEMENTS IN THE MANUFACTURE OF STEEL, AND
IN THE LINING OF BESSEMER CONVERTERS."
In the manufacture of Bessemer steel it has hitherto been found necessary to use
only certain pure and relatively expensive kinds of pig iron, viz., those which
contain only a very small proportion of phosphorus. This is due to the fact that in
the Bessemer process, as at present conducted, phosphorus is not appreciably removed.
This non-removal of phosphorus I have ascertained by experiment to be due to the
presence in the molten contents of the converter of an excess of silica derived from
the lining of the converter. The linings at present in use consist in great part or
entirely of silica, either as ganister or in combination. Now my Invention consists
in the use of certain linings containing but a small per-centage of silica, whereby
the per-centage of silica in the converter cinder is approximated to that commonly
found in the cinder from puddling furnaces, and pig iron containing much more
than two-tenths per cent. of phosphorus may be successfully converted into steel,
which at present can not be done. By the use of my linings a considerable amount
of sulphur is also removed.
I construct my linings by one of the following methods:-I take limestone, and
grind it to powder, and then add as much silicate of soda as will moisten the whole
mass, and mix thoroughly with a little water to get a uniform mass.
I then ram
the mixture round the converter in the usual manner.

page_text: In place of limestone I sometimes use magnesian limestone, but limestone is pre-
ferable; or I use limestone, together with calcined plaster of Paris, and a small
quantity of silicate of soda; or I take well and recently burnt lime, and grind it
with a small quantity of silicate of soda, and use it as in the last-mentioned case;
or, instead of lime, well-calcined magnesia may be used, in which case a little water
may be added to the mass.
A mixture of lime and magnesia may also be used.
Alumina in the form of emery ground with silicate of soda, and 5 to 10 per cent.
of clay may also be used as a lining.
Bauxite (or highly aluminous iron ore) mixed with silicate of soda and a little
graphite or coke dust, and not more than 5 per cent. of clay, may also be used. Of
these I prefer limestone and silicate of soda, or magnesia and silicate of soda.
When a charge of metal is acted on in a converter having a lining of the nature
above described it will be found that a large portion of the phosphorus and sulphur
originally in the iron is taken up in the slag, and at the completion of the blowing
operation I draw off the slag from the purified metal before adding to it spiegeleisen
or ferro-inanganese to complete its conversion into steel.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sidney Gilchrist Thomas in the Great Seal Patent Office on the 22nd
May 1878.
SIDNEY GILCHRIST THOMAS, of 3, Queen's Road Villas, Queen's Road, Battersea,
in the County of Surrey. "IMPROVEMENTS IN THE MANUFACTURE OF STEEL, AND
IN THE LINING OF BESSEMER CONVERTORS."
This Invention has for its object improvements in the manufacture of steel, and
in the lining of Bessemer convertors.
In the manufacture of Bessemer steel it has hitherto been found necessary to use
only certain relatively pure and expensive kinds of pig iron, namely, those which
contain only a very small proportion of phosphorus. This is due to the fact that in
the Bessemer process, as at present carried out, phosphorus is not appreciably
eliminated. This non-removal of phosphorus I have proved by experiment to be
solely due to the presence in the molten contents of the convertor of an excess of
silica derived from the lining of the convertor, and I find that by using certain
basic linings phosphorus may be readily removed in the Bessemer convertor. The
linings now in use consist of ganinster or fire-clay, or other highly silicious substances.
Now my Invention consists in the use of certain refractory, coherent, and durable
basic linings, containing but a comparatively small proportion of silica, thus allowing
of the per-centage of silica in the convertor cinder being approximated to that
commonly found in the cinder from the puddling furnace. By this means pig iron
containing a very considerable amount of phosphorus may be successfully converted
into good merchantable steel or ingot iron containing very little phosphorus,

page_text: I construct my linings in the following manner:-Limestone or maguesian lime-
stone or chalk (preferably those kinds which are of an aluminous character) is
ground finely (in a mortar mill or otherwise), with about ten per cent. of its weight
of a solution of silicate of soda (or silicate of potash, silicate of soda being however
preferable), and a little water, till the whole is intimately mixed, and forms a moist
pasty putty-like mass. The solution of silicate of soda, on which the above propor-
tion is calculated, has a specific gravity of 15, but a more or less dilute solution
may be used. The total amount of silica present in the dried but uncalcined mixture
of stone and silicate of soda should not exceed about twelve per cent. by weight of
the whole as a maximum, and should preferably be less.
The presence of alumina in the limestone or chalk used is desirable, as it acts as
a cementing material to the lime, aud thus augments the effect of the silicate of
soda without impeding in any way the slag becoming basic. The presence of oxide
of iron (which generally accompanies alumina) in the limestone or chalk used has a
similar effect to that of alumina, but it is more fluxing than alumina, which restricts
the amount permissible in the mixture.
The silica naturally present in aluminous and some other limestones is also a
strong binding material, but, as has been before mentioned, it must not be present
in excess, as it would not only promote the fusibility of the lining, but would impede
the slag becoming basic. As an example, I have found that a lias limestone con-
taining nine per cent. of silica, three per cent. of alumina, and one per cent. of
peroxide of iron makes with silicate of soda a good lining, and it is not desirable
that this amount of oxide of iron and alumina should be very materially increased,
or the refractory character of the lining will be generally impaired.
Magnesia ground with silicate of soda may be sometimes used in place of lime-
stone, but is much more expensive than the latter. The presence of magnesia in
the limestone used is generally advantageous.
The moist pasty mixture produced, as above described, may be either rammed
round the convertor as gannister linings are now generally put in, or it may be first
made into bricks. These bricks should be thoroughly dried at a moderate temperature
before being used to line the convertor, but should not be fired or calcined. They
should be set in a basic cement, which may be made of the same materials as the
bricks themselves.
.
Alumina, as in the form of emery, may be also sometimes used as a lining, after
being ground with about ten per cent. of silicate of soda solution, and five or ten
per cent. of clay. It may be used either as highly-fired bricks, or as a rammed
lining; this however is an expensive lining.
When a convertor has a basic lining the tuyeres should also be made of similar
basic materials; thus, a good tuyere may be inade from limestone ground with about
ten per cent. of silicate of soda solution.
When a charge of pig iron is blown in a convertor having such a basic lining as
is above described, it will be found that a great part of the phosphorus (and some-
times much of the sulphur) originally contained in the pig iron is carried into the
slag produced. I prefer to tap off this basic phosphorus containing slag from the
purified metal before adding to it spiegeleisen (or its equivalent) in order that no
part of the phosphorus may be carried back into the metal. The slag may be con-
veniently tapped off in the ladle into which the converted metal is poured. In this
case the spiegel is added in the ladle and not in the convertor. It is desirable to
line the ladle also with one of the basic mixtures above described.
Having thus described the nature of my said Invention, and the manner of per-
forming the same, I would remark that the use of certain basic substances for
linings has before been suggested, but not adopted, owing to the want of coherence
and durability, or unsuitability in other respects of the substances proposed to be
used; what I claim as my improvements in the manufacture of steel, and in the lining
of Bessemer convertors, especially when phosphoretic pig iron is to be treated is,-
First. Lining the Bessemer convertor used in the said manufacture with a

page_text: mixture of limestone or chalk, or magnesian limestone and silicate of soda or silicate
of potash.
Second. Lining the Bessemer convertor used in the said manufacture with a
mixture of magnesia and silicate of soda, or silicate of potash.
Third. Lining the Bessemer convertor used in the said manufacture with a mixture
of emery, clay, and silicate of soda, or silicate of potash.
Fourth. Treating pig or cast iron in a Bessemer convertor having a basic lining;
then removing the phosphorus containing slag which has been produced, and after-
wards adding to the metal spiegeleisen or its equivalent.
In witness whereof, I, the said Sidney Gilchrist Thomas, have hereunto set
my hand and seal, this Twenty-first day of May, in the year of our Lord One
thousand eight hundred and seventy-eight.
SIDNEY GILCHRIST THOMAS. (L.S.)