IMPROVEMENTS IN THE MANUFACTURE OF STEEL
Year: 1858

page_text: LETTERS PATENT to Edmund Leopold Benzon, of Sheffield, in the County
of York, Steel Manufacturer, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF STEEL."-A communication from Franz Anton Lohage,..
residing at Unna in the Kingdom of Prussia.
PROVISIONAL SPECIFICATION left by the said Edmund Leopold Benzon
at the Office of the Commissioners of Patents, with his Petition, on the
27th September 1858.
I, EDMUND LEOPOLD BENZON, of Sheffield, in the County of York, Steel
Manufacturer, do hereby declare the nature of the said Invention for "Im-
PROVEMENTS IN THE MANUFACTURE OF STEEL," to be as follows:-
This Invention of improvements in the manufacture of stect is based upon
certain discoveries made by the Inventor of the behaviour of pig or cast iron
under certain circumstances, such as while being heated or boiled in a
reverberatory furnace, and consists in the application of the knowledge of the
scientific facts so obtained to the treatment of crude, pig, or cast iron or
refined metal, so that guided by a close observation of the behaviour of such
iron in a reverberatory or melting furnace the workman may be enabled with
certainty and precision to decarbonize the iron to a definite and determined
extent, and leave or retain a proper amount or atomic proportion of carbon in
chemical combination with the iron, and by this means be enabled to produce
steel of any required temper or degree of hardness.
Owing to the discoveries made by the Inventor the chemical changes which

page_text: from time to time take place in the furnace can be detected and ascertained
with accuracy, and therefore he is enabled to conduct with precision and
certainty processes and operations connected with the conversion of pig or
cast iron into steel which have heretofore been carried on very much by guess,
and which consequently very frequently gave unsatisfactory and imperfect
results.
In practical experiments made by the Inventor to ascertain at what point
of decarbonization crude, pig, or cast iron first became a malleable metal, he
discovered that the particles of the metal invariably, at certain stages of the
process, assumed certain definite forms, and that such forms of the particles
indicated certain definite degrees of carbonization and the possession of
certain definite physical properties, and he thus ascertained the form the
particles of metal assumed when they possessed the physical properties of
weldable steel, and from this he was enabled infallibly to determine at what
stage of the process steel having such properties could be obtained.
Into a reverberatory furnace of the usual construction (giving a preference
to a furnace with a flat bottom) a convenient charge of crude pig iron, or of
refined metal (say about 360 lbs. weight) is to be introduced, and in the first
stage of the puddling process the usual mode of operation is adopted, the
object being to bring the mass to a perfect state of boiling. During the
boiling and rising of the mass globular grains begin to appear on the surface
of the melted cinder, and will increase gradually in number as the process
continues. These grains, as long as they continue of a globular form, will be
found to be grains of cast iron having neither malleability nor a welding
property. At this stage of the process the cinder acts very powerfully on the
carbon of the pig iron, the decarbonization of which goes on very rapidly, and
it becomes important to watch the process with great care, when it will be
seen that the particles of metal which break through the cinder will gradually
lose their globular form and will become pointed at one end, or of a pear like
form. This form of particles will indicate the presence of that amount or
proportion of carbon in the metal which constitutes the hardest kind of steel
which is ductile or malleable, but not weldable. As the decarbonization
continues the grains will become more and more pointed and even elongated,
and on touching each other during their motion through the fluid mass will
not separate as before, but will now adhere to each other, and on uniting will
sink through the cinder. This elongated form and adhesion of the particles
will indicate the presence of that per-centage of carbon which constitutes the
hardest weldable steel. This stage of the process having been attained will
form a starting point for the workman, and will enable him to produce stecl

page_text: of the different degrees of temper and hardness required for various applica-
tions and purposes.
As soon as the proper amount of decarbonization has been effected, and the
furtlier progress thereof stopped, the metal is to be formed into balls, care
being taken always to keep the metal as much as possible immersed in or
covered by the cinder, and when the balls are made they may be removed
from the furnace and forged into blooms at the welding heat of steel.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Edmund Leopold Benzon in the Great Seal Patent Office on
the 26th March 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDMUND
LEOPOLD BENZON, of Sheffield, in the County of York, Steel Manufacturer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-seventh day of September in the year of our
Lord One thousand eight hundred and fifty-eight, in the twenty-second year. of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Edmund Leopold Benzon, Her special license that I, the said Edmund
Leopold Benzon, my executors, administrators, and assigns, or such others as
I, the said Edmund Leopold Benzon, 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 "Ix-
PROVEMENTS IN THE MANUFACTURE OF STEEL," being a communication from
Franz Anton Lohage, of Unna, in the Kingdom of Prussia, upon the
condition (amongst others) that I, the said Edmund Leopold Benzon, by an
instrument in writing under my hand and seal 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 Edmund Leopold Benzon, do hereby
declare the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement (that is to say) :-

page_text: This Invention of "Improvements in the Manufacture of Steel" is based
upon certain discoveries which the Inventor has made of the behaviour of pig
or cast iron under certain circumstances, such as while being heated or boiled
in a reverberatory furnace, and the Invention consists in the application of the
knowledge of the scientific facts so obtained to the treatment of crude, pig, or
cast iron, or refined metal, so that, guided by a close observation of the
behaviour of such iron in a reverberatory or other melting furnace, the
workmen may be enabled with certainty and precision to decarbonize the
iron to a definite and determined extent, and leave or retain a proper amount
of atomic proportion of carbon in chemical combination with the iron, and by
this means be enabled to produce steel of any required temper or degree of
hardness.
Owing to the discoveries made by the Inventor of the process of the.
behaviour of fused iron in the puddling or reverberatory furnace he can detect
and ascertain with accuracy the chemical changes which from time to time
take place in the furnace, and therefore he is enabled to conduct with precision
and certainty any process and operation connected with the conversion of pig
or cast iron into steel. The ordinary puddling or reverberatory furnace has
been found to be best adapted for carrying out the improved process, because
the workman can therein best control the chemical action of the cinder or
slag upon the cast or pig iron. The process will also be materially assisted
by the mechanical action of the puddling tool, and in the puddling furnace the
eye will guide the workman to attain accuracy in the production of the desired
quality of steel.
It has been long known to scientific men that the different physical
properties of pig iron, steel, and wrought iron depend upon the per-centage
of carbon they respectively contain, and that in making pig iron into wrought
iron in the puddling furnace the metal at some stage of the process must
contain that atomic proportion or per-centage of carbon which will constitute
it the substance known as steel; starting from this known fact the Inventor
commenced studying the physical properties of pig iron and steel, and
after various careful experiments and observations he came to the conclusion
not only that the physical properties of pig iron, such as its non-malleability,
and of various qualities or tempers of steel, such as their malleability and
welding property, as well as the different degrees of hardness of steel depended
upon the proportion of carbon the different samples contained, but that during
the process of manufacture the state of decarbonization required to impart
these physical properties to the iron might be distinctly recognized.
The Inventor considers that in crude, pig, or cast iron, the carbon is partly in

page_text: It
mechanical and partly in chemical combination with the iron, and that the
carbon so mechanically and chemically combined may be separately or
successively removed or eliminated from the iron by proper treatment.
will, however, always be found that the mechanically combined carbon will
disappear first, and when this is removed, the carbon which is in chemical
combination with the iron will speedily follow. The result of the Inventor's
experiments have demonstrated that with a high bright red heat ("rothgluhitze")
the mechanically combined carbon will be withdrawn from the pig iron, but
that with a white heat ("weissgluhitze,") both kinds of carbon will be removed.
and lost. If, therefore, the mechanically combined carbon is eliminated or
driven off from the pig iron by application of a high bright red heat
("rothgluhitze,") a chemical combination is obtained of iron and carbon
(Fe. C.) which is steel. By increasing the heat, however, to a white heat
("weissgluhitze") all the carbon will be driven off, and the pig iron will be
converted into pure iron or wrought iron.
In the Inventors practical experiments to ascertain at what point of
decarbonization crude, pig, or cast iron first became a malleable metal, he
discovered that the particles of the metal invariably at certain stages of the
process assumed certain definite forms, and that such forms of the particles
indicated certain definite degrees of decarbonization, and the possession of
certain definite physical properties; he thus ascertained the form the particles
of metal assumed when they possessed the physical properties of weldable
steel, and from this he was enabled infallibly to determine at what stage of the
process steel having such properties could be obtained.
Having further determined by practical experiments the point at which pig i
iron first becomes malleable and which is the point corresponding to the
highest temper of steel, and having carefully watched every stage of the
process of decarbonization as herein-after more fully described, he was enabled
to determine at what point of decarbonization, and at which corresponding
form of particles crude, pig, or cast iron in the puddling or reverberatory
furnace becomes first malleable and next weldable steel.
This led to the discovery that by closely watching the various changes and
controlling or regulating the process, the workman could with certainty.
produce in the puddling furnace every degree of temper of steel, from the
hardest steel, so hard as only to be fit for melting into cast steel, down to the
softest steel, which in the form of German shear or cast steel, would not
perceptibly harden at the highest heat, if plunged into cold water.
I will now proceed to illustrate the practical application of the above

page_text: mentioned discoveries, and to do so more clearly will explain the manner in
which it may be carried into effect in a puddling or reverberatory furnace.
I introduce into a reverberatory furnace of the usual construction (giving a
preference to a furnace with a flat bottom) a convenient charge of crude pig
iron, or of refined metal (say about three hundred and sixty pounds weight),
and in the first stage of the puddling process I adopt the usual mode of
operation, my object being to bring the mass to a perfect state of boiling.
As the different descriptions of pig or cast iron vary in their nature they
require a somewhat different treatment, which is effected, as is well known, by
opening or closing dampers, as may be required, or by adding a mixture of
manganese and salt, or by employing other known means for the purpose of
securing perfect boiling, and a good rising of the entire mass. This point
having been attained I make up a good fire by means of an additional
charge of coal, and work with an open damper in order to accumulate
sufficient heat for the subsequent operations. During the boiling and
raising of the mass globular grains begin to appear on the surface of the
melted cinder, and these will increase gradually in number as the process con-
tinues. The grains, as long as they continue of a form which the Inventor calls
globular will be found to be grains of cast iron, having neither malleability
nor a welding property, and in their motion through the cinder the grains
will pass each other without any apparent attraction; and even if they
touch each other will quickly separate. At this stage of the process the heat
should never be allowed to exceed a high bright red heat ("rothgluhitze"),
when the cinder will act very powerfully on the carbon that is mechanically
combined with the iron, and the elimination of the mechanically combined
carbon will go on very rapidly. It now becomes important to watch the
process with great care, when it will be seen that the particles of metal which
break through the cinder will gradually lose their globular form, and will
become pointed at one end, or of what I call a pear-like form. This form of
particles will indicate the presence of that amount or proportion of carbon in
the metal which constitutes the hardest kind of steel which is ductile or
malleable, but not weldable, and is fit only for melting into hard cast steel.
These pear-like grains when they meet in their motion through the fluid cinder
may perhaps come in contact with and touch each other, but will separate
having apparently as yet no attraction for each other; but as the decarboni-
zation continues the grains will become more and more pointed, and even
elongated, and on touching each other during their motion through the fluid
mass will not separate as before, but will now adhere to each other, and on

page_text: uniting will sink through the cinder. This elongated form and adhesion or
fusion of the particles together will indicate the presence of that per-centage of
carbon which constitutes the hardest weldable steel. This stage of the process
having been attained, and which may also be recognized by the workman feeling
greater resistance to the puddling tool, it will form a starting point for the
workman, and will enable him to produce steel of the different degrees of
temper and hardness required for various applications and purposes. While
these changes in the form of the particles of metal are taking place care must-
be taken that the heat be never allowed to exceed a high bright red heat
("rothgluhitze.") I would here remark that the Inventor uses the term
high bright red heat ("rothgluhitze,") in contradistinction to white heat
("weissgluhitze,") at which heat the steel, if worked in the furnace,
would be converted into iron. If it be desired to produce a bloom of the
hardest weldable steel, the process of decarbonization is only to be continued
long enough after the appearance of the indications just described to bring the
entire mass into one uniform state; after which the further progress of decar-
bonization must be stopped, either by closing the damper or otherwise.
If it be desired to produce a milder temper of steel, the decarbonization of
the mass in the furnace must be allowed to continue for a shorter or longer
time according to the degree of temper required for the use or purpose to
which the steel is intended to be applied. As soon as the proper amount of
decarbonization has been effected, and the further progress thereof stopped,
the metal is to be formed into balls, care being taken always to keep the
metal as much as possible immersed in or covered by the cinder, and when
the balls are made they must be removed from the furnace and forged into
blooms at the welding heat of steel.
Having now described this Invention of "Improvements in the Manufacture
of Steel," and having explained the manner of carrying the same into effect,
as communicated to me by my foreign correspondent, I would observe that
what I consider to be new in the above described process is the discovery of
the precise points at which cast iron or crude pig iron becomes so far decar-
bonized as to be brought into the state of malleable steel, and weldable steel
of various tempers or degrees of hardness, and also the discovery of the in-
dications or phenomena, whereby such points of decarbonization may always
be infallibly known and recognized in the manufacture of steel as aforesaid.
What I claim as the Invention secured to me by Letters Patent as aforesaid,
is the manufacture of steel by working in a puddling or reverberatory
furnace in the manner above described, whereby the workman may, by

page_text: observing the indications or phenomena above set forth, be enabled to stop the
decarbonization of the mass of metal in the furnace at the precise point
required to produce with certainty steel of any desired temper or hardness.
In witness whereof, I, the said Edmund Leopold Benzon, have here-
unto set my hand and seal, the Twenty-sixth day of March, in the
year of our Lord One thousand eight hundred and fifty-nine.
Witness,
FRED. WALKDEN,
66, Chancery Lane.
E. L. BENZON. (L.S.)