IMPROVEMENTS. IN HARDENING AND TEMPERING STEEL
Year: 1865

page_text: LETTERS PATENT to Elliot Savage, of West Meriden, Connecticut,
United States of America, Engineer, for the Invention of "IMPROVEMENTS.
IN HARDENING AND TEMPERING STEEL."
PROVISIONAL SPECIFICATION left by the said Elliot Savage at the
Office of the Commissioners of Patents, with his Petition, on the 28th
March 1865.
I, ELLIOT SAVAGE, of West Meriden, Connecticut, United States of America,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE.
MENTS IN HARDENING AND TEMPERING STEEL," to be as follows:-
This Invention or discovery consists in improvements in hardening and
tempering steel, whereby any piece or article of steel may be hardened or
tempered to any degree required, at such low temperatures of the preliminary
heating that the shape or configuration or finish of the most delicate or com-
plicated character is not altered, and the requisite tenacity being at the same
time preserved. The principle upon which these results are effected lies in the
employment of solutions in which to immerse the heated steel which possess a
very high degree of conducting character for heat, so that the utmost rapidity
in the cooling will be attained, for in this the true theory of the operation
appears to be involved. I have discovered that metals having the greatest
conducting power for heat, and which can be held chemically in solution,
constitute those solutions media whereby results may be attained in hardening

page_text: steel which have hitherto been wholly unattainable. Thus I employ solutions
of gold, silver, copper, and other metals, and the results obtained are in the
direct ratio of the respective conducting powers of the metals and the specific
gravity of the solution. Silver possesses the highest conducting power, but the
specific gravity of any solution of that metal is limited to a degree less than
that of copper, which is next in order, but which possesses the property of
being held in solution to a much greater density, thereby rendering it for many
articles equal to silver, while it has also the advantage of cheapness. I
prefer to prepare these solutions from a metal in the form of a chloride, since
it is then free from acid, and can be readily dissolved in a proper fluid, but
they may be in the form of sulphates, as the sulphate of copper for example.
The process then will be as follows:-For very fine articles, such as engraved
bank note plates of steel, a silver solution is preferred; of this take the chloride
and dissolve it in a solution of cyanuret of potassium in water, or of water of
ammonia, until it has the strength of about 10° Beaumé observing however
that the greater the specific gravity the lower the temperature at which the
steel may be at the moment of immersion, and consequently the risk of change
of shape or of fracture is lessened accordingly. If the solution is to be of.
copper, dissolve in a vat containing water, chloride of copper, until by trials
the proper specific gravity is obtained. As soon as the temperature of the
steel has been raised sufficiently for the purpose, plunge it suddenly into the
liquid and let it remain to cool. An experienced operator can always pro-
portion the strength of the liquid to the article to be hardened, and also
determine the right temperature the steel must have attained in the fire before
immersing it in the solution to secure the exact degree of hardness. If it should
happen that the steel had been made too hard, the temper can be drawn by
any of the usual methods. It bas been remarked above that the chlorides
are preferable on account of being free from acid; solutions, however prepared
from sulphates or other oxysalts should have their acid neutralized before
immersing the steel, to prevent the surface of the steel from being attacked
by the oxygen.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-eighth day of March, in the year of our Lord,
One thousand eight hundred and sixty-five, in the twenty-eighth year.
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said Elliot Savage, Her special licence that I, the said
Elliot Savage, my executors, administrators, and assigns, or such others as:
I, the said Elliot Savage, 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 "In-
PROVEMENTS IN HARDENING AND TEMPERING STEEL," upon the condition (amongst
others) that I, the said Elliot Savage, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and seals,
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 Elliot Savage, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, that is to say:-
This Invention or discovery is an improvement in the art of hardening steel,
whereby any piece or article of steel may be hardened or tempered to any
degree required, at such low temperatures of the preliminary heating that the
shape or configuration or finish of the most delicate or complicated character.
is not altered, preserving also at the same time the requisite tenacity. The
principle upon which these results is effected lies in the employment of solutions
in which to immerse the heated steel which possess a very high degree of con-
ducting character for heat, so that the utmost rapidity in the cooling will be
attained, for in this the true theory of the operation appears to be involved.
I have discovered that metals having the greatest conducting power for heat, and
which can be held chemically in solution, constitute those solutions media,
whereby results may be attained in the art of hardening steel which have been
wholly unattainable hitherto. Thus solutions of gold, silver, copper, &c., are
employed by me, and the results obtained are in the direct ratio of the respective
conducting powers of the metals and the specific gravity of the solution. Silver
possesses the highest conducting power, but the specific gravity of any solution
of that metal is limited to a degree less than that of copper, which is next

page_text: in order, but which possesses the property of being held in solution to a much
greater density, thereby rendering it for many articles equal to silver, while
it has also the advantage of cheapness. I prefer to prepare these solutions
from a metal in the form of a chloride; since it is then free from acid, and
can be readily dissolved in a proper fluid, but they may be in the form of
sulphates, as the sulphate of copper, &c.
The process then will be as follows:-For very fine articles, such as engraved
bank note plates of steel, a silver solution is to be preferred; of this dissolve
the chloride in a solution of cyanuret of potassium in water, or of water of
ammonia, until it has the strength of about ten degrees of Beaume's hydro-
meter, observing however that the greater the specific gravity, the lower the
temperature at which the steel may be at the moment of immersion, and
consequently the risk of change of shape or of fracture is lessened accordingly.
If the solution is to be of copper, dissolve in a vat containing water chloride
of copper, until by trials the proper specific gravity is obtained. As soon as
the temperature of the steel has been raised sufficiently for the purpose plunge
it suddenly into the liquid and let it remain to cool. An experienced operator
can always proportion the strength of the liquid to the article to be hardened,
and also determine the right temperature the steel must have attained in the
fire before immersing it in the solution to secure the exact degree of hardness.
If it should happen that the steel had been made too hard, the temper can be
drawn by any of the usual methods. It has been remarked above, that the
chlorides are preferable on account of being free from acid; solutions,
however, prepared from sulphates or other oxysalts should have their acid
neutralized before immersing the steel, to prevent the surface of the steel from
being attacked by the oxygen.
I claim the use or employment in hardening steel, of metallic solutions, in
the manner and for the purpose substantially as set forth.