IMPROVEMENTS IN HARDENING IRON AND STEEL
Year: 1856

page_text: LETTERS PATENT to George James Farmer, of Birmingham, in the
County of Warwick, Machinist, for the Invention of "IMPROVEMENTS IN
HARDENING IRON AND STEEL."
Sealed the 21st November 1856, and dated the 23rd August 1856.
PROVISIONAL SPECIFICATION left by the said George James Farmer
at the Office of the Commissioners of Patents, with his Petition, on the
23rd August 1856.
I, GEORGE JAMES FARMER, of Birmingham, in the County of Warwick,
Machinist, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN HARDENING IRON AND STEEL," to be as follows:-
I take of prussiate of potash, saltpetre, and sal ammoniac equal parts,
reduce them to powder; and thoroughly incorporate them together. I then
take the article to be hardened and heat it in à furnace to a red heat, or
thereabouts, and removing it from the fire, I roll it well in the mixture above
nammed; so as to cover it entirely. I then place it in a bath, consisting of
prussiate of potash two ounces, saltpetre two ounces, and sal amnioniác four
ounces, or about these proportions, to every gallon of cold water, and leave it
then until cold, when it will be found to be so thoroughly hardened that a file
will not touch it. Should it to be required to reconvert the article to its original
character, it can be readily done by placing it in a furnace under a tolerably
strong blast.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George James Farmer in the Great Seal Patent Office on
the 21st February 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
JAMES FARMER, of Birmingham, in the County of Warwick, Machinist, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of August, in the year of our Lord
One thousand eight hundred and fifty-six, in the twentieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
George James Farmer, Her special licence that I, the said George James
Farmer, my executors, administrators, and assigns, or such others as I, the said
George James Farmer, my executors, administrators, and assigns, should. at
any time agree with, and no others, from time to time and at all times there-
after 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 "IMPROVEMENTS IN
HARDENING IRON AND STEEL," upon the condition (amongst others) that I,
the said George James Farmer, 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 causo
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 George James Farmer, do hereby
declare the nature of my said Invention, and the manner in which the same is
to be performed, to be particularly described and ascertained in and by the
following statenient, that is to say :-
My Innvention consists in the employment of certain chemical agents,
herein-after more particularly defined, for the purpose of hardening, after they
have been cast or otherwise formed, articles of iron or steel, such, for instance,
as dies for stamping press tools, lathe chocks, files, certain kinds of cutting
tools, the journals, bearings, and axle boxes of running machinery, and all
other similar articles or parts of machines, the form, mode of manufacture,
bulk or weight of which would not prevent them from being subjected, with
facility, to the treatment herein-after described; and which is as follows:-I
take the ferrocyanide of potassium (the prussiate of potash of commerce), the
hydrochlorate of ammonia (the sal ammoniac of commerce), and. the nitrate
of potash (the saltpetre of commerce), each in equal proportions, or there-

page_text: abouts, reduce them to a fine powder, and thoroughly incorporate them
together. I then prepare a bath by mixing the following proportions, or.
thereabouts, of these several ingredients in cold water, namely, the prussiate of
potash two ounces, saltpetre two ounces, and sal ammoniac four ounces, to
every gallon of water. Having thus prepared these compounds, the first in
the form of a fine powder, and the second in a bath, I heat the article I am
operating upon in a furnace or other fire until it has attained a red heat. I
then remove it from the fire, and if it be of a size and weight susceptible of
such handling, I roll it in the dry powder already described until every portion
of the article shall have taken up a sufficient quantity of the mixture, or until
all such portion of the article as I may require to be hardened shall be covered
with the powder, which, when in contact with the heated metal, becomes
immediately fused; I then plunge the article into the bath before described,
where it is to be left until cold; when taken out it will be thoroughly hardened,
and not only on the surface, as in case-hardening, but through the entire
substance, unless the article be of considerable dimensions. Thus far my
description would apply to the treatment of such masses as could readily be
turned or moved about by manual labour. For larger bodies, and such as
must be raised and moved by mechanical appliances, instead of rolling them
over when hot in the dry composition, which would be impracticable or
difficult, I cover the mass of heated metal with the powder by employing a
vessel with a perforated or colander top, from which I sift the mixture over the
article under treatment, covering the surface thereof, or such portions of the
surface which I may require to harden, with a thin coating of the powder, after
which the immersion in the bath is to follow, as already particularized. Should
it be requisite to reconvert any article thus hardened for the purpose of
sharpening, facing up, or for any other operation, which, in its hardened state
it will not admit of, this operation can be readily effected by subjecting the
article to beat under a tolerably strong blast, after which it can be cut or faced
at pleasure, and subsequently re-hardened to fit it for use. I would remark,
that I am well aware that a process has long been known of hardening iron
and steel, whilst in course of manufacture, by the introduction of the ferro-
cyanide of potassium (the prussiate of potash), into a molten mass of metal, or,
as it is generally termed, "phyiscking "the metal, but this of course renders the
formation of tools or other articles from such metal more laborious and costly,
it is utterly inapplicable to effect the result which is attained by my Inven-
tion. I am also aware that the same agent, namely, the prussiate of potash,
has been long employed for case-hardening the surfaces of rolls, to give them
a stecly face, but used alone and without the other ingredients I have named.

page_text: By my process the metal will be indurated to a considerable depth, and I am
consequently enabled to mould or otherwise shape an article into the desired
forin whilst the metal is tractable and easy of manipulation; many things may,
therefore, be manufactured in cast iron, such as diés and other press or stamping
tools, files, rasps, lathe chocks, and such like articles, and I am enabled to cut,
pläne, or finish them in any way I please whilst in the soft state, and after
being subjected to the process herein described they will present all thè
appearance of cast steel, will be equally hard and durable, present as fine a
surface, and for most practical purposes will prove as useful, while à con-
siderable economy in cost of manufacture will be effected.
Having thus described the nature of my said Invention, and in what manner
the same is to be practically carried into effect, I wish it to be understood
that I do not confine myself to these precise details, nor to the exact propor-
tions of the several chemical compounds herein stated, as I have merely
specified those details and. proportions which I have hitherto found the best
suited to effect the intended purpose, and they may, probably, admit of some
slight variation when operating upon different qualities of metal, nor do I mean
or intend to confine myself to the use of the chemical agents I have described
in their several integral or compounded states, as their respective constituents
or components, taken separately, and brought into combination, may be found
to answer equally well; but that which I claim and desire to have secured to
me by the hercin-before in part recited Letters Patent is, the hardening of
articles formed of iron or steel by the employment of a compound composed
of the ferrocyanide of potassium (the prussiate of potash of commerce), the
hydrochlorato of ammonia (the sal ammoniae of commerce), and the nitrate of
potash (the saltpetre of commerce), or the respective constituents, components,
or equivalents of these materials, in manner herein more fully set forth and
spécified.
In witness, whereof, I, the said George James Farmer, have hereunto
set my hand and seal, this Twentieth day of Febuary, in the year of
our Lord One thousand eight hundred and fifty-seven.
GEORGE JAMES (L.B.) TAKMEK.