AN IMPROVED METHOD OF HARDENING AN ARDENTNO CAST AND WROUGHT IRON
Year: 1856

page_text: LETTERS PATENT to Horace Vaughn, of Providence, Rhode Island, in
the United States of America, but now of the City of Manchester,
Gentleman, for the Invention of "AN IMPROVED METHOD OF HARDENING
AN ARDENTNO CAST AND WROUGHT IRON"
Scaled the 26th June 1857, and dated the 29th December 1856.
PROVISIONAL SPECIFICATION left by the said Horace Vaughn at the
Office of the Commissioners of Patents, with his Petition, on the
29th December 1856.
I, HORACE VAUGHN, of Providence, Rhodo Island, in the United States
of America, but now of the City of Manchester, Gentleman, do hereby
declare the nature of the said Invention for "AN IMPROVED. METHOD OF
HARDENING AND TEMPERING STEEL, AND OF HARDENING CAST AND WROUGHT IRON,"
to be as follows:-
This Invention consists in heating the articles to be hardened and tempered
in a bath made of suitable chemical agents, instead of heating the articles in
the fire, as now customary. The chemical agents employed for making the
bath are a combination of chloride of sodium, bichromate of potash, and

page_text: prussiate of potash, or other substances possessing the same properties. The
chemical agents being put into a suitable vessel are heated in a furnace or
otherwise, and the articles to be operated upon are kept in the bath until they
are sufficiently heated; they are then dipped into water or oil as usual.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Horace Vaughn in the Great Seal Patent Office on the
29th June 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HORACE
VAUGHIN, of Providence, Rhode Island, in the United States of America, but
now of the City of Manchester, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-ninth day of December, 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
Horace Vaughn, Her special licence that I, the said Horace Vaughn, my
executors, administrators, and assigns, or such others as I, the said Horace
Vaughn, 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 "AN IMPROVED METHOD OF HARDEN-
ING AND TEMPERING STEEL, AND OF HARDENING CAST AND WROUGHT IRON," upon
the condition (amongst others) that I, the said Horace Vaughn, my execu-
tors 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 per-
formed, 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 Horace Vaughn, do hereby declare
the nature of my 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):-
The nature of my said Invention consists in heating the articles to be

page_text: hardened and tempered in a bath composed of certain chemical agents or
ingredients in a state of igneous fusion, from which bath the articles to be
hardened and tempered are removed when sufficiently heated, and dipped into.
water, oil, or certain solutions, in the usual manner.
In performing my Invention, the chemical agents or ingredients required for
making a bath suitable for hardening and tempering articles of steel consist of
bichromate of potash, chloride of sodium, and prussiate of potash, mixed
together in the proportions of two pounds of bichromate of potash, twelve
pounds of chloride of sodium, and four pounds of prussiate of potash. The
quantity of prussiate of potash may be diminished by adding some bone dust
or pulverized animal charcoal to the above ingredients. These ingredients,
after being pulverized and mixed together, are placed in a box of iron, or into
a vessel of any other suitable material, and of the required shape, which is put
into a furnace similar to those used for heating crucibles, or for case-hardening,
or other purposes; or the vessel in which the bath is made may be heated
in any other manner. I prefer to cover the ingredients with pounded wood
charcoal, to prevent the escape of the gases during the process of heating, or
the pounded wood charcoal may be mixed with the other ingredients. The
vessel is heated until the ingredients are in a state of igneous fusion, thereby
forming a bath, into which the articles to be hardened and tempered are
plunged and allowed to remain until they are sufficiently heated. The length of
time required for heating the articles will depend upon their bulk. When the
articles have acquired the same temperature as the bath, they are taken from
it and dipped into water, oil, or certain solutions in the usual manner, other
articles are then put into the bath and taken out when heated, the same bath
answering for a great number of operations. In some cases the articles to be
hardened and tempered are placed in a suitable vessel, and the ingredients
above mentioned, or others possessing the same or similar properties, are put
into the vessel with the articles; the whole are then placed in the furnace and
heated until the ingredients are in a state of igneous fusion; the articles are
then removed from the vessel and dipped into water, oil, or certain solutions,
in the usual manner, as described.
In preparing a bath suitable for hardening wrought iron, I take twenty-five
per cent. of prussiate of potash, sixty-five per cent. of chloride of sodium, and
ten per cent. of bichromate of potash, and add thereto bone dust or animal
charcoal, or a mixture of both. These ingredients must all be pulverized;
they are then placed in a suitable vessel or crucible, and heated until they are
in a state of igneous fusion. The articles to be hardened are then put in the

page_text: vessel or crucible, and the whole may be covered with pounded wood charcoal,
to prevent the escape of the gases. When the articles in the bath are suf-
ficiently beated they are taken out and dipped into water, or any prepared
solution, as usual. In preparing the above bath, the quantity of prussiate of
potash may be reduced by adding more bone dust or animal charcoal, and instead
of ten per cent. of bichromate of potash five per cent. of it, with five per cent.
of borax, may be used. When the articles have been removed from the bath
others may be put in, as before described. When articles of cast iron or
malleable cast iron are to be hardened I prepare the bath in the manner above
described in reference to hardening articles of wrought iron, but I reduce the
quantity of animal charcoal or bone dust, and increase the proportion of
chloride of sodium.
As bone dust, animal charcoal, and wood charcoal have before been
employed for bardening purposes, I wish it to be understood that I make no
claim thereto except when used in combination with chemical agents or in-
gredients, to form a bath in a state of igneous fusion.
It is sometimes desirable to heat articles to be hardened and tempered
before they are plunged into the baths above described; the object of this is to
economise time in the operation. This preliminary heating of the articles
may be effected by placing them in a chamber or vessel heated by the flue
of the furnace, by which the bath is kept in a state of fusion, or otherwise.
The advantages resulting from this improved method of hardening and
tempering are,-
First, the articles to be operated upon, instead of being exposed to the direct
influence of the products of combustion while being heated, as in the ordinary
mode of operation, are immersed in the bath, and consequently protected from
the air; they are, therefore, uniformly heated in all parts simultaneously and
are free from the injuries resulting from unequal heating, which in the ordinary
mode are unavoidable.
Secondly, the temperature required to maintain the bath in a state of igneous
fusion may be varied according to the hardness required. The articles to be
operated upon, after remaining in the bath a sufficient time to acquire the same
temperature, must, when taken from the bath and dipped into the water or oil,
or other solutions, become equally hard.
Thirdly, when articles of steel are operated upon, the process of "letting
down," that is to say, heating a second time, to render the steel less brittle, is
in most cases dispensed with.
Fourthly, the ingredients of which the bath is composed become chemically

page_text: combined with the articles of steel, cast iron, wrought iron, or malleable cast
iron, and impart a certain degree of toughness to them, which in most cases is
very beneficial.
Fifthly, when articles of wrought iron, cast iron, or malleable cast iron are
hardened according to this improved method, the hardening penetrates deeper
than in the usual mode of case-hardening.
And, lastly, a great saving in time is effected, as the vessel containing the
bath may be large enough to contain any convenient number of articles which
are taken out of the bath and dipped into the water, or oil, or other solution in
succession. In hardening polished articles of steel, the bichromate of potash
may be reduced in quantity or entirely omitted, and carbonate of potash and
borax, combined in equal proportions or used separately, may be employed in
its stead in order to prevent the said articles from being discoloured by the pro-
cess of hardening, the said bichromate of potash having a tendency to injure
the colour or polish of the articles to be hardened.
Having thus described the nature of my Invention, and the manner of per-
forming the same, I wish it to be distinctly understood that in preparing the
baths, as described, I do not confine myself to the proportions given, nor to
the ingredients named, as the proportions may be varied according to the par-
ticular object for which the bath is intended, and other ingredients possessing
the same or similar properties may be employed. I would also remark
that I do not confino myself to the use of all the ingredients when combined
as described, as for some hardening purposes a bath may be prepared of
chloride of sodium in combination with any of the ingredients named, or
others possessing the same or similar properties in a state of igneous fusion;
but what I do claim is,-
First, hardening and tempering articles made of steel by heating them in a
bath composed of bichromate or carbonate of potash, chloride of sodium, and
prussiate of potash, or other ingredients possessing the same or similar pro-
perties, when in a state of igneous fusion, as above described.
Secondly, I claim hardening wrought iron by heating it in a bath composed
of chloride of sodium, prussiate of potash, and bichromate of potash, or other
ingredients possessing the same or similar properties, in combination with
animal and vegetable charcoal, as described.
Thirdly, I claim hardening articles of cast and malleable cast iron, by
heating them in a bath composed of prussiate of potash, chloride of sodium,
and bichromate of potash, or other ingredients possessing the same or similar
properties, in combination with animal and vegetable charcoal, as described.

page_text: And, fourthly, I claim the use of a bath composed of suitable chemical
agents or ingredients, in a state of igneous fusion, for the purposes described.
In witness whereof, I, the said Horace Vaughn, have hereunto set my
hand and seal, this Twenty-seventh day of June, in the year of our
Lord One thousand eight hundred and fifty-seven.
Witness,
H. B. BARLOW,
Manchester.
HORACE VAUGHN. (L.S.)