IMPROVEMENTS IN THE METHODS OF, AND COMPOSITION FOR CASEHARDENING METALS
Year: 1885

page_text: католик ше
I, JOHN ROBB of Dundee, in the County of Forfar N.B. Blacksmith do hereby
declare the nature of my invention for IMPROVEMENTS IN THE METHODS OF,
AND COMPOSITION FOR CASEHARDENING METALS to be as follows:-
My Invention has for its object a novel method of treating metals, whereby the
casehardening of such is accomplished much more speedily, more effectively, and
at much less cost than hitherto. For the purpose of my Invention I employ a
peculiar kind of composition consisting of one lb of prussiate of potash; two lbs of
Rock Salt; one and a half lb of Bone dust; one half pint of Spirits of Salts; and
two to three ounces of charcoal. In combination with the above mentioned
composition, I treat the metals in the following manner. I heat the metal red hot
by any convenient means; then immerse it (until it has turned black) in a
quantity of the composition. I then take it out and reheat it as before. After
reheating, I again iminerse it amongst the composition for a few seconds, and while
still red hot, I take it from amongst the composition, and immediately plunge it,
(in the red hot state), into a quantity of cold water, which completes the process.
To suit circumstances, I sometimes vary the ingredients, and the quantities of
such, which form the composition. The length of time during which I allow the
metal to remain in the composition or in the water, is regulated by the thickness
of the bar or plate of metal under treatment.

page_text: COMPLETE SPECIFICATION.
Improvements in the Methods of and Composition for Case-
hardening Metals.
I, JOHN ROBB of Dundee in the County of Forfar N.B. Blacksmith do hereby
declare the nature of my invention for IMPROVEMENTS IN THE METHODS OF AND
COMPOSITION FOR CASEHARDENING METALS and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:
My invention has for its object a novel method of treating metals whereby
the Casehardening of such is accomplished much more speedily, more effectively
and at much less cost than hitherto. For the purpose of my said invention
I employ a peculiar kind of Composition consisting of one lb of prussiate of potash;
two lbs of Rock salt; one and a half lb of bone dust; one half pint of Spirits
of Salts; and from two to three ounces of charcoal. In combination with the
above mentioned composition I treat the metals in the following manner. I heat
the metal to a good red heat by any convenient means, then immerse it (until it
has turned black) in a quantity of the composition. I then take it out and reheat
it as before. After releating, I again immerse it amongst the composition for a
few seconds, and while still red hot I take it out from amongst the composition, and
immediately plunge it (in the red hot state) into a quantity of cold water; which
completes the process. To suit circumstances I sometimes vary the ingredients
and the quantity of such which form the composition, by substituting the following
for those hereinbefore mentioned. Two and a half lbs of prussiate of potash; two
and a half lbs of bone dust; one half lb of animal charcoal; one quarter lb of
pure charcoal; four lbs of rock salt; one pint of muriatic acid; and one quarter lb
of unslacked lime. The length of time during which I allow the metal to remain
in the composition or in the water is regulated by the bar or plate of metal under
treatment. To caseharden small iron under one inch square or less than one inch
diameter, I
1. Heat the Metal red hot; and
2. At once immerse it amongst the composition until it has become black.
3. Again heat it red hot; and
4. Again immerse it amongst the composition for a few seconds (about
30 seconds for a 4 inch bar).
"
5. And while it is still red; take it out and plunge it smartly into cold water.
The above treatment secures a 'skin" of 11th inch, when working with a
4th inch bar.
When treating large iron over one inch square or over one inch diameter,
I adopt the following proces.
1. Heat the metal a good red heat.
2. Immerse it amongst the composition, and leave it there as long as it will
remain red; but before the red heat commences to go off, take it out and plunge it
smartly amongst cold water.
The above process gives a very hard surface to the metal (varying in thickness
according to the thickness of the metal) which a file will not touch. The longer

page_text: the metal remains red hot amongst the composition, the further the hardening
effect penetrates into the metal.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed; I declare that what
I claim is:-
1. Chemical compositions consisting of one or other or all of the ingredients and
the quantities of such substantially as hereinbefore described.
2. Processes for casehardening metals, all substantially as hereinbefore described.
Deted this 21at der of Mamb 1000
JOHN ROBB,