An Improved Thin Liquid Substance for Case-hardening Iron.
Year: 1895

page_text: Date of Application, 15th May, 1895
Complete Specification Left, 12th Feb., 1896-Accepted, 14th Mar., 1896
An Improved Thin Liquid Substance for Case-hardening Iron.
A communication by HANS SCHAAF, of 55 Berlinerstrasse, Charlottenburg, in
the Empire of Germany, Merchant.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street,
Manchester both in the County of Lancaster, 118 New Street, Birmingham in
the County of Warwick and 31 High Holborn in the County of Middlesex,
Civil Engineer, do hereby declare the nature of this invention to be as follows:-
With the improved thin liquid substance for case-hardening iron which forms
the object of this invention, wrought iron articles and the like may be case-
hardened by entirely coating them therewith, and thus enclosing them with the
dried on substance. They are then placed in an open furnace of coal or preferably
wood charcoal and heated without special arrangements or preparations. The
substance then melts at a temperature which may be determined, varying within
certain limits, and effects the case-hardening.
The case-hardening substance is applied by being spread with a brush, and the
articles to be treated are warmed in a suitable manner. In consequence of this,
the substance smeared thereon first dries on the metallic surface from the inside
outwards, so that a thorough drying is obtained. At the same time the result is
attained of preventing the drying coating of the case-hardening substance from
cracking. The substance is spread several times on the articles until the covering
is of the required or necessary thickness.
By smearing with this case-hardening substance, articles of any suitable form
and shape may be quite evenly case-hardened as the substance adheres closely to
the form of the article.
In using this case-hardening substance the article which is to be case-hardened
is encased during the entire heating process in the substance. The atmospheric
air is thus almost entirely excluded from the surface of the article, so that any
oxidation is thoroughly prevented. Should this however take place, it can be
removed by means of the substance itself or by means of a constituent of the same,
namely alkaline silicate. This latter may be easily decomposed by the carbonic
acid of the furnace, and capable of dissolving metallic oxide. In this manner
waterglass will act on any oxidation of the metallic surface which may take place
so that this surface always remains metallic and clean. With this case-hardening
substance therefore, very fine delicately ornamented, and smooth polished articles
may be case-hardened without any damage.
In consequence of the peculiar but firm covering which the case hardening
substance forms round the articles which are to be case-hardened, thus preventing
oxidation, it is peculiarly suitable for the case-hardening of small articles. The
articles may be allowed to lie when coated a considerable time before they are
placed in the fire. The case-hardening may therefore be completed only if desired
after a considerable time when sufficient articles have been made. The workman

page_text: who has to carry out the hardening need therefore not be interrupted in this
occupation and can therefore better devote his attention to the same.
This case-hardening substance also allows the work to be largely distributed.
The improved case-hardening substance contains, like all usual case-bardening
substances, ferro-cyanide of potassium from which under certain circumstances
poisonous fumes which attack the respiratory organs are developed. With this
improved case-hardening substance these fumes need only attack the respiratory
organs of the workman during the short time which the latter requires for removing
the articles from the fire and throwing them into water, which operation he can
also perform with outstretched arm in order to avoid as far as possible breathing
the fumes. The action of these poisonous fumes is much more considerable and
takes place for a much longer time where case-hardening substances into which
the articles are dipped are employed; or when solid or rather powdered ferro-
cyanide of potassium is used, as the workman must observe the case-hardening
process from close proximity.
This improved case-hardening substance consists of waterglass, ferro-cyanide of
potassium, chalk, and ammonia, and may be made preferably in the following
manner -
200 grammes of ferro-cyanide of potassium and 40 grammes of powdered chalk
are stirred together to a liquid mass, a mixture of 100 grammes of waterglass and
75 to 100 grammes of water being gradually added. Waterglass is then added
under constant stirring until the mass begins to thicken to a gelatinous
substance. As much ammonia is then added to the mixture until it has become
of such a thin liquid consistency that a further thickening of the same no longer
takes place.
The proportionate weights and the specific weights of the above mentioned
substances and more particularly of the waterglass must be selected according to
the temperature at which the hardened substance is intended to melt.
Dated this 14th day of May 1895
An improved Thin Liquid Substance for Case-nardening iron.
A communication by HANS SCHAAF, of 55 Berlinerstrasse, Charlottenburg, in
the Empire of Germany, Merchant.
I, WILLIAM PHILLIPS THOMPSON, F.C.S. M.I.M.E. of The Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street,
Manchester both in the County of Lancaster, 118, New Street, Birmingham in
the County of Warwick and 31, High Holborn in the County of Middlesex,
Civil Engineer, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
With the improved thin liquid substance for case-hardening iron which forms
the object of this invention, wrought iron articles and the like may be case-
hardened by entirely coating them therewith, and thus enclosing them with the
dried on substance. They are then placed in an open furnace of coal or preferably
wood charcoal and heated without special arrangements or preparations. The
substance then melts at a temperature which may be determined, varying within
certain limits, and effects the case-hardening.

page_text: The case-hardening substance is applied by being spread with a brush, and the
articles to be treated are warmed in a suitable manner. In consequence of this,
the substance smeared thereon first dries on the metallic surface from the inside
outwards, so that a thorough drying is obtained. At the same time the result is
attained of preventing the drying coating of the case-bardening substance from
cracking. The substance is spread several times on the articles until the covering
is of the required or necessary thickness.
By smearing with this case-hardening substance articles of any suitable form and
shape may be quite evenly case-hardened as the substance adheres closely to the
form of the article.
In using this case-hardening substance the article which is to be case-hardened
is encased during the entire heating process in the substance. The atmospheric
air is thus almost entirely excluded from the surface of the article, so that any
oxidation is thoroughly prevented. Should this however take place, it can be
removed by means of the substance itself or by means of a constituent of the
same, namely alkaline silicate. This latter may be easily decomposed by the
carbonic acid of the furnace, and is capable of dissolving metallic oxide. In this
manner waterglass will act on any oxidation of the metallic surface which may
take place so that this surface always remains metallic and clean. With this case-
hardening substance therefore, very fine delicately ornamented, and smooth polished
articles may be case-hardened without any damage.
In consequence of the peculiar but firm covering which the case hardening
substance forms round the articles which are to be case-hardened, thus preventing
oxidation, it is peculiarly suitable for the case-hardening of small articles. The
articles may be allowed to lie when coated a considerable time before they are
placed in the fire. The case-hardening may therefore only be completed
(if desired) after a considerable time when sufficient articles have been made.
The workman who has to carry out the hardening need therefore not be
interrupted in this occupation and can therefore better devote his attention to
the same.
This case-hardening substance also allows the work to be largely distributed.
The improved case-hardening substance contains, like all usual case-hardening
substances, ferro-cyanide of potassium from which under certain circumstances
poisonous fumes which attack the respiratory organs are developed. With this
improved case-hardening substance these fumes need only attack the respiratory
organs of the workman during the short time which the latter requires for
removing the articles from the fire and throwing them into water, which operation
be can also perform with outstretched arm in order to avoid as far as possible
breathing the fumes. The action of these poisonous fumes is much more
considerable and takes place for a much longer time where case-hardening
substances into which the articles are dipped are employed; or when solid or rather
powdered ferro-cyanide of potassium is used as the workman must observe the
case-hardening process from close proximity.
This improved case-hardening substance consists of waterglass, ferro-cyanide
of potassium, chalk, and ammonia, and may be made preferably in the following
manner :-
200 grammes of ferro-cyanide of potassium and 40 grammes of powdered chalk
are stirred together to a liquid mass, a mixture of 100 grammes of waterglass and
75 to 100 grammes of water being gradually added. "Waterglass is then added
under constant stirring until the mass begins to thicken to a gelatinous
substance. As much ammonia is then added to the mixture until it has become
of such a thin liquid consistency that a further thickening of the same no longer
takes place.
The proportionate weights and the specific weights of the above mentioned
substances and more particularly of the waterglass must be selected according to
the temperature at which the hardened substance is intended to melt.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me by
my foreign correspondent, I declare that what I claim is :-
A thin liquid substance for case hardening iron, consisting of waterglass,
ferro-cyanide of potassium, chalk and ammonia, substantially as hereinbefore set
forth.
Dated this 11th dow of 1000
WM. P. THOMPSON & Co.,
Agents.