Improvements in the Manufacture of Chilled Iron Globules.
Year: 1891

page_text: Date of Application, 24th Feb., 1891-Accepted, 6th June, 1891
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Chilled Iron Globules.
We, BENJAMIN CHEW TILGHMAN, Chemist, of Philadelphia, Pennsylvania,
United States of America, present address being % George Richards & Co.,
Broadheath, near Manchester, England, and RICHARD ALBERT TILGHMAN,
Chemist, residing at 321 South Eleventh Street, Philadelphia, Pennsylvania,
United States of America, do hereby declare the nature of their invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
Our invention relates to the manufacture of chilled iron globules such as are
used in the process of abrasion described in B. C. Tilghman's American Patent
re-issue No. 7499 dated February 6th, 1877, and also to some extent in the sand-
blast process. These globules are manufactured by atomizing a stream of melted
iron by means of a jet of high pressure steam or gas in such a way that they will
remain in the air for a time long enough for them to assume a spherical form and
chill on the surface so as to take a permanent set or form. The still very hot
globules are then permitted to fall into a tank of water where they are chilled to
an intense hardness; they are then removed from the water and dried preparatory
to packing them for shipment. At two stages of this method of manufacture the
globules are exposed to a rapid oxidation, namely, when the melted iron is sprayed
in the air, when a burning action takes place on the surface of the globules with
formation of a crust or scales of oxide, and during the process of drying when a
dark red friable coat of rust forms upon them.
In the treatment of some delicate stones trouble has been met with from the rust
coating of the globules staining the surface and where the globules are used for
frosting metal the rust is driven into the metal under treatment discoloring and
injuring the surface. The coating is also unsightly and owing to its friable nature
it soils anything it comes in contact with.
The object of our invention is to furnish the globules with a bright clean though
unpolished metallic surface while retaining the desirable physical qualities they
have heretofore had. Of several methods for obtaining the globules of this kind
with which we have experimented the following is, we believe, the best. We spray
the melted metal in a non-oxidizing atmosphere, one for instance from which the
oxygen has been eliminated, as by passing air through a deep bed of ignited fuel;
this prevents the direct oxidation of the globules of melted metal and the formation
of the black scale and they fall into the water tank with bright surfaces. The
globules, while covered by water, are not subject to any noticeable oxidation but
preferably we dissolve a little lime or other alkali in said water. We then remove
the globules from the tank and dry them under conditions which preclude the
formation of rust; preferably we pour over them a solution of lime in water which
should preferably contain a small proportion of finely divided hydrate of lime in
suspension. This lime water, or dilute white-wash, displaces the plain water and
the globules may, after this treatment, be safely handled and dried without danger
of rusting. The reason for this is because the oxygen of the air is unable to rust
an iron surface even in presence of water without the presence of free carbonic
acid in solution, and free carbonic acid is of course impossible in a solution con-
taining lime or other alkali in excess, for the carbonic acid combines with the
alkali forming, for instance, carbonate of lime and the free lime in suspension
then dissolves maintaining the saturation of the solution, this chemical action
going on until the globules are entirely dry and free from any considerable
danger of rusting, even if their protecting shield of alkali was absent which it
is not, as of course a film of lime is deposited over them. Of course the chilling

page_text: tank may be filled with the dilute white-wash and the globules dried immediately
on removal, but the use of the lime water or white-wash as described is more
economical and for other reasons we believe preferable.
Instead of using the lime-water to prevent rusting, the globules may be dried
in a non-oxidizing atmosphere with the same results except as to the formation
of the lime film.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what
we claim is :-
First The described method of manufacturing chilled iron globules with bright
metallic surfaces which consists in atomizing melted metal in a non-oxidizing
atmosphere, chilling the resulting globules by immersion in water and subsequently
drying them under conditions which preclude the formation of rust.
Second The described method of manufacturing chilled iron globules with
bright metallic surfaces which consists in atomizing melted metal in a non-oxidizing
atmosphere, chilling the resulting globules by immersion in water, removing the
globules from the water and wetting them with a saturated solution of lime or its
equivalent, and then drying them.
Third: The described method of manufacturing chilled iron globules with bright
metallic surfaces which consists in atomizing melted metal, chilling the resulting
globules by immersion in water, removing the globules from the water and wetting
them with a saturated solution of lime or its equivalent, and then drying them.
Dated this 24th day of February 1891
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.