IMPROVEMENTS IN THE MANUFACTURE OF PIG IRON AND IN APPARATUS THEREFOR."
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by James Baird Thorneycroft at the
Office of the Commissioners of Patents on the 17th February 1881.
JAMES BAIRD THORNEYCROFT, of the Portland Iron Works, Hurlford, in the
County of Ayr, North Britain, Ironmaster. "IMPROVEMENTS IN THE MANUFACTURE
OF PIG IRON AND IN APPARATUS THEREFOR."
This Invention has for its object to improve the quality of pig iron as obtained
from smelting furnaces, and to render it more uniform and better suited for casting
purposes than as hitherto supplied.
In the ordinary process of running iron from the smelting furnace into the
open sand trougbs or moulds by which it is shaped into pigs, the iron is too rapidly
cooled and is chilled, and that in an irregular and unequal manner, so that the
crystalline structure and grey color which are recognised as indicating high quality
are not fully or uniformly developed. It is believed that too rapid cooling causes
the carbon and silicon, which are held in solution or otherwise in the molten metal,
to become chemically combined or otherwise changed in a manner to cause a lower
grade of pig iron to be produced. By the present Invention the deterioration
referred to is prevented by avoiding the too rapid and unequal cooling, and
for this purpose special moulds are provided, together with apparatus and
arrangements for heating such moulds before the iron is run into them. The
moulds are made of iron or other suitable metal or material, and by preference in
the form of open-topped troughs shaped internally to give approximately the usual
form to the pigs cast in them, but by preference having ribs across their bottoms
to form indentations across the pigs so that the pigs may be easily broken. Each
mould may be made for a single pig or for two or more parallel pigs. The moulds
may be arranged in a variety of ways, but according to one convenient arrangement
a number of moulds are placed end to end so as to form a row having a slight
inclination downwards from one end of the row to the other, sufficient for the
molten metal which is led into the mould at the higher end of the row to run from
one mould into the next. A number of the rows of moulds are placed parallel to
each other or in a radiating manner as may be convenient or suit the character of
the ground surface about the furnace. The molten metal on issuing at the tapping
hole first passes along a short spout or rhone from the end of which it runs into

page_text: the head of a radiating rhone which is movable on a centre at its head, so that its
delivering end can be set over any of the rows of moulds. If found necessary an
adjustable delivering spout may be adapted to the end of the radiating rhone to
direct the stream of metal properly into the moulds. At the junction of each
mould with the next a movable piece may be applied, being formed with a shallow
groove across its top for the metal to flow over from one mould into the next. This
movable piece bridges the joint between the two moulds, and it is by preference
shaped with its bottom somewhat broader than its top so that it is partly under
the pigs. The bridge pieces are made with handles and may be used for tilting
up the pigs to facilitate their removal. When the bridge pieces are not used,
grooves or indentations are by preference formed to be filled up with fireclay or
other suitable material, which will allow of the insertion of instruments to facilitate
the removal of the pigs. For heating the moulds channels are formed in the bed
built for carrying the moulds, and these channels are covered by the moulds and
thus made into flues through which heated air or other gases are passed. The
combustible gases leaving the smelting furnace are in every way advantageously
applicable for heating the flues under the moulds and may be ignited in those flues,
the air necessary for their combustion being also supplied, and the gases being led
from the flues to any convenient chimney. For some purposes it may be found
desirable to employ vertical moulds, in which case the heating arrangements must
be suitably modified.