IMPROVEMENTS IN OR CONNECTED WITH THE MANUFACTURE OF TIN PLATE
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Arthur James Maskrey at the Office
of the Commissioners of Patents on the 24th February 1882.
ARTHUR JAMES MASKREY, of Coatbridge in the County of Lanark North
Britain "IMPROVEMENTS IN OR CONNECTED WITH THE MANUFACTURE OF TIN
PLATE
"
This Invention relates to certain improvements in or connected with the manu-
facture of tin plate, and it has mainly for its object to simplify and lessen the cost
of the process of preparing the iron plates or sheets for the tinning operation.
"
In the manufacture of tin plate as at present carried on, the iron plates are
pickled " in an acid bath for the purpose of removing the oxide of iron from their
surface, and are afterwards annealed, but according to my Invention the removal
of the oxide of iron from the surface of the plates is effected while they are within
the annealing pots, or otherwise subjected to the annealing operation, and one
process of the manufacture, namely, the pickling in acid, is entirely dispensed
with.
The improvements consist essentially in subjecting the iron plates when within
the annealing pots or chambers, or within a close furnace, and while at a red heat,
to the action of carbonic oxide, for the purpose of reducing the oxide of iron on the
surface of the plates; the carbonic oxide being forined from charcoal or other
carbonaceous substance placed within the annealing vessel or furnace, or being
led from a separate furnace through the hot chamber or vessel containing the
plates.
In carrying out the Invention, according to one modification, the iron plates are
placed within the annealing pot, either horizontally as usual, or on edge. The
bottom of the pot or vessel is filled with a layer of powdered or broken charcoal or
carbonaceous matter, covered with a perforated plate for the purpose of separating
the plates from contact with the char; and on the top of the plates is placed a flat
box also containing powdered char. The cover of the pot is fitted over the iron
plates, and the joint luted with sand as usual in annealing. The pots are then
placed in an annealing furnace or subjected to a temperature at which the plates
become red hot, and the char burns with the formation of carbon monoxide
(carbonic oxide gas). At this temperature the oxygen of the oxide of iron on the

page_text: surface of the plates combines with the gaseous carbon monoxide to form carbon
dioxide (carbonic acid), and the carbon dioxide by uniting with a further quantity
of free carbon of the powdered char reproduces carbon monoxide; the action of
reducing the oxide of iron being repeated until by the time the annealing is
effected no iron oxide remains. It is essential that sufficient charcoal should be
placed within the vessel to produce an excess of carbonic oxide, so that every trace
of iron oxide may be removed; and when the plates are taken from the annealing
pots they are ready for the tinuing operation.
The reduction of the oxide of iron may be effected by means of charcoal strewed
on the plates in the annealing vessels, or by means of carbonic oxide gas produced
in a separato furnace and caused to pass through the plates within a heating or
annealing furnace.