FURNACES FOR RE-HEATING STEEL, PREPARATORY TO HARDENING, TEMPERING, OR ANNEALING
Year: 1858

page_text: PROVISIONAL SPECIFICATION left by Perry Green Gardiner at the
Office of the Commissioners of Patents, with his Petition, on the 27th
October 1858.
I, PERRY GREEN GARDINER, of the City, County, and State of New York,
Mechanical Engineer, (U. States of America), do hereby declare the nature
of the said Invention for "FURNACES FOR RE-HEATING STEEL, PREPARATORY TO
HARDENING, TEMPERING, OR ANNEALING," to be as follows:-
The object and nature of my Invention consists in so arranging the furnace
as to cause the flame and heat to act upon a closed oven, or chamber, or
chambers in which the metal to be operated upon is placed, in such manner
as to distribute the heat under, above, and on the back of the oven or chambers,
and to communicate a powerful and steady heat to the interior of the oven or
chambers, while such interior and its contents have no communication with
the flame or gases of combustion, and as little as possible with the external
atmosphere.
In
In the reheating of steel for the purposes of hardening or tempering, or
annealing, it has heretofore been done by reverberatory furnaces, in which the
flame and heat come in direct contact with the metal above or below.
some instances ovens have been constructed so as to have the heat and flame
pass under the floor of the heating oven, so as not to come in contact at first
with the metal itself, and the heat and flame have then passed above the metal,
but in the same chamber with the metal. The difficulty with all such methods
of reheating steel arises from the fact that the steel being exposed to the flame

page_text: and atmosphere from the furnace, contracts impurities that impair its qualities,
the carbon in the steel becomes oxydated by the oxygen of the atmosphere,
and one part being more heated than another, the steel loses its uniformity of
texture, and is harder in one part than another, and it also loses its homo-
geneousness of quality. The uniformity of texture in the steel which is so
desirable and which is more or less imperfectly obtained by melting different
pieces together, as in cast steel, is, to some extent, destroyed, and always
unfavourably affected by heating the steel with the flame and atmosphere in
contact with the metal itself.
The general shape of the improved furnace is rectangular and oblong; the
brick walls and structure are contained above the body of the stack in reduced
size for the exit flue and damper; iron clamps with rods, with nuts and screws,
are provided for securing the brickwork together; there are two doors to the
heating oven (which is divided into two chambers) a blast pipe communicating
with the fire place is employed, but is used only occasionally when the fire is
first started. There is another air tube or pipe which runs along at the
bottom and back of the vertical flues.
The grate bars of the furnace and the floor of the heating ovens are placed
nearly upon the same plane, the oven floor being a little lower than the grate
bars, the grate bars and chamber for the fuel being at one end of the furnace,
extending across the body of the furnace and parallel with the oven. The door
of the fire-place is in the back of the furnace, upon the side opposite to that
or which the doors of the oven are placed; underneath the grate bars is the
ash-pit and chamber. Behind the bridge wall of the fire-place, which extends
along the whole length of the fire chamber, are four vertical flues, through
which all the heat and flame from the fire passes, the bridge wall being lower
than the sides of the flues, in order to leave horizontal openings into the flues;
the four vertical flues are continued downward until they are at a point suffi-
ciently below the floor of the oven, when they are turned at right angles, and
run horizontally until they reach beyond the floors of the heating oven.
floor of this oven is constructed of tiles made of fire clay, and the tiles
must reach across the apartments, and be laid so as to be tight, and not to
admit the flame or external air; the sides and top of the oven are arched, and
must be built of fire brick and made tight, so as to exclude the flame and
external air. The heating apartment is divided into two chambers by a
division wall extending from top to bottom. The flues after passing under the
oven, ascend vertically, and the flame and heat are thus carried into extended
horizontal flues or spaces at right angles to each other; by means of these
spaces of extended fire flues, the upper portions of the back and of the side of
The

page_text: the oven farthest from the fire chamber are exposed to the heat like the other
parts. The heat and flame are then carried up vertically to the level of the
exterior of the roof of the oven: it is then continued from the front to the
back of the roof of the oven by dividing walls extending part way across, so
that the heat and flame are conducted in a circuitous direction back and forth
on the roof of the oven before ascending into the exit flue or chimney. The
flue at the top is provided with a sliding damper to close or open the flue at
the top.
Openings are constructed in the walls of the furnace for the admission of
air to keep the exterior of the furnace from being too highly heated. At the
foot of the vertical descending flues I place the air tube, which is of metal,
and extends along the whole length of the grate bars on the opposite side of
the bridge wall. Where the tube crosses the descending flues it is pierced
with many holes, so as to supply the external air freely to the smoke, and
flame, and gases of the fuel.
The steel to be reheated is placed within the ovens upon fire-brick trestles,
or supports slightly elevated from the floor; the doors should be tightly closed
and kept tight except when the steel is being taken out or put in. This
arrangement of the oven into two distinct parts is convenient for having a
constant supply of the properly heated metal.
The ovens thus constructed and heated, if kept closed, will retain their heat
a very long time, and the heat can be graduated to the degree desired with
ease and accuracy. The blast through the blast pipe will rarely be required,
and only at the first starting of the fires. After the steel has been heated to
the desired degree it is to be submitted to a process of hardening, tempering,
or annealing. For some purposes, the longer the steel is subjected to the heat
of the oven the better it will be.