The Packing Department
: HEAT TREATMENT OF STEEL
: The Working Of Steel
In Fig. 56 is shown the packing pots where
the work is packed. These are of malleable cast iron, with an internal
vertical flange around the hole A. This fits in a bell on the
end of the cast-iron pipe B, which is luted in position with
fireclay before the packing begins. At C is shown a pot ready
for packing. The crown gears average 10 to 12 in. in diameter and
weigh about 11 lb. each. When placed in the pots, they su
the central tube, which allows the heat to circulate. Each pot
contains five gears. Two complete scrap gears are in each furnace
(i.e., gears which fail to pass machining inspection), and at
the top of front pot are two or more short segments of scrap gear,
used as test pieces to gage depth of case.
After filling to the top with compound, the lid D is luted on.
Ten pots are then placed in a furnace. It will be noted that the
pots to the right are numbered 1, 2, 3, 4, indicating the position
they are to occupy in the furnace.
The cast-iron ball shown at E is small enough to drop through
the pipe B, but will not pass through the hole A in the bottom
of the pot. It is used as a valve to plug the bottom of the pot
to prevent the carburizing compound from dropping through when
removing the carburized gears to the quenching bath.
Without detracting from the high quality of the work, the metallurgist
in this plant has succeeded in cutting out one entire operation
and reducing the time in the hardening room by about 24 hr.
Formerly, the work was carburized at about 1,700 deg.F. for 9 hr. The
pots were then run out into the yard and allowed to cool slowly.
When cool, the work was taken out of the pots, reheated and quenched
at 1,600 deg.F. to refine the core. It was again reheated to 1,425 deg.F.
and quenched to refine the case. Finally, it was drawn to the proper