Category: HEAT TREATMENT OF STEEL
Forgings which are too hard to machine are put
in pots with a little charcoal to cause a reducing atmosphere and
to prevent scale. The covers are then luted on and the pots placed
in the furnace. Carbon steel from 15 to 25 points is annealed at
1,600 deg.F. Nickel steel of the same carbon and containing in addition
3-1/2 per cent nickel is annealed at 1,450 deg.F. When the pots are
heated through, they are rolled to the yard and allowed to cool.
This method of annealing gives the best hardness for quick machining.
The requirements in the machine operations are very rigid and, in
spite of great care and probably the finest equipment of special
machines in the world, a small percentage of the product fails
to pass inspection during or at the completion of the machine
operations. These pieces, however, are not a loss, for they play
an important part in the hardening process, indicating as they do
the exact depth of penetration of the carburizing material and
the condition of both case and core.
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