are hardened. The higher the carbon contents
the lower is the hardening heat, but this should in no case be
less than 1,450 deg.F.

ANNEALING ALLOY STEEL

The term alloy steel, from the steel maker's point of view, refers
largely to nickel and chromium steel or a combination of both. These
steels are manufactured very largely by the open-hearth process,
although chromium steels are also a crucible product. It is next
to impossible to give proper directions for the proper annealing
of alloy steel unless the composition is known to the operator.

Nickel steels may be annealed at lower temperatures than carbon
steels, depending upon their alloy content. For instance, if a
pearlitic carbon steel may be annealed at 1,450 deg.C., the same analysis
containing 2-1/2 per cent nickel may be annealed at 1,360 deg.C. and
a 5 per cent nickel steel at 1,270 deg..

In order that high chromium steels may be readily machined, they
must be heated at or slightly above the critical for a very long
time, and cooled through the critical at an extremely slow rate.
For a steel containing 0.9 to 1.1 per cent carbon, under 0.50 per
cent manganese, and about 1.0 per cent chromium, Bullens recommends
the following anneal:

1. Heat to 1,700 or 1,750 deg.F.
2. Air cool to about 800 deg.F.
3. Soak at 1,425 to 1,450 deg.F.
4. Cool slowly in furnace.

HIGH-CARBON MACHINERY STEEL

The carbon content of this steel is above 30 points and is hardly
ever above 60 points or 0.60 per cent. Annealing such steel is
generally in quantity production and does not require the care that
the other steels need because it is very largely a much cheaper
product and a great deal of material is generally removed from
the outside surface.

The purpose for which this steel is annealed is a deciding factor
as to what heat to give it. If it is for machineability only, the
steel requires to be brought up slowly to just below the critical and
then slowly cooled in the furnace or ash pit. It must be thoroughly
covered so that there will be no access of cool air. If the annealing
is to increase ductility to the maximum extent it should be slowly
heated to slightly over the upper critical temperature and kept at
this heat for a length of time necessary for a thorough penetration
to the core, after which it can be cooled to about 1,200 deg.F., then
reheated to about 1,360 deg.F., when it can be removed and put in an
ash pit or covered with lime. If the annealin