Heat Treatment Of Punches And Dies Shears Taps Etc
: HIGH-SPEED STEEL
: The Working Of Steel
HEATING.--The degree to which tools of the above classes should
be heated depends upon the shape, size and use for which they are
intended. Generally, they should not be heated to quite as high a
heat as lathe tools or milling cutters. They should have a high
heat, but not enough to make the flux run on the steel (by pyrometer
1,900 to 2,100 deg.F.).
COOLING.--Depending on the tools, some should be dipped
all over, some only part way, and others allowed to cool down in
the air naturally, or under air blast. In cooling, the toughness
is retained by allowing some parts to cool slowly and quenching
parts that should be hard.
DRAWING THE TEMPER.--As in cooling, some parts of these tools will
require more drawing than others, but, on the whole, they must
be drawn more than water hardening tools for the same purpose or
to about 500 deg.F. all over, so that a good file will just touch
the cutting or working parts.
BARIUM CHLORIDE PROCESS.--This is a process developed for treating
certain classes of tools, such as taps, forming tools, etc. It is
being successfully used in many large plants. Briefly the treatment
is as follows:
In this treatment the tools are first preheated to a red heat,
but small tools may be immersed without preheating. The barium
chloride bath is kept at a temperature of from 2,000 to 2,100 deg.F.,
and tools are held in it long enough to reach the same temperature.
They are then dipped in oil. The barium chloride which adheres
to the tools is brushed off, leaving the tools as dean as before