Heat Treatment Of Punches And Dies Shears Taps Etc

: 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
in oil

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