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Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

Hardening
Steel is hardened by quenching from above the upper critical....

Piston Pin
The piston pin on an aviation engine must possess maximum res...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

The Forging Of Steel
So much depends upon the forging of steel that this operation...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

Chromium
Chromium when alloyed with steel, has the characteristic func...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...



Annealing To Relieve Internal Stresses






Category: HARDENING CARBON STEEL FOR TOOLS

Work quenched from a high temperature and not afterward tempered
will, if complex in shape, contain many internal stresses which may
later cause it to break. They may be eased off by slight heating
without materially lessening the hardness of the piece. One way
to do this is to hold the piece over a fire and test it with a
moistened finger. Another way is to dip the piece in boiling water
after it has first been quenched in a cold bath. Such steps are
not necessary with articles which will afterward be tempered and
in which the strains are thus reduced.

In annealing steels the operation is similar to hardening, as far
as heating is concerned. The critical temperatures are the proper
ones for annealing as well as hardening. From this point on there
is a difference, for annealing consists in cooling as slowly as
possible. The slower the cooling the softer will be the steel.

Annealing may be done in the open air, in furnaces, in hot ashes
or lime, in powdered charcoal, in burnt bone, in charred leather
and in water. Open-air annealing will do as a crude measure in
cases where it is desired to take the internal stresses out of
a piece. Care must be taken in using this method that the piece
is not exposed to drafts or placed on some cold substance that
will chill it. Furnace annealing is much better and consists in
heating the piece in a furnace to the critical temperature and
then allowing the work and the furnace to cool together.

When lime or ashes are used as materials to keep air away from
the steel and retain the heat, they should be first heated to make
sure that they are dry. Powdered charcoal is used for high-grade
annealing, the piece being packed in this substance in an iron box
and both the work and the box raised to the critical temperature
and then allowed to cool slowly. Machinery steel may be annealed in
spent ground-bone that has been used in casehardening; but tool
steel must never be annealed in this way, as it will be injured
by the phosphorus contained in the bone. Charred leather is the
best annealing material for high-carbon steel, because it prevents
decarbonizing taking place.





Next: Double Annealing

Previous: Preventing Decarbonization Of Tool Steel



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