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Hardening
The forgings can be hardened by cooling in still air or quen...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

Sulphur
SULPHUR is another element (symbol S) which is always found i...

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

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

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Crankshaft
The crankshaft was the most highly stressed part of the entir...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

Heating
Although it is possible to work steels cold, to an extent de...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

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

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...



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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