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   Home - Steel Making - Categories - Manufacturing and the Economy of Machinery

Steel Making

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

Hardness Testing
The word hardness is used to express various properties of me...

Critical Points
One of the most important means of investigating the properti...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

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

Conclusions
Martien was probably never a serious contender for the honor ...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

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

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...



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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