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Steel Making

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

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

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

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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

The material used for all gears on the Liberty engine was sel...

Impact Tests
Impact tests are of considerable importance as an indication ...

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...

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

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

Annealing Work
With the exception of several of the higher types of alloy s...

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

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

Annealing To Relieve Internal Stresses


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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