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Steel Making

Crucible Steel
Crucible steel is still made by melting material in a clay or...

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

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

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

Annealing
There is no mystery or secret about the proper annealing of d...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

The Thermo-couple
With the application of the thermo-couple, the measurement of...

Care In Annealing
Not only will benefits in machining be found by careful anne...

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

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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



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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