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

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Manganese
Manganese adds considerably to the tensile strength of steel,...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

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

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

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

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

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

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

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

Furnace Data
In order to give definite information concerning furnaces, fu...

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

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

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

Drop Forging Dies
The kind of steel used in the die of course influences the he...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...



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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