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Compensating Leads
By the use of compensating leads, formed of the same materia...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

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

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

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

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

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

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

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

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

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

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

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



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.





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Previous: Preventing Decarbonization Of Tool Steel



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