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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

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

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

Corrosion
This steel like any other steel when distorted by cold worki...

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

High Speed Steel
For centuries the secret art of making tool steel was handed ...

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

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

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

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



Preventing Cracks In Hardening






Category: HARDENING CARBON STEEL FOR TOOLS

The blacksmith in the small shop, where equipment is usually very
limited, often consisting of a forge, a small open hard-coal furnace,
a barrel of water and a can of oil must have skill and experience.
With this equipment the smith is expected to, and usually can,
produce good results if proper care is taken.

In hardening carbon tool steel in water, too much cannot be said in
favor of slow, careful heating, nor against overheating if cracks
are to be avoided.

It is not wise to take the work from the hardening bath and leave
it exposed to the air if there is any heat left in it, because
it is more liable to crack than if left in the bath until cold.
In heating, plenty of time is taken for the work to heat evenly
clear through, thus avoiding strains caused by quick and improper
heating, In quenching in water, contraction is much more rapid
than was the expansion while heating, and strains begin the moment
the work touches the water. If the piece has any considerable size
and is taken from the bath before it is cold and allowed to come to
the air, expansion starts again from the inside so rapidly that the
chilled hardened surface cracks before the strains can be relieved.

Many are most successful with the hardening bath about blood warm.
When the work that is being hardened is nearly cold, it is taken
from the water and instantly put into a can of oil, where it is
allowed to finish cooling. The heat in the body of the tool will
come to the surface more slowly, thus relieving the strain and
overcoming much of the danger of cracking.

Some contend that the temper should be drawn as soon as possible
after hardening: but that if this cannot be done for some hours, the
work should be left in the oil until the tempering can be done. It
is claimed that forming dies and punch-press dies that are difficult
to harden will seldom crack if treated in this way.

Small tools or pieces that are very troublesome because of peculiar
shape should be made of steel which has been thoroughly annealed.
It is often well to mill or turn off the outer skin of the bar,
to remove metal which has been cold-worked. Then heat slowly just
through the critical range and cool in the furnace, in order to
produce a very fine grain. Tools machined from such stock, and
hardened with the utmost care, will have the best chance to survive
without warping, growth or cracking.





Next: Shrinking And Enlarging Work

Previous: Hints For Tool Steel Users



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