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

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

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

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

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

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

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

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

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



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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