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Steel Making

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

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

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

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

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

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

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

Crankshaft
The crankshaft was the most highly stressed part of the entir...



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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