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Steel Making

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

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

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

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

Sulphur is another impurity and high sulphur is even a greate...

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

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

A combination of the characteristics of nickel and the charac...

Preventing Cracks In Hardening


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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