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Steel Making

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

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

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

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

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

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

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

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

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

Heating
Although it is possible to work steels cold, to an extent de...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

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

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

Piston Pin
The piston pin on an aviation engine must possess maximum res...

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

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

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...



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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