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Steel Making

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

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

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

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

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

Furnace Data
In order to give definite information concerning furnaces, fu...

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

Hardening
Steel is hardened by quenching from above the upper critical....

Nickel
Nickel may be considered as the toughest among the non-rare a...

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

Impact Tests
Impact tests are of considerable importance as an indication ...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

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

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

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

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

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

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

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...



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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