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Steel Making

Alloying Elements
Commercial steels of even the simplest types are therefore p...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

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

Connecting Rods
The material used for all connecting rods on the Liberty engi...

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

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

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

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

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

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

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

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

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

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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