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Steel Making

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

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

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

Drop Forging Dies
The kind of steel used in the die of course influences the he...

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

Nickel-chromium
A combination of the characteristics of nickel and the charac...

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

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

Hardening
The forgings can be hardened by cooling in still air or quen...

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

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

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

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



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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