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Steel Making

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

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

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

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

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

Compensating Leads
By the use of compensating leads, formed of the same materia...

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...



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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