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Steel Making

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Corrosion
This steel like any other steel when distorted by cold worki...

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Sulphur
SULPHUR is another element (symbol S) which is always found i...

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

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

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

Silicon
SILICON is a very widespread element (symbol Si), being an es...

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

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



Quenching Tool Steel






Category: HARDENING CARBON STEEL FOR TOOLS

To secure proper hardness, the cooling of quenching of steel is
as important as its heating. Quenching baths vary in nature, there
being a large number of ways to cool a piece of steel in contrast
to the comparatively few ways of heating it.

Plain water, brine and oil are the three most common quenching
materials. Of these three the brine will give the most hardness,
and plain water and oil come next. The colder that any of these
baths is when the piece is put into it the harder will be the steel;
but this does not mean that it is a good plan to dip the heated
steel into a tank of ice water, for the shock would be so great
that the bar would probably fly to pieces. In fact, the quenching
bath must be sometimes heated a bit to take off the edge of the
shock.

Brine solutions will work uniformly, or give the same degree of
hardness, until they reach a temperature of 150 deg.F. above which
their grip relaxes and the metals quenched in them become softer.
Plain water holds its grip up to a temperature of approximately
100 deg.F.; but oil baths, which are used to secure a slower rate of
cooling, may be used up to 500 deg. or more. A compromise is sometimes
effected by using a bath consisting of an inch or two of oil floating
on the surface of water. As the hot steel passes through the oil,
the shock is not as severe as if it were to be thrust directly
into the water; and in addition, oil adheres to the tool and keeps
the water from direct contact with the metal.

The old idea that mercury will harden steel more than any other
quenching material has been exploded. A bath consisting of melted
cyanide of potassium is useful for heating fine engraved dies and
other articles that are required to come out free from scale. One
must always be careful to provide a hood or exhaust system to get
rid of the deadly fumes coming from the cyanide pot.

The one main thing to remember in hardening tool steel is to quench
on a rising heat. This does not mean a rapid heating as a slow
increase in temperature is much better in every way.





Next: The Theory Of Tempering

Previous: Double Annealing



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