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Steel Making

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

Protective Screens For Furnaces
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Silicon
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Annealing
ANNEALING can be done by heating to temperatures ranging from...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Steel Before The 1850's
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Knowing What Takes Place
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S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

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

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

Furnace Data
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Protectors For Thermo-couples
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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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