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Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is parti...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

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

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

Annealing Work
With the exception of several of the higher types of alloy s...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

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

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...



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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