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

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

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

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

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

Annealing
ANNEALING can be done by heating to temperatures ranging from...

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

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

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

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

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

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

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

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

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

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



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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