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Steel Making

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

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

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

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

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

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

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

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

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

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

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Care In Annealing
Not only will benefits in machining be found by careful anne...

The material used for all gears on the Liberty engine was sel...

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

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

The Pyrometer And Its Use


In the heat treatment of steel, it has become absolutely necessary
that a measuring instrument be used which will give the operator an
exact reading of heat in furnace. There are a number of instruments
and devices manufactured for this purpose but any instrument that
will not give a direct reading without any guess work should have
no place in the heat-treating department.

A pyrometer installation is very simple and any of the leading
makers will furnish diagrams for the correct wiring and give detailed
information as to the proper care of, and how best to use their
particular instrument. There are certain general principles, however,
that must be observed by the operators and it cannot be too strongly
impressed upon them that the human factor involved is always the
deciding factor in the heat treatment of steel.

A pyrometer is merely an aid in the performance of doing good work,
and when carefully observed will help in giving a uniformity of
product and act as a check on careless operators. The operator
must bear in mind that although the reading on the pyrometer scale
gives a measure of the temperature where the junction of the two
metals is located, it will not give the temperature at the center
of work in the furnace, unless by previous tests, the heat for
penetrating a certain bulk of material has been decided on, and
the time necessary for such penetration is known.

Each analysis of plain carbon or alloy steel is a problem in itself.
Its critical temperatures will be located at slightly different
heats than for a steel which has a different proportion of alloying
elements. Furthermore, it takes time for metal to acquire the heat
of the furnace. Even the outer surface lags behind the temperature
of the furnace somewhat, and the center of the piece of steel lags
still further. It is apparent, therefore, that temperature, although
important, does not tell the whole story in heat treatment. Time
is also a factor.

Time at temperature is also of great importance because it takes
time, after the temperature has been reached, for the various internal
changes to take place. Hence the necessity for soaking, when
annealing or normalizing. Therefore, a clock is as necessary to
the proper pyrometer equipment as the pyrometer itself.

For the purpose of general work where a wide range of steels or
a variable treatment is called for, it becomes necessary to have
the pyrometer calibrated constantly, and when no master instrument
is kept for this purpose the following method can be used to give
the desired results:

Next: Calibration Of Pyrometer With Common Salt

Previous: The Thermo-couple

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