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

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

There is no mystery or secret about the proper annealing of d...

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

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

The Electric Process
The fourth method of manufacturing steel is by the electric f...

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

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

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

The Thermo-couple
With the application of the thermo-couple, the measurement of...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

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

It is considered good practice to quench alloy steels from th...

Double Annealing
Water annealing consists in heating the piece, allowing it to...

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

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

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

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

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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