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MANGANESE is a metal much like iron. Its chemical symbol is M...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

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

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

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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

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

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

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

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

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

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

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...

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

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

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

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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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