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Steel Making

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

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

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

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

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

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

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

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

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

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

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

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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