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Steel Making

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Critical Points
One of the most important means of investigating the properti...

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

Hardness Testing
The word hardness is used to express various properties of me...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

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...

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

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

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

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

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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