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Steel Making

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

This steel like any other steel when distorted by cold worki...

Molybdenum steels have been made commercially for twenty-five...

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

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

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

The forgings can be hardened by cooling in still air or quen...

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

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

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

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

Bessemer Process
The bessemer process consists of charging molten pig iron int...

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

Chromium when alloyed with steel, has the characteristic func...

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

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

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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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