It has been suggested that this puzzle was a great favourite among the young apprentices of the City of London in the sixteenth and seventeenth centuries. Readers will have noticed the curious brass grasshopper on the Royal Exchange. This long-lived ... Read more of THE GRASSHOPPER PUZZLE. at Math Puzzle.caInformational Site Network Informational
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The Modern Hardening Room
A hardening room of today means a very different place from ...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

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

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

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

Manganese adds considerably to the tensile strength of steel,...

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

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Nickel may be considered as the toughest among the non-rare a...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

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

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

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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