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

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

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

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

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

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

Connecting Rods
The material used for all connecting rods on the Liberty engi...

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

Hardening
Steel is hardened by quenching from above the upper critical....

Care In Annealing
Not only will benefits in machining be found by careful anne...

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

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

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

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

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

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

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...



The Pyrometer And Its Use






Category: PYROMETRY AND PYROMETERS

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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