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Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

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

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

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

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

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Annealing Work
With the exception of several of the higher types of alloy s...

Impact Tests
Impact tests are of considerable importance as an indication ...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

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

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

Nickel-chromium
A combination of the characteristics of nickel and the charac...



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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