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Steel Making

The Modern Hardening Room
A hardening room of today means a very different place from ...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

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

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

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

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

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

The Electric Process
The fourth method of manufacturing steel is by the electric f...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

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

Sulphur
SULPHUR is another element (symbol S) which is always found i...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...



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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