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Steel Making

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Quenching The Work
In some operations case-hardened work is quenched from the bo...

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

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

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

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

Heating
Although it is possible to work steels cold, to an extent de...

Gears
The material used for all gears on the Liberty engine was sel...

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...



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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