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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

High Speed Steel
For centuries the secret art of making tool steel was handed ...

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

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

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

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

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

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

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



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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