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

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

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

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

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

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

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

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

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

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

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

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

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

PHOSPHORUS is an element (symbol P) which enters the metal fr...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Complete Calibration Of Pyrometers


For the complete calibration
of a thermo-couple of unknown electromotive force, the new couple
may be checked against a standard instrument, placing the two bare
couples side by side in a suitable tube and taking frequent readings
over the range of temperatures desired.

If only one instrument, such as a millivoltmeter, is available,
and there is no standard couple at hand, the new couple may be
calibrated over a wide range of temperatures by the use of the following

Water, boiling point 212 deg.F.
Tin, under charcoal, freezing point 450 deg.F.
Lead, under charcoal, freezing point 621 deg.F.
Zinc, under charcoal, freezing point 786 deg.F.
Sulphur, boiling point 832 deg.F.
Aluminum, under charcoal, freezing point 1,216 deg.F.
Sodium chloride (salt), freezing point 1,474 deg.F.
Potassium sulphate, freezing point 1,958 deg.F.

A good practice is to make one pyrometer a standard; calibrate it
frequently by the melting-point-of-salt method, and each morning
check up every pyrometer in the works with the standard, making the
necessary corrections to be used for the day's work. By pursuing
this course systematically, the improved quality of the product
will much more than compensate for the extra work.

The purity of the substance affects its freezing or melting point.
The melting point of common salt is given in one widely used handbook
at 1,421 deg.F., although chemically pure sodium chloride melts at
1,474 deg.F. as shown above. A sufficient quantity for an extended
period should be secured. Test the melting point with a pyrometer
of known accuracy. Knowing this temperature it will be easy to
calibrate other pyrometers.

Next: Placing Of Pyrometers

Previous: Calibration Of Pyrometer With Common Salt

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