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Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

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

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

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

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

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

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

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

Piston Pin
The piston pin on an aviation engine must possess maximum res...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

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

Phosphorus is one of the impurities in steel, and it has been...

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

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

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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