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

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

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

The Influence Of Size
The size of the piece influences the physical properties obta...

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

ANNEALING can be done by heating to temperatures ranging from...

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

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

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

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

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

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

Care In Annealing
Not only will benefits in machining be found by careful anne...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

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.

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