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Steel Making

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

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

It is considered good practice to quench alloy steels from th...

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

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

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

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

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

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

Critical Points
One of the most important means of investigating the properti...

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...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

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

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

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

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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