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Steel Making

Furnace Data
In order to give definite information concerning furnaces, fu...

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

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

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

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

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

SULPHUR is another element (symbol S) which is always found i...

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

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

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

Steel is hardened by quenching from above the upper critical....

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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