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

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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

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

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

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

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

SILICON is a very widespread element (symbol Si), being an es...

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

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

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

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

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

Annealing Work
With the exception of several of the higher types of alloy s...

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

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

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer


For extremely high temperature, the optical pyrometer is
largely used. This is a comparative method. By means of the rheostat
the current through the lamp is adjusted until the brightness of
the filament is just equal to the brightness of the image produced
by the lens L, Fig. 123, whereupon the filament blends with or
becomes indistinguishable in the background formed by the image
of the hot object. This adjustment can be made with great accuracy
and certainty, as the effect of radiation upon the eye varies some
twenty times faster than does the temperature at 1,600 deg.F., and some
fourteen times faster at 3,400 deg.F. When a balance has been obtained,
the observer notes the reading of the milliammeter. The temperature
corresponding to the current is then read from a calibration curve
supplied with the instrument.

As the intensity of the light emitted at the higher temperatures
becomes dazzling, it is found desirable to introduce a piece of red
glass in the eye piece at R. This also eliminates any question
of matching colors, or of the observer's ability to distinguish
colors. It is further of value in dealing with bodies which do
not radiate light of the same composition as that emitted by a
black body, since nevertheless the intensity of radiation of any
one color from such bodies increases progressively in a definite
manner as the temperature rises. The intensity of this one color
can therefore be used as a measure of temperature for the body
in question. Figures 124 to 126 show the way it is read.

Next: Correction For Cold-junction Errors

Previous: Leeds And Northrup Optical Pyrometer

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