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

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

There is no mystery or secret about the proper annealing of d...

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

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

Silicon prevents, to a large extent, defects such as gas bubb...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

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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