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Annealing Method
Forgings which are too hard to machine are put in pots with ...

Impact Tests
Impact tests are of considerable importance as an indication ...

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

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Molybdenum steels have been made commercially for twenty-five...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

The crankshaft was the most highly stressed part of the entir...

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

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

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

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

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

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

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

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

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

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

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.

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