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

Drop Forging Dies
The kind of steel used in the die of course influences the he...

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

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

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

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

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

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

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

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

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

Chromium
Chromium when alloyed with steel, has the characteristic func...

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

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

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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



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






Category: PYROMETRY AND PYROMETERS

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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Previous: Leeds And Northrup Optical Pyrometer



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