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Steel Making

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

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

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

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

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

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

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

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Quenching
It is considered good practice to quench alloy steels from th...

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

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

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

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

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

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...



Correction For Cold-junction Errors






Category: PYROMETRY AND PYROMETERS

The voltage generated by a thermo-couple of an electric pyrometer is
dependent on the difference in temperature between its hot junction,
inside the furnace, and the cold junction, or opposite end of the
thermo-couple to which the copper wires are connected. If the
temperature or this cold junction rises and falls, the indications
of the instrument will vary, although the hot junction in the furnace
may be at a constant temperature.

A cold-junction temperature of 75 deg.F., or 25 deg.C., is usually adopted
in commercial pyrometers, and the pointer on the pyrometer should
stand at this point on the scale when the hot junction is not heated.
If the cold-junction temperature rises about 75 deg.F., where base metal
thermo-couples are used, the pyrometer will read approximately 1 deg.
low for every 1 deg. rise in temperature above 75 deg.F. For example, if the
instrument is adjusted for a cold-junction temperature of 75 deg., and
the actual cold-junction temperature is 90 deg.F., the pyrometer will
read 15 deg. low. If, however, the cold-junction temperature falls below
75 deg.F., the pyrometer will read high instead of low, approximately
1 deg. for every 1 deg. drop in temperature below 75 deg.F.

With platinum thermo-couples, the error is approximately 1/2 deg. for
1 deg. change in temperature.





Next: Correction By Zero Adjustment

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



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