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Steel Making

The forgings can be hardened by cooling in still air or quen...

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

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

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

Armor plate makers sometimes use the copper ball or Siemens' ...

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

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

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

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

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

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

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

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

Crucible Steel
Crucible steel is still made by melting material in a clay or...

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

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

Correction For Cold-junction Errors


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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