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   Home - Steel Making - Categories - Manufacturing and the Economy of Machinery

Steel Making

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

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

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

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

Furnace Data
In order to give definite information concerning furnaces, fu...

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

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

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

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

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

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

Manganese
Manganese adds considerably to the tensile strength of steel,...



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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