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Steel Making

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

A combination of the characteristics of nickel and the charac...

SULPHUR is another element (symbol S) which is always found i...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

This steel like any other steel when distorted by cold worki...

Bessemer Process
The bessemer process consists of charging molten pig iron int...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

Martien was probably never a serious contender for the honor ...

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

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

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

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

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Quenching The Work
In some operations case-hardened work is quenched from the bo...

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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