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

Steel Making

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

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

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

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

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

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

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

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

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



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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