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Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

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

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

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

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

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

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

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

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

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

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

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

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

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...



Pyrometry And Pyrometers






Category: PYROMETRY AND PYROMETERS

A knowledge of the fundamental principles of pyrometry, or the
measurement of temperatures, is quite necessary for one engaged
in the heat treatment of steel. It is only by careful measurement
and control of the heating of steel that the full benefit of a
heat-treating operation is secured.

Before the advent of the thermo-couple, methods of temperature
measurement were very crude. The blacksmith depended on his eyes
to tell him when the proper temperature was reached, and of course
the color appeared different on light or dark days. Cherry
to one man was orange to another, and it was therefore almost
impossible to formulate any treatment which could be applied by
several men to secure the same results.

One of the early methods of measuring temperatures was the iron
ball method. In this method, an iron ball, to which a wire was
attached, was placed in the furnace and when it had reached the
temperature of the furnace, it was quickly removed by means of
the wire, and suspended in a can containing a known quantity of
water; the volume of water being such that the heat would not cause
it to boil. The rise in temperature of the water was measured by a
thermometer, and, knowing the heat capacity of the iron ball and
that of the water, the temperature of the ball, and therefore the
furnace, could be calculated. Usually a set of tables was prepared
to simplify the calculations. The iron ball, however, scaled, and
changed in weight with repeated use, making the determinations
less and less accurate. A copper ball was often used to decrease
this change, but even that was subject to error. This method is
still sometimes used, but for uniform results, a platinum ball,
which will not scale or change in weight, is necessary, and the
cost of this ball, together with the slowness of the method, have
rendered the practice obsolete, especially in view of modern
developments in accurate pyrometry.





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Previous: Furnace Data



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