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Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

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

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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Connecting Rods
The material used for all connecting rods on the Liberty engi...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

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

Air-hardening Steels
These steels are recommended for boring, turning and planing...



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.





Next: Pyrometers

Previous: Furnace Data



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