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

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Heating
Although it is possible to work steels cold, to an extent de...

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

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

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

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

The Influence Of Size
The size of the piece influences the physical properties obta...



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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