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Steel Making

Hardness Testing
The word hardness is used to express various properties of me...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

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

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

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

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

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

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

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

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

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

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

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

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

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

Sulphur is another impurity and high sulphur is even a greate...

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

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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