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Steel Making

The material used for all gears on the Liberty engine was sel...

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

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

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

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

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

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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

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

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

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

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

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

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

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

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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