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Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

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

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

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

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

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

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

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

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

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

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

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

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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