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Steel Making

Hardening
The forgings can be hardened by cooling in still air or quen...

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

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

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

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

High Speed Steel
For centuries the secret art of making tool steel was handed ...

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

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

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

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

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

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

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



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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