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

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Impact Tests
Impact tests are of considerable importance as an indication ...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

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

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

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

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

Corrosion
This steel like any other steel when distorted by cold worki...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

Manganese
Manganese adds considerably to the tensile strength of steel,...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

Compensating Leads
By the use of compensating leads, formed of the same materia...



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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