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Steel Making

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

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

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

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

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

It is considered good practice to quench alloy steels from th...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

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

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

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

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

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

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

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

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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