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Steel Making

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

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

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

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

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

There is no mystery or secret about the proper annealing of d...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

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

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

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

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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