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Steel Making

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

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

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

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

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

Hardening
Steel is hardened by quenching from above the upper critical....

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

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

Bessemer Process
The bessemer process consists of charging molten pig iron int...

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

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

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

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

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

Annealing Work
With the exception of several of the higher types of alloy s...

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



Calibration Of Pyrometer With Common Salt






Category: PYROMETRY AND PYROMETERS

An easy and convenient method for standardization and one which
does not necessitate the use of an expensive laboratory equipment
is that based upon determining the melting point of common table
salt (sodium chloride). While theoretically salt that is chemically
pure should be used (and this is neither expensive nor difficult
to procure), commercial accuracy may be obtained by using common
table salt such as is sold by every grocer. The salt is melted in
a clean crucible of fireclay, iron or nickel, either in a furnace
or over a forge-fire, and then further heated until a temperature
of about 1,600 to 1,650 deg.F. is attained. It is essential that this
crucible be clean because a slight admixture of a foreign substance
might noticeably change the melting point.

The thermo-couple to be calibrated is then removed from its protecting
tube and its hot end is immersed in the salt bath. When this end
has reached the temperature of the bath, the crucible is removed
from the source of heat and allowed to cool, and cooling readings
are then taken every 10 sec. on the milli-voltmeter or pyrometer. A
curve is then plotted by using time and temperature as cooerdinates,
and the temperature of the freezing point of salt, as indicated
by this particular thermocouple, is noted, i.e., at the point
where the temperature of the bath remains temporarily constant
while the salt is freezing. The length of time during which the
temperature is stationary depends on the size of the bath and the
rate of cooling, and is not a factor in the calibration. The melting
point of salt is 1,472 deg.F., and the needed correction for the instrument
under observation can be readily applied.

It should not be understood from the above, however, that the salt-bath
calibration cannot be made without plotting a curve; in actual
practice at least a hundred tests are made without plotting any curve
to one in which it is done. The observer, if awake, may reasonably
be expected to have sufficient appreciation of the lapse of time
definitely to observe the temperature at which the falling pointer
of the instrument halts. The gradual dropping of the pointer before
freezing, unless there is a large mass of salt, takes place rapidly
enough for one to be sure that the temperature is constantly falling,
and the long period of rest during freezing is quite definite.
The procedure of detecting the solidification point of the salt
by the hesitation of the pointer without plotting any curve is
suggested because of its simplicity.





Next: Complete Calibration Of Pyrometers

Previous: The Pyrometer And Its Use



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