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   Home - Steel Making - Categories - Manufacturing and the Economy of Machinery

Steel Making

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

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

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

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

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

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

Piston Pin
The piston pin on an aviation engine must possess maximum res...

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

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

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...



Refining The Grain






Category: CASE-HARDENING OR SURFACE-CARBURIZING

This is remedied by reheating the piece to a temperature slightly
above the critical temperature of the case, this temperature
corresponding ordinarily to that of steel having a carbon content
of 85 points, When this is again quenched, the temperature, which
has not been high enough to disturb the refined core, will have
closed the grain of the case and toughened it. So, instead of but
one heat and one quenching for this class of work, we have three
of each, although it is quite possible and often profitable to
omit the quenching after carburizing and allow the piece or pieces
and the case-carburizing box to cool together, as in annealing.
Sometimes another heat treatment is added to the foregoing, for
the purpose of letting down the hardness of the case and giving
it additional toughness by heating to a temperature between 300 deg.
and 500 deg.. Usually this is done in an oil bath. After this the piece
is allowed to cool.

It is possible to harden the surface of tool steel extremely hard
and yet leave its inner core soft and tough for strength, by a
process similar to case-hardening and known as pack-hardening.
It consists in using tool steel of carbon contents ranging from
60 to 80 points, packing this in a box with charred leather mixed
with wood charcoal and heating at a low-red heat for 2 or 3 hr.,
thus raising the carbon content of the exterior of the piece. The
article when quenched in an oil bath will have an extremely hard
exterior and tough core. It is a good scheme for tools that must
be hard and yet strong enough to stand abuse. Raw bone is never
used as a packing for this class of work, as it makes the cutting
edges brittle.





Next: Case-hardening Treatments For Various Steels

Previous: The Quenching Tank



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