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

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

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

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

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

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

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

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

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...

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

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

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



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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