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

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

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

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

Conclusions
Martien was probably never a serious contender for the honor ...

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

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

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

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

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

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

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...



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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