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

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

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

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is parti...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

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

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

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

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

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

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

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...



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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