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Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

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

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

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

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Furnace Data
In order to give definite information concerning furnaces, fu...

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

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

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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

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

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...



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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