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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...

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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

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

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

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

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

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Hardness Testing
The word hardness is used to express various properties of me...

Annealing
There is no mystery or secret about the proper annealing of d...

Sulphur
SULPHUR is another element (symbol S) which is always found i...

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

Air-hardening Steels
These steels are recommended for boring, turning and planing...



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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