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Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Drop Forging Dies
The kind of steel used in the die of course influences the he...

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

The Modern Hardening Room
A hardening room of today means a very different place from ...

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...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

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

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

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...



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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