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Steel Making

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

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

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

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

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

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

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

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

Quenching The Work
In some operations case-hardened work is quenched from the bo...

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

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...



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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