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Steel Making

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

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

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

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

Compensating Leads
By the use of compensating leads, formed of the same materia...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

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

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

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

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Double Annealing
Water annealing consists in heating the piece, allowing it to...

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

Manganese
Manganese adds considerably to the tensile strength of steel,...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Alloying Elements
Commercial steels of even the simplest types are therefore p...



Case-hardening Treatments For Various Steels






Category: CASE-HARDENING OR SURFACE-CARBURIZING

Plain water, salt water and linseed oil are the three most common
quenching materials for case-hardening. Water is used for ordinary
work, salt water for work which must be extremely hard on the surface,
and oil for work in which toughness is the main consideration. The
higher the carbon of the case, the less sudden need the quenching
action take hold of the piece; in fact, experience in case-hardening
work gives a great many combinations of quenching baths of these
three materials, depending on their temperatures. Thin work, highly
carbonized, which would fly to pieces under the slightest blow if
quenched in water or brine, is made strong and tough by properly
quenching in slightly heated oil. It is impossible to give any
rules for the temperature of this work, so much depending on the
size and design of the piece; but it is not a difficult matter to
try three or four pieces by different methods and determine what
is needed for best results.

The alloy steels are all susceptible of case-hardening treatment;
in fact, this is one of the most important heat treatments for such
steels in the automobile industry. Nickel steel carburizes more
slowly than common steel, the nickel seeming to have the effect
of slowing down the rate of penetration. There is no cloud without
its silver lining, however, and to offset this retardation, a single
treatment is often sufficient for nickel steel; for the core is not
coarsened as much as low-carbon machinery steel and thus ordinary
work may be quenched on the carburizing heat. Steel containing
from 3 to 3.5 per cent of nickel is carburized between 1,650 and
1,750 deg.F. Nickel steel containing less than 25 points of carbon,
with this same percentage of nickel, may be slightly hardened by
cooling in air instead of quenching.

Chrome-nickel steel may be case-hardened similarly to the method just
described for nickel steel, but double treatment gives better results
and is used for high-grade work. The carburizing temperature is the
same, between 1,650 and 1,750 deg.F., the second treatment consisting
of reheating to 1,400 deg. and then quenching in boiling salt water,
which gives a hard surface and at the same time prevents distortion
of the piece. The core of chrome-nickel case-hardened steel, like
that of nickel steel, is not coarsened excessively by the first
heat treatment, and therefore a single heating and quenching will
suffice.





Next: Carburizing By Gas

Previous: Refining The Grain



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