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Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

Bessemer Process
The bessemer process consists of charging molten pig iron int...

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

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

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

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

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

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

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

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

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

Corrosion
This steel like any other steel when distorted by cold worki...

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



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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