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Crankshaft
The crankshaft was the most highly stressed part of the entir...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

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

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...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

Piston Pin
The piston pin on an aviation engine must possess maximum res...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

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

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

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

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

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

Gears
The material used for all gears on the Liberty engine was sel...



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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