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Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

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

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

Conclusions
Martien was probably never a serious contender for the honor ...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

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

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

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

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

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

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

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

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

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



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.





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Previous: Refining The Grain



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