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Steel Making

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

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

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

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...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

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



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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