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Steel Making

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

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

Annealing Work
With the exception of several of the higher types of alloy s...

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

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

Chromium
Chromium when alloyed with steel, has the characteristic func...

Crucible Steel
Crucible steel is still made by melting material in a clay or...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

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

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...



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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