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Hardness Testing
The word hardness is used to express various properties of me...

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

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

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

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

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

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

Manganese
Manganese adds considerably to the tensile strength of steel,...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

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

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

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

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

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

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

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...



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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