The Line of Head, or indication of the Mentality of the subject, must in all cases be considered as the most important line on the hand. The greatest attention should be paid to it, so as to obtain a clear grasp of the Mentality under consid... Read more of The Line Of Head And Its Variations at Palm Readings.orgInformational Site Network Informational
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Steel Making

Connecting Rods
The material used for all connecting rods on the Liberty engi...

Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...

Quenching The Work
In some operations case-hardened work is quenched from the bo...

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

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

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

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

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

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

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

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

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

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

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

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



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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