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Steel Making

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

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

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

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

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

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

Silicon
SILICON is a very widespread element (symbol Si), being an es...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

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

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

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

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

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

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

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

Impact Tests
Impact tests are of considerable importance as an indication ...

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

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



Refining The Grain






Category: CASE-HARDENING OR SURFACE-CARBURIZING

This is remedied by reheating the piece to a temperature slightly
above the critical temperature of the case, this temperature
corresponding ordinarily to that of steel having a carbon content
of 85 points, When this is again quenched, the temperature, which
has not been high enough to disturb the refined core, will have
closed the grain of the case and toughened it. So, instead of but
one heat and one quenching for this class of work, we have three
of each, although it is quite possible and often profitable to
omit the quenching after carburizing and allow the piece or pieces
and the case-carburizing box to cool together, as in annealing.
Sometimes another heat treatment is added to the foregoing, for
the purpose of letting down the hardness of the case and giving
it additional toughness by heating to a temperature between 300 deg.
and 500 deg.. Usually this is done in an oil bath. After this the piece
is allowed to cool.

It is possible to harden the surface of tool steel extremely hard
and yet leave its inner core soft and tough for strength, by a
process similar to case-hardening and known as pack-hardening.
It consists in using tool steel of carbon contents ranging from
60 to 80 points, packing this in a box with charred leather mixed
with wood charcoal and heating at a low-red heat for 2 or 3 hr.,
thus raising the carbon content of the exterior of the piece. The
article when quenched in an oil bath will have an extremely hard
exterior and tough core. It is a good scheme for tools that must
be hard and yet strong enough to stand abuse. Raw bone is never
used as a packing for this class of work, as it makes the cutting
edges brittle.





Next: Case-hardening Treatments For Various Steels

Previous: The Quenching Tank



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