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Steel Making

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

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

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

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

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

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

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

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

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

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

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



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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