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

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

Furnace Data
In order to give definite information concerning furnaces, fu...

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

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

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

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

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

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

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

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

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

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

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



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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