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High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

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

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

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

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

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

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

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

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

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

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

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

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

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



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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