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   Home - Steel Making - Categories - Manufacturing and the Economy of Machinery

Steel Making

Annealing
There is no mystery or secret about the proper annealing of d...

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

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

The Influence Of Size
The size of the piece influences the physical properties obta...

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

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

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

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Hardening
Steel is hardened by quenching from above the upper critical....

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

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

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



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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