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Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

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

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

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

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

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

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

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

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

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

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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



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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