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Steel Making

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

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

Impact Tests
Impact tests are of considerable importance as an indication ...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

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

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

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

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

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

A combination of the characteristics of nickel and the charac...

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

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

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

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

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

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

Refining The Grain


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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