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Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

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

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

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

Quenching
It is considered good practice to quench alloy steels from th...

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...

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

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

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

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

The Electric Process
The fourth method of manufacturing steel is by the electric f...



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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