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Steel Making

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

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

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

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

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

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

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

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

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

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

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Effects Of Proper Annealing
Proper annealing of low-carbon steels causes a complete solu...



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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