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

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

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

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

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

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

Piston Pin
The piston pin on an aviation engine must possess maximum res...

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Sulphur
SULPHUR is another element (symbol S) which is always found i...

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

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

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

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

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

Chromium
Chromium when alloyed with steel, has the characteristic func...

Heating
Although it is possible to work steels cold, to an extent de...

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



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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