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Steel Making

Corrosion
This steel like any other steel when distorted by cold worki...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

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

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

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

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

Manganese
Manganese adds considerably to the tensile strength of steel,...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

Hardening
The forgings can be hardened by cooling in still air or quen...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

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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