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

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

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

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

The Influence Of Size
The size of the piece influences the physical properties obta...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

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

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

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

Hardness Testing
The word hardness is used to express various properties of me...

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

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

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



Annealing To Relieve Internal Stresses






Category: HARDENING CARBON STEEL FOR TOOLS

Work quenched from a high temperature and not afterward tempered
will, if complex in shape, contain many internal stresses which may
later cause it to break. They may be eased off by slight heating
without materially lessening the hardness of the piece. One way
to do this is to hold the piece over a fire and test it with a
moistened finger. Another way is to dip the piece in boiling water
after it has first been quenched in a cold bath. Such steps are
not necessary with articles which will afterward be tempered and
in which the strains are thus reduced.

In annealing steels the operation is similar to hardening, as far
as heating is concerned. The critical temperatures are the proper
ones for annealing as well as hardening. From this point on there
is a difference, for annealing consists in cooling as slowly as
possible. The slower the cooling the softer will be the steel.

Annealing may be done in the open air, in furnaces, in hot ashes
or lime, in powdered charcoal, in burnt bone, in charred leather
and in water. Open-air annealing will do as a crude measure in
cases where it is desired to take the internal stresses out of
a piece. Care must be taken in using this method that the piece
is not exposed to drafts or placed on some cold substance that
will chill it. Furnace annealing is much better and consists in
heating the piece in a furnace to the critical temperature and
then allowing the work and the furnace to cool together.

When lime or ashes are used as materials to keep air away from
the steel and retain the heat, they should be first heated to make
sure that they are dry. Powdered charcoal is used for high-grade
annealing, the piece being packed in this substance in an iron box
and both the work and the box raised to the critical temperature
and then allowed to cool slowly. Machinery steel may be annealed in
spent ground-bone that has been used in casehardening; but tool
steel must never be annealed in this way, as it will be injured
by the phosphorus contained in the bone. Charred leather is the
best annealing material for high-carbon steel, because it prevents
decarbonizing taking place.





Next: Double Annealing

Previous: Preventing Decarbonization Of Tool Steel



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