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

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

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

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

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

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

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

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

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

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

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

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

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

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

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

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...



Double Annealing






Category: HARDENING CARBON STEEL FOR TOOLS

Water annealing consists in heating the piece, allowing it to cool
in air until it loses its red heat and becomes black and then
immediately quenching it in water. This plan works well for very
low-carbon steel; but for high-carbon steel what is known as the
double annealing treatment must be given, provided results are
wanted quickly. The process consists in heating the steel quickly to
200 deg. or more above the upper critical, cooling in air down through
the recalescence point, then reheating it to just above the critical
point and again cooling slowly through the recalescence, then quenching
in oil. This process retains in the steel a fine-grained structure
combined with softness.





Next: Quenching Tool Steel

Previous: Annealing To Relieve Internal Stresses



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