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Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

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

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

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

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

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

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

Drop Forging Dies
The kind of steel used in the die of course influences the he...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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



Carburizing Material






Category: CASE-HARDENING OR SURFACE-CARBURIZING

The simplest carburizing substance is charcoal. It is also the
slowest, but is often used mixed with something that will evolve
large volumes of carbon monoxide or hydrocarbon gas on being heated.
A great variety of materials is used, a few of them being charcoal
(both wood and bone), charred leather, crushed bone, horn, mixtures
of charcoal and barium carbonate, coke and heavy oils, coke treated
with alkaline carbonates, peat, charcoal mixed with common salt,
saltpeter, resin, flour, potassium bichromate, vegetable fibre,
limestone, various seed husks, etc. In general, it is well to avoid
complex mixtures.

H. L. Heathcote, on analyzing seventeen different carburizers, found
that they contained the following ingredients:

Per cent
Moisture 2.68 to 26.17
Oil 0.17 to 20.76
Carbon (organic) 6.70 to 54.19
Calcium phosphate 0.32 to 74.75
Calcium carbonate 1.20 to 11.57
Barium carbonate nil to 42.00
Zinc oxide nil to 14.50
Silica nil to 8.14
Sulphates (SO3) trace to 3.45
Sodium chloride nil to 7.88
Sodium carbonate nil to 40.00
Sulphides (S) nil to 2.80

Carburizing mixtures, though bought by weight, are used by volume,
and the weight per cubic foot is a big factor in making a selection.
A good mixture should be porous, so that the evolved gases, which
should be generated at the proper temperature, may move freely
around the steel objects being carburized; should be a good conductor
of heat; should possess minimum shrinkage when used; and should
be capable of being tamped down.

Many secret mixtures are sold, falsely claimed to be able to
convert inferior metal into crucible tool steel grade. They are
generally nothing more than mixtures of carbonaceous and cyanogen
compounds possessing the well-known carburizing properties of those
substances.





Next: Quenching

Previous: Rate Of Absorption



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