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The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

Crankshaft
The crankshaft was the most highly stressed part of the entir...

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

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

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

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Annealing Work
With the exception of several of the higher types of alloy s...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

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

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...

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

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

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

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

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...



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.





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Previous: Rate Of Absorption



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