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Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...

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

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

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

Sulphur
SULPHUR is another element (symbol S) which is always found i...

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

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

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

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

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

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

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

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

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

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...



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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