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Steel Making

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

Hardening
Steel is hardened by quenching from above the upper critical....

Alloying Elements
Commercial steels of even the simplest types are therefore p...

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

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Silicon
SILICON is a very widespread element (symbol Si), being an es...

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Nickel
Nickel may be considered as the toughest among the non-rare a...

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

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

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Corrosion
This steel like any other steel when distorted by cold worki...

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

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



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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