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Steel Making

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Annealing
There is no mystery or secret about the proper annealing of d...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

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

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

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

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

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

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

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Machineability
Reheating for machine ability was done at 100 deg. less than ...



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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