Carburizing By Gas
: CASE-HARDENING OR SURFACE-CARBURIZING
: The Working Of Steel
The process of carburizing by gas, briefly mentioned on page 88,
consists of having a slowly revolving, properly heated, cylindrical
retort into which illuminating gas (a mixture of various hydrocarbons)
is continuously injected under pressure. The spent gases are vented
to insure the greatest speed in carbonizing. The work is constantly
and uniformly exposed to a clean carbonizing atmosphere instead
of partially spent carbonaceous solids which may give off very
complex compounds of phosphorus, sulphur, carbon and nitrogen.
Originally this process was thought to require a gas generator but
it has been discovered that city gas works all right. The gas consists
of vapors derived from petroleum or bituminous coal. Sometimes the
gas supply is diluted by air, to reduce the speed of carburization
and increase the depth.