Process Of Carburizing
: HEAT TREATMENT OF STEEL
: The Working Of Steel
Carburizing imparts a shell of high-carbon
content to a low-carbon steel. This produces what might be termed
a dual steel, allowing for an outer shell which when hardened
would withstand wear, and a soft ductile core to produce ductility
and withstand shock. The operation is carried out by packing the
work to be carburized in boxes with a material rich in carbon and
maintaining the box so charged at a temperature in ex
ess of the
highest critical point for a length of time to produce the desired
depth of carburized zone. Generally maintaining the temperature
at 1,650 to 1,700 deg. F. for 7 hr. will produce a carburized zone
1/32 in. deep.
Heating to a temperature slightly above the highest critical point
and cooling suddenly in some quenching medium, such as water or oil
hardens the steel. This treatment produces a maximum refinement
with the maximum strength.
Drawing to a temperature below the highest critical point (the
temperature being governed by the results required) relieves the
hardening strains set up by quenching, as well as the reducing
of the hardness and brittleness of hardened steel.