Table 2-4.Properties and Average Cooling Abilities of Quenching Media
heavy-sectioned parts, the temperature rise may exceed
can cause cracking or stress in high-carbon or low-alloy
20°F, but should be kept as low as possible. For wrought
steels that are uneven in cross section.
products, the temperature of the water should be about
65°F and should never exceed 100°F before the piece
Because of the corrosive action of salt on nonfer-
rous metals, these metals are not quenched in brine.
enters the liquid.
Brine is the result of dissolving common rock salt
in water. This mixture reduces the absorption of atmos-
pheric gases that, in turn, reduces the amount of bubbles.
As a result, brine wets the metal surface and cools it
more rapidly than water. In addition to rapid and uni-
form cooling, the brine removes a large percentage of
any scale that may be present.
The brine solution should contain from 7% to 10%
salt by weight or three-fourths pound of salt for each
gallon of water. The correct temperature range for a
brine solution is 65°F to 100°F.
Low-alloy and carbon steels can be quenched in
brine solutions; however, the rapid cooling rate of brine
Oil is used to quench high-speed and oil-hardened
steels and is preferred for all other steels provided that
the required hardness can be obtained. Practically any
type of quenching oil is obtainable, including the vari-
ous animal oils, fish oils, vegetable oils, and mineral
oils. Oil is classed as an intermediate quench. It has a
slower cooling rate than brine or water and a faster rate
than air. The quenching oil temperature should be kept
within a range of 80°F to 150°F. The properties and
average cooling powers of various quenching oils are
given in table 2-4.
Water usually collects in the bottom of oil tanks but
is not harmful in small amounts. In large quantities it
can interfere with the quenching operations; for exam-
ple, the end of a long piece may extend into the water at