the bottom of the tank and crack as a result of the more
Nonferrous metals are not routinely quenched in oil
unless specifications call for oil quenching.
A solution of water and caustic soda, containing 10
percent caustic soda by weight, has a higher cooling rate
than water. Caustic soda is used only for those types of
steel that require extremely rapid cooling and is NEVER
used as a quench for nonferrous metals.
CAUSTIC SODA REQUIRES SPECIAL
HANDLING BECAUSE OF ITS HARMFUL
EFFECTS ON SKIN AND CLOTHING.
This type of quenching uses materials other than
liquids. Inmost cases, this method is used only to slow
the rate of cooling to prevent warping or cracking.
Air quenching is used for cooling some highly
alloyed steels. When you use still air, each tool or part
should be placed on a suitable rack so the air can reach
all sections of the piece. Parts cooled with circulated air
are placed in the same manner and arranged for uniform
cooling. Compressed air is used to concentrate the cool-
ing on specific areas of a part. The airlines must be free
of moisture to prevent cracking of the metal.
Although nonferrous metals are usually quenched
in water, pieces that are too large to fit into the quench
tank can be cooled with forced-air drafts; however, an
air quench should be used for nonferrous metal only
when the part will not be subjected to severe corrosion
conditions and the required strength and other physical
properties can be developed by a mild quench.
The solids used for cooling steel parts include cast-
iron chips, lime, sand, and ashes. Solids are generally
used to slow the rate of cooling; for example, a cast-iron
part can be placed in a lime box after welding to prevent
cracking and warping. All solids must be free of mois-
ture to prevent uneven cooling.