Process Annealing

An imprecise term denoting various treatments used to improve workability. For the term to

Progressive Aging

Aging by increasing the temperature in steps or continuously during the aging cycle. See aging and compare with interrupted aging and step aging.

Pusher Furnace

A type of continuous furnace in which parts to be heated are periodically charged into the furnace in containers, which are pushed along the hearth against a line of previously charged containers thus advancing the containers toward the discharge end of the furnace, where they are removed.

Pyrometer

A device for measuring temperatures above the range of liquid thermometers.

Pitot Tube

An instrument that measures the stagnation pressure of a flowing fluid, consisting of an open tube pointing into the fluid and connected to a pressure-indicating device. Also known as impact tube .

Plastic Deformation

The permanent (inelastic) distortion of metals under applied stresses that strain the material beyond its elastic limit .

Polymorphism

The property of a chemical substance crystallizing into two or more forms having different structures, such as diamond and graphite.

Precipitation Hardening

Hardening caused by the precipitation of a constituent from a supersaturated solid solution. See also age hardening and aging .

Precipitation Heat Treatment

Artificial aging in which a constituent precipitates from a supersaturated solid solution.

Pack Carburizing

A method of surface hardening of steel in which parts are packed in a steel box with the carburizing compound and heated to elevated temperatures.