Technical Data

Metallurgical Terms

P.

Chemical symbol for phosphorus.

Pack Carburizing.

(See Carburizing).

Passivity.

This applies to a metal or alloy which is normally chemically active; it is said to be passive when its behaviour resembles that of a more noble metal.

Patented Steel.

(See Patenting).

Patenting.

Heating to a suitable temperature well above the transformation range, followed by cooling in air or in a bath of molten lead or salt maintained at a suitable temperature, to produce a structure which will facilitate subsequent cold working and give the desired mechanical properties in the finished state. In wire making, the process is applied to medium or high carbon steel between drawings.

Pb.

Chemical symbol for lead, from the Latin plumbum.

Pd.

Chemical symbol for palladium.

Pearlite.

The lamellar conglomerate of ferrite and cementite which constitutes the eutectoid in the iron-carbon equilibrium system. It results from the transformation of austenite at or below Ar₁, and is so called from the mother-of-pearl lustre given by an etched surface when viewed under the microscope. This pearly appearance is due to the fine and regular alternation of the two constituents. The lamellar arrangement of ferrite and cementite  produces a tough structure and is responsible for the mechanical properties of the unhardened steels. Pearlite is present in small quantities in low carbon steels and increases in quantity as the carbon increases, until in a plain carbon steel, containing about 0.83% of carbon, the structure consists entirely of pearlite.

Peltier Effect.

The phenomenon whereby heat is liberated or absorbed at a junction where an electric current passes from one metal to another.

Pencil Test.

A small ingot cast from a sample of liquid steel to provide test material for analysis, for carbon or hydrogen, for example.

Peritectic.

A reaction when an alloy freezes which takes place between a liquid and a solid phase to produce another solid phase.