PACK ROLLING
Rolling two or more pieces of thin sheet at the same time, a method usually practiced in rolling sheet into thin foil.

PASS
A term indicating the process of passing metal through a rolling mill.

PATENTING
Treatment of steel, usually in wire form, in which the metal is gradually heated to about 1830癋, with subsequent cooling, usually in air, in a bath of molten lead, or in a fused salt mixture held between 800癋 and 1050癋.

PATENT LEVELING
(See Stretcher Leveling)

PATTERNED OR EMBOSSED SHEET
A sheet product on which a raised or indented¹ pattern has been impressed on either one or both surfaces by the use of rolls.

PEARLITE
Lamellar structure resembling mother of pearl. A compound of iron and carbon occurring in steel as a result of the transformation² of austenite into aggregations³ of ferrite and iron carbide.

PERMALLOY
Nickel alloys⁵ containing about 20 to 60% Fe, used for their high magnetic permeability and electrical resistivity.

PERMANENT SET
Non-elastic⁶ or plastic, deformation⁷ of metal under stress, after passing the elastic limit.

PHOSPHOR BRONZE
Copper⁸ base alloys, with 3.5 to 10% of tin, to which has been added in the molten state phosphorous in varying amounts of less than 1% for deoxidizing and strengthening purposes. Because of excellent toughness, strength, fine grain, resistance to fatigue⁹ and wear, and chemical resistance, these alloys find general use as springs and in making fittings. It has corrosion¹⁰ resisting properties comparable to copper.

PHOSPHOR BRONZE STRIP
A copper-based alloy⁴ containing up to 10% tin, which has been deoxidized with phosphorous in varying amounts of less than 1 % (see Phosphor Bronze). Temper is imparted by cold rolling, resulting in greater tensile strength and hardness than in most copper-base alloys or either of its alloying elements copper or tin. The various tempers from “One Number Hard” to “Ten Numbers Hard” are classified in hardness by the number of B & S Gages reduction in dimension from the previous soft or as annealed state (See Brown & Sharpe Gages). Phosphor Bronze is not heat treatable for purposes of hardness development. It does not withstand elevated temperatures very well and should not be used in service above 225癋. even after stress relieving treatment at 325 to 350癋. It has excellent electrical properties, corrosion resistant¹² comparable to copper; great toughness and resistance to fatigue. Rated good for soft soldering¹³, silver alloy brazing, oxyacetylene, carbon arc and resistance welding.

PHOSPHORUS
(Chemical symbol P) - Element No. 15 of the periodic system; atomic weight 30.98. Non-metallic element occurring in at least three allotropic forms; melting point 111癋.; boiling point 536癋.; specific gravity 1.82. In steels it is usually undesirable¹⁴ with limits set in most specifications¹⁵. However, it is specified¹⁶ as an alloy in steel to prevent the sticking of light-gage¹¹ sheets; to a degree it strengthens low carbon steel; increases resistance to corrosion, and improves machinability in free-cutting steels. In the manufacture of Phosphor Bronze it is used as a deoxidizing agent.

PHOTOMICROGRAPH
A photographic reproduction of any object magnified more than ten diameters. The term micrograph may be used.

PHYSICAL PROPERTIES
Those properties familiarly discussed in physics, exclusive of those described under mechanical properties; for example, density¹⁸, electrical conductivity, co-efficient of thermal¹⁹ expansion. This term often has been used to describe mechanical properties, but this usage is not recommended. (See Mechanical Properties)

PICKLING
The process of chemically removing oxides and scale from the surface of a metal by the action of water solutions of inorganic²¹ acids.

PICKLING PATCH
A defect in tin plate, galvanized or terne plated steel due to faulty pickling, leaving areas from which the oxide²⁰ has not been completely removed.

PIG IRON
Iron produced by reduction of iron ore in a blast furnace. Pig iron contains approximately 92% iron and about 3.5% carbon. The balance is largely silicone and manganese with a small percentage of phosphorus, sulphur, and other impurities²².

PINCH PASS TEMPER
(See Soft Skin Rolled Temper and/or Temper Rolling)

PINCHERS
Long fern like creases¹⁷ usually diagonal to the direction of rolling.

PINHOLES
Microscopic²³ imperfections of the coatings, that is, microscopic bare spots, also microscopic holes penetrating²⁴ through a layer or thickness of light gage metal.

PIPE
(Defect) - Contraction²⁵ cavity, essentially²⁶ cone-like in shape, which occurs in the approximate center, at the top and reaching down into a casting; caused by the shrinkage of cast metal.

PIT
(Defect) - A sharp depression in the surface of the metal.

PLANIMETRIC METHOD
A method of measuring grain size, in which the grains within a definite area are counted.

PLASTIC DEFORMATION
Permanent distortion of a material under the action of applied²⁷ stresses.

PLASTICITY
The ability of a metal to be deformed²⁸ extensively without rupture²⁹.

PLATING
A thin coating of metal laid on another metal. (See Electroplating, Galvanizing, Tinning and Tinplating)

POLISHED SURFACE
(Buffed Surface) - The finish obtained by buffing with rouge³⁰ or similar fine abrasive³¹, resulting in a high gloss³² or polish.

POLYMORPHISM
The ability of a material to exist in more than one crystallographic structure. Numerous metals change in crystallographic structure at transformation temperatures during heating or cooling. If the change is reversible, it is allotropy. The allotropy of iron, particularly the changes between the alpha body-centered and the gamma face centered form, is of fundamental importance in the hardening of steel.

POT
A vessel³³ for holding molten metal. Also used to refer to the electrolytic reduction cell employed in winning certain metals, such as aluminum³⁴, from a fused electrolyte.

POT ANNEALING
Is the same as Box Annealing.

POURING
The transfer of molten metal from the ladle into ingot molds or other types of molds; for example, in castings.

POWDER METALLURGY
The art of producing metal powders and of utilizing³⁵ metal powders for the production of massive materials and shaped objects.

PRECIPITATION HARDENING
A process of hardening an alloy in which a constituent³⁶ precipitates³⁷ from a supersaturated solid solution. (See also Age Hardening and Aging)

PRECIPITATION HEAT TREATMENT
Any of the various aging treatments conducted at elevated temperature to improve certain of the mechanical properties through precipitation from solid solution. (See Artificial Aging, Interrupted Aging, and Progressive Aging)

PREHEATING
(1) A general term used to describe heating applied as a preliminary to some further thermal or mechanical treatment. (2) A term applied specifically to tool steel to describe a process on which the steel is heated slowly and uniformly to a temperature below the hardening temperature and is then transferred to a furnace in which the temperature is substantially above the preheating temperature. (3) Heating a metal to a relatively³⁸ high temperature for a relatively long time in order to change the structure before working. Ingots are homogenized by preheating.

PRIMES
Metal products, such as sheet and plate, of the highest quality and free from visible surface defects.

PROCESS ANNEALING
In the sheet and wire industries, a process by which a ferrous alloy is heated to a temperature close to, but below, the lower limit of the transformation range and is subsequently cooled. This process is applied in order to soften³⁹ the alloy for further cold working.

PROGRESSIVE AGING
An aging process in which the temperature of the alloy is continually increased during the aging cycle. The temperature may be increased in steps or by any other progressive method.

PROPORTIONAL LIMIT
The greatest stress that the material is capable of sustaining without a deviation⁴⁰ from the law of proportionality of stress to strain. (Hooke’s Law)

PUNCH
The movable part that forces the metal into the die in equipment for sheet drawing, blanking, coining, embossing and the like.

PUNCHING
Shearing holes in sheet metal with punch and die.

PYROMETER
An instrument of various types used for measuring temperatures