P

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

Packed lance
An oxygen lance with steel rods or wires.

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

Passivation
The changing of the chemically active surface of a metal to a much less reactive state.

Patent Leveling
(See Stretcher Leveling)

Patenting
A heat treatment applied to medium and high-carbon steel prior to cold drawing to wire.
The treatment involves austenitization followed by isothermal transformation at a temperature that produces a microstructure of very fine pearlite.
The metal is gradually heated to about 1830 (degrees) F., with subsequent cooling, usually in air, in a bath of molten lead, or in a fused salt mixture held between 800 (degrees) F. and 1050 (degrees) F.

Pattern Welding
A process in which strips or other small sections of iron or steel are twisted together and then forge welded. Homogeneity and toughness are thereby improved. A regular decorative pattern can be developed in the final product. Commonly used for making swords as early as the 3rd century A.D.

Patterned or Embossed Sheet
A sheet product on which a raised or indented pattern has been impressed on either on or both surfaces by the use of rolls.

Peak Earnings
The ultimate earnings level of a company at the top of the business cycle. This is the expected profit during the time of the highest commodity demand and the strongest product pricing.

Pearlite
A eutectoid transformation product of ferrite and cementite that ideally has a lamellar structure but that is always degenerate to some extent.
Lamellar structure resembling mother of pearl. A compound of iron and carbon occurring in steel as a result of the transformation of austenite into aggregations of ferrite and iron carbide.

Peening
Mechanical working of metal by hammer blows or shot impingement.

Pellets
(See Agglomerating Processes)

Penetrant Inspection
A method of non-destructive testing for determining the existence and extent of discontinuities that are open to the surface in the part being inspected. The indications ore made visible through the use of a dye or fluorescent chemical in the liquid employed as the inspection medium.

Penetration bead
Weld metal protruding through the root of a fusion weld made from one side only.

Peritectic
An isothermal reversible reaction in which a liquid phase reacts with a solid phase to produce another solid phase.

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

Permanent Set
Non-elastic or plastic, deformation of metal under stress, after passing the elastic limit.

Phase Diagram
Synonymous with constitutional diagram.

Phosphor Bronze
Copper 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 fatigue and wear, and chemical resistance, these alloys find general use as springs and in making fittings. It has corrosion resisting properties comparable to copper.

Phosphor Bronze Strip
A copper-based alloy 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°F. even after stress relieving treatment at 325 to 350°F. It has excellent electrical properties, corrosion resistant comparable to copper; great toughness and resistance to fatigue. Rated good for soft soldering, 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°F.; boiling point 536°F.; specific gravity 1.82. In steels it is usually undesirable with limits set in most specifications. However, it is specified as an alloy in steel to prevent the sticking of light-gage 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, density, electrical conductivity, co-efficient of thermal expansion. This term often has been used to describe mechanical properties, but this usage is not recommended.

Pickling

• WHAT
  Process that cleans a steel coil of its rust, dirt and oil so that further work can be done to the metal.

 
• WHY
  When hot-rolled coils cool, rust forms on the unprotected metal; often coils are stored or transported while exposed to outside air and water.

 
• HOW
  Through a continuous process, the steel is uncoiled and sent through a series of hydrochloric acid baths that remove the oxides (rust). The steel sheet is then rinsed and dried.

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

Pig Iron
The name for the melted iron produced in a blast furnace, containing a large quantity of carbon (above 1.5%). Named long ago when molten iron was poured through a trench in the ground to flow into shallow earthen holes, the arrangement looked like newborn pigs suckling. The central channel became known as the "sow," and the molds were "pigs."

Piling (Sheet Piling)
A structural steel product with edges designed to interlock; used in the construction of cofferdams or riverbank reinforcement.

Pin Expansion Test
A test for determining the ability of tubes to be expanded or for revealing the presence of cracks or other longitudinal weaknesses, made by forcing a tapered pin into the open end of a tube.

Pinch Pass Temper
(See Soft Skin Rolled Temper and/or Temper Rolling)

Pinchers
Long fern like creases usually diagonal to the direction of rolling.

Pinholes
Microscopic imperfection of the coatings, that is, microscopic bare spots, also microscopic holes penetrating through a layer or thickness of light gage metal.

Pipe
Technically a tube used to transport fluids or gases. However, pipe and tube are often used interchangeably in steel lexicon, with a given label applied primarily as a matter of historical use.

Pit
A sharp depression in the surface of the metal.

Pitting
Forming small sharp cavities in a metal surface by non-uniform electro-deposition or by corrosion.

Pitting factor
The ratio of the depth of the deepest pit resulting from corrosion divided by the average penetration as calculated from mass loss.

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

Planishing
Producing a smooth surface finish on metal by rapid succession of blows delivered by highly polished dies or by a hammer designed for the purpose, or by rolling in a planishing mill.

Plastic Deformation
Deformation that remains, or will remain, permanent after release of the stress that caused it.

Plasticity
The ability of a metal to be deformed extensively without rupture.

Plate
Sheet steel with a width of more than eight inches, with a thickness ranging from one quarter of an inch to more than one foot (see Sheet Steel).

Plate Martensite
Martensite formed, partly in steels containing more than about 0.5% C and solely in steels containing more than about 1.0% C, as lenticular-shape plates on irrational habit planes that are near (225)A, or {259}A in very-high-carbon steels

Plating
A thin coating of metal laid on another metal.

Plug weld
A weld made by filling a hole in one component of a work piece so as to join it to the surface of an overlapping component exposed through the hole.

PM 2.5
The moniker for the Environmental Protection Agency's new Particulate Matter standards. The EPA is revising current PM standards and establishing a new PM 2.5 standard regarding the release of particulate matter down to 2.5 micrometers in diameter (less than one-third the width of a human hair).

Polished Surface
The finish obtained by buffing with rouge or similar fine abrasive, resulting in a high gloss or polish.

Polishing
Producing a specularly reflecting surface.

Polycrystalline
Comprising an aggregate of more than one crystal, and usually a large number of crystals.

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.

Porosity
A group of gas pores.

Postheating
Heating weldments immediately after welding, for tempering, for stress relieving, or for providing a controlled rate of cooling to prevent formation of a hard or brittle structure.

Post-weld heat treatment (PWHT)
Also referred to as stress relieving, this process is used to soften the heat affected zones and relieve residual stresses created during welding.

Pot
A vessel for holding molten metal. Also used to refer to the electrolytic reduction cell employed in winning certain metals, such as aluminum, 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 cutting
Oxygen cutting in which powder is injected into the cutting oxygen stream to assist the cutting action.

Powder lance
An oxygen lance in which powder is mixed with the oxygen stream.

Powder Metallurgy
The art of producing metal powders and of utilizing metal powders for the production of massive materials and shaped objects.

Powder Metals
Fabrication technology in which fine metallic powder is compacted under high pressure and then heated at a temperature slightly below the melting point to solidify the material. Primary users of powder metal parts are auto, electronics and aerospace industries.

Precipitation Hardening (PH)
Hardening caused by the precipitation of a constituent form a supersaturated solid solution.
A small group of stainless steels with high chromium and nickel content, with the most common types having characteristics close to those of martensitic (plain chromium stainless class with exceptional strength) steels. Heat treatment provides this class with its very high strength and hardness. Applications for PH stainless steels include shafts for pumps and valves as well as aircraft parts.

Precipitation Heat Treatment
Any of the various aging treatments conducted at elevated temperatures to improve certain of the mechanical properties through precipitation from solid solution.

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 in 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) Nonfer. met.-Heating a metal to a relatively high temperature for a relatively long time in order to change the structure before working. Ingots are homogenized by preheating.

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 soften the alloy for further cold working.

Proeutectoid (phase)
Particles of a phase that precipitate during cooling after austenitizing but before the eutectoid transformation takes place.

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 deviation from the law of proportionality of stress to strain. (Hooke’s Law)

Puddling Process
A process for making wrought iron in which cast ore is melted in a hearth furnace and rabbled with slag and oxide until a pasty mass is obtained. This process was developed by Henry Cort about 1784 and remained in use until 1957, although on a very small scale during the present century.

Pulse-Echo Method
A nondestructive test in which pulses of energy are directed onto a part, and the time for the echo to return from one or more reflecting surfaces is measured.

Pulverized Coal Injection System (PCI)
A blast furnace enhancement to reduce an integrated mill's reliance on coke (because of environmental problems with its production). Up to 30% of the coke charged into the blast furnace can be replaced by this talcum-like coal powder, which is injected through nozzles at the bottom of the furnace.

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.

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