Unified Alloys: Pipe fittings, Stainless Steel tubing, pipe, Parker fittings, flanges - Edmonton Alberta Canada home | sitemap | terms | privacy & security | client login  
ABOUT US PRODUCTS RESOURCES CONTACTS
 

 

 

Resources

Glossary

FAQs

Downloads

Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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.

(2) Hot rolling a pack of two or more sheets of metal; scale prevents the sheets from being welded together.

(3) Hot rolling a pack of two or more sheets of metal; scale prevents their being welded together.

Pancake Forging
A rough forged shape which may be obtained quickly with a minimum of tooling. It usually requires considerable machining to attain the finish size.

Pancake Grain Structure
A structure in which the lengths and widths of individual grains are large compared to their thicknesses.

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

(2) A single transfer of metal through a stand of rolls.

(3) The open space between two grooved rolls through which metal is processed.

(4) The weld metal deposited in one run along the axis of a weld.

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

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.

(2) Treatment of steel, usually in wire form, in which the metal is gradually heated to about 1830 (degrees) F., with subsequent colling, 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.

Pearlite
A eutectoid transformation product of ferrite and cementite that ideally has a lamellar structure but that is always degenerate to some extent.

(2) 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.

(3) A lamellar aggregate of ferrite and cementite, oftern occurring in steel and case iron.

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

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.

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
A physically homogeneous and distincy portion of a material system.

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 phosphorus 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-base alloy containing up to 10% tin, which has been deoxidized with phosphorus in varying amounts of less than 1%. 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. 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 (degrees) F. even after stress relieving treatment at 325 (degrees) to 350 (degrees) 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 (degrees) F.; boiling point 536 (degrees) 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
Properties other than mechanical properties, that pertain to the physical nature of a material; e.g., density, electrical conductivity, thermal expansion, reflectivity, magnetic susceptibility, etc.

(2) The properties, other than mechanical properties, that pertain to the physics of a material; for example, density, electrical conductivity, heat conductivity, thermal expansion.

(3) 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
Removing surface oxides from metals by chemical or electrochemical reaction.

(2) The process of chemically removing oxides and scale from the surface of a metal by the action of water solutions of inorganic acids.

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
High-carbon iron made by reduction of iron ore in the blast furnace.

(2) Cast iron in the form of pigs.

(3) Iron produced by reduction of iron ore in a blast furnace. Pig iron contains approximately 92% iron and about 3.5% carbon. Balance largely silicone and manganese with small percentages of phosphorus, sulphur, and other impurities.

(4) High-carbon iron made by reduction of iron ore in the blast furnace. (2) Cast Iron in the form of pigs.

Piling
A process in which several bars are stacked and hot rolled together with the objective of improving the homogeneity of the final product. Used in primitive iron making.

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.

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
(1) The central cavity formed by contraction in metal, especially ingots, during solidification. (2) The defect in wrought or cast products resulting from such a cavity. (3) An extrusion defect due to the oxidized surface of the billet flowing toward the center of the rod at the back end. (4) A tubular metal product, cast or wrought.

Pipe (defect)
Contraction cavity, essentially 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 depresssion in the surface of the metal.

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

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.

Plastic Deformation
Permanent distortion of a material under the action of applied stresses.

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

(2) The capacity of a metal to deform non-elastically without rupturing.

Plate
A flat-rolled metal product of some minimum thickness and width argitrarily dependent on the type of metal.

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.

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.

Polymorphism
The property whereby certain substances may exist in more than one crystalline form, the particular form depending on the conditions of crystallization - e.g., temperature and pressure. Among elements, this phenomenon is also called allotropy.

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.

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

Precipitation Hardening
Hardening caused by the precipitation of a constituent form a supersaturated solid solution.

(2) A process of hardening an alloy in which a constituent precipitates from a supersaturated solid solution.

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

Preferred Orientation
A condition of a polycrystalline aggregate in which the crystal orientations are not random.

Preheating
Heating before some further thermal or mechanical treatment. For tool steel, heating to an intermediate temperature immediately before austenitizing. For some nonferrous alloys, heating to a high temperature for a long time, in order to homogenize the structure before working.

(2) A general term used to describe heating applied as a preliminary to some further thermal or mechanical treatment.

(3) 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.

(4) 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.

Press Forging
Forging metal, usually hot, between dies in a press.

Primary Crystal
The first type of crystal that separates from a melt during solidifacation.

Primes
Metal products, principally sheet and plate, of the highest quality and free from visible defects.

(2) 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, heating a ferrous alloy to a temperature close to, but below, the lower limit of the transformation range and then cooling, in order to soften the alloy for futher cold working.

(2) In the sheet and wire industries, a process by whcih 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 continuously increased during the aging cycle. The temperature may be increased in steps or by any other progressive method. Compare with interrupted aging.

Proof Stress
(1) The stress that will cause a specified small permanent set in a material. (2) A specified stress to be applied to a member or structure to indicate its ability to withstand service loads.

Propertional Limit
The greatest stress that the material is capable of sustaining without a deviation from the law of proportionally of stress to strain (Hooke's Law).

(2) the maximum stress at which strain remains directly propertional to stress.

Puddling Process
A process for making wrought iron in which cast orn 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.

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 any of various types used for measuring temperatures.