Welding Glossary P

Parallel A term describing the relationship of two lines or surfaces tat, if extended, will never touch.
Parameters Welding conditions or variables.
Parent metal The same as base metal.
Parts positioner A device that holds the weldment and rotates or otherwise positions it for welding operations.For robotic welding, the positioner may be positioned by a controller and computer program.
Pascal (Pa) The unit of measurement for pressure in the SI metric system.
Pass Weld metal created by one progression along a weld.
Peak current During pulsed MIG (GMAW) welding, the higher current that is used for welding.The lower background current maintains the arc and allows the weld to cool.
Peel test A destructive test in which a resistance welded lap joint is mechanically separated by peeling one piece away from the other.
Peening The mechanical working of metal by means of repeated hammer blows.
Penetrant A liquid applied to the surface of a weld to locate discontinuities and make them visible.
Penetration The penetration of a weld is the distance from the original surface of the base metal to that point at which fusion ceases.
Percent heat control On a resistance welding machine, the control that permits fine adjustment of current within the amperage limits of the tap switch setting.
Petroleum A natural hydrocarbon compound that is processed into lubricants (grease and oil) and liquid fuels such as kerosene, heating oil and gasoline.
Petroleum-based A term used to describe lubricants.Flammable lubricants derived from petroleum must not be used to lubricate any part of a welding or cutting outfit.
Phosgene gas A highly toxic (poisonous) gas that can be released by the action of heat on cleaning chemicals that contain chlorinated hydrocarbons.
Photons Units of light energy emitted by a laser.
Physical properties The physical characteristics used to identify or describe a metal, such as color, melting temperature, or density.
Pinch force On short circuiting MIG (GMAW) metal transfer, the magnetic force that squeezes off the droplet of molten electrode metal.
Pipe A hollow cylinder with a relatively thick wall; pipe size is identified by its inside diameter and schedule number.
Pipe schedule number A one-, two-, or three digit number that classifies pipe.Schedule numbers are determined by a combination of the pipeâs inside diameter and its wall thickness.
Plasma A temporary physical state assumed by a gas after it has been exposed to, and reacted to, an extremely high temperature.An ionized state of a gas, also known as the fourth state of matter.
Plasma Arc Cutting (PAC) A cutting process for any metal that conducts electricity, it uses a constricted arc to melt a small area of the workpiece with a fast flowing ionized plasma gas.
Plasma arc welding (PAW) A process in which an electronic arc ionizes a gas, creating a plasma that generates the heat for welding.PAW is similar to TIG (GTAW) except that the arc is constricted through a constricting tip orifice.
Plasma arc spraying (PSP) A thermal spraying process that uses a nontransferred plasma arc to melt and propel a coating material onto a base material.
Plastic state A state of metal when it is soft and easily shaped due to high temperature; a metal that is in a plastic state is almost molten.
Plastics Synthetically produced nonmetallic compounds that can be shaped or molded into desired form.
Plastic welding A process in which heated air is used to soften and fuse plastic materials.
Plug weld A weld which holds two pieces of metal together.It is made by making a hole in one piece of metal which is then lapped over the other piece and welded.
Polarity The direction of the flow of electrons in a closed direct current welding circuit.When the electrons flow from the electrode to the base metal, the polarity is DCEN, or DCSP.When the current flows from the base metal to the electrode, the polarity is DCEP, or DCRP.
Pooling The process of creating a weld pool and moving it along several inches.Pooling provides practice in torch and arc control.
Porosity The presence of gas pockets or voids in the metal or weld bead.
Postheating The temperature to which a metal is heated after an operation has been performed on the metal such as welding, cutting or forming.
Post flow Refers to shielding gas flow that continues for a short time after the weld current stops to assure shield gas coverage of the weld zone until it is cool.
Post flow adjustment The control on a welding machine that allows variation in the length of time that post flow continues.
Pounds Per Square Inch (PSI) A measurement of pressure, it is the amount of weight applied to one square inch of surface area.
Power Efficiency A term to describe how well a machine uses incoming electrical power.
Power Factor Correction A way to reduce the amount of primary amperage demanded from the power company while welding, generally used on single-phase, constant current power sources.
Preheating A process that heats the metal to a specified temperature prior to a surfacing or welding operation.Also, the process of heating base metal to its kindling temperature before cutting.
Pressure The force exerted on a given area, expressed in psi or Pascals.
Pressure regulators Devices used to reduce the cylinder pressure of a gas to a usable (working) pressure for welding.
Pressure roll In MIG (GMAW) welding, the drive roll on the wire feeder that applies pressure to the electrode wire.Also know as feeder rollers.
Pressure test A procedure used to determine the maximum pressure that a cylinder or tank can hold.The test consists of forcing a gas or fluid into the cylinder or tank under increasing pressure until the vessel fails.
Primary Power Expressed in watts or kilowatts, it is the amount of amperage available to the welding machine from the shopâs main power line.
Procedure qualification record (PQR) Documentation containing the actual welding variables used produce an acceptable weld.The procedure qualification record is used to qualify a welding procedure specification.
Process An operation used to produce a product.
Prods A pair of hand held electrodes used to magnetize a part for a magnetic particle inspection.
Program A series of step-by-step directions and process parameters (times, pressures) set on the automatic controls of a welding machine or placed in the memory of a computer/controller.
Projection A bump stamped into one piece to be resistance welded.A weld nugget forms at the point where the projection touches the surface of the second part.
Projection welding (PW) A resistance spot welding process in which current is concentrated at points where projections on adjacent pieces are in contact.
Prototype parts The first models of parts that later may be mass-produced.
Puddle The portion of a weld that is molten at the place the heat is applied.
Pull gun A MIG (GMAW) welding gun that pulls the electrode wire through the cable.
Pulsed current Similar to direct current except that it has two current levels- a high current period followed by a low current period.
Pulsed MIG (MIG-P) A spray transfer process that produces no spatter as the wire does not touch the welding puddle.In this process the current is pulsed to take advantage of the spray mode of metal transfer, but with current values below the spray transition current.
Pulsed TIG (TIG-P) A TIG process used for welding thin materials.
Pulses Regular alternations of level or intensity, as in pulsed current.
Pulsing Controlling the amount of current, frequency and duration of the welding arc.
Purge Dam


A temporary barrier placed within the weld zone for the purpose of containing the shielding gas.
Purge Paper A special non permeable paper used to create a purge dam in a welding zone.For example, a circular dam can be created from purge paper to plug a pipe around the weld joint to capture the shielding gas within the joint area.
Purge switch A switch on a welding machine used to manually control the flow of shielding gas.
Purging The process of passing the correct gas through a regulator, torch and hose to clean out any air or undesirable gas that may be in the system.
Push-pull setup A system formed when a MIG (GMAW) pull gun pulls the electrode wire through the cable and the wire feeder pushes the wire.