Glossary - P
A group of hydrocarbons with the general formula CnH2n+2. They are also known as Alkanes and include methane CH4, propane C3H8 and octane C8H18. Particulate fume is the discrete solid particles produced during welding and cutting. It consists of the complex oxides and silicates of metals in the parent plate and filler wire which are generally under 0,5 microns in diameter. This falls into the "respirable " size range meaning that the particles can be breathed in and reach the lungs. Penetration area is the measurement of the area of the weld bead below the level of the plate surface. Penetration depth is the measurement of the distance between the level of the plate surface and the bottom of the weld. Penetration profile describes the shape of the weld bead below the level of the plate surface. A table of the chemical elements arranged in order of atomic number in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in vertical columns. A Phase Diagram shows the effect of changes in temperature and pressure has on the physical state of a product. A phase diagram may also show the effect of temperature and composition on an alloy of two or more metals. Pitting Resistance Equivalent (PRE) A number indicating the resistance of a stainless steel to pitting corrosion, related to chemical composition and derived from the equation: PRE = %Cr + 3.3x%Mo + 16x%N MIG wire can be supplied as a continuous coil wound onto cylindrical reels or spools of various designs and diameters. Traditionally, MIG reels have been made of plastic. Reel sizes vary from the standard 300mm diameter reels to small, 50mm diameter, for spool-on-gun equipment. The amount of wire will vary with reel diameter and type of alloy, a standard reel holding about 15kg of steel MIG wire, or 6kg of aluminium MIG wire. A large compound which is formed from repeated units of smaller molecules. Also called Polyethane. A large hydrocarbon molecule formed by the polymerisation of ethylene (ethane). A process in which the double or triple bonds in hydrocarbon molecules break and the molecules combine together to form very large molecules. Cavities formed in the weld metal by gas entrapped during solidification. A weld made in any position other than flat or horizontal,i.e. overhead. Any heat treatment after welding. An apparatus for supplying current and voltage suitable for welding, thermal cutting, or thermal spraying. Parts per billion (1 x 10-9) Parts per million (1 x 10-6). A convenient means of expressing very low concentrations of a substrate in a mixture, or a low level contaminant in a pure product. An alloy consisting of an intrinsically soft metal matrix, stiffened by finely dispersed particles of harder substances, to give a combination of strength and ductility. The application of heat to the base metal immediately before welding, brazing, soldering, thermal spraying, or cutting. A specified temperature that the base metal must attain in the welding, brazing, soldering, thermal spraying, or cutting area immediately before these operations are performed. The filling pressure of gas cylinders is far greater than the working pressure required at the torch. Pressure Regulators reduce the gas pressure to the working pressure and maintain it as the cylinder empties. A fuel gas. A member of the di-olefin family. A hydrocarbon molecule comprising three carbon atoms and four hydrogen atoms, C3H4. Each carbon atom forms a double covalent bond with another carbon atom in which two pairs of electrons are shared. A fuel gas. A member of the paraffin family. A hydrocarbon molecule comprising three carbon atoms and eight hydrogen atoms, C3H8. A fuel gas. A member of the olefin family. A hydrocarbon molecule comprising three carbon atoms and six hydrogen atoms, C3H6. Two of the carbon atoms form a double covalent bond in which two pairs of electrons are shared. Pounds per square inch absolute. Pounds per square inch gauge A procedure in which a gas or liquid is forced into a component to remove contaminants from the system. A type of MIG welding torch containing a separate set of drive rolls within the head of the torch to assist with pulling the filler wire through the torch liner. This type of torch is most widely used for feeding soft wires such as aluminium which may buckle within the liner causing snags or bird-nesting at the wire feed unit.
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