Glossary - R
A radical is a molecule or atom which has an unpaired outer electron. It is very reactive because it needs to gain an electron. Radicals may exist independently for short periods during the course of a chemical reaction, such as in the combustion of a fuel gas. A method of reeling MIG wire in which the wire is wound onto the spool without attempting to ensure it forms in regular, controlled layers. The act in which a substance brings about the chemical change of reduction, the process in which an electron is added to an atom or ion such as removal of oxygen from a molecule, in another substance, itself being oxidised. Also called a carburising flame. Caused when there is an excess of fuel gas to oxygen in the oxy-fuel gas mixture. A term used in tensile testing, comparing the original diameter of a test specimen with its diameter after fracture, and used as an indication of the ductility of the material under test. %Reduction of Area = 100 x (A - a) / A, where A = original cross-sectional area, The excess weld metal which stands proud of the surface of the plate. Excessive reinforcement induces stresses where the weld meets the parent plate and can lead to cracks forming. Reinforcement Height is the measurement of the distance between the level of the plate surface and the top of the weld bead, or the distance between a line stretched between the attachment points of the weld on the parent plate and the top of the weld bead. Reinforcement area is the measurement of the area of the weld bead above the level of the plate surface. A flashback arrestor designed to provide a visual indication that a flashback has occurred, prompting the operator to check the system for faults. As the pressure wave hits the non-return valve it pushes up a button or lever, stopping the pressure wave from entering the regulator. Small quantities of undefined impurities. Welding processes which produce welds between two faying surfaces by means of the heat produced by resistance to electric current, combined with pressure. That fraction of welding fume that can be breathed in, and is capable of reaching the lungs. This includes all gases, and particulate welding fume which is less than about 7 microns in diameter. A method of restricting undue or excessive movement of components during welding, often by means of clamping, jigging, or tack-welding. Too much restraint of some alloy systems can result in cracking. A term used to describe the amount of surface irregularity on the cut surface. Gouges and styrations on the cut face are normally caused by the use of incorrect parameters.
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