Glossary - L
A joint between two overlapping members in parallel planes. A thermal cutting process which uses the heat obtained from a focused laser beam, often in conjunction with gas jets, to cut and remove metal. A welding process which uses the heat from a concentrated coherent beam of light to effect melting and fusion. A method of reeling MIG wire so that the wire is wound onto the spool in layers, one on top of the other, to ensure it feeds off smoothly during welding. Liquation cracking is caused by the melting of low melting-point grain boundary constituents which lead to small micro-cracks. These micro-cracks may not prove to be a serious problem, providing that they do not provide sites for more serious cracks to occur. A substance which is gaseous at ambient temperature and atmospheric pressure but has been transformed into liquid by changing its temperature and/or pressure. If the Critical Temperature for the substance is above ambient temperature it can be liquefied by either lowering the temperature or increasing the pressure, or both. If it's Critical Temperature is below ambient it cannot be liquefied by applying pressure alone, it must also be cooled. The phase of a substance in which the constituent molecules, atoms or ions are relatively free to move but are restricted by forces to the extent that the liquid maintains a fixed volume. The minimum temperature at which a metal or alloy is completely liquid. This is the general term used to describe the easily liquefiable gases contained in crude oil and natural gas - propane, butane, ethane, propylene and butylene.. LPG sold for fuel use is generally a mixture of two or more of these products.
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