Metal Glossary

Designed to be a quick reference guide for customers, the Cashmores glossary provides definitions of the latest metal industry terms.

Metal Glossary

Designed to be a quick reference guide for customers, the Cashmores glossary provides definitions of the latest metal industry terms.
  • Ageing, Age Hardening
    Precipitation Hardening
    The second stage in the process (solution treatment and ageing) for those aluminium alloys that respond to heat treatment as a means of increasing their mechanical properties. It entails the precipitation of a constituent from a supersaturated solid solution. The rate of precipitation, and hence ageing, is both temperature and time dependent, with some alloys ageing at room temperature. It is more usual to perform ageing at higher temperatures. It should be noted that routinely operating aged alloys at unusually high ambient temperatures will permit further ageing and even over ageing leading to loss of properties.
  • Alloy
    A combination of two or more metals, or of metals and other elements. An alloy is formed by adding the 'alloying elements' to the 'parent' metal in the molten state. The parent metal usually accounts for more than 50% of the resultant mixture.
  • Alocroming, Alocrom
    Chromating
    A family of proprietary chemical conversion coating processes based on chromate (hexavalent chromium) solutions that act as a surface pre-treatment before painting or insulation foaming. This also increases the corrosion resistance. More environmentally benign processes based on trivalent chromium are being introduced.
  • Alumina
    Aluminium Oxide – A white powder that is produced from the aluminium ore Bauxite and then smelted to produce aluminium metals.
    Related Terms: Hall Heroult Process
  • Aluminium Alloy Classifications
    Wrought aluminium alloys are specified in British, European and other National standards and are classified in an agreed 4 digit system. They fall into 2 distinct sub groups:- 1xxx, 3xxx and 5xxx series that develop strength by cold working, the number will be followed by the digit H and other numbers referring to the degree of annealing or cold work, e.g. 3105H22. 2xxx, 6xxx, 7xxx and 8xxx alloys that develop properties by solution treatment and precipitation hardening. The number is usually followed by a T and a number, defining the heat treatment condition of the alloy, e.g. 6082T6. Thus the 4 digits, the letter and following digits for a product clearly define the chemical composition and the mechanical properties of that material.
    Related Terms: Temper Designations
  • Anodising
    An electrochemical method for artificially thickening the naturally occurring oxide surface film on Aluminium and Aluminium Alloy surfaces to improve appearance and/or corrosion resistance. Not all alloy grades are suitable for decorative anodising, with the general rule being the purer the aluminium, the better it will anodise. The thickness and other film characteristics can be controlled to meet varied requirements for improved corrosion resistance, improved abrasion resistance, electrical insulation or as a pre-treatment for subsequently applied coatings. Colour can also be applied using dyes. Anodising film thickness is typically 5 to 25 microns.
  • Anodising Quality Material
    Material with characteristics that make it suitable for decorative anodising after a suitable preliminary treatment
  • Artificial Ageing
    Precipitation Treatment
    The thermal treatment of an alloy that increases the hardness and strength by precipitation of constituents from the super-saturated solid solution at above room temperature.
  • As-Quenched Condition
    The condition of an alloy during the time immediately following the quench and before the mechanical properties have been significantly raised by precipitation hardening (ageing).
  • Back-End Defect
    A defect found in extruded products due to incorrect extrusion procedures at the mill.
  • Backwards Extrusion
    Indirect Extrusion
    The extrusion method in which there is no relative movement between the billet and the container. This is accomplished by:- Either pushing the die held on the end of a long, hollow, stem through the billet. Or moving the billet and container together over the die, again held on the end of a long, hollow, stem. As there is no movement between the billet and container the friction, and hence extrusion loads, are reduced by up to 30% compared to direct extrusion and grain structures can be improved. The process is limited by the size, length and strength of the stem which holds the die.
    Related Terms: Direct Extrusion
  • Bauxite
    The main ore of aluminium, found in great abundance in the earth’s crust, near the surface. It is mined using open cast mining and has a yield of 25%.