The welding of aluminium and its alloys

Designation criteria

Aluminium alloys may be divided into two broad classes, cast and wrought products. These two classes can be further subdivided into families of alloys based on chemical composition and finally on temper designation. Temper designations are used to identify the condition of the alloy, in other words the amount of cold work the alloy has undergone or its heat treatment con­dition. There are a number of schemes available for identification of the alloy and its condition. In this book the numeric method adopted by the European Committee for Standardisation (CEN) will be used as standard. This system uses four digits to identify the wrought alloys and five digits to identify the cast alloys, and is broadly the same as the ISO and US nu­merical methods of identification where a four digit number identifies the unique alloy composition. This is in agreement with the recommendation made in the early 1970s for an International Designation System issued by the Aluminum Association in the USA. The chemical composition limits specified in the CEN specifications are identical with those registered with the Aluminum Association for the equivalent alloys. This should simplify the sourcing of alloys and remove the confusion that can surround the iden­tification of specific grades. One perennial problem for the welding engi­neer is the use of superseded specification designations to identify alloy compositions. As an aid to identification a table of comparative specifica­tion designations is included as Appendices C and D.