Page 45 - Welding of Aluminium and its Alloys

Material standards, designations and alloys 37

• Part 3 Writing Rules for Chemical Composition.
• Part 4 Form of Products.
In the European system the prefix ‘AB’ denotes ingots for remelting, ‘AC’
denotes a cast product, ‘AM’ a cast master alloy, the prefix ‘AW’ a wrought
product. For the wrought alloys this is followed by the four digit number
which uniquely identifies the alloy. The first digit indicates the main alloy-
ing element, with numbers 1 to 9 being used as follows:
• AW 1XXX – commercially pure aluminium.
• AW 2XXX – aluminium–copper alloys.
• AW 3XXX – aluminium–manganese alloys.
• AW 4XXX – aluminium–silicon alloys.
• AW 5XXX – aluminium–magnesium alloys.
• AW 6XXX – aluminium–magnesium–silicon alloys.
• AW 7XXX – aluminium–zinc–magnesium alloys.
• AW 8XXX – other elements e.g. lithium, iron.
• AW 9XXX – no alloy groups assigned.
Except in the case of the commercially pure aluminium alloys, the last three
digits are purely arbitrary and simply identify the specific alloy. In the case
of the pure aluminium, however, the last two digits indicate the minimum
percentage aluminium in the product to the nearest 0.01%, e.g. AW-1098-
99.98% Al, AW-1090-99.90% Al. The second digit gives the degree of
control on impurities: a zero indicates natural impurity limits, a figure
between 1 and 9 that there is special control of one or more of the indi-
vidual impurities or alloying elements.
There are a total of 36 separate compositions of casting alloys, divided
into 11 subsections as follows. It is worth mentioning that 29 of the alloys
are based on the Al-Si system.
• AC 2 1 XXX – Al Cu.
• AC 4 1 XXX – Al SiMgTi.
• AC 4 2 XXX – Al Si7Mg.
• AC 4 3 XXX – Al Si10Mg.
• AC 4 4 XXX – Al Si.
• AC 4 5 XXX – Al Si5Cu.
• AC 4 6 XXX – Al Si9Cu.
• AC 4 7 XXX – Al Si(Cu).
• AC 4 8 XXX – Al SiCuNiMg.
• AC 5 1 XXX – Al Mg.
• AC 7 1 XXX – Al ZnMg.
As with the wrought alloys the third and fourth digits identify the specific
alloy in the group and are arbitrary.