Page 201 - Welding of Aluminium and its Alloys

184 The welding of aluminium and its alloys

Of the 9 parts of the EN 288 specification only Parts 1, 2 and 4 are dealt
with in this review.
Part 1 contains definitions and discusses briefly the methods of approval
contained in Parts 3 to 8. It also requires WPSs to be prepared in accor-
dance with Part 2.
Part 2 specifies the requirements for the contents of welding procedure
specifications for arc welding, listing all of the variables that need to be
included and giving instructions as to how the weld shall be made. There is
also in Appendix A of the specification a copy of a suggested form for a
WPS. See also Fig. 10.1.
Part 4 is the most important part within the series with respect to
aluminium. It specifies how a WPS for the welding of aluminium or its alloys
shall be approved. It gives the limits of validity of the WPS within the
range of variables and includes an example of a WPAR and the accom-
panying approval certificate. Copies of these are included in Appendix
A of the specification. It lists the size and shape of the test pieces and the
non-destructive and mechanical tests required to prove the properties
of the weld. It covers TIG, MIG and plasma-arc welding processes only,
although it may be used as the basis for approving other processes by
agreement.
In order to reduce the number of tests required the alloys are formed
into groups, each group having similar characteristics as listed in Table 10.1.
The test pieces are representative of the joints to be welded in produc-
tion, comprising plate and pipe butt welds, branch welds and fillets. Test
piece sizes are illustrated in Fig. 10.2. The test piece form, type of test
and methods and extent of examination of the test pieces are detailed in
Table 10.2.

Table 10.1 Aluminium alloy grouping system

Group Type of alloy
21 Pure aluminium
Aluminium with less than 1.5% impurities, e.g. 1050, 1080, 1200, 1350
Aluminium with less than 1.5% alloy additions, e.g. 3103
22 Non-heat-treatable alloys divided into two groups:
22.1 Aluminium–magnesium alloys with 3.5% Mg or less, e.g. 3105, 5005,
5052, 5154, 5454
22.2 Aluminium–magnesium alloys with between 4% and 5.6% Mg, e.g.
5083, 5182, 5086
23 Heat-treatable alloys. These include the Al-Mg-Si and the Al-Zn-Mg
alloys, e.g. 6060, 6063, 6082, 6463, 7020, 7022, 7075