Page 209 - Welding of Aluminium and its Alloys

192 The welding of aluminium and its alloys

Table 10.9 Range of approval for dissimilar metal
joints

Test piece material group Range of approval
W21 W21 welded to W22
W22 W22 welded to W21
W23 W22 welded to W21
W23 welded to W21
W23 welded to W22

The filler metal must correspond to one of the
parent metal groups.

Table 10.10 Range of approval on thickness

Test piece thickness t (mm) Range of approval
t £ 6 0.7t to 2.5t
6 < t £ 15 6mm < t £ 40mm

Over 40mm thick a test at the specific thickness is
required.

An approval test on wrought material gives approval to weld both cast
and wrought alloys within the same group and combinations of wrought
and cast material.Any alloys not contained within the grouping system must
be approved individually.
The approval range for the filler metal and the shield gas is not perhaps
as clear as that with the parent metal groups. A test made with a specific
filler metal and shielding gas gives approval to weld with any other filler
metal compatible with the parent metal group provided that there is no
change in the process or shield gas and that this does not require a change
in the welder’s technique. This last variable is unfortunately not quantified.
Thickness and pipe diameter are both essential variables; the ranges of
approval are given in Tables 10.10 and 10.11.
Joint type is an essential variable. An approval test on a pipe also
approves the welder for welding plate; a plate approval for welding pipe of
over 500mm; a plate butt weld made in the flat (PA) or horizontal–vertical
position (PC) position approves for butt joints in pipes of 150mm or more
in diameter welded in similar positions. A butt weld approves a fillet weld.
Welding a backed test piece approves a double sided joint with a back-
gouge but not for unbacked joints.
An approval test with a specific filler metal and gas combination approves
the welder to weld with any filler metal and gas that are compatible with