Aluminium Design and Construction John Dwight

Table 6.1 HAZ softening factor for heat-treated material at MIG-welded joints
Note. *The second row of values of 7xxx-series material in the T6 temper (shown in brackets) may be used
when strict thermal control is exercised during welding (see Section 6.2).
6.4.3 Work-hardened material
For work-hardened material, it may be assumed that the material in
region 1 of the HAZ has the same properties as those for annealed material
(Figure 6.3). Also, there is no dip at point A. The softening factor may
therefore be taken as follows:
(6.2a)
(6.2b)
where f o , , f u are the 0.2% proof stress and tensile strength of parent metal,
and f oo , f uo are the same in the annealed condition.
6.5 EXTENT OF THE SOFTENED ZONE
6.5.1 General considerations
In the design of joints, one only needs to know the severity of softening
in the HAZ. In member design, one must also know its extent, so that
the total softened area at any critical cross-section can be determined.
In discussing HAZ extent, two broad categories of welded joint may be
recognized (Figure 6.6):
1. long straight joints, comprising one or more welds, as used for
assembling a fabricated member from its component parts;
2. irregular attachment welds, as used for connections between members,
or for securing local attachments, such as lugs, stiffeners, brackets, etc.
In massive members with multi-pass welds, category 1 joints cause softening
in only a small proportion of the total section, and have a minor effect
on the resistance. For these, a very approximate estimate of the HAZ
extent is acceptable. But for small members, containing single-pass welds,
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