5. Conclusions
Based on the experimental work reported above, it is evident
that the surface condition of the sheet material produced through
different manufacturing processes has a significant effect on the
RSW process, electrode condition and weld quality.
(a) For RSW structural applications; an incomplete removal of
‘disrupted surface layer’ prior to surface pretreatment has a
detrimental effect on the RSW process. Therefore, ‘full clean’
manufacturing process is recommended to avoid the occurrence
of sticking and to maintain the electrode condition. This
should also ensure a consistent processwindowthat is essential
for a manufacturing situation.
(b) Removing the wax lubricant reduces the static contact resistance,
but in practice lubricant is a necessary component of the
overall process. Therefore, a weld schedule with a low current
pre-pulse, made prior to the main weld can be used to displace
the lubricant and normalize the surface reducing the risk of
expulsion.
(c) For RSW closure applications; AA6111T4 with either MF or EDT
surface have acceptable spot welding process windows. The use
of an EDT surface has been shown here to extend the useable
welding range.
(d) Close participation between materials suppliers and automotive
manufacturing centre’s is required to ensure optimum
process parameters are applied at all stages of manufacturing
for specific applications.