Surface appearance of the welded dissimilar materials is
shown in Fig. 3. Normally the surface appearance of a spot
weld should be relatively smooth; round or oval in the case
of contoured work; and free from surface fusion, electrode
deposits pits, cracks and deep electrode indentation [1]. In
this study, the smooth weld surface appearance is almost
obtained (Fig. 3). However, the nugget size of IF steel side
of welded materials was found bigger than that of austenitic
stainless steel (Fig. 4). It is thought that the difference
between the nugget sizes comes from the different diameters
of electrodes. In addition, it was also found that the weld
nugget lost its symmetric form because of the unbalanced
heat resulting from different physical properties of the steel
sheets. As known the heat balance may present a problem
when spot welding together unequal thickness of the same
metal, equal thicknesses of two metals with a significant
difference in electrical conductivities, or a combination of
the two. Electrode configurations and compositions can
be used to overcome unbalanced heating to some extent
[1]. IF 7114 steel side of welded materials was observed
deep electrode indentation rather than austenitic stainless
steel side due to low yield strength of IF steel. The yield
and tensile strength of base materials were given in Table 3.