As seen in Fig. 7, an important difference in hardness
value was observed among weld nugget, HAZ’s and base
metals in both side of weldment due to nature of dissimilar
materials chemical composition. Results show that weld
nugget and HAZ hardness of IF steel side of welded materials
lower than that of stainless steel. In addition, it was
not observed fluctuations on hardness values of both side
of weldment related with peak weld current (4–7–9 kA)
because of the chemical composition of base metals in
which there is not so much alloying elements such as carbon,
manganese that affects the hardenability. Spot welds
in thin sheet can have relatively high hardness when the
carbon content exceeds about 0.08% [11]. As seen in Table
1, both of base metals that had been used in this study had
less than that of percent carbon so the ductility of weldment
found acceptable.