Wires, 5.5 to 6.5mm diameter from different stainless steels, were butt resistance welded, with high respectively low heat input. As the weld molten metal is squeezed out the heat affected zone HAZ becomes the critical structure. Standard FeCl₃ testing revealed that in most cases there is a drop in critical pitting temperature, CPT of 10 to 30° C, the highest drop for a super-austenitic steel. On the other hand super-duplex wire is as good or even better in the weldment as in the as delivered wire. The good properties of super-duplex HAZ is explained in terms of a very narrow single phase d -region for that steel type. A standard Schlatter MicroWeld machine was used. The cooling rates for HAZ were monitored with high resolution video, D t8/5 being 11 to 12 and 2–3 sec respectively. Low energy inputs give better properties, which is discussed in terms of the widths of the temperature range for the single phase grain growth region.

No larger drop in weldment strength was seen except for the super-austenitic steel. In all 10 wires with PRE from 20 up to 47 units were tested with CPT temperatures from ± 0° C up to 68° C. Also surface treatment was studied. CPT could be increased by a pickling treatment, and the base materials and welds were more or less sensitive to this treatment. For materials showing a large drop in CPT at welding, the properties can be regained by a solution heat treatment.