Soldering by definition is a process performed below 450 deg C. A review of the literature found that resistance methods are sometime used for soldering when open flames are not practical or permitted. Automation is possible but manual operation is common. The electrodes are generally highly resistive as in graphite, carbon or tungsten. The carbon or graphite may be copper clad. The tungsten could be a copper tungsten RWAMA Class 11.
This process is using relatively hot electrodes to generate heat to help melt the solder.
Reference: ASM Handbook Vol. 6 Welding, Brazing, Soldering