Mechanical properties of welded joints in two fine-grained steels with yield strength of 370 N/mm

The report deals with the results of welding tests for two microalloyed steels (plate thickness 40 mm): normalised Raex 386 P Arctic (Nb-V) and controlled rolled RR St 52-3U (Ti-N). Both steels represent the yield strength level of 370 N/mm2. The welding tests were carried out using gas metal arc narrow gap, shielded metal arc, submerged arc and electroslag welding in the arc energy range from 8 to 425 kJ/cm. The test results showed that the most favourable joint toughness - even superior to that of the base material - could be obtained in narrow gap welding (8 kJ/cm). In conventional SMAW and SAW the arc energy had to be reduced below 30 kJ/cm to obtain the most favourable joint toughness. Also higher heat inputs of 40 - 50 kJ/cm were found possible to increase the productivity of SAW when Charpy-V notch 27 J transition temperature of -40...-50 °C is a sufficient requirement for the joints. The Ti-N steel RR St 52-3U allowed even somewhat higher arc energies to fulfill this toughness level. In high energy welding (ESW: 425 kJ/cm) the Ti-N steel yielded markedly more favourable HAZ transition behaviour (T27J = -25 °C) than did the Nb-V steel Raex 386 Arctic (T27J = +5 °C). The same type of difference was also found between Ti-B-microalloyed and conventional weld metals