Abstract: At the Institute of Welding in Gliwice a thermal - and stress - strain cycle simulator has been devel- oped, which is now used in research projects on weldability evaluation of steels. For the tested S460ML steel (40 mm in thickness) with a notch toughness of 280 J, the TTT diagram has been prepared. Thermal welding cycles with the peak temperature of 125℃ and cooling tinies t8/5 = 8÷300 s were simulated on (10 × 10 × 55) mm specimens and KV notch toughness, hardness and microstructure of the simulated HAZ's have been determined. It was found that cooling times t8/5 shorter than 60 s have no influence on the Charpy V notch toughness at room temperature. At lower test temperatures the KV values are much lower than those of the parent material. A pronounced fors of notch toughness has been noticed on simulated HAZ's treated by a second thermal cycle with the peak temperature between Acl- Ac3. Butt joints hare been MAG and submerged arc arc welded with the heat input between 12 and 35 kJ/ cm. Mechanical properties of the joints hare been determined as well as notch toughness and CTOD values for the HAZ,weld metal and parent material at room temperature and down to -75℃. A high brittle fracture resistance of the HAZ's was found at a wide temperature range for all heat inputs.

Key words: S460 ML steel, Weldability, simulation, mechanical property