COMPARISON OF WELDABILITY OF HIGH-STRENGTH PIPE STEELS MICROALLOYED WITH NIOBIUM, NIOBIUM AND VANADIUM

摘要

Weldability is studied for two high-strength pipe steels of strength class K60 with different microalloying based on modelling physical processes occurring in heat-affected zone (HAZ) metal, and correlation of cooling rate (heat input during welding) with HAZ metal structure and properties. Test steel HAZ metal structure and properties are described in relation to welding parameters. The optimum cooling rate range after welding is established providing the maximum level of HAZ metal impact strength. The advantage of using more economically alloyed (niobium alone) steel is demonstrated.