Comparison of procedures for evaluation of effect of welding thermal cycle on impact toughness of HAZ metal of welded joints from low-alloy steels

Abstract

One of the most important indices of mechanical properties, which together with other factors determine the quality and working capacity of the welded joints, is impact toughness. Impact toughness is characterized by material capability to absorb mechanical energy in process of deformation and fracture under impact load effect. This paper carries a comparative evaluation of effect of welding on impact toughness of HAZ metal of specimens, produced from bead-onplate tests, and reference ones, treated on welding thermal cycle, from steel 10G2FB. It is determined that effect of the welding thermal cycles on impact toughness indices of HAZ metal of welded joints from steel 10G2FB is ambiguous. Rapid decrease of KCU and KCV values is observed at w 6/5 < 6 °C/s cooling rates. Increase of cooling rate provides for rise of HAZ metal impact toughness and in some cases it reaches KCU and KCV values of base metal. Therefore, it is a good correlation of the values of impact toughness between the specimens, treated on welding thermal cycle, and specimens, produced from welded joints. It is insignificant difference in nature of their fracture. 7 Ref., 2 Tables, 6 Figures.