Effect of the thermal cycle of welding on impact toughness components of different zones of welded joints in 10G2SB and 10G2SFB steels

Abstract

Investigations were carried out to determine the effect of average heat input (3.6–16.3 kcal/cm) in automatic arc welding on the work of initiation ai and propagation ap of a ductile crack in different zones of welded joints in the 10G2SB and 10G2SFB steels in the condition after strengthening by heat treatment and after controlled rolling. Beads were deposited on 20 mm × 250 mm × 300 mm plates by automatic arc welding under FI-16 flux using Sv-10GNMA wire with a diameter of 5 mm. It is shown that increasing average heat input results in a decrease of the values of ai and ap. For the case in which an inflection point appears on the KCU–B curves (here B is the ductile component on the fracture surface of the impact specimens), it is proposed to approximate this curve by two linear sections. The point of intersection of the straight lines corresponds to the boundary of the heat-affected zone (HAZ). The experimental results also show that the mean-weighted estimate of the values of ap in the HAZ and in the parent metal are closely linked by the linear dependence , where T50 is the critical brittleness temperature, corresponding to the appearance of 50% of the ductile component on the fracture surface of the specimens.