EFFECT OF TEMPER-BEAD THERMAL CYCLE ON TOUGHNESS OF WELD ICCGHAZ OF LOW-ALLOY STEEL SQV-2A

In order to examine HAZ properties of SQV-2A steel welded by the tempe r-bead technique, the; effect of temper-bead thermal cycle on the toug hness has been investigated for the simulated ICCGHAZ (intercritically reheated coarse-grained HAZ). The simulated ICCGHAZ specimen was prod uced by applying double thermal cycle consisting of first thermal cycl e with a peak temperature of 1 623 K and subsequent second thermal cyc le with various peak temperatures T-p2 involving A(c1) and A(c3) tempe ratures. At T-p2 from 973 to 1 003 K, serious embrittlement of the ICC GHAZ occurred which could be attributed to the formation of coarse nec klace-like M-A constituent along the prior austenite grain boundary re gion and fine elongated M-A constituent within the prior austenite gra in. When the cooling rate of the second thermal cycle was slow, seriou s embrittlement was also observed at T-p2 from 1 073 to 1 100 K, and t his could be attributed to the formation of upper bainite in the reaus tenitized area during the second thermal cycle. The temper-bead (third ) thermal cycle with a peak temperature of 673 K could improve signifi cantly the tough ness of ICCGHAZ embrittled at T-p2 from 973 to 1 003 K. However, the temper-bead thermal cycle was not effective in improvi ng the toughness of the ICCGHAZ embrittled at T-p2 from 1 073 to 1 100 K in case of slow cooling rate.