input represents the base metal. The impact toughness of
base metal for high titanium content steel (B steel) is
87 J higher than that of low titanium content steel (A
steel), as shown in Fig. 1a, but with the heat input
increasing, the toughness of both A steel and B steel all
decreases. When the welding heat input reaches
80 kJcm-1, the low-temperature impact toughness of
high titanium content steel was only 18 J, and the
toughness deteriorates sharply.
The hardness of both A steel and B steel are all higher
than that of base metal experienced welding heat cycle, and
both hardness ascends at first and then descends last, as
shown in Fig. 1b; it is because the austenite transforms to
the lath bainite and granular bainite under the continuous
cooling conditions. The amount of granular bainite
increases and the amount of lath bainite decreases with the
cooling time increasing from 800 to 500 C (T8/5), which
leads to the hardness and toughness of CGHAZ gradually
decreasing [9].