times for underwater wet welds. Fox
(Ref. 18) and Pope (Ref. 19) investigated
the water temperature and water
depth influences on hydrogen-induced
cracking, microstructure, and mechanical
properties in underwater wet
welding, and the importance of water
temperature and water depth, quenching,
and diffusible hydrogen levels in
underwater wet welding have been
demonstrated. Postweld heat treatment
(PWHT) is frequently used to reduce
hardened structure and allow hydrogen
to diffuse away from the weld
metal and heat-affected zone (HAZ)
(Ref. 20). Szelagowski (Refs. 21, 22)
used a H2
-O2 cutting torch and an underwater
high-velocity oxyfuel (UWHVOF)
thermal spraying device to
serve as PWHT on wet welds. The hydrogen
content of the weld metal was
reduced and the bend testing result
showed a higher plastic property.
However, the control of heat input
could not be accurate and efficient.
In this paper, a novel real-time induction
heating-assisted underwater
wet welding process was employed for
the first time. Induction heating could
reduce the cooling rates of the joint in
underwater wet welding, especially the
t8/5 (the cooling time range from 800° to
500°C) was extended. According to
welding CCT diagrams, it reduced the
hardened and brittle transformation
products. That is, the content of
martensite (M) and upper bainite (BU)
phases decreased as the content of
proeutectoid ferrite (PF) and acicular
ferrite (AF) phases increased. Therefore,
the purpose of this work was to develop