  We study a local twist move on welded knots that is an analog of the
virtualization move on virtual knots. Since this move is an unknotting
operation we define an invariant, unknotting twist number, for welded knots. We
relate the unknotting twist number with warping degree and welded unknotting
number, and establish a lower bound on the twist number using Alexander quandle
coloring. We also study the Gordian distance between welded knots by twist move
and define the corresponding Gordian complex.
