Some pattern welded blades are made to have a mono steel edge. Just sayin'.
I have one of Vic's (Bluesman) San Mai pattern blades. It is a three layer pattern, so the edge is a single steel that takes a great edge. The layered pattern gives the blade an attractive look, but it shaves quite well.
I had a friend who purchased a blade that had a "Damascas" type pattern. I do not know what steels were combined, but he never could get a shaving edge from the blade, so he had to return it to the craftsman for a refund. Not all steels blend successfully.