Following info is from a review of the Mizuno JPX919 wedges,
"The JPX919 wedge is cast from X30 soft steel. The material is similar to the 8620 steel used in competitor wedges, and while Mizuno purists may feel like they’re losing something in a cast wedge, I’d simply point out that the #1 wedge both on tour and at retail is cast, and nobody seems to be suffering for it",