It is called an OD transition. Fittings manufacturers make their fittings thicker to provide reinforcement in critical areas like the intrados in an elbow, crotch in a tee, etc. You can either do it two ways. One way is to add the extra thickness on the outside of the fitting and you will have...
ASTM A105 requires all flanges Class 300 and higher to be heat treated, not particularly normalized. I believe this is more of a ASTM issue rather than ASME.
