I would not recommend using the IIW block for this examination. This block was designed primarily for weld examination.

Check the specification for the casting that needs to be examined. It will most likely direct you to an examination standard suitable for the UT of castings, and this would give guidance/instructions/requirements for the calibration standard and techniques, scanning procedure, and acceptance criteria.
Mankenberg

s_palanivelu,

I would recommend getting your hands on a copy of ASTM A609. It spells out two procedures for performing the tests you are inquiring about. There is more to it than calibrating your unit and scrubbing. You will need to either make or purchase some calibration blocks that are comarable metalurgically speaking. Almost every detail you need is there. As always, reveiw your contract documents to see what is required by the purchaser or end user.

TheKoz