First, AISI no longer maintains standards with respect to chemical compositions, etc. Second, ASTM A 723 is a product specification for alloy steel forgings, not just a chemical composition.
My limited search did not find anything as a direct equivalent. There are a couple of BS standards for alloy steel forgings, with BS EN 10222 having several parts that are specific to pressure vessel applications:
Thanks for your response.
Basically I need to find out a material as AFNOR 30NCD12.
The ASTM A723 was found out by some web-site. So does any AISI material is similate to AFNOR 30NCD12?