Luis,
Your question tells us that you do not understand that ASTM standards are specifically developed for the product form.
SA516-70 is fully killed, rolled carbon steel that would be the plate material used to fabricate the shell of an ASME pressure vessel.
SA216-WCB is also carbon steel, but it is a cast material and would be specified for something like a gate or globe valve body.
hope that this helps...
MJC