ASME takes an ASTM spec, adds an "S" in front, and publishes the spec in IIA. Most of the time the spec's are identical, sometimes they differ in the details. I don't have the current edition of IIA handy, but in the 1998 edition on page xlii it states that SA-182 / SA-182M is identical except for the clarified heat treatment requirements by the addition of Note 4 to Table 1. You should check the 2007 edition. Most mills will dual certify the plates they produce so chances are you'll receive plate which is considered A-182 / SA-182.
