ASTM A724 Grade A in the standard ASTM A724/A724M is a kind of carbon steel plates material used to fabric welded multilayer pressure vessels. jwvivian98 (at) yahoo (dot) com Skype jw-vivian (at) hotmail (dot) com Tel 86, 371, 63332179 A724 Grade A is also a Quenching + Tempering steel material. ASTM A724 have three types grade A, grade B, and grade D .