ASTM A 105 is a common specification for carbon (0.35% max) steel forgings and piping applications including pressure containing parts, flanges, valves, etc. See the ASTM web site for a list of their standards. You may also find many ASTM specifications as incorporated by ASME with the same number preceded by S such as SA 105. Also refer to ASME B16.5 for flanges through nominal pipe size 24.