Differences between ASTM A335 P5 and Grade P9 , P11 ,P12 alloy pipe ?  ASTM A335 is a standard specification for seamless ferritic alloy-steel pipe for high-temperature service. The specification covers nominal wall and minimum wall chrome-molybdenum (also known as Cr-Mo, or Cr-Moly) alloy steel pipe intended for use at high temperatures. The steel material