In ASTM A350 standard,there are 7 different steel grades,LF1,LF2,LF3,LF5,LF6,LF9,LF787.ASTM A350 LF2 flange is the most widely used material in the low temperature pipeline system.
ASTM A350 Grade LF2 is a general carbon steel usually supplied in the Normalised,Normalised and Tempered or Quench and Tempered condition.It is typified by having moderate strength and impact toughness and is used extensively for the manufacture of flanges and fittings,and applications which require cold temperature service where corrosion resistance is not important.(How to use the ASTM A350 LF2 flange)
Besides the grades in the standard,there are also many classes,different classes have different technical requirements,such as the mechanical properties,chemical compositions and impact test data.Some grades have three classes,class 1,class 2,class 3,and some grades have two classes.
ASTM A350 LF2 grade have two class,class1 and class2,these two classes materials have same mechanical and chemical data,but the impact test request is different.A350 LF2 class1 test temperature is -46℃,while class2 is in -18℃,the two classes also have different average energy and minimum energy requirements.