toughness class (from cv1 to cv2zx)
please, could anybody explain to me in brief how to menage with toughness classes(cv1 to cv2zx). is it some characteristic to ask steel manufacturer to test toughness in special way and how it reflects wpq cvn testing? what the supplier must do with cvn testing?if i am preparing wpq for structural welding for joint with characteristic of toughness class cv2zx which kind of cvn testing i have to do. which values of cvn to obtain. why the same type of steel (astm a 131)can be used for different toughness class?