The effect of three kinds of process quenching + lamellarizing ( quenching from intercritical temperature) + tempering (QLT)
quenching + tempering( QT)
double normalizing + tempering ( NNT) on low temperature toughness of 5 mm 9Ni steel plate has been studied. The results show that the steel plate with NNT has good ductility at low temperature
good plate shape and 8. 0% reverse austenite content by using double normalizing and tempering process. Through industrial trial production
the -196 ℃ charpy absorption energy of 5 mm 9Ni steel plate with 3. 3 mm thickness specimen is 40 J; and that with the 2. 5 mm thickness specimen is m27 J.