In order to investigate the negative temperature impact properties of 14Cr1MoR steel extra thick plates

the negative temperature impact tests at 0~-30℃

for 136 mm thick 14Cr1MoR steel plates produced by a steel plant with delivery ( normalizing + tempering) and max PWHT state are carrued out

and by metallographic microscope

the full thickness structure

grain size and inclusions in steel with delivery and max PWHT state are analyzed. The results show that the ultimate impact temperature of 14Cr1 MoR steel extra thick plate is -30°C

the -30 °C impact energy at 1/2 plate thickness with delivery and max PWHT state are respectively 150 ~ 173 J and 19. 5 ~ 97 J. The metallographic structure study shows that the main reason that affects the negative temperature impact performance of steel plate after max. PWHT is the carbides aggregate and grow up in the grain and grain boundary

and tend to spheroidize

which weakens the toughness of matrix and the properties of grain boundary

thus resulting in a significant decrease in impact energy.