Influences of Temperature-holding Thickness and Finish Rolling Temperature on Martensite/Austenite Islands in X80 Pipeline Steel

Morphology and distribution of martensite/austenite(M/A) islands in X80 pipeline steel hot rdled with different processes were observed by optical microscopy,scanning electron microscopy and transmission electron microscopy.The results show that the temperature-holding thickness and finish rolling temperature exerted a great influence on the size and distribution of M/A islands.When the temperature-holding thickness of the billet went up and the finish rolling temperature went down,it could facilitate the refiment of M/A structure ,reduce the size and volumn fraction of M/A islands,and improve drop-weight-tear-test(DWTT) performance of the steel.