The correlation of microstructure and Charpy V-notch (CVN) impact properties of a high-toughness API X70 pipeline steel was investigated in this study. Six kinds of steel were fabricated by varying the hot-rolling conditions, and their microstructures, effective grain sizes, and CVN impact properties were analyzed. The CVN impact test results indicated that the steels rolled in the single-phase region had higher upper-shelf energies (USEs) and lower energy-transition temperatures (ETTs) than the steels rolled in the two-phase region because their microstructures were composed of acicular ferrite (AF) and fine polygonal ferrite (PF). The decreased ETT in the steels rolled in the single-phase region could be explained by the decrease in the overall effective grain size due to the presence of AF having a smaller effective grain size. On the other hand, the absorbed energy of the steels rolled in the two-phase region was considerably lower because a large amount of dislocations were generated inside PF's during rolling. It was further decreased, when coarse martensite or cementite was formed during the cooling process.
Effective grain size and charpy impact properties of high-toughness X70 pipeline steels
Effektive Korngröße und Kerbschlag-Eigenschaften von hochzähem X70 Pipeline-Stählen
Metallurgical and Materials Transactions A, Physical Metallurgy and Materials Science ; 36A , 8 ; 2107-2114
2005
8 Seiten, 9 Bilder, 4 Tabellen, 36 Quellen
Aufsatz (Zeitschrift)
Englisch
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