Effect of Molybdenum Addition and Specimen Orientation on Microstructure and Mechanical Properties of API X70 Linepipe Steels

Dong-Kyu Oh; Seung-Hyeok Shin; Byoungchul Hwang

doi:10.3740/MRSK.2023.33.6.251

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2023 Vol.33, Issue 6 Preview Page Next Page

Research Paper

Effect of Molybdenum Addition and Specimen Orientation on Microstructure and Mechanical Properties of API X70 Linepipe Steels Mo 첨가 및 시편 방향에 따른 API X70 라인파이프강의 미세조직과 기계적 특성

27 June 2023. pp. 251-256

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Abstract

This study aims to examine the correlation between microstructures and the mechanical properties of two high-strength API X70 linepipe steels with different specimen directions and Moaddition. The microstructure of the Mo-added steel has an irregularly shaped AF, GB matrix with pearlite because of the relatively large deformation in the non-recrystallization temperature region, while that of the Mo-free steel shows a PF matrix with bainitic microstructure. In the Mo-added steel, the M/A (martensite-austenite) in granular bainite (GB) and pearlite act as crack initiation sites with decreased upper shelf energy and an increased ductile to brittle transition temperature (DBTT). Regardless of Mo addition, all of the steels demonstrate higher strength and lower elongation in the T direction than in the L direction because of the short dislocation glide path and ease of pile-up at grain boundaries. In addition, the impact test specimens with T-L direction had a lower impact absorbed energy and higher DBTT than those with the L-T direction because the former exhibit shorter unit crack path compared to the latter.

Keywords

linepipe

microstructure

molybdenum

anisotropy

mechanical properties

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Information

Publisher :Materials Research Society of Korea
Publisher(Ko) :한국재료학회
Journal Title :Korean Journal of Materials Research
Journal Title(Ko) :한국재료학회지
Volume : 33
No :6
Pages :251-256
Received Date : 2023-05-18
Revised Date : 2023-06-17
Accepted Date : 2023-06-19
DOI :https://doi.org/10.3740/MRSK.2023.33.6.251

Korean Journal of Materials Research ISSN:1225-0562(Print) 2287-7258(Online) 한국재료학회지

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