High-Temperature Tempered Martensite Embrittlement in Quenched-and-Tempered Offshore Steels

Metals

Ching-Yuan Huang¹  Hung-Wei Yen²  Meng-Hsuan Chiang²  Yu-Chen Lin²  Delphic Chen³  Hsin-Chih Lin³ 

[1] D Department, China Steel Corporation, Chung Kang Road, Kaohsiung 81233, Taiwan;Department of Materials Science and Engineering, National Taiwan University, Roosevelt Road, Taipei 10617, Taiwan;;Iron and Steel R&

关键词: tempered martensite embrittlement;    lenticular martensite;    offshore steels;    electron backscattering diffraction;    Kernel average misorientation;    transmission Kikuchi diffraction;   

DOI  :  10.3390/met7070253

来源: DOAJ

【 摘 要 】

Embrittlement induced by high-temperature tempering was investigated in two quenched-and-tempered offshore steels. Electron backscattering diffraction and analysis of Kernel average misorientation were applied to study the coalescence of martensite; transmission Kikuchi diffraction coupled with compositional mapping was used to characterize the martensite/austenite (M/A) phases. It is suggested that the formation of lenticular martensite along prior austenite grain boundaries or packet boundaries primarily explains the embrittlement in conventional S690Q steel, which has a higher carbon content. This embrittlement can be cured by additional heat treatment to decompose martensite into ferrite and cementite. In a newly designed NiCu steel with reduced carbon content, new lath martensite formed along interlath or inter-block boundaries of prior martensite. This microstructure is less detrimental to the impact toughness of the steel.

【 授权许可】

Unknown