Journal Published Online: 03 March 2023
Volume 51, Issue 5

Investigation of the Abnormally Large Grains of a Super304H Heat-Resistant Steel Tube over Long-Term, High-Temperature Service

CODEN: JTEVAB

Abstract

Abnormally large grains (ALGs) were detected in the outer walls of Super304H superheater steel tubes of an ultra-supercritical unit in long-term service. In this study, the microstructure and mechanical properties of steel tube samples were investigated to reveal the formation mechanism of the ALGs. The results showed that the room-temperature and high-temperature strength and plasticity of the coarse-grain zone were much lower than those of the fine-grain zone. Inhomogeneous residual strain distribution in the outer wall led to high distortion energy differences in the as-supplied steel tube. The low-distortion austenite grains annex the neighboring high-distortion grains via the strain-induced grain boundary migration mechanism. Moreover, the two-dimensional step mechanism of the faceted grain boundaries also causes the ALGs to form.

Author Information

Zhan, Xianqiang
School of Materials Science and Engineering, Hefei University of Technology, Hefei, China
Wu, Yue
Datang Boiler and Pressure Vessel Testing Center Co. Ltd., Hefei, China
Liu, Run
School of Materials Science and Engineering, Hefei University of Technology, Hefei, China
Liu, Junjian
Datang Boiler and Pressure Vessel Testing Center Co. Ltd., Hefei, China
Wang, Wanli
Datang Boiler and Pressure Vessel Testing Center Co. Ltd., Hefei, China
Wang, Yan
Datang Boiler and Pressure Vessel Testing Center Co. Ltd., Hefei, China
Tang, Wenming
School of Materials Science and Engineering, Hefei University of Technology, Hefei, China
Pages: 17
Price: $25.00
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Stock #: JTE20220535
ISSN: 0090-3973
DOI: 10.1520/JTE20220535