| Mod. 9Cr-1Mo강 LB 및 GTA 용접부 열이력에 따른 δ 페라이트 생성거동 |
| 정남훈1, 안장호2, 이명진1, 강남현1, 조경목1 |
1부산대학교 재료공학부
2한국 ESI 주식회사 기술사업부 |
| Formation Behavior of δ Ferrite Within LB and GTA Weld Zones of Mod. 9Cr-1Mo Steel in Terms of Thermal History |
| Nam-hun Jung1, Jang-ho Ahn2, Myung-jin Lee1, Nam-hyun Kang1, Kyung-Mox Cho1 |
1Department of Materials Science & Engineering, Pusan National University, Busan 46241, Republic of Korea
2ESI Korea Co. Ltd, Seoul 07530, Republic of Korea |
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Received: 29 September 2017; Accepted: 28 November 2017. Published online: 5 February 2018. |
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| ABSTRACT |
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The toughness and creep strength of Mod. 9Cr-1Mo steel, a ferritic heat resistant steel, are closely related to the amount of delta ferrite remaining in the weld. This study compared the amount of retained δ ferrite in the laser beam (LB) weld with low heat input and the gas tungsten arc (GTA) weld with high heat input. A greater amount of retained δ ferrite in both the LB and GTA welds was found in the fusion zone (FZ) interface than in the FZ center and coarse-grain heat affected zone (CGHAZ). LB welds had more retained δ ferrite than GTA welds. Thermal history of the welding process and location in the welds were calculated by finite element analysis. By simulating the thermal history, calculated at the FZ interface for each welding process, it was confirmed that the LB welds had more retained δ ferrite than the GTA welds in the specimens. The amount of retained δ ferrite increased as the time spent in the δ ferrite phase region increased and as the cooling rate increased. The effect of the cooling rate on the amount of retained δ ferrite was greater than the time spent in the δ ferrite phase region upon heating. |
| Keywords:
Mod. 9Cr-1Mo, δ ferrite, thermal history, finite element analysis, Gleeble test |
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