2023 Fiscal Year Annual Research Report
Oxide Accelerating Primary Ferrite Nucleation of Austenitic Stainless Steel Weldment
| Project/Area Number |
22K14510
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| Research Institution | Osaka University |
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Principal Investigator |
HOU YUYANG 大阪大学, 接合科学研究所, 助教 (60905933)
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| Project Period (FY) |
2022-04-01 – 2024-03-31
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| Keywords | Stainless steel / Weld metal / Nucleation / Oxide / TiN / δ-ferrite / Austenite / Tensile property |
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| Outline of Annual Research Achievements |
The double-side bead-on plate TIG welding was adopted in this study with commercial Type 304 stainless steel as the base metal. The composition of weld metal was modified to achieve primary ferrite nucleation (PFN) by Ti-Al-Mg alloying using the addition of sponge titanium, aluminum block, and Ni-50% Mg alloy. The weld specimens were cut and polished to observe the microstructures, primary ferrite nucleation, and austenite formation using OM, SEM, EDS, and EBSD. The tensile properties of the weld metal were evaluated, and the surface and cross-section of the fracture were investigated by SEM and EDS to reveal the fracture mechanism. The PFN was achieved in FA solidification mode by Ti-Al-Mg alloying, with the δ-ferrite network being changed into random Vermicular-δ. However, PFN has limited influence on austenite formation under FA mode because the formation and growth of austenite were independent of the primary ferrite. The tensile test revealed that ultimate tensile strength and elongation deteriorated after the addition of Ti, Al, and Mg. The fracture observation found TiN was inside the dimples, indicating that the fragment TiN initiated the fracture and deteriorated tensile properties.
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Research Products
(2 results)
