Oxide Accelerating Primary Ferrite Nucleation of Austenitic Stainless Steel Weldment

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14510
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26050:Material processing and microstructure control-related
• Research Institution: Osaka University
• Principal Investigator: HOU YUYANG 大阪大学, 接合科学研究所, 助教 (60905933)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: Stainless steel / Weld metal / Nucleation / Grain refinement / Solidification / Tensile property

Outline of Final Research Achievements

In this study, primary ferrite nucleation (PFN) was accelerated by Oxide+TiN to achieve the equiaxed δ-ferrite of stainless steel with FA solidification mode. The effective oxide for PFN was revealed as Ti2O3, (Al,Ti)Ox, and MgAl2O4, where MgAl2O4 is the optimal oxide. Under the double side bead on plate welding, the PFN was achieved by Ti-Al-Mg alloying, and significantly transformed the δ-ferrite form network morphology to random Vermicular-δ. However, PFN have limited influence on austenite formation under FA mode because the formation and growth of austenite were independent to the primary ferrite. The UTS and elongation was deteriorated by PFN, because the formation of fragment TiN initiated the tensile fracture.

Free Research Field

材料加工および組織制御関連

Academic Significance and Societal Importance of the Research Achievements

This research developed a new method for primary ferrite nucleation in stainless steel with FA mode. These results offer an effective method for the control of weld microstructure. The fracture mechanism offers an important guidance for further improvement of mechanical performance.