Establishment of a new creep strengthening concept for heat-resistant steel focusing on the change in diffusion rate due to magnetic transformation

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15277
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26010:Metallic material properties-related
• Research Institution: Kyushu University
• Principal Investigator: Yamasaki Shigeto 九州大学, 工学研究院, 准教授 (00804741)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: クリープ / 磁性 / 拡散

Outline of Final Research Achievements

In this study, the relationship between the change in magnetic properties and creep strength associated with the addition of Co in ferrite steels containing 15 mass% Cr was investigated. The addition of Co increased the volume magnetization of steel in the temperature range from room temperature to about 800℃, and the ratio of the minimum strain rate and the difference in volume magnetization between the steels with different amounts of Co added showed similar changes with respect to temperature. Therefore, it was shown that the magnitude of the magnetization of steel is closely related to the creep strength, and that the larger the magnetization, the higher the creep strength. In particular, it was clarified that a remarkable difference in creep strength is shown in the temperature range in which only the low Co steel loses ferromagnetism, but the high Co steel maintains the magnetization.

Free Research Field

高温強度学

Academic Significance and Societal Importance of the Research Achievements

本研究成果はフェライト系耐熱鋼の強化法に対して新たな観点を与えるものであり、次世代の耐熱鋼開発において重要な知見となる。とくに、コバルトは希少かつ高価な元素であるため、その添加量を最適化する上で本研究で明らかとなった「磁化と強度の相関関係およびその温度依存性」は極めて有用なものである。