Incomplete transformation of upper bainite in Nb bearing low carbon steels

被引:33
作者
Furuhara, T. [1 ]
Yamaguchi, T. [2 ]
Miyamoto, G. [1 ]
Maki, T. [3 ]
机构
[1] Tohoku Univ, Inst Mat Res, Aoba Ku, Sendai, Miyagi 9808577, Japan
[2] Technol Res Inst Osaka Prefecture, Izumi 5941157, Japan
[3] Nippon Steel Corp Ltd, Futtsu 2938511, Japan
关键词
Steel; Phase transformation; Bainite; Ferrite; Cementite; Pearlite; Microalloying; ALLOYING ELEMENTS; MN STEELS; FE-C; FERRITE; NIOBIUM; NUCLEATION; MECHANISM; KINETICS; HAZ;
D O I
10.1179/026708309X12512744
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Kinetics and microstructure of bainite transformation in Fe-(0.15 or 0.05)C-0.2Si-1.5Mn (mass%) alloys with Nb addition of 0.03 mass%. Bainite transformation occurs at temperatures below 873 K. At 853 K, transformation rapidly proceeds by formation of bainitic ferrite without carbide precipitation, but transformation stasis appears for a certain period in the Nb added alloys leaving untransformed austenite film between neighbouring bainitic ferrites. On the other band, the Nb free alloys do not show such a stasis until the transformation is completed. By further holding, the transformation in the Nb added alloy restarts by forming the mixture of dislocation free ferrite with cementite precipitation in the austenite films. In contrast, bainite transformation accompanying cementite precipitation occurs in both Nb free and Nb added alloys at 773 K, resulting in no difference in transformation kinetics. It is proposed that the incomplete transformation is caused by suppression of ferrite nucleation at interphase boundaries between pre-existing bainitic ferrite and austenite due to Nb segregation.
引用
收藏
页码:392 / 397
页数:6
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