J. Mater. Sci. Technol. ›› 2012, Vol. 28 ›› Issue (3): 241-248.

• Novel Processing and Characterization Methods • 上一篇    下一篇

Analytical investigation of prior austenite grain size dependence of low temperature toughness in steel weld metal

Xin-Fang Zhang1,P. Han2,H. Terasaki3,M. Sato2,Y.Komizo1   

  1. 1. Osaka University
    2. Technical Development Department, Welding Business, Kobe Steel Ltd., 100-1, Miyamae, Fujisawa, Kanagawa 251-8551, Japan
    3. 日本大阪大学
  • 收稿日期:2011-09-14 修回日期:2011-11-09 出版日期:2012-03-31 发布日期:2012-03-31
  • 通讯作者: Xin-Fang Zhang

Analytical Investigation of Prior Austenite Grain Size Dependence of Low Temperature Toughness in Steel Weld Metal

X.F. Zhang1) , P. Han2), H. Terasaki1), M. Sato2), Y. Komizo1)   

  1. 1) Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
    2) Technical Development Department, Welding Business, Kobe Steel Ltd., 100-1, Miyamae, Fujisawa, Kanagawa 251-8551, Japan
  • Received:2011-09-14 Revised:2011-11-09 Online:2012-03-31 Published:2012-03-31
  • Contact: Xin-Fang ZHANG

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摘要： Prior austenite grain size dependence of the low temperature fracture toughness was addressed in the bainitic weld metals by in situ observations. Usually, decreasing the grain size is the only mechanism by which both the strength and the toughness of a steel is increased. However, low carbon bainitic steel with small grain size shows a weakening of the low temperature fracture toughness in this study. By direct tracking of the morphological evolution during phase transformation, it is found that large austenite grain size dominated the nucleation of intragranular acicular ferrite, whereas small austenite grain size led to grain boundary nucleation of bainite. This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.

Abstract: Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations. Usually, decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased. However, low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study. By direct tracking of the morphological evolution during phase transformation, it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite, whereas small austenite grain size leads to grain boundary nucleation of bainite. This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.

Key words: In situ observation, Prior austenite grain size, Low temperature toughness, Intragranular nucleation, Grain boundary nucleation