J. Mater. Sci. Technol. ›› 2012, Vol. 28 ›› Issue (3): 249-254.

• Novel Processing and Characterization Methods • 上一篇    下一篇

Secondary austenite morphologies in fusion zone of welded joint after postweld heat treatment with a continuous wave laser

刘和平   

  1. 上海交通大学
  • 收稿日期:2010-07-12 修回日期:2010-11-15 出版日期:2012-03-31 发布日期:2012-03-31
  • 通讯作者: 刘和平

Secondary Austenite Morphologies in Fusion Zone of Welded Joint after Postweld Heat Treatment with a Continuous Wave Laser

Heping Liu, Xuejun Jin   

  1. School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
  • Received:2010-07-12 Revised:2010-11-15 Online:2012-03-31 Published:2012-03-31
  • Contact: He-Ping LIU
  • Supported by:

    the National Basic Research Program of China (973 Program, No. 2010CB630800), and the Shanghai Municipal Science and Technology Commission Foundation of China (Grant No. 0852nm02500)

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摘要： In order to improve the weldability of duplex stainless steels, obtaining more secondary austenite in the weld metal is an effective way. Therefore, optimizing the secondary austenite by changing its morphology, volume fraction and stability may be expected to enhance the ductility of the weld. The secondary austenite morphologies in the fusion zone of the laser continuously heat treated welds of 2205 duplex stainless steel were investigated. The secondary austenite morphologies were found to be influenced by different laser power level. The secondary austenite with penniform, freely grown and dendritic shape appeared in the course of 4kw, 6kw and 8kw continuous heat treatment, respectively. It was found that there are three kinds of morphologies of secondary austenite in the fusion zone treated by different power, i.e., widmannst?tten austenite, grain boundary austenite and intragranular austenite. The results demonstrated that the mechanisms of the secondary austenite formation are a displacive mechanism during the initial austenite lath formation and a diffusional mechanism during cooling. The nitrides provide the nitrogen for the transformation and at the same time act as nucleation sites for the secondary austenite.

Abstract: In order to improve the weldability of duplex stainless steels, obtaining more secondary austenite in the weld metal is an effective way. Therefore, optimizing the secondary austenite by changing its morphology, volume fraction and stability may be expected to enhance the ductility of the weld. The secondary austenite morphologies in the fusion zone of the laser continuously heat treated welds of 2205 duplex stainless steel were investigated. The secondary austenite morphologies were found to be influenced by different laser power level. The secondary austenite with penniform, freely grown and dendritic shape appeared in the course of 4, 6 and 8 kW continuous heat treatment, respectively. It was found that there were three kinds of morphologies of secondary austenite in the fusion zone treated by different power, i.e., widmannstatten austenite, grain boundary austenite and intragranular austenite. The results demonstrated that the mechanism of the secondary austenite formation was a displacement mechanism during the initial austenite lath formation and a diffusion mechanism during cooling. The nitrides provided the nitrogen for the transformation and at the same time acted as nucleation sites for the secondary austenite.

Key words: Secondary austenite morphology, CO2 laser weld, Continuous heat treatment