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| HIGH SPEED AND HIGH MAGNIFICATION IN SITU OBSERVATION OF RESIDUAL LIQUID METAL DURING LASER WELDING PROCESS |
| WEN Peng1,Shinozaki Kenji2, Yamamoto Motomichi2 |
1.Mechanical Engineering Department, Tsinghua University, Beijing 10084
2.Mechanical Engineering Department, Hiroshima University, Japan 739–8527 |
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Cite this article:
WEN Peng Shinozaki Kenji Yamamoto Motomichi. HIGH SPEED AND HIGH MAGNIFICATION IN SITU OBSERVATION OF RESIDUAL LIQUID METAL DURING LASER WELDING PROCESS. Acta Metall Sin, 2011, 47(3): 305-310.
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Abstract Weld solidification cracking is resulted from the low ductility during solidification progress of weld metal, which is considered to be determined by the distribution of residual liquid metal at solidification front. Thus, the in situ observation of residual liquid metal during welding can give significant information of solidification progress and weld solidification cracking. Few reports have been found so far in this aspect though many in situ observation researches have been carried out in welding field, for example, the observation of droplet transfer, weld pool shape, weld plasma and phase transformation etc.. In this paper, solidification behavior of residual liquid metal at the trailing edge of the weld molten pool was in situ observed directly during laser welding by using high speed camera and high magnification optical lens. The precipitation of columnar grain from the molten pool and the solidification of the residual liquid metal at the trailing edge of weld molten pool were recorded in detail by using the high speed video system. Meanwhile, the solidifying structures in solidification process were frozen and reserved to room temperature by using the liquid Sn quenching method during laser welding. The quantity and morphology of residual liquid metal in quenched samples were observed and compared with the in situ observation results. It was found that the in situ observed residual liquid metal was the initial part of the coexistence range of liquid and solid during solidification progress. The in situ observed existence range of residual liquid metal has correspondence with the solidification cracking susceptibility in accordance with the fan–shaped hot cracking test results for three different austenite stainless steels. Consequently, this research provides experimental basis for the relationship between residual liquid metal and solidification cracking susceptibility. It shows the possibility to develop an in situ observation method to directly evaluate solidification cracking susceptiility of different materials during welding process.
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Received: 04 November 2010
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