Solidification Mode in Aluminum Weld Metal :

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  • KATO,Mitsuaki
    Metallurgical Department, Kyushu Institute of Technology:Osaka University
  • MATSUDA,Fukuhisa
    Welding Department, Faculty of Engineering, Osaka University
  • SENDA,Tomio
    Welding Department, Faculty of Engineering, Osaka University

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Abstract

Solidification conditions have been estimated from the theory of heat conduction in the weld metal which had been welded with a moving arc heat source. The nominal growth rate in the weld metal increases generally as the inward growth proceeds, white the temperature gradient decreases. Then, a change of solidification structure in the weld metal was predicted based on the solidification conditions and the solidification theory. Besides, this prediction was substantiated by observing the actual solidification structure in the weld metal with the aid of optical microscope. The solidification structure in the weld metal, in general, changes from planar to cell and cellular dendrite as the inward growth proceeds and sometimes an equiaxed dendrite develops near the weld center. These changes of solidification structure can be accounted for in terms of the phenomenon of constitutional supercooling. When the weld metals are obtained under the condition that the bead width is almost the same, it becomes easy for an equiaxed dendrite to develop in the weld metal as the welding speed increases.

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