Solidification process of submerged arc weld metals (Report 3) - A quantitative investigation of solute behaviour during solidification.

From the viewpoint of fundamentally examining the weld metal solidification process by referring to knowledges of casting to prevent the high speed SAW solidification defect, investigations were previously made on the relationship between the solidification variables in weld pool and the solidified microstructures using 25Cr-20Ni austenitic steels (Reports Nos. 1 and 2). In the present report, solute behaviours during weld metal solidification have been discussed.In the weld pool quickly solidifying close to a high-temperature heat source, a violent liquid flow occurs. This is a large difference between welding and casting. In the previous examination, however, it was shown that the formation mechanisms of solidified microstructures for both welding and casting are identical owing to a great thermal influence, in spite of their difference in liquid flow condition.On the other hand, the influence of liquid flow was clearly revealed on the solute behaviours such as micro- and macro-segregation. The present report has quantitatively pointed out the features of such behaviours. Moreover, the micro-segregation results have been applied to Burton's analytical solution concerning the degree of liquid-phase mixing to estimate the flow actions at various parts of SAW weld pool.