The Mechanism of Formation of the V Segregation in Steel Ingot

Abstract

According to many studies on the formation of the V segregation, the formation seems to be affected by the following three factors; the thermal state, the gravitational action, and the dendrite morphology. In order to show how the V segregation would be influenced when each factor was varied independently or mutually, some investigations were made on sand-cast ingots.
The results obtained are summarized as follows:
1) The V segregation appeared in the acceralated solidification area of small ta pered ingots with a large ratio of height to diameter; the area did not suffer the both end and riser effects.
2) The gravity itself did not have any direct effect on the V segregation, but the shape of the segregation was rather influenced by the change of dendrite morphology and the distributio n of chemical compositions which were caused by the gravity action.
3) The V segregation tended to disappear with an increase of the amount of taper. With the great taper, the concentrated melts to become the V segregation was found to be squeezed from the area corresponding to the V segregation zone toward the feeder head with the progress of solidification.
A discussion was made on the formation mechanism of the V segregation based upon the results described above, and the theory of the suction by the volume shrinkage of molten steel on solidification could well explain the experimental results.