Formation Condition of “A” Segregation

Abstract

A simulation test of “A” segregation was made successfully by means of horizontal unidirectional solidification of 14kg ingot. “A” segregations reproduced by this method under several cooling conditions were investigated from the viewpoints of cooling and solidification rates.
The results obtaind are as follows
1) “A” segregation is formed at the solidification front where the fraction solid is about 0.35 and it's inclination is determined by the vecter sum of the proceeding velocity of the solidification front and the upward velocity of solute enriched liquid metal.
2) The critical condition for formation of “A” segregation of 0.7%C steel can be expressed by the following formula. where, R is solidification rate (mm/min) and ε is the cooling rate (°C/min)
3) The size of “A” segregation spots are determined by the staying time in solid-liquid zone.