Influence of Alloying Elements on the Formation of “A” Segregates in Steel Ingot

Abstract

In order to investigate the influence of alloying elements, Ni, Cr, Mo and V on the occurrence of “A” segregates and dendrite structure, simulation tests for “A” segregates were made using 14kg ingot solidified horizontally and unidirectionally.
The solute-enriched phenomenon, investigated by taking samples from the solidification front, was discussed in connection with the influence of alloying elements.
The results obtained are summarized as follows:
1) Adding 1% Mo to plain carbon steel made “A” segregates eliminate and made the solute-enriched liquid distribute homogeneously to form fine structure.
2) Ni, Cr and V did not have a great influence on “A” segregates and dendrite structure, but Cr made “A” segregates eliminate a little and V made them increase a little.
3) The cooling rate of the solidification front in the solid-liquid zone decreased as the solidification proceeded and consequently shifting the solidification front to higher solid fraction side made the solute concentration increase.
4) The reason that “A” segregates are eliminated by adding 1% Mo is caused by suppressing a shift of the solidification front to higher solid fraction side. which means that there does not occur the solute enrichment enough to form the segregates at the solidification front.