STUDY ON INGOT-MAKING PRACTICE (IV)

Distribution of Sand in the Ingot and its Consideration

Abstract

The authors stndied on the distribution of sand and the causes of it concerning silicon or silicon-aluminum killed low-carbon Cr-Mo steel ingots which were melted with an Héroult electric furnace. The results obtained were as follows:
(1) Ingot No. 1 (which was deoxidized with manganese and silicon in the furnace.)
Content of sand was at minimum at the outside and it increased as the inspection went inside, but MnO/SiO₂ and (FeO+MnO)/SiO₂ in it showed a reverse change against the above results, while FeO and MnO decreased and SiO₂ increased as the inspection went inside. But the sand content was low at the center of ingot top.
The sand at the outside of ingot where the total amount of the sand small, had no-constant forms and were very large, but as the inspection went further inside they became spherical and very fine in size.
It was concluded that the large sand at the outside of ingot were not deoxidation products produced in the mold but most of it had been included in the molten steel just before casting.
These large sands were not found at the inside, and as the inside portion was cooled slowly in comparison with the outside portion, it could be supposed that these large sand floated up in the mold during solidification.
On the other hand, the total content of sand showed the maximum value at the inside and their form was finely spherical and as SiO₂ increased but FeO and MnO decreased in their composition in comparison with the inside. It was concluded that this fine and spherical sand at the inside were deoxidation products produced in the mold during solidification.
(2) Ingot No. 2 (which was deoxidized with manganese and silicon in the furnace and added to aluminum in the ladle.)
Content of sand was at maximum at the outside and it decreased as the inspection went inside but at the neighbourhood of the bottom it did not show a low content.
This sand was composed of Al₂O₃, and then SiO₂, FeO and MnO in sand were very few and had fine and no constant forms.
It was concluded that this sand was deoxidation products by aluminum and most of it was not produced in the mold but in the ladle.