On the Non-metallic Inclusions in Segregated Zone in Low Carbon Rimmed Steel Ingot

Study of non-metallic inclusions in low carbon rimmed steel-III

Abstract

In the 1st report, the influence of inclusions on the formability of a rimmed steel sheet was studied, and it was shown that the formability of a steel sheet was injured by a large sulphide existing in the position correspond to the segregated zone in the ingot top.
In this report, in order to making clear the origin of such inclusions and how to eliminate them, the shapes, distribution and deformation of inclusions at the segregated zone in the ingot top during slabbing were observed: Moreover, author studied the influence of refining and deoxidation process on the cleanliness of the segregated zone. The conclusions of 1st and 2nd report were as follows:
1) In the segregated zone at the ingot top, the network ofthe large flaked type sulphide rich in FeS is found.
It was considered that these inclusions suffer a few fractures during rolling process, for they change from FeS to MnS by soaking and reheating. Those large sulphides injured the formability of the steel sheet.
2) The cleanliness of ingot top is closely connected with the segregation and it is mainly influenced by the [S] and [O] in ladle.
3) In order to decrease the large sulphide mentioned in 1st report, the S-content in the segregated zone should be kept under 0.10% in the check analysis of slab, as the ladle [Mn] is about 0.30%.