Globular oxide inclusion in high carbon wire rod steel

Globular oxide inclusion in high carbon wire rod steel

Figure 1: A typical X-ray map of constituent elements of globular oxide inclusions observed in wire rod samples. SEM, scale bar: 8 µm.

Inclusion name: Globular oxide inclusion
Record No.: 852
Inclusion formula: No data
Inclusion type (Macro/Micro/Nano): Micro
Inclusion type (Exogenous/Indigenous): No data
Inclusion classification: Oxide
Inclusion composition in weight %: No data
Sample: High carbon wire rod steel
Steel composition in weight %: 0.70-0.80% C, 0.65-0.70% Mn, 0.16-0.30% Si, max. 0.020% P, max. 0.020% S, max. 60 ppm N.
Note: Large numbers of globular oxide inclusions of 5–20 µm sizes were seen in all wire rod samples. In the SEM-EDS examination, those globular inclusions were found to contain CaO, SiO2 and Al2O3 and minute quantity (less than 2 percent) of MgO and TiO2. Fig. 1 presents the X-ray map of constituent elements of two such inclusions. Cavity associated with cracks in the steel matrix can be clearly seen in the Fig.. Also, a sulfide ring of CaS-MnS precipitated around those inclusions. Presence of such inclusions in the wire rods would become potential sites for cracks at the subsequent fine wire drawing stage. In addition to these, almost pure alumina inclusions were also found in some of the wire rod samples. In spite of an apparent improvement in the steel cleanliness, the gross behavior pattern of globular oxide inclusions remained almost same in wire rods produced from the billets cast during the pre and post upgradation periods.
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