Broken corners - Slab defects

Broken corners - Slab defects

Figure 1: Cogged bloom from thin-skinned rimming-steel ingot, showing broken corners and shells caused by exposure and oxidation of the blowholes in the soaking pit.

Defect name: Broken corners
Record No.: 316
Type of defect (Internal/Surface): Surface
Defect classification: Slab defects
Steel name: Steel
Steel composition in weight %: No data.
Note: A breaking—up of the corners of the bloom or slab owing to the exposure and oxidation of subcutaneous blowholes, being most apparent at the corners of the blooms or at the edges of the slabs. An example is shown in Fig. 1.
Oxidation of subcutaneous blowholes in the ingot can be caused either:
(a) by a too thin ingot skin, or
(b) in the case of a well-made balanced ingot, by excessive length of time in the soaking pit.
The defect has every visible appearance of 'burnt' steel and may also be mistaken for 'hot-shortness', although arising from a different cause.
Note: Defects in semi-finished and finished products arising from ingot defects.
Reference: Not shown in this demonstration version.