Abstract
To decrease skin blowholes and get a sound surface quality, the effects of deoxidation degree and chromium addition on the size and distribution of blowholes in the rim zone were studied.
The results obtained are as follows;
1. The thickness of solid skin and the distribution of blowholes in the rim zone are greatly influenced by the balance of carbon, manganese, and oxygen in liquid steel.
2. It is believed that the thickness of solid skin is required at least 17mm to prevent seamy defects of slab. The next relation is obtained as the condition of deoxidation to keep the thickness of solid skin larger than 17mm.
[C]·[O]-0.56 [Mn]≥0.0182 υ-5, 135 Where, [C], [O], [Mn]: content in liguid steel (10-2%)υ: teeming rate (mm/min)
3. Chromium addition is effective to decrease the number and size of blowholes in the rim zone. It is considered that this phenomenon is based on the decreasing of surface tention by chromium addition.
