Argon Bubbles in Slabs

Abstract

In addition to the assessment of the oxidic contamination of slabs, the assessment of argon bubbles is essential for certain steel grades. The standard clean steel assessment method at Hoogovens BOS No. 2, which was based on the microscopic counting of alumina clusters, has been extended to the counting of argon bubbles. The dimensionless size distribution of argon bubbles has been established for LC and ULC steel grades in the bubble size range of 100 to 750 μm. Radiographic methods show that the distribution of large argon bubbles (diameter >0.5 mm) in slabs is non-homogeneous in respect of width and depth. Therefore it was concluded that the assessment of argon bubbles on small slab samples is only useful for process control and not for quality control. The floatation mechanism of alumina clusters by argon is illustrated. The effect of applying an EMBR was studied.