Investigation of Blast-furnace Hearth Sidewall Erosion by Core Sample Analysis and Consideration of Campaign Operation

摘要

The sidewall core boring of the Tobata No. 1 BF, which had been blown out in 1998, was carried out. Bricks and residue in the hearth were sampled and investigated in order to estimate the erosion and protection mechanism of the hearth sidewall. Sampled carbon bricks were observed. [1] A metal-rich layer, [2] a layer which a large amount of metal penetrated, [3] a solid layer which a small amount of metal penetrated, and [4] a weakened layer in which the block has become brittle although metal did not penetrate, [5] a sound layer were observed in this order from the furnace inside side. Na and K are widely distributed from the hot face side to the cold face side, while zinc is accumulated in a high concentration in the brittle layer. As a result of investigation of the residue in the hearth near sidewall bricks, it became apparent that the residue in the hearth is a layer mainly composed of iron with high carbon concentration. It was estimated that the solidification structure is molten iron which solidified gradually while entraining carbon sources. TiN was observed in some samples by microscopic observation. From the consideration of period and spatial distribution of temperature rise, it was estimated that flows of molten iron which move in the hearth toward tapholes are the cause of the sidewall temperature rise. The mechanism of sidewall erosion by the shrinkage of the viscous layer and solidified layer near bricks was estimated.