Abstract：The mechnanism of ring crack in BF hearth is analyzed in this paper. In the BF hearth, alkali oxides and alkali carbonates are transformed into purified alkali metal vapor, and the pressure of alkali vapor is very low. Alkali vapor is not the direct cause for the erosion of carbon brick in BF hearth.But for most of relative papers, the erosion of carbon bricks is due to the alkali vapor, and it’s obviously wrong. Thermal stress is very high when the temperature gradient is high in carbon brick, and then it causes microcracks in carbon bricks, and alkali vapor can flows and spread through these microcracks into the low temperature field in bricks, so thermal stress is the precondition for erosion of carbon bricks in BF hearth. At high pressure in BF hearth , the alkali voper liquidizes into purified liquid alkali metal between 800~900℃ in those microcracks, gradually, it edriches in these micrcracks. The volume of ash in the carbon brick’s microcracks expands by 30%-50% after it reacts with liquid alkali, and then the microcracks expand because of the expansion of ash’s volume, and then it is much more advantageous for the flow and spread of alkali voper, and this is the neccesary condition for the ring crack of carbon bricks in BF hearth. Calculation proves that, in the microcracks, only liquid alkali can be react with carbon monoxide and then depositcarbon forms, and its volume expands during the transformation between the depositcarbon and graphit, so the microcracks could constantly expand as long as this reaction happens, and then cuts off carbon bricks and ring crack forms. It is of great importance to improve the heat transfer performance of carbon bricks and prevent carbon monoxide penetrating inside of carbon bricks for the avoidance of ring crack.
2011, Vol. 46 
