Development of dolomite bricks with positive plc

摘要

Dolomite brick is the most important stable refractory under the working conditions of Argon Oxygen De-carbonization (AOD). For AOD applications, the Dolomite bricks should have positive Permanent Linear Change (PLC) on re-heating. A positive PLC dolomite brick has higher life and most suitable for joint less refractory lining with no cobble stoning defect. So the development of dolomite bricks having positive PLC during applications is a challenge for refractory manufacturing industry. In the present investigation, dolomite refractory bricks were prepared by varying different additive with an intention to get the positive PLC of the brick. It is well known that Iron Oxide is a good additive for dolomite brick sintering.It has also been reported that monoclinic zirconia (m-ZrO2) additive improves the BD, CCS and PLC of dolomite brick. In this background, first trial composition was containing a fixed amount of 1% m-ZrO2 and different concentration and types of iron oxide. Mill scale containing Fe2O3 was added in two different concentrations 0.5%, 1% and in another trial 0.25% of nano Fe2O3 was added. Fe2O3 containing bricks showed a good improvement in BD and CCS due to the better sintering of dolomite grains in presence of liquid formation during sintering by the presence of Fe2O3.The CCS value was in the range 750-800 kg/cm2. However, the PLCvalue was negative in the range of -0.2 to -0.35%. Depending on this result, new additive, Chrome Green oxide was then used. It has been found that the PLC tends to be positive with increase in Cr2O3 content. However, in presence of Cr2O3 the m ZrO2 it was not performing well. Finally m-ZrO2 was removed and a higher percentage of Cr2O3 additive showed the positive PLC (+ 0.12%) of the dolomite brick. The brick showed a CCS value of 650 kg/cm2. This is in the acceptable limit.