Study On Properties Of Unburned Brick Without Chromium For RH Immersion Tubes

As one of the important equipments in steelmaking and smelting,RH refining furnace is particularly important for the smelting of clean steel.The inserting tube of RH refining furnace plays an important role in steelmaking process.At present,magnesia-chromium refractory is commonly used on inserting tube lining in China.Magnesia-chromium refractories have certain excellent properties,but the hexavalent chromium is produced in the production process.Because the hexavalent chromium is harmful to the environment and the human body,therefore,chromium-free refractory materials is urgent to developed to replace the chromium-containing refractories.Due to the Magnesium-aluminum spinel refractories have excellent physical properties and slag resistance,magnesium-chromium materials are replaced by magnesium-aluminum spinel materials for RH refining furnaces.In order to improve the physical properties and slag resistance of periclase-magnesium aluminate spinel（Mg O-MA）refractories,fused magnesia,tabular corundum powder,ZrO₂,TiO₂,metal Al and silicon powder were used as raw materials and the phenolic resin was used as the binder to make the refractories.The properties of Mg O-MA refractories were studied from three aspects: particle size distribution（q value）,particle size and addition amount of corundum powder,and addition amount of ZrO₂ and TiO₂.The following results were obtained:（1）The sample has the closest packing degree when the q value is 0.38,and the overall performance is the best.The overall performance of materials is improved by change of q value,and（2）The size of corundum can affect the formation of spinel.When the corundum size is 325 mesh and the addition amount is 3.2wt%,the overall performance of the sample is the best.（3）.When the ZrO₂ is added,the thermal shock resistance of the sample can be obviously improved.When the ZrO₂ content is 0.9-1wt%,the overall performance of the sample is optimal.When the TiO₂ is added,it helps to promote the sintering of the sample and increase the bulk density and compressive strength of the sample.When the content of TiO₂ is 1.5²wt%,the overall performance of the sample is the best.