Adding magnesite flotation concentrate powder in the production of fused magnesia has become an important method for reducing costs and improving the yield.However,the extensive use of concentrate powder also reduces ...Adding magnesite flotation concentrate powder in the production of fused magnesia has become an important method for reducing costs and improving the yield.However,the extensive use of concentrate powder also reduces the quality of fused magnesia raw materials,which is a major cause of the reduced slag corrosion resistance and service life of magnesia-carbon refractories.The effects of concentrate powder additions(0,30%,60%,and 90%,by mass)on the chemical composition,phase composition,microstructure,bulk density,and apparent porosity of the produced 97-grade fused magnesia were investigated.The results show that as the concentrate powder addition increases,the bulk density first increases and then decreases,while the apparent porosity first decreases and then increases.The crystal size of the fused magnesia increases,and the pores at the grain boundaries become larger.The CaO/SiO_(2)molar ratio(C/S ratio)in the fused magnesia increases from 1.17 to 4.17.The bonding phases between the fused magnesia grains change from low-melting-point phases such as CMS(CaMgSiO_(4))and C_(3)MS_(2)(3CaO·MgO·2SiO_(2))to high-melting-point phases like C_(2)S(2CaO·SiO_(2)),C_(3)S(3CaO·SiO_(2)),and CaO,which is beneficial for improving the high-temperature performance of the fused magnesia.However,during production,the volume effects resulting from the polymorphic transformation of dicalcium silicate(C_(2)S)and the low-temperature decomposition of tricalcium silicate(C_(3)S)create significant voids around the fused magnesia grains.These voids can provide pathways for slag corrosion in subsequent magnesia-carbon products,which is likely the primary reason for the decline in the slag corrosion resistance and service life of carbon-containing refractories made from this type of fused magnesia.展开更多
基金support from the National Natural Science Foundation of China(U20A20239 and U1908227).
文摘Adding magnesite flotation concentrate powder in the production of fused magnesia has become an important method for reducing costs and improving the yield.However,the extensive use of concentrate powder also reduces the quality of fused magnesia raw materials,which is a major cause of the reduced slag corrosion resistance and service life of magnesia-carbon refractories.The effects of concentrate powder additions(0,30%,60%,and 90%,by mass)on the chemical composition,phase composition,microstructure,bulk density,and apparent porosity of the produced 97-grade fused magnesia were investigated.The results show that as the concentrate powder addition increases,the bulk density first increases and then decreases,while the apparent porosity first decreases and then increases.The crystal size of the fused magnesia increases,and the pores at the grain boundaries become larger.The CaO/SiO_(2)molar ratio(C/S ratio)in the fused magnesia increases from 1.17 to 4.17.The bonding phases between the fused magnesia grains change from low-melting-point phases such as CMS(CaMgSiO_(4))and C_(3)MS_(2)(3CaO·MgO·2SiO_(2))to high-melting-point phases like C_(2)S(2CaO·SiO_(2)),C_(3)S(3CaO·SiO_(2)),and CaO,which is beneficial for improving the high-temperature performance of the fused magnesia.However,during production,the volume effects resulting from the polymorphic transformation of dicalcium silicate(C_(2)S)and the low-temperature decomposition of tricalcium silicate(C_(3)S)create significant voids around the fused magnesia grains.These voids can provide pathways for slag corrosion in subsequent magnesia-carbon products,which is likely the primary reason for the decline in the slag corrosion resistance and service life of carbon-containing refractories made from this type of fused magnesia.
