Research And Development Of Structures And Materials Of Submerged Entry Nozzle For Thin Slab Continuous Casting

Submerged entry nozzle (SEN) technologies are the core of thin slab continuous casting process. The structure, body materials, lining materials and slag line of SEN which using in thin slab continuous casting process were studied in this paper. The structure of SEN in the steel-making corporation was optimized by using mathematical and physical simulation method. Effects of side outlet angle, side outlet dimension and outlet in bottom of nozzle on flow field of mold were investigated. And the effects of ratio of raw materials, distribution of particle size, additive on body materials were studied in order to improve the properties of strength and thermal shock resistance. C-B4C and ZrB2-Al2O3composite powder were synthesized by using carbon and aluminum thermal reduction method, respectively. The effects of ratio of raw materials, temperature on powder were explored. The formation mechanism of powder was discussed. And then, C-B4C and ZrB2-Al2O3composite powder were added into body materials of nozzle. The influences on properties of thermal shock resistance and antioxidant were investigated. And the effect mechanism had been discussed. In addition, magnesium aluminum spinel powder was synthesized by using chemical coprecipitation, low temperature combustion and solid state reaction methods. The effects of reaction condition on powder were studied. And the influences on sintering performance were explored when adding them into magnesium aluminum spinel lining materials of SEN. And also, ZrB2powder was synthesized by using sol-gel method. The effects of ZrB2additive on slag corrosion performance of ZrO2-C slag line materials were investigated. The following conclusions were obtained.(1) The structure of SEN was studied by using mathematical and physical simulation method. The result showed that three-outlet nozzle was good for diversion of side outlet. It not only decreased level fluctuation, but also made short penetration depth. It could be obtained fine slab after using the optimized nozzle.(2) The effects of ratio of raw materials, distribution of particle size, additive on body materials were studied. The results indicated that oxidation resistance of Al2O3-C materials decreased and thermal shock resistance increased as the content of graphite increased. The oxidation resistance of materials could be improved obviously after adding B4C as antioxidant. The ability of thermal shock resistance increased firstly and then decreased as the value of size distribution coefficient (4) decreased. The properties were optimum when the content of graphite was25mass%, the value of q0.44and with B4C or B4C-SiC additive.(3) Nano-size and submicron-size C-B4C composite powder could be synthesized with carbon thermal reduction method by using carbon black and boric acid as raw materials. The graphitization of carbon black increased, content of B4C decreased and particle size of B4C increased as the synthetic temperature increased. And graphitization of carbon black and relative content of B4C all increased with the amount of boric acid increased. The performance of thermal shock resistance and oxidation resistance of Al2O3-C materials could be improved obviously when adding C-B4C composite powder as additive.(4) The yield synthesized ZrB2powder was higher when the molar ratio of raw materials ZrOCl2·8H2O:H3BO3:Al was3:9:15or3:6:20. And residual Al powder would be good for the property of oxidation resistance. But the regular mechanical properties decreased when in-situ synthesized ZrB2powder in the Al2O3-C refractory, because lots of pores would be formed after aluminum thermal reaction. The performance of thermal shock resistance of Al2O3-C materials could be improved obviously when adding ZrB2powder as additive.(5) Magnesium aluminum spinel powder was synthesized by using chemical coprecipitation, low temperature combustion and solid state reaction methods. The effects of reaction condition on synthesized powder were studied. The results showed that nano-size magnesium aluminum spinel powder could be obtained with chemical coprecipitation when using ammonium carbonate or the mixture of ammonium carbonate and ammonia as precipitating agent. Nano-size magnesium aluminum spinel powder could be also obtained with low temperature combustion method when using urea as fuel, but could not be obtained using citric acid as fuel. In addition, micro-size powder would be synthesized using solid state reaction method.(6) The sintering ability could be improved obviously when adding2mass%nano-size magnesium aluminum spinel powder into magnesium aluminum spinel refractory. And also, magnesium aluminum spinel refractory with high density and strength could be fabricated when adding2mass%TiO2at the relative low sintering temperature.(7) ZrB2powder was synthesized with sol-gel method by using ZrOCl2·8H2O, phenolic resin and H3BO3as raw materials. The results indicated that high purity ZrB2powder could be synthesized when the molar ratio of Zr:B:C was1:2.4:6and the synthetic temperature was1500℃. And the performance of slag corrosion resistance would be improved obviously after adding20mass%ZrB2to ZrO2-C materials.