基于热丝法对CaO-SiO_2-Al_2O_3保护渣结晶性能与凝固分数的研究
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摘要
针对髙铝包晶钢连铸设计了Ca O-Si O2-Al2O3系保护渣.采用单丝法研究w(Ca O)/w(Al2O3)对保护渣结晶性能的影响;采用双丝法模拟了保护渣渣膜形成及凝固过程,研究了w(Ca O)/w(Al2O3)对保护渣固相体积分数φ的影响.结果表明:实验保护渣系结晶能力随w(Ca O)/w(Al2O3)增大而增强,按结晶能力分为两个区间,w(Ca O)/w(Al2O3)>1.30时保护渣结晶能力强于w(Ca O)/w(Al2O3)≤1.30的保护渣;在等温结晶过程中,w(Ca O)/w(Al2O3)=1.00的实验保护渣中析出枪晶石,w(Ca O)/w(Al2O3)=2.50时渣中析出硅酸二钙;w(Ca O)/w(Al2O3)增大使保护渣渣膜双丝间固相体积分数增大,结晶层增厚,不利于保证结晶器内润滑.与浇注常规包晶钢的Ca O-Si O2系保护渣性能对比表明,Ca O-Si O2-Al2O3系保护渣在w(Ca O)/w(Al2O3)≤1.30时的结晶能力和固相体积分数都与对照渣相近,设计的Ca O-Si O2-Al2O3系保护渣适用于高铝包晶钢连铸.
A mold slag based on Ca O-Si O2-Al2O3 system was designed for casting high-aluminum peritectic steels. Single hot thermocouple technique( SHTT) was applied to study the impact of w( Ca O) / w( Al2O3) on crystallization behaviors. Double hot thermocouple technique( DHTT)was used to simulate the formation of slag film and define the impact of w( Ca O) / w( Al2O3) on solidification fraction. The results showthat the slags can be divided into two groups according to crystallization characters: the group with w( Ca O) / w( Al2O3) higher than 1. 30( Group Ⅱ) has a higher tendency of crystallization than that with w( Ca O) / w( Al2O3) lower 1. 30( Group Ⅰ).Cuspidine( Group Ⅰ) and dicalcium silicate( Group Ⅱ) were precipitated respectively in these two groups during isothermal process. As the w( Ca O) / w( Al2O3) increased,the crystallization tendency increased sharply which causes the solidification fraction in slag film increased. The slags were also compared with industrial slag used for casting common peritectic steels,showing that the slags with w( Ca O) / w( Al2O3) ≤1. 30 have similar properties with industrial slag. The designed Ca O-Si O2-Al2O3 slag can be used in casting high-aluminum peritectic steels.
A mold slag based on Ca O-Si O2-Al2O3 system was designed for casting high-aluminum peritectic steels. Single hot thermocouple technique( SHTT) was applied to study the impact of w( Ca O) / w( Al2O3) on crystallization behaviors. Double hot thermocouple technique( DHTT)was used to simulate the formation of slag film and define the impact of w( Ca O) / w( Al2O3) on solidification fraction. The results showthat the slags can be divided into two groups according to crystallization characters: the group with w( Ca O) / w( Al2O3) higher than 1. 30( Group Ⅱ) has a higher tendency of crystallization than that with w( Ca O) / w( Al2O3) lower 1. 30( Group Ⅰ).Cuspidine( Group Ⅰ) and dicalcium silicate( Group Ⅱ) were precipitated respectively in these two groups during isothermal process. As the w( Ca O) / w( Al2O3) increased,the crystallization tendency increased sharply which causes the solidification fraction in slag film increased. The slags were also compared with industrial slag used for casting common peritectic steels,showing that the slags with w( Ca O) / w( Al2O3) ≤1. 30 have similar properties with industrial slag. The designed Ca O-Si O2-Al2O3 slag can be used in casting high-aluminum peritectic steels.
引文
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[2]Wang W L,Blazek K,Cramb A.A study of the crystallization behavior of a new mold flux used in the casting of transformation-induced-plasticity steels[J].Metallurgical and Materials Transaction B,2008,39(1):66-74.
[3]Kim M S,Kang Y B,Lee S W.A reaction mechanism between high Mn-high Al steel and molten mold fluxes[C]//The 5th International Congress on the Science and Technology of Steelmaking.Dresden,2012:1-3.
[4]王欢,唐萍,文光华,等.氧化锂对髙铝钢保护渣结晶行为及渣膜传热的影响[J].北京科技大学学报,2011,33(5):544-549.(Wan Huan,Tang Ping,Wen Guang-hua,et al.The influence of Li2O to high aluminum steels on crystallization and heat transfer[J].Journal of University of Science and Technology Beijing,2011,33(5):544-549.)
[5]Kashiwaya Y,Nanauchi T,Pham K S.Crystallization behaviors concerned with TTT and CCT diagrams of blast furnace slag using hot thermocouple technique[J].ISIJ International,2007,47(1):44-52.
[6]Kashiwaya Y,Cicutti C E,Cramb A W.An investigation of the crystallization of a continuous casting mold slag using the single hot thermocouple technique[J].ISIJ International,1998,38(4):357-365.
[7]Ramirez-Lopez P E,Lee P D,Mills K C.A new approach for modelling slag infiltration and solidification in a continuous casting mould[J].ISIJ International,2010,50(12):1797-1804.
[8]Ramirez-Lopez P E,Lee P D,Mills K C.Explicit modeling of slag infiltration and shell formation during mould oscillation in continuous casting[J].ISIJ International,2010,50(3):425-434.
[9]Li Z,Thackray R,Mills K C.A test to determine crystallinity of mould fluxes[C]//VII International Conference on Molten Slags,Fluxes and Salts.Cape Town:The South African Institute of Mining and Metallurgy,2004:813-819.
[10]Mills K C,Fox A B,Li Z,et al.Performance and properties of mould fluxes[J].Ironmaking and Steelmaking,2005,32(1):26-33.