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

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.

Study on Crystallization and Solidification Behaviors of CaO-SiO2-Al2O3 Mold Slags with Hot Thermocouple Technique

A mold slag based on CaO-SiO₂-Al₂O₃ system was designed for casting high-aluminum peritectic steels. Single hot thermocouple technique (SHTT) was applied to study the impact of w(CaO)/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(CaO)/w(Al₂O₃) on solidification fraction. The results show that the slags can be divided into two groups according to crystallization characters: the group with w(CaO)/w(Al₂O₃) higher than 1.30 (Group Ⅱ) has a higher tendency of crystallization than that with w(CaO)/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(CaO)/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(CaO)/w(Al₂O₃)≤1.30 have similar properties with industrial slag. The designed CaO-SiO₂-Al₂O₃ slag can be used in casting high-aluminum peritectic steels.