Influence of alkali metal oxides on the melt structure and viscosity properties of CaO-Al2O3 based mold flux
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摘要: 低反应性CaO-Al2O3基保护渣可以大幅降低高铝钢连铸过程中的渣-钢反应强度,但此类保护渣黏度较大,结晶性能较强,易在结晶器弯月面处产生较大渣圈,造成铸坯缺陷。采用分子动力学模拟方法结合黏度测试试验,解析同为碱金属氧化物的Li2O、Na2O和K2O对CaO-Al2O3基保护渣熔体结构和黏性特性影响的异同,结果表明,碱金属氧化物对[AlO4]5−四面体进行电荷补偿遵循Li2O<Na2O<K2O的顺序,对铝酸盐网络结构的解聚能力遵循Li2O>Na2O>K2O的顺序。Abstract: Low reactivity CaO-Al2O3 based mold flux can significantly reduce the intensity of slag-steel reaction in the continuous casting process of high-alumina steel. But the viscosity of this kind of mold flux is larger and the crystallization performance is stronger, which is easy to produce larger slag rims at the mold meniscus and cause casting defects. In this paper, the molecular dynamics simulation method combined with viscosity test experiment was used to analyze the similarities and differences of the effects of Li2O, Na2O and K2O, which are alkali metal oxides, on the melt structure and viscosity properties of CaO-Al2O3 based mold flux. The results show that the charge compensation of [AlO4]5− tetrahedra by alkali metal oxides follows the order of Li2O<Na2O<K2O, and the depolymerization ability of aluminate network structure follows the order of Li2O>Na2O>K2O.
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Key words:
- mold flux /
- aluminates /
- alkali metals /
- melt structure /
- viscosity
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表 1 配加不同碱金属氧化物(Li2O、Na2O、K2O)体系的分子动力学模拟体系组成
Table 1. Composition of molecular dynamics simulation system with different alkali metal oxides (Li2O, Na2O, K2O) systems
质量分数/% 粒子数量/个 密度/(g·cm−3) CaO Al2O3 Li2O Na2O K2O CaO Al2O3 Li2O Na2O K2O 总数 1 50 50 2107 1157 9999 2.77 2 48 48 4 1 920 1055 295 10000 2.70 3 48 48 4 2 009 1104 154 10000 2.72 4 48 48 4 2 042 1122 102 10000 2.74 表 2 分子动力学模拟中采用的Buckingham势参数[21-23]
Table 2. Buckingham potential parameters used in molecular dynamics simulations
粒子对 Aij/eV ρij/nm Cij×106/(eV·nm6) Li-O 37795.00 0.0165 4.34 Na-O 282278.80 0.016 8.67 K-O 2149947.00 0.0165 13.00 Ca-O 717827.00 0.0165 8.67 Al-O 86057.58 0.0165 0.00 O-O 1497049.00 0.017 17.34 表 3 黏度测试用保护渣化学成分
Table 3. Chemical compositions of mold flux for viscosity test
% CaO Al2O3 Li2O Na2O K2O CaF2 B2O3 1 40 40 10 10 2 38 38 4 10 10 3 38 38 4 10 10 4 38 38 4 10 10 -
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