Effect of fluxing agent on the properties of CaO-Al2O3 based mold flux
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摘要: 针对高铝钢用钙铝基连铸保护渣在浇铸过程中存在的渣条严重、粘结漏钢报警频发等问题，通过调整助熔剂含量，考察了以B2O3替代CaF2对保护渣熔化温度、黏度及结晶性能的影响。结果表明，随着B2O3替代CaF2质量分数的增加，保护渣的熔化温度和转折点温度不断降低，高温下的黏度不断提高。而且，CaF2质量分数较高时，保护渣的析晶性能较强，高温处析出Ca12Al14O32F2。随着B2O3取代CaF2质量分数的增加，保护渣的析晶性能受到明显抑制，析晶物相的变化规律为Ca12Al14O32F2 →2CaO·Al2O3·SiO2 →单一液相。B2O3取代CaF2质量分数为10%时，保护渣的析晶性能得到有效抑制，可有效降低粘结报警频率，满足高铝钢种的浇铸需求。Abstract: In order to address the problems of serious slag strips and breakout alarms in the process of high-aluminum steel continuous casting using calcium-aluminum-based mold flux, the comprehensive effect of B2O3 and CaF2 on the melting temperature, viscosity and crystalline properties were investigated. The results showed that as the mass fraction of CaF2 replaced by B2O3 increased, the melting temperature and breaking temperature of the mold flux decreased, and the viscosity showed an increasing trend. Moreover, the mold flux had stronger crystallization ability with high content of CaF2, leading to the precipitation of Ca12Al14O32F2 at a high temperature. As the mass fraction of CaF2 replaced by B2O3 increases, the crystallization ability had been obviously inhibited, and the crystalline phases changes as follows: Ca12Al14O32F2 → 2CaO·Al2O3·SiO2 → a single liquid phase.When B2O3 replaces CaF2 with a mass fraction of 10%, the crystallization performance of the mold flux was effectively suppressed, which could effectively reduce the sticking breakout alarm and meet the casting requirements of high-aluminum steel.
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Key words:
- high-aluminum steel /
- continuous casting mold flux /
- viscosity /
- crystallization /
- fluxing agent
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图 1 CaO-Al2O3-B2O3体系和 CaO-Al2O3-CaF2体系等温截面
Figure 1. Isothermal sections of CaO-Al2O3-B2O3 system and CaO-Al2O3-CaF2 system
图 2 不同B2O3代替CaF2质量分数条件下保护渣的黏度-温度曲线
Figure 2. Viscosity-temperature curves of mold flux with different contents of B2O3 as replacement for CaF2
图 3 S1渣在不同温度下淬冷渣样的扫描电镜形貌以及充分析晶 (5 Pa·s)下淬冷渣样的XRD图谱
P1：Ca12Al14O32F2 ；M：液相
Figure 3. SEM images of S1 mold flux quenched at different temperatures，and XRD patterns of S1 mold flux quenched at full crystallization (5 Pa·s)
图 4 S2渣在不同温度下淬冷渣样的扫描电镜形貌以及在充分析晶 (5 Pa·s)下淬冷渣样的XRD分析图谱
P2：2CaO·Al2O3·SiO2；M：液相
Figure 4. SEM images of S2 mold flux quenched at different temperatures，and XRD patterns of S2 mold flux quenched at full crytallization (5 Pa·s)
图 5 S3渣在不同温度下淬冷渣样的扫描电镜图片以及在充分析晶 (5 Pa·s)下淬冷渣样的XRD分析图谱
Figure 5. SEM images of S3 mold flux quenched at different temperatures，and XRD patterns of S3 mold flux quenched at full crytallization (5 Pa·s)
图 6 不同B2O3代替CaF2质量分数条件下保护渣结晶物相的析出情况
Figure 6. Crystallization of different phases for mold flux with different contents of B2O3 as replacement for CaF2
表 1 国内某钢厂高铝钢连铸保护渣主要化学成分
Table 1. Min chemical compositions of high-aluminum steel continuous casting mold flux in a domestic steel plant
% CaO SiO2 Al2O3 CaF2 Li2O CaO/Al2O3 31.81 7.58 19.7 25.74 9.14 1.33 
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表 2 试验用高铝钢连铸保护渣化学成分
Table 2. Chemical compositions of mold flux used for high-Al steel continuous casting
% 序号 CaO SiO2 Al2O3 Na2O CaF2 Li2O B2O3 CaO/Al2O3 S1 32 6 24 5 23 5 5 1.33 S2 32 6 24 5 18 5 10 1.33 S3 32 6 24 5 13 5 15 1.33
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表 3 不同B2O3代替CaF2质量分数条件下保护渣在1300 ℃的黏度以及转折点温度
Table 3. Viscosity at 1 300 ℃ and breaking temperature of mold flux with different contents of B2O3 as replacement for CaF2
序号 1300 ℃黏度/(Pa·s) 转折点温度/℃ S1 0.076 1260 S2 0.102 1004 S3 0.118 975
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表 4 S1渣在不同温度下淬冷渣样相关物相的能谱分析
Table 4. EDS analysis of S1 mold flux quenched at different temperatures
淬冷温度/℃ 物相 摩尔分数/% Ca Al Si Na F O 1260 P1 20.53 27.05 5.22 47.20 M 25.20 3.83 5.25 2.56 18.25 49.07 1207 P1 19.73 26.67 4.53 49.07 M 21.59 8.01 4.76 2.45 18.76 44.43
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表 5 S2渣在不同温度下淬冷渣样相关物相的能谱分析
Table 5. EDS analysis of S2 mold flux quenched at different temperatures
淬冷温度/℃ 物相 摩尔分数/% Ca Al Si Na F O 1004 P2 17.46 22.04 6.98 53.51 M 19.25 13.74 3.70 2.51 9.72 51.08 975 P2 18.49 23.28 7.08 51.14 M 19.69 13.69 3.64 2.09 10.42 50.49
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表 6 S3渣在不同温度下淬冷渣样相关物相的能谱分析
Table 6. EDS analysis of S3 mold flux quenched at different temperatures
淬冷温度/℃ 物相 摩尔分数/% Ca Al Si Na F O 975 M 17.51 14.23 3.16 3.26 6.74 55.10 952 M 17.93 14.43 3.30 2.81 7.02 54.51
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