Study on crystallization and heat transfer performance of solid slag film in mold flux for titanium-bearing microalloyed steel
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摘要: 保护渣固态渣膜是结晶器和铸坯间的关键介质。基于渣膜热流模拟仪制取的含钛微合金钢保护渣固态渣膜，对渣膜的厚度、孔隙度、粗糙度等物理性质进行分析；使用XRD、扫描电镜、矿相显微镜分析渣膜的析晶性能；此外，对渣膜的热阻、热流密度等传热性能进行研究。研究结果表明，渣膜表面粗糙度在固态渣膜凝固初期就已形成，受液渣温度变化影响明显；固态渣膜呈现玻璃态和结晶态两层结构，且矿相主要为钙钛矿；铜探头浸入液渣初期，热流密度迅速增大，当水冷铜探头浸入液渣时间13 s时，保护渣的热流密度均到达了最大值，分别为0.988、1.208 MW/m2和1.355 MW/m2，随着铜探头浸入时间的增加，固态渣膜逐渐变厚，热阻变大，热流密度逐渐降低。Abstract: The solid slag film of mold flux is a key medium between the mold and the continuous casting slab. Based on the solid slag film of mold flux for Ti-containing microalloyed steel prepared by a slag film heat flux simulator, the physical properties of the slag film, such as thickness, porosity, and roughness, were analyzed. XRD, scanning electron microscopy (SEM), and mineral phase microscopy were used to analyze the crystallization performance of the slag film. In addition, the heat transfer properties of the slag film, including thermal resistance and heat flux density, were studied. The results show that the surface roughness of the slag film is formed at the initial stage of solidification of the solid slag film and is significantly affected by the temperature of the liquid slag. The solid slag film has a two-layer structure: glassy and crystalline, with perovskite as the main mineral phase. At the initial stage when the copper probe is immersed in the liquid slag, the heat flux density increases rapidly. When the water-cooled copper probe is immersed in the liquid slag for 13 seconds, the heat flux densities of the mold flux reach their maximum values, which are 0.988 MW·m−2, 1.208 MW·m−2, and 1.355 MW·m−2 respectively. With the increase of the immersion time of the copper probe, the solid slag film gradually thickens, the thermal resistance increases, and the heat flux density decreases gradually.
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Key words:
- mold flux /
- slag film /
- crystallization /
- heat transfer /
- Ti-containing alloy steel
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图 7 渣膜横截面电子图像及EDS分析结果
(a)钙钛矿电子图像；(b)钙钛矿能谱分析结果
Figure 7. Cross-sectional electron image of the slag film and EDS analysis result
图 3 固态渣膜截面形貌和孔隙度
（a）截面形貌；（b）孔隙度
Figure 3. Cross-sectional morphology and porosity of solid slag film
图 4 渣膜与铜探头壁接触形貌和固渣膜与水冷铜壁接触表面3D形貌
（a）渣膜与铜探头壁接触形貌；（b）固渣膜与水冷铜壁接触表面3D形貌
Figure 4. Morphologies of the contact interface between slag film and copper probe wall and the 3D contact surface between solid slag film and water-cooled copper wall
图 5 渣膜与水冷铜壁接触表面粗糙度
Figure 5. Surface roughness of the slag film in contact with the water-cooled copper wall
图 6
1300 ℃、浸入45 s时渣膜X射线衍射结果Figure 6. X-ray diffraction results of the slag film at
1300 ℃ for 45 s
图 8 保护渣不同凝固时间下的渣膜截面形貌
Figure 8. Cross-sectional morphology of the slag film under different solidification times of mold flux
（a）15 s；（b）30 s；（c）45 s；（d）60 s。
图 9 渣膜截面观察图
(a)固态渣膜孔洞附近晶体形貌；(b)钙钛矿晶体形貌
Figure 9. Cross-sectional observation images of the slag film
图 10 固态渣膜热阻与厚度的拟合曲线
Figure 10. Fitting curve of thermal resistance and thickness of the solid slag film
图 11 不同液渣温度的热流密度变化
Figure 11. Heat flux density variation at different liquid slag temperatures
表 1 含钛微合金钢保护渣成分及性能
Table 1. Composition and properties of mold flux for titanium-bearing microalloyed steel
Composition/% Viscosity/
（Pa·s）Melting
temperature/℃CaO Al2O3 TiO2 SiO2 BaO Na2O MgO Li2O B2O3 Tc 24 24.2 10.1 4.0 9.9 8.1 3.0 0.9 8.2 8.1 0.37 1070 
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表 2 保护渣固态渣膜厚度统计
Table 2. Statistics on the thickness of the solid slag film of mold flux
mm 1200 ℃1300 ℃1400 ℃15 s 30 s 45 s 60 s 15 s 30 s 45 s 60 s 15 s 30 s 45 s 60 s 2.82 3.15 3.75 4.22 2.09 2.36 2.67 2.94 1.30 1.72 1.86 2.33
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