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摘要: 連續鑄鋼工藝的成功與保護渣的正確使用密不可分，但保護渣在結晶器內發生的氟化物揮發、卷渣、控熱與潤滑的矛盾又制約了綠色和高效連鑄的發展。重慶大學通過對保護渣在結晶器內進行物理化學研究，發現保護渣中以鋁為代表的網絡形成中間體元素具有適應結晶器工況環境的功效。這些功效包括：（1）抑制保護渣與水之間離子交換程度，起到固氟和固鈉的作用；（2）形成異類網絡結構，使熔渣產生明顯的剪切稀化行為，實現保護渣不同位置黏度大小控制；（3）在低堿度條件下表現出獨特的熱擴散效應，促使玻璃渣膜變成晶體渣膜。在此基礎上，提出連鑄結晶器“自適應保護渣”設計理論，利用這一理論開發出環境友好、非牛頓流體及熱擴散效應保護渣。工業應用結果表明這類保護渣無需降氟就可達到環境友好、降低超低碳鋼冷軋板封鎖率及提升304D高氮不銹鋼板坯表面質量的效果。Abstract: The success of the continuous casting process is inseparable from the correct use of mold powders. However, fluoride volatilization and the contradiction between slag entrapment, heat transfer, and lubrication that occurs in the mold restrict the development of green and efficient continuous casting. Through the physical and chemical research of mold powders, Chongqing University found that the intermediate elements of network formation represented by aluminum in the mold powders have remarkable effects of adapting to the working environment of the mold. These effects include: (1) These elements inhibit the degree of ion exchange between the slag and the water and fix fluorine and sodium. (2) They also form a heterogeneous network structure such that the slag produces shear and thinning behaviors and realizes slag viscosity control in different positions. (3) Under the condition of low basicity, aluminum shows a unique thermal diffusion effect, which promotes the transformation of glass slag film to a crystal slag film. On this basis, the design theory of “Smart Mold Powders” for continuous casting, which is referred to as the “SMP” theory, is proposed. This theory was used to develop environmentally friendly non-Newtonian fluids and thermal diffusion effects to mold powders. Industrial application results show that this type of mold powders can achieve environmental friendliness without fluoride reduction, minimize the rejecting ratio of cold-rolled plates, and improve the surface quality of slabs for high-nitrogen stainless steel.
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Key words:
- continuous casting /
- mold powders /
- adaptive /
- intermediate /
- Soret effect
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圖 4 剪切力對與鋁相關單元結構進化示意圖. (a) Q2Si (1Al); (b) Q3Si (1Al)
Figure 4. Structural evolution for the Al-related species at high shear rate: (a) Q2 Si (1Al); (b) Q3 Si (1Al)
圖 5 含鋁保護渣. (a) 雙絲法; (b) 圖5(a)中選定區域所對應的微觀結構; (c) X衍射
Figure 5. Slag with Al2O3: (a) DHTT; (b) microstructure corresponding to the selected area in Fig.5(a); (c) XRD
圖 6 不含鋁保護渣. (a) 雙絲法; (b) 圖6(a)中選定區域所對應的微觀結構
Figure 6. Al2O3-free slag: (a) DHTT; (b) microstructure corresponding to the selected area in Fig.6(a)
圖 7 含鋁保護渣. (a) 拉曼光譜; (b) 核磁共振
Figure 7. Slag with Al2O3: (a) Raman spectrum; (b) nuclear magnetic resonance
圖 8 保護渣中Al2O3含量對水樣中F?和pH的影響. (a) F?; (b) pH
Figure 8. Effects of Al2O3 content on F? and pH of leaching water: (a) F?; (b) pH
圖 9 Al2O3對保護渣剪切稀化性能的影響. (a) 黏度η; (b) 流動行為指數n
Figure 9. Effect of Al2O3 on shear-thinning performance of slag: (a) viscosity η; (b) flow behavior index n
圖 10 含鋁低堿度保護渣. (a) 渣膜斷面形貌; (b) 圖10(a)中選定區域所對應的微觀結構
Figure 10. Low basicity slag with Al2O3: (a) section morphology of slag film; (b) microstructure corresponding to the selected area in Fig.10(a)
圖 11 含鋁低堿度保護渣黏度?溫度曲線
Figure 11. Viscosity–temperature curve of low basicity slag with Al2O3
表 1 渣樣失重量（質量分數）
Table 1. Weight loss of the slags
% Samples Chemical compositions Losses (1000–1400 ℃) CaO SiO2 CaF2 Na2O 1# 35.0 35.0 15.0 15.0 4.57 2# 42.5 42.5 15.0 0.46 
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表 2 保護渣主要化學成分
Table 2. Main chemical compositions of mold powders
Samples Basicity Chemical composition (Mass fraction)% CaO/SiO2 Al2O3 Na2O+F 1# 0.76 7.50 16.0 2# 0.76 0 16.0
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