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摘要: 鋁脫氧齒輪鋼中易生成大量的高熔點Al2O3類夾雜物，容易導致水口結瘤及鋼材性能惡化，目前較常采用鈣處理將鋼中高熔點的Al2O3類夾雜物改性為低熔點的鈣鋁酸鹽類夾雜物。合理的鈣處理可以減輕水口結瘤并提高連鑄過程鋼液的可澆性，工業試驗研究了喂鈣前鋼液中T.Ca含量、喂鈣速度、喂鈣量、凈空高度及渣厚等參數對齒輪鋼中鈣收得率的影響，并在1.5 m·s?1的喂鈣速度條件下研究了不同喂鈣量對鈣處理過程中齒輪鋼中非金屬夾雜物改性的影響。研究結果表明，當喂鈣前鋼液中T.Ca的質量分數小于10×10?6，喂鈣速度為1.5 m·s?1，適當降低喂鈣量和凈空高度和渣厚，鋼液中鈣收得率均高于20%。當鋼液中T.Ca的質量分數高于17×10?6時，鋼中生成大量高熔點CaS型夾雜物，三元相圖中夾雜物的平均質量分數遠離液相區。隨著齒輪鋼中T.Ca含量的增加，夾雜物的平均尺寸和數密度逐漸增加。熱力學計算結果與工業試驗鈣處理對鋼中非金屬夾雜物改性效果具有較好的一致性。Abstract: Obtaining high-quality gear steel calls for strict requirements on the oxygen content, shape, composition, size, and distribution of nonmetallic inclusions to ensure high-quality steel and castability of the molten steel during the continuous casting process. Al2O3 inclusions with high melting point are easily generated in Al-deoxidized gear steel, and they easily result in nozzle clogging and deterioration in the properties of the steel. A reasonable calcium treatment can reduce the nozzle clogging and increase improving the castability of the molten steel, and thus it has been widely used in steel plants. Calcium treatment is often used to convert Al2O3 inclusions with high melting point to calcium aluminate with low melting point. The factors of calcium treatment on nonmetallic inclusions in gear steel were investigated through industrial trials. The dependency of calcium yield on various factors, namely, the amount of calcium addition, feeding speed of calcium wire, and feeding position and slag thickness were discussed. The effect of the amount of calcium addition on nonmetallic inclusions in the molten steel was studied at a feeding rate of 1.5 m·s?1. With the initial mass fraction of T.Ca lower than 10×10?6 in the steel and a feeding rate of 1.5 m·s?1, the calcium yield can be higher than 20% if the amount of calcium addition, clearance height, and slag thickness during the refining process are appropriate. Large numbers of nonmetallic CaS inclusions with high melting point are formed in the molten steel with the mass fraction of T.Ca higher than 17×10?6, and the inclusions are formed far away from the liquidus region. With increase in the T.Ca content in the steel, the average size and number density of the nonmetallic inclusions gradually increase. The effect of calcium treatment on the modification of nonmetallic inclusions studied by thermodynamic calculation results agrees well with the measurements taken via industrial trials.
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Key words:
- calcium treatment /
- calcium yield /
- nonmetallic inclusions /
- gear steel /
- thermodynamic calculation
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圖 1 鈣收得率的影響因素。（a）喂鈣前T.Ca質量分數；（b）喂鈣速度；（c）喂鈣量；（d）精煉渣厚度+鋼包凈空高度
Figure 1. Influencing factors of calcium yield: (a) T.Ca before calcium treatment; (b) feeding rate; (c) length of wire; (d) slag thickness and ladle clearance height
圖 2 高喂鈣量爐次喂鈣前非金屬夾雜物成分分布。（a）Al2O3?MgO?CaO三元相圖；（b）Al2O3?CaS?CaO三元相圖
Figure 2. Composition distribution of nonmetallic inclusions before calcium treatment of high calcium addition heat: (a) Al2O3?MgO?CaO ternary phase diagram; (b) Al2O3?CaS?CaO ternary phase diagram
圖 3 高喂鈣量爐次中間包鋼液中非金屬夾雜物成分分布。（a）Al2O3?MgO?CaO三元相圖；（b）Al2O3?CaS?CaO三元相圖
Figure 3. Composition distribution of nonmetallic inclusions in the molten steel of tundish of high calcium addition heat: (a) Al2O3?MgO?CaO ternary phase diagram; (b) Al2O3?CaS?CaO ternary phase diagram
圖 4 高喂鈣量爐次鈣處理后鋼中典型非金屬夾雜物形貌及成分
Figure 4. Morphology and composition of typical nonmetallic inclusions after calcium treatment of high calcium addition heat
圖 5 合適喂鈣量爐次喂鈣前非金屬夾雜物成分分布。（a）Al2O3?MgO?CaO三元相圖；（b）Al2O3?CaS?CaO三元相圖
Figure 5. Composition distribution of nonmetallic inclusions before calcium treatment of appropriate calcium addition heat: (a) Al2O3?MgO?CaO ternary phase diagram; (b) Al2O3?CaS?CaO ternary phase diagram
圖 6 合適喂鈣量爐次中間包鋼液中非金屬夾雜物成分分布。（a）Al2O3?MgO?CaO三元相圖；（b）Al2O3?CaS?CaO三元相圖
Figure 6. Composition distribution of nonmetallic inclusions in the molten steel of tundish of appropriate calcium addition heat: (a) Al2O3?MgO?CaO ternary phase diagram; (b) Al2O3?CaS?CaO ternary phase diagram
圖 7 合適喂鈣量爐次鈣處理后鋼中典型非金屬夾雜物形貌及成分
Figure 7. Morphology and composition of typical nonmetallic inclusions after calcium treatment of appropriate calcium addition heat
圖 8 低喂鈣量爐次喂鈣前非金屬夾雜物成分分布。（a）Al2O3?MgO?CaO三元相圖；（b）Al2O3?CaS?CaO三元相圖
Figure 8. Composition distribution of nonmetallic inclusions before calcium treatment of low calcium addition heat: (a) Al2O3?MgO?CaO ternary phase diagram; (b) Al2O3?CaS?CaO ternary phase diagram
圖 9 低喂鈣量爐次中間包鋼液中非金屬夾雜物成分分布。（a）Al2O3?MgO?CaO三元相圖；（b）Al2O3?CaS?CaO三元相圖
Figure 9. Composition distribution of nonmetallic inclusions in molten steel of tundish of low calcium addition heat: (a) Al2O3?MgO?CaO ternary phase diagram; (b) Al2O3?CaS?CaO ternary phase diagram
圖 10 低喂鈣量爐次鈣處理后鋼中典型非金屬夾雜物形貌及成分
Figure 10. Morphology and composition of typical nonmetallic inclusions after calcium treatment of low calcium addition heat
圖 11 不同T.Ca含量條件下鋼中非金屬夾雜物成分分布。（a）Al2O3·MgO·CaO三元相圖；（b）Al2O3·CaS·CaO三元相圖
Figure 11. Distribution of nonmetallic inclusions in steel with different T.Ca: (a) Al2O3·MgO·CaO; (b) Al2O3·CaS·CaO
圖 12 T.Ca質量分數對鋼中非金屬夾雜物平均成分的影響
Figure 12. Effect of T.Ca on the distribution of nonmetallic inclusions in steel
圖 13 實驗結果與熱力學理論計算的對比
Figure 13. Comparison between experimental results and thermodynamic calculation
圖 14 不同T.Ca含量對鋼中非金屬夾雜物的影響。（a）最大尺寸；（b）平均尺寸；（c）數密度；（d）面積分數
Figure 14. Effect of T.Ca on nonmetallic inclusions in steel: (a) maximum diameter; (b) average diameter; (c) number density; (d) area fraction
圖 15 不同T.Ca質量分數條件下鋼中非金屬夾雜物固液相線溫度變化
Figure 15. Effect of T.Ca on solidus and liquidus of nonmetallic inclusions
圖 16 100%液相和20%液相的夾雜物喂鈣窗口的對比
Figure 16. Comparison between 100% and 20% liquid windows of calcium treatment
久色视频表 1 不同喂鈣量爐次中間包內鋼液的主要成分（質量分數）
Table 1. Main composition of the molten steel in the tundish with different calcium feeding heats
% Heat No. C Si Mn Cr Ti P S T.Al [Al] T.Ca 1# 0.21 0.25 0.87 1.08 0.057 0.021 0.001 0.019 0.016 0.0029 2# 0.19 0.29 0.88 1.08 0.053 0.013 0.001 0.022 0.021 0.0017 3# 0.18 0.28 0.88 1.08 0.057 0.017 0.001 0.026 0.024 0.0013 
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