Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud
Abstract
:1. Introduction
2. Thermodynamic Analysis on Composition of RM-Based Flux
3. Experimental
3.1. Materials
3.2. Equipments
3.2.1. Measurement of Melting Temperature and Lime Dissolution Rate
3.2.2. Experiment of Oxygen Blowing Steelmaking
3.3. Methods
3.3.1. Measurement of Melting Temperature
3.3.2. Measurement of Lime Dissolution Rate
3.3.3. Experiment of Oxygen Blowing Steelmaking
4. Results and Discussion
4.1. Melting Temperature of RM-Based Flux
4.2. Melting Mechanism of RM-Based Flux
4.3. Lime Dissolution Rate of RM-Based Flux
4.4. Application of Flux in Dephosphorization in 10 kg Induction Furnace
5. Conclusions
- The addition of lime to Bayer red mud showed a trend of initially decreasing and then increasing melting points. This is primarily due to the formation of low-melting-point CAF phases during the melting process. The more CAF phases formed, the lower the melting point. When lime was added to the red mud A, as indicated in the text, to prepare RM-based flux, the melting point reached a minimum of 1161 °C. This flux rapidly melts under steelmaking conditions, with components like Al2O3, Na2O, and Fe2O3 in the red mud effectively reducing the lime’s melting point. This facilitates the formation of a fluid initial slag, showing promise for use as a fluoride-free flux in steelmaking.
- The dissolution rates of lime in various RM-based fluxes were analyzed. The results indicated that the lower the melting temperature in RM-based flux, the higher the corresponding lime dissolution rate. Notably, flux A4, with the lowest melting point of 1161 °C, exhibited an average lime dissolution rate of g/s, which is 10 to 15 times that of the early basic oxygen steelmaking slag systems (with R about 1).
- Experiments in a 10 kg induction furnace demonstrated that the addition of RM-based fluxes resulted in a pre-dephosphorization rate of nearly 40% under hot metal conditions without oxygen blowing, surpassing the performance of CaF2 fluxes in the absence of oxidizers like Fe2O3. The primary reason for this enhanced performance is the high Fe2O3 content and low melting point in RM-based fluxes, which provide favorable thermodynamic and kinetic conditions for hot metal dephosphorization. Under oxygen-blowing conditions, the dephosphorization rate with RM-based fluxes was comparable to that of CaF2, significantly higher than scenarios without any flux, especially at high [C] content. The data suggest that RM-based fluxes are highly suitable as fluoride-free alternatives in the steelmaking process, with considerable potential for widespread application.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Sample | Al2O3 | SiO2 | Fe2O3 | TiO2 | CaO | MgO | Na2O | Bal. |
---|---|---|---|---|---|---|---|---|
Red mud A | 13.76 | 13.12 | 42.53 | 8.33 | 11.83 | 0.17 | 8.70 | 1.56 |
Red mud B | 16.30 | 14.60 | 31.70 | 6.62 | 17.80 | 0.32 | 8.50 | 4.16 |
C | Si | Mn | P | S |
---|---|---|---|---|
4.30 | 0.40 | 0.32 | 0.16 | 0.04 |
Group | Red Mud | Quality of Red Mud (g) | Quality of Added CaO (g) |
---|---|---|---|
A1 | 100 | 0 | |
A2 | 100 | 3 | |
A3 | Red mud A | 100 | 10.6 |
A4 | 100 | 18 | |
A5 | 100 | 28.5 | |
A6 | 100 | 33 | |
B1 | 100 | 0 | |
B2 | 100 | 2.3 | |
B3 | Red mud B | 100 | 4.5 |
B4 | 100 | 8.9 | |
B5 | 100 | 18.4 | |
B6 | 100 | 22.3 |
No. | Slag Material | %CaO/%SiO2 | Slag Ratio | T/℃ | Continuous Oxygen Blowing/min | |
---|---|---|---|---|---|---|
CaO | Flux | |||||
1 | 27 g | - | 3 | 2–3% | 1350 | 4 + 6 |
2 | 27 g | 5 g CaF2 | 3 | 2–3% | 1350 | 4 + 6 |
3 | 30.2 g | 35.4 g A4 | 3 | 2–3% | 1350 | 4 + 6 |
No | Point | Element Content (Atom, wt%) | Phase | ||||||
---|---|---|---|---|---|---|---|---|---|
O | Fe | Al | Ca | Si | Na | Ti | |||
1 | 50.57 | 43.38 | 4.03 | 2.01 | Hercynite | ||||
A1 | 2 | 50.67 | 4.45 | 11.95 | 17.67 | 9.93 | 5.33 | Slag1 | |
3 | 54.79 | 4.94 | 21.66 | 1.98 | 16.63 | CaTiO3 | |||
1 | 47.77 | 27.98 | 15.47 | 8.77 | Hercynite | ||||
B1 | 2 | 52.29 | 4.96 | 10.64 | 11.94 | 8.75 | 7.92 | 3.5 | Slag |
3 | 52.87 | 6.00 | 23.42 | 17.70 | CaTiO3 | ||||
1 | 40.44 | 52.87 | 6.69 | Hercynite | |||||
2 | 46.26 | 4.34 | 18.40 | 22.43 | 8.58 | CAF | |||
A4 | 3 | 50.88 | 9.66 | 3.42 | 22.60 | 2.51 | 10.92 | CaTiO3 | |
4 | 44.49 | 11.97 | 11.96 | 11.71 | 5.51 | 12.59 | 1.78 | NCA2 | |
1 | 32.22 | 60.27 | 6.61 | 0.89 | Hercynite | ||||
B4 | 2 | 42.43 | 4.71 | 18.29 | 24.77 | 9.80 | CAF | ||
3 | 48.07 | 7.11 | 1.68 | 24.68 | 1.62 | 16.85 | CaTiO3 | ||
4 | 42.23 | 13.25 | 13.26 | 10.97 | 5.55 | 13.59 | 1.15 | NCA2 |
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Zhao, Z.; Zhang, Y.; Yu, K. Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud. Metals 2024, 14, 315. https://doi.org/10.3390/met14030315
Zhao Z, Zhang Y, Yu K. Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud. Metals. 2024; 14(3):315. https://doi.org/10.3390/met14030315
Chicago/Turabian StyleZhao, Zheng, Yanling Zhang, and Kan Yu. 2024. "Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud" Metals 14, no. 3: 315. https://doi.org/10.3390/met14030315