Mechanism of Floater Formation in the Mold during Continuous Casting of Ti-Stabilized Austenitic Stainless Steels
Abstract
:1. Introduction
2. Methodology
2.1. Characterization
2.2. Laboratory Investigations
3. Results and Discussions
3.1. Characteristic of Floater and 321 Stainless Steel
3.2. Thermodynamic Analysis of Inclusions of 321 Stainless Steel
3.3. Calculation of Planar Disregistry
- (hkl)s = a low-index plane of the substrate,
- [uvw]s = a low-index direction in (hkl)s,
- (hkl)n = a low-index plane in the nucleated solid,
- [uvw]n = a low-index direction in (hkl)n,
- d[uvw] = the interatomic spacing along [uvw]n,
- d[uvw]s = the interatomic spacing along [uvw]s, and
- θ = the angle between the [uvw]s and [uvw]n.
3.4. Characteristics of Inclusions in Floater and 321 Stainless Steel
3.5. Reaction Performances of Steel-Slag
4. Conclusions
- (1)
- The densities of the floaters at ambient temperature and 1450 °C were 7.53 g/cm3 and 6.83 g/cm3, respectively. These values were lower than the 321 steel. The liquidus temperature of the floater was 27 °C higher than the 321 steel, because of the differences in alloys composition.
- (2)
- Both the size and number density of TiN cluster and other inclusions in the floaters were larger than that in the 321 steel, which lead to the preferential nucleation of discrepant precipitates. The formation of floaters occurred during the casting of the 321 steel, which solidified with a preferential and primary precipitation of δ-Fe.
- (3)
- Calculations of the planar disregistry between the inclusions and the metallic phases showed that magnesium oxide, titanium carbide, and titanium nitride were very effective as nucleating agents for the δ-Fe phase, but inferior for the γ-Fe phase. In contrast, silicon dioxide, aluminum oxide and titanium dioxide were reasonably effective at nucleating γ-Fe but were poor at nucleating the δ-Fe phases. However, manganous oxide could not act as a nucleating agent for both phases.
- (4)
- The high-reactivity between slag and steel leads to variations in the SiO2 Al2O3, TiO2, and Na2O contents. Therefore, the basicity, melting temperature, and viscosity of the crust slag were higher than that of the liquid slag because of the high-reactivity with steel.
Author Contributions
Funding
Conflicts of Interest
References
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Samples | Fe | Ni | Cr | Ti | Mn | Si | Tm1 (°C) | ρ20 °C (g/cm3) | ρ1450 °C (g/cm3) |
---|---|---|---|---|---|---|---|---|---|
321 steel | 70.16 | 8.76 | 18.95 | 0.29 | 0.76 | 1.08 | 1441 | 7.92 | 6.98 |
Floater | 82.22 | 4.15 | 13.63 | - | - | - | 1468 | 7.53 | 6.83 |
Ladle | Tundish | Inlet of SEN | Outlet of SEN | TL1 |
---|---|---|---|---|
1600 | 1540 | 1480 | 1470 | 1441 |
Compound | Crystal System | Room Temperature, Lattice Parameter (Å) | 1450 °C, Lattice Parameter (Å) | Ref. | ||
---|---|---|---|---|---|---|
a0 | c0 | a0 | c0 | |||
γ- Fe | BCC | - | - | 3.681 | - | [27] |
δ-Fe | FCC | - | - | 2.9396 | - | [27] |
MgO | NaCl | 4.2112 | - | 4.3028 | - | [28] |
MnO | NaCl | 4.4457 | - | 4.5481 | - | [29] |
TiN | NaCl | 4.246 | - | 4.304 | - | [30] |
SiO2 | β-cristobalite | - | - | 7.1487 (1200 °C) | - | [31] |
Al2O3 | α-Al2O3 | 4.7589 | 12.991 | 4.8203 | - | [32] |
TiO2 | rutile | 4.5937 | 2.9587 | 4.6529 | 3.0063 | [33] |
Ti2O3 | α-Ti2O3 | - | - | 5.1251 | - | [34] |
Metallic Phase | MgO | MnO | TiC | TiN | SiO2 | Al2O3 | TiO2 | Ti2O3 |
---|---|---|---|---|---|---|---|---|
δ-Fe | 3.52 | 9.42 | 5.53 | 3.55 | 14.02 | 7.86 | 7.69 | 6.86 |
γ-Fe | 16.49 | 11.73 | 14.87 | 16.47 | 1.9 | 0.51 | 7.71 | 0.51 |
No. | Status | Basicity | SiO2 | CaO | Al2O3 | MgO | Na2O | TiO2 | Tm (°C) | η1300 °C (Pa·s) |
---|---|---|---|---|---|---|---|---|---|---|
1 | Initial slag | 0.78 | 30.79 | 23.87 | 6.7 | 3.18 | 11.57 | 0.18 | 1049 | 0.131 |
2 | Liquid slag | 0.97 | 24.51 | 23.69 | 7.63 | 3.21 | 8.18 | 7.4 | 1036 | 0.185 |
3 | Crust slag | 1.15 | 21.26 | 23.68 | 7.86 | 3.25 | 7.18 | 9.1 | 1270 | >2.0 |
4 | Exp. Liquid slag 1 | 0.91 | 25.73 | 23.37 | 7.69 | 3.58 | 9.18 | 8.2 | 1054 | 0.24 |
5 | Exp. Crust slag 1 | 1.1 | 21.47 | 23.7 | 9.62 | 3.4 | 11.49 | 9.6 | 1258 | - |
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Chen, Z.; Li, M.; Wang, X.; He, S.; Wang, Q. Mechanism of Floater Formation in the Mold during Continuous Casting of Ti-Stabilized Austenitic Stainless Steels. Metals 2019, 9, 635. https://doi.org/10.3390/met9060635
Chen Z, Li M, Wang X, He S, Wang Q. Mechanism of Floater Formation in the Mold during Continuous Casting of Ti-Stabilized Austenitic Stainless Steels. Metals. 2019; 9(6):635. https://doi.org/10.3390/met9060635
Chicago/Turabian StyleChen, Zhuo, Min Li, Xufeng Wang, Shengping He, and Qian Wang. 2019. "Mechanism of Floater Formation in the Mold during Continuous Casting of Ti-Stabilized Austenitic Stainless Steels" Metals 9, no. 6: 635. https://doi.org/10.3390/met9060635