Free Access
Issue
Metall. Res. Technol.
Volume 116, Number 6, 2019
Article Number 612
Number of page(s) 11
DOI https://doi.org/10.1051/metal/2019042
Published online 06 September 2019

© EDP Sciences, 2019

1 Introduction

High-grade type 304 stainless steel products, such as 2A, BA, 8K grade mirror plate, have high requirements on surface quality. However, there are always defects in the final products such as surface line-scale defect and point-shape defect after polishing, which seriously affect the appearance of the finished product [13]. It is mainly caused by the inclusions in stainless steel. Although the amount of B-type inclusion in Si-deoxidised stainless steel is very low, it is enough to cause various defects of the product. Calcium treatment can effectively modify the solid inclusions into the liquid ones in steelworks, which is advantageous for the mechanical properties of final steel production [47]. Owing to the importance of inclusions, scholars have conducted many researches on the inclusion control in stainless steel, such as size distribution, thermodynamic calculation, formation mechanism, reaction kinetics and dynamic evolution of the nonmetallic inclusions [816], mostly for Al-deoxidised stainless steel at steelmaking temperature. Until now, the researches involved in Si-deoxidised 304 stainless steel, especially the discussions on the relationship between industrial trial and thermodynamic calculation, are limited [1719]. Jong et al. [17] and Kim et al. [18] respectively clarified the formation mechanism of CaO-SiO2-Al2O3-MgO-TiO2 complex inclusion and spinel inclusions in Si-deoxidised stainless steel. Li et al. [19] studied the reoxidation behavior and inclusions in Si-deoxidised stainless steel in the tundish a casting sequence with three heats. It is not good for the optimization of refining process and the inclusion control in Si-deoxidised stainless steel. In addition, the composition and morphology of the inclusions at the solidification temperature are directly related to the properties of the inclusions in the final product. Less attention has been paid to the oxide inclusions at the solidification temperature.

In current work, the experiments with different element contents were conducted. The objective is to clarify the influence of initial aluminum content and calcium treatment intensity on the characteristics of inclusions in Si-deoxidized type 304 stainless steel. The samples were collected from AOD process to mold process; and the inclusions were detected and analyzed by field emission-scanning electronic microscope (FE-SEM). Meanwhile, the thermodynamics calculations on the stable phase diagrams including all possible inclusions in the range from 1673 to 1823 K were conducted. Present works would provide a few guides for the process optimization of Si-deoxidized type 304 stainless steel.

2 Methodology

2.1 Production process

The process route of Si-deoxidized stainless in a Chinese plant is as follows: submerged arc furnace → AOD (including ferrosilicon deoxidation) → ladle furnace (LF) refining (including feeding Ca-Si wire) → tundish → continuous casting. Three experimental heats were performed, in which two heats were deoxidized with low-Al ferrosilicon, and the other one with high-Al ferrosilicon. When the ladle reached the LF station, different amounts of Ca-Si wires were added into the ladle to modify the inclusions during calcium treatment process. Thereafter, liquid melt was cast into a six-strand curved-type continuous caster. The composition of ferrosilicon, ferromanganese and Ca-Si wire adopted in current research are listed in Table 1.

Table 1

The compositions of the ferrosilicon, ferromanganese and Ca-Si wire (mass.%).

2.2 Sampling and analysis approach

Specimens of molten steel and top slag were taken with pail samplers at the AOD-end of every heat, LF-start, after calcium-treatment, tundish and mold. The distribution of non-metallic inclusions in different positions into the samples can be heterogeneous, as was reported in some articles [2021]. Therefore, the same positions into the samples were selected for analysising. The schematic of the location the sample analyzed in current work is shown in Figure 1. The red area in the figure is the sampling position. The central part of each steel specimen was cut into two parts. One-half of the steel samples was used for chemical analysis by the inductively coupled plasma optical emission spectrometry (ICP-OES) with an accuracy of ± 0.5 ppm, and the total oxygen level of the sample was measured by the inert gas fusion-infrared absorptiometry technique with an accuracy of ± 1 ppm. Tables 2 and 3 show the compositions of the top slags and molten steel of the three heats. The same composition refining slag was adopted for all heats. In order to investigate the influence of the aluminum and calcium contents on the type of inclusion in steels, three aluminum and calcium addition content levels were designed and conducted in the present study. The experimental melts were divided into three types: low Al-low Ca (No. 1 heat), low Al-high Ca (No. 2 heat) and high Al-high Ca (No. 3 heat). In other word, two different levels of Ca-Fe wires were added to the steel, which represent different calcium-treatment intensities.

The other halves of the steel sample were prepared for characterization analysis of the inclusions. The morphology and composition of the inclusions were detected and analyzed by field scanning electron microscopy and energy dispersive spectroscopy (Zeiss Ultra-Plus) under 10-kV accelerating voltage to obtain the morphology, size, and chemical composition of the inclusions. Considering the accuracy, the smallest size of the inclusions that was analyzed in the present study is 0.5 µm. The planar size distribution of particles in the polished cross section of each sample was evaluated in this work. Total observed area of each sample was 19.86 mm2 which corresponds to the 36 observation areas consisting of the continuous six observation areas to the horizontal direction and the continuous six observation areas to the vertical direction at the magnification of 500 by using FE-SEM&EDS.

thumbnail Fig. 1

The schematic of the location of the sample analyzed in current work.

Table 2

Chemical compositions of the refining slag samples (mass.%).

Table 3

The compositions of the steel samples in different stages of all heats (mass.%).

3 Results and discussion

3.1 Types and morphologies of the typical inclusions

The morphology and composition of the inclusions can reflect their influence on the quality of steel product. The characters of the typical inclusion during the whole process of all three heats are shown in Figures 2 and 3. As present in Table 3, the Al content of No. 1 heat and No. 2 heat are relative lower than that of No. 3 heat. Figure 2 shows the morphology of the typical inclusions at the AOD end of No. 1 heat and No. 3 heat. Abundent spherical Al2O3-SiO2-type inclusions with a small content of MgO were observed at the end stage of AOD process in No. 1 heat, which contains a relative low Al content. However, the typical inclusions in the samples at the AOD end of No. 3 heat is an irrugular one, in which the high Al2O3 content was derived. Table 1 shows there is no Al in Ferromanganese.

The morphologies and types of the typical inclusions at LF refining, tundish, mold process of all three heats are shown in Figure 3. It is obvious that the Al2O3-SiO2-MgO type inclusion are transformed into the CaO-Al2O3-SiO2-MgO type inclusions after Ca treatment in LF refining process. It is worth to notice that the inclusions in the samples taken from all process in No. 1 heat are spherical. With the time increasing, the calcium content in the inclusions reduced from 25 mass pct at LF refining process to 16 mass pct at the cast process. It probably because that Ca is dispersed during the whole process. In general, comparing with No. 1 heat, the shape of the inclusions in No. 2 heat has no change from the calcium treatment at refining process. The only difference is a little increase in calcium content of the inclusions. The reason is that the addition amount of calcium in No. 2 heat is relatively higher than that of No. 1 heat, as present in composition table. The laws are nearly same as the massive data for many analyzed inclusions in the following section. As shown in Figure 3, the inclusions observed in the samples after calcium treatment of No. 3 heat are spherical ones. However, the SiO2-Al2O3 and the SiO2-Al2O3-CaO complex inclusions with a little amount of CaO were mainly observed at tundish process, and their morphologies were irregular. In the mold sample, most inclusions observed either as a pure Al2O3 or spinel inclusions, and others presented as the calcium aluminate.

To summarize, the inclusions were mainly of the spherical ones in No. 1 and No. 2 heat, while they were of the irregular ones in No. 3 heat, wherein the Al2O3 content in the inclusions is higher due to the addition of aluminum in ferrosilicon.

thumbnail Fig. 2

The morphology and types of the typical inclusions at the AOD end of No. 1 heat and No. 3 heat.

thumbnail Fig. 3

The morphologies and types of the typical inclusions at LF refining, tundish, mold process of all three heats.

3.2 Evolution of the inclusion composition during the whole process

The liquidus temperature as well as solidus temperature of the steel adopted in current work can be evaluated by using the empirical formula reported by Choudhary and Ghosh [22], as shown in equations (1) and (2). According to the steel composition listed in Table 3, the liquidus and the solidus temperature are respectively about 1463 °C (1736 K) and 1446 °C (1719 K) by calculation. (1) (2) where TL is the liquidus temperature and TS is the solidus temperature.

From the view of the inclusion control, the morphology of the inclusions before and during the solidification process has direct effect on the characteristic of the inclusions in final products. Therefore, the inclusion control of the molten steel at solidification temperature is significant to improve the quality of the product. Therefore, the 1823 K (refining temperature) and 1673 K (under solidification temperature) are two key temperatures to addressed in current work. Furthermore, the inclusions involved in all heats have a certain content range from 2 to 10% MgO. So, the Al2O3-SiO2-MgO ternary phase diagram and Al2O3-SiO2-CaO-5%MgO pseudo-ternary phase diagram at p(O2) = 10−14 atm were selected to analyse the variation of the inclusion composition in the current study. They were calculated by thermodynamics software (FactSageTM 7.2) with the FToxide database, as shown in Figure 4. As presented, solid phases, such as SiO2, Al2O3, CaO, MgO, calcium–aluminate, mullite, spinel and some other complex phases, are shown to be in equilibrium with the liquid phase. It is remarkable that the liquid region at 1823 K (1550 °C) is large. In other word, the inclusion in the molten steel can be easily controlled in this region. It is consistent with the actual production process of the steel, which has no clogging problem at all. However, as can be seen from Figure 4a, the 1673 K (1400 °C) liquid phase area of the Al2O3-SiO2-MgO phase diagram is very small. It requires calcium treatment to move the inclusion composition into the 1673 K (1400 °C) liquid phase region of the Al2O3-SiO2-CaO-5%MgO phase diagram, as shown in Figure 4b.

To assess the transient behavior of the inclusion, the compositions obtained from FE-SEM&EDS are converted into mass fractions of Al2O3, SiO2, MgO, and CaO, which are then plotted on the above system phase diagram, as presented in Figures 57. Each plot represents an individual inclusion, and the red lines are the 1673 K (1400 °C) liquid line. The experiment found that the oxide inclusions were mainly of the Al2O3-SiO2-MgO system at the end of the AOD process and the start of the LF process. Thereafter, the inclusions were modified to the ones that contained a small amount of MgO (about 5 mass percent) at Ca treatment process in the LF refining process, the tundish process and the mold process. It can be clearly seen in Figures 5a and 5b that most oxide inclusions in No. 1 heat at the end of the AOD process and the start of the LF process is complex inclusion of mullite or (and) MgO. It is because that the aluminum content of No. 1 heat is about 30 ppm, and it is relative low after deoxidation process. The compositions of all inclusions in the LF sample after Ca treatment locate in the CaSiO3 (CaO · SiO2) or CaAl2Si2O8 (CaO · Al2O3 · 2SiO2) region, and the composition of the inclusion in tundish and mold gradually move into the CaAl2Si2O8 region. The compositions of the inclusion in the samples after Ca treatment ([Ca] = 10 ppm) all locate in the liquid region.

It can be seen from the composition table that No. 2 heat has similar composition to No. 1 heat, especially the content of aluminum. Therefore, the compositions of the inclusions in LF start stage samples of No. 2 heat are also located in the SiO2 or mullite phase region as shown in Figure 6a. It makes that the position of the inclusion compositions shifts throughout the process. A greater strength of the calcium treatment is adopted in No. 2 heat, namely, No. 2 heat has higher calcium content (about 25 ppm). Therefore, after the calcium treatment, the inclusion composition is not only located in the region of CaSiO3 or CaAl2Si2O8, but also located in the region of Ca2SiO4 and Ca2Al2SiO7. The increase of CaO content of inclusions significantly increases the melting point of the inclusions, and some other inclusions have deviated from the liquid phase region. Even pure CaO inclusions can be observed in the sample. Subsequently, the inclusions in the tundish and mold samples are completely transformed into CaSiO3 or CaAl2Si2O8 complex inclusions. Therefore, excessive calcium treatment can reduce the proportion of liquid phase inclusions.

A higher amount of aluminum is added into the steel during AOD deoxidation process of No. 3 heat, to further decrease the oxygen content of the steel. However, a relative higher content of aluminum (120 ppm) has a significant influence on the type and composition of the inclusion existed in steel. As shown in Figures 7a and 7b, the type of the inclusions in the samples taken from the end of the AOD process and the start of the LF process are spinel inclusions except for SiO2 or mullite phase observed in No. 1 and No. 2 heat. As observed in the samples after calcium addition, the composition of the inclusions shows significant scattering trend. However, the compositions of inclusions in the tundish and mold samples are mainly distributed in the regions of CaMg2Al16O27 (CaO · 6Al2O3 + 2MgO · Al2O3) and alumina. The inclusions are mostly solid, and such hard inclusions are easy to produce defects in final products. It can be easily seen that the content of aluminum in steel also plays an important role in the control of inclusions.

thumbnail Fig. 4

Phase diagram of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems with 1673 K liquidus (red line) and 1823 K liquidus (blue line) at p(O2) = 10−14 atm.

thumbnail Fig. 5

The phase diagram, 1673 K liquidus (red line) and 1823 K liquidus (blue line) of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems and with experimental data in No. 1 heat.

thumbnail Fig. 6

The phase diagram, 1673 K liquidus (red line) and 1823 K liquidus (blue line) of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems and with experimental data in No. 2 heat.

thumbnail Fig. 7

The phase diagram, 1673 K liquidus (red line) and 1823 K liquidus (blue line) of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems and with experimental data in No. 3 heat.

3.3 Size distribution of the inclusions during the whole process

The size distribution of the inclusions in the whole process were analyzed by FE-SEM with magnification 500 times, and the inclusions were classified into four classes of 0.5–2, 2 to 5, 5 to 10, and > 10 µm. However, too small (< 0.5 µm) or too large (> 15 µm) inclusions are respectively considered as solidified precipitates and liquid slag entrainment, and they are not counted during the statistics process. The size distributions of the inclusions in the steels are summarized in Figure 8. In general, the proportion of inclusions smaller than 2 µm are about 70 ∼ 85% from AOD end to LF start in all heat, while it slightly increases at calcium treatment process. Thereafter, this value shows an obvious decrease tendency during the later process (the tundish and the mold). It is worth noting that the tundish and mold sample of No. 3 heat have a little more larger inclusions (> 2 µm) than that of No. 1 and No. 2 heat. It is probably because that the solid inclusions show a stronger aggregation tendency than liquid inclusions in current study.

The number density and average size of the inclusions for three heats, as respectively marked with bar and plot, are shown in Figure 9. The number density of the inclusions in the samples, which is taken from the start stage of LF process, is nearly identical in all heat. Through the process of calcium treatment, the number of inclusions sharply increased in all heats. However, the number of inclusions in the tundish and mold samples of No. 3 heat is significantly lower than that of No. 1 and No. 2 heat. It may be related to the decrease in the proportion of small size inclusions shown in Figure 8. On the other hand, the average size of inclusions in all heats decreases obviously from AOD end to calcium treatment, suggesting that LF refining is very effective for controlling the inclusion size. Nevertheless, it increases in the tundish and mold process. It is specially mentioned that the average size of the inclusions in No. 3 heat has a larger size than the other two heats.

thumbnail Fig. 8

Size distribution of the observed inclusions in all melts (parameter A presents AOD end, L-LF start, C-after calcium treatment, T-Tundish, M-Mold).

thumbnail Fig. 9

Number density (bar) and average size (plot) of the observed inclusions in all melts (parameter A presents AOD end, L-LF start, C-after calcium treatment, T-Tundish, M-Mold).

3.4 Thermodynamic consideration of Si-Al–Ca–O system complex inclusions in Si-deoxidized stainless steel

Thermodynamic calculations were carried out to explain the modification of inclusions in different processes. Therefore, the equilibrium relationships of [Al], [Ca] content and the generated inclusions at 1823 K (1550 °C) and 1673 K (1400 °C) were calculated using Factsage 7.2 with the FToxid, FactPS and FSstel databases, to get a clear understanding of the evolution mechanism of the inclusions in Fe-Cr-Ni-Si-Al-Ca-O melt, as shown in Figure 10.

Figures 10a and 10b show that the initial steel compositions of Fe-Cr-Ni-Si-Al-Ca-O in mass pct with various aluminum and calcium contents were calculated at 1823 K (1550 °C). As shown in Figure 10a, when [Al] = 0.003 pct in the melts, there is a liquid inclusion region in the melt with a relatively lower calcium content (less than 25 ppm). When Ca content of the melt is higher than 30 ppm, Ca2SiO4 type oxide inclusions are generated in the melt. However, when [Al] = 0.012 pct in the melt, the precipitation curves are the very opposite of the above situation. It can be clearly seen in Figure 10b that liquid inclusion would be formed in the melt, which contains more calcium (more than 24 ppm). If the calcium content of the melt increases to 40 ppm, the solid Ca2SiO4 phase begins to appear in the melt.

Although the refining temperature is about 1823 K (1550 °C), as calculated above, the solidification temperature of the steel is over 1673 K (1400 °C). The characters of inclusions during the solidification process are crucial to the final product quality. Therefore, the equilibrium relation between the inclusion and the element content of molten steel is also calculated and shown in Figures 10c and 10d. Figure 10c shows that when [Al] = 30 ppm in the melts, the liquid region of the inclusions only exists under low Ca content (less than 10 ppm). Although, in the interval of Ca addition amount between 10 and 25 ppm, the inclusion in steel is liquid at the refining temperature, it is gradually transformed into Ca2Al2SiO7 type solid phase inclusion during the solidification process. The same situation happens in high aluminum content (0.012 mass.%) of steel. There is hardly any liquid inclusion precipitated at 1673 K (1400 °C), and no matter how much calcium content in the steel. The hard inclusions produced in the solidification process will have much adverse effect on the quality of steel products.

For the usual case of Si-deoxidized stainless steel in current article, the typical inclusions generated in the steel during solidification process were also analyzed. As presented in Figure 11a, when [Al] = 30 ppm and [Ca] = 10 ppm, the liquid phase exists at 1823 K (1550 °C) in steel. During the solidification process of the steel, the transformed trajectory of oxide inclusions is liquid inclusion → CaO · 6Al2O3 → CaAl2Si2O6 → mullite → Al2O3. However, if the calcium content of steel reaches to 25 ppm, solid inclusion (Ca2Al2SiO7) can be generated at a relative high temperature (1793 K). As the temperature decreases, CaO · 2Al2O3, CaO · 6Al2O3, Al2O3 will successively precipitate, as shown in Figure 11b. On the other hand, the precipitation phase and amount of the melt with 0.012 pct aluminum and 30 ppm calcium are very different to above. The main inclusions in the melt are solid calcium aluminates during solidification process, replacing the Ca-Si-Al-O complex inclusion, as presented in Figure 11c.

It can be summarized that an appropriate calcium treatment level contributes to modify inclusions to liquid ones in Si-deoxidized steel, comparing the observed inclusions with the thermodynamic calculation results. Different amount of calcium should be added to the steel with different initial aluminum content. It is easily summarized that lower aluminum content is necessary to modify the inclusions into the liquid phase ones by calcium treatment. If aluminum content is too high, liquid inclusion is only generated at 1823 K, and it will be modify to the solid ones during the following process. Therefore, the calcium addition amount of Si-deoxidized steel needs to control to a relatively lower value.

thumbnail Fig. 10

Equilibrium precipitation of inclusions for Fe-Cr-Ni-Si-Al-Ca-0.005O in mass pct steel different temperature: (a) Al = 0.003 pct, T = 1823 K; (b) Al = 0.012 pct, T = 1823 K; (c) Al = 0.003 pct, T = 1673 K; (d) Al = 0.012 pct, T = 1673 K.

thumbnail Fig. 11

Equilibrium precipitation of inclusions during solidification for steel of composition, Fe-Cr-Ni-Si-Al-Ca-0.005O in mass pct: (a) Al = 0.003 pct, Ca = 0.001 pct; (b) Al = 0.003 pct; Ca = 0.0025 pct; (c) Al = 0.012 pct, Ca = 0.003 pct.

4 Conclusions

Inclusion evolutions after calcium addition in Si-deoxidized stainless steels with different aluminum content have been carried out by the experiments and thermodynamics calculations. The main findings can be summarized as follows.

The morphology, composition and size distribution of the oxide inclusions in Si-deoxidized stainless steels are significantly influenced by aluminum and calcium content during the whole production process. It can be summarized that appropriate calcium treatment intensity could modify inclusions into liquid ones in the molten steel. Although spherical inclusions can also be formed under excessive calcium treatment ([Ca] = 25 ppm), the melting point is obviously increased. Therefore, the calcium treatment intensity of Si-deoxidized stainless steels should be controlled to a relatively lower value ([Ca] = 10 ppm). In addition, the content of aluminum in steel also has an important influence on the inclusion control. When the content of aluminum ([Al] = 0.012%) is too high, the inclusions in steel are difficult to be controlled within the liquid phase. The evolution of the inclusions in steel at high temperature and during solidification process were comprehensively calculated, considering all types of inclusions such as calcium oxide, aluminum oxide, silicon oxide, calcium aluminate, calcium silicate, mullite, and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of the inclusions in Si-deoxidized stainless steels.

Acknowledgments

The authors wish to thank the National Natural Science Foundation of China (U1760202) and Guangdong Guangqing Metal Technology Co., Ltd for the financial support.

References

  1. J.H. Park, H. Todoroki, ISIJ Int. 50, 1333–1346 (2010) [CrossRef] [Google Scholar]
  2. S. Inada, H. Todoroki, No. 182nd and 183rd Nishiyama Memorial Seminar, ISIJ, Tokyo, 2004, p. 227 [Google Scholar]
  3. L. Zhang, B.G. Thomas, ISIJ Int. 43, 271–291 (2003) [CrossRef] [EDP Sciences] [Google Scholar]
  4. T. Zhang, Y. Min, C. Liu, M. Jiang, ISIJ Int. 55, 1541–1548 (2015) [CrossRef] [Google Scholar]
  5. J.H. Park, D.S. Kim, S-B Lee, Metall. Trans. B 36B, 67–73 (2005) [CrossRef] [Google Scholar]
  6. T. Zhang, Y. Min, C. Liu, M. Jiang, ISIJ Int. 57, 314–321 (2017) [CrossRef] [Google Scholar]
  7. C. Shi, W. Yu, H. Wang, J. Li, M. Jiang, Metall. Trans. B 48B, 146–161 (2017) [CrossRef] [Google Scholar]
  8. T. Nishi, K. Shimme, Tetsu-to-Hagané 84, 837–843 (1998) [CrossRef] [Google Scholar]
  9. G. Okuyama, K. Yamauchi, S. Takeuchi, K. Sorimachi, ISIJ Int. 40, 121–128 (2000) [CrossRef] [Google Scholar]
  10. H. Matsuno, Y. Kikuchi, Tetsu-to-Hagané 88, 48–50 (2002) [CrossRef] [Google Scholar]
  11. H. Todoroki, K. Mizuno, ISIJ Int. 44, 1350–1357 (2004) [CrossRef] [Google Scholar]
  12. W.Y. Cha, D.S. Kim, Y.D. Lee, J.J. Pak, ISIJ Int. 44, 1134–1139 (2004) [CrossRef] [Google Scholar]
  13. J.H. Park, D.S. Kim, Metall. Trans. B 36B, 495–502 (2005) [CrossRef] [Google Scholar]
  14. J.H. Park, J. Am. Ceram. Soc. 89, 608–615 (2006) [Google Scholar]
  15. J.H. Park, Mater. Sci. Eng. A 472, 43–51 (2008) [CrossRef] [Google Scholar]
  16. Y. Ren, L. Zhang, P.C. Pistorius, Metall. Trans. B 48B, 2281–2292 (2017) [CrossRef] [Google Scholar]
  17. J.W. Kim, K.S. Kim, D.S. Kim, D.Y. Lee, K.P. Yang, ISIJ Int. 36, S140–143 (1996) [CrossRef] [Google Scholar]
  18. Y. Ehara, S. Yokoyama, M. Kawakami, Tetsu-to-Hagané 93, 208–214 (2007) [CrossRef] [Google Scholar]
  19. S. Li, L. Zhang, Y. Ren, W. Fang, W. Yang, S. Shao, J. Yang, W. Mao, ISIJ Int. 56, 584–593 (2016) [CrossRef] [Google Scholar]
  20. O.T. Ericsson, A.V. Karasev, P.G. Jönsson, Steel Res. Int. 82, 222–229 (2011) [CrossRef] [Google Scholar]
  21. Z. Zhang, A. Tilliander, A. Karasev, P.G. Jönsson, ISIJ Int. 50, 1746–1755 (2010) [CrossRef] [Google Scholar]
  22. S.K. Choudhary, A. Ghosh, ISIJ Int. 49, 1819–1827 (2009) [CrossRef] [Google Scholar]

Cite this article as: Wanlin Wang, Liwen Xue, Tongsheng Zhang, Lejun Zhou, Daoyuan Huang, Weiguang Tian, Jialin Xu, Thermodynamics and transient behavior of the inclusion in Si deoxidized stainless steel for high-grade plate, Metall. Res. Technol. 116, 612 (2019)

All Tables

Table 1

The compositions of the ferrosilicon, ferromanganese and Ca-Si wire (mass.%).

Table 2

Chemical compositions of the refining slag samples (mass.%).

Table 3

The compositions of the steel samples in different stages of all heats (mass.%).

All Figures

thumbnail Fig. 1

The schematic of the location of the sample analyzed in current work.

In the text
thumbnail Fig. 2

The morphology and types of the typical inclusions at the AOD end of No. 1 heat and No. 3 heat.

In the text
thumbnail Fig. 3

The morphologies and types of the typical inclusions at LF refining, tundish, mold process of all three heats.

In the text
thumbnail Fig. 4

Phase diagram of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems with 1673 K liquidus (red line) and 1823 K liquidus (blue line) at p(O2) = 10−14 atm.

In the text
thumbnail Fig. 5

The phase diagram, 1673 K liquidus (red line) and 1823 K liquidus (blue line) of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems and with experimental data in No. 1 heat.

In the text
thumbnail Fig. 6

The phase diagram, 1673 K liquidus (red line) and 1823 K liquidus (blue line) of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems and with experimental data in No. 2 heat.

In the text
thumbnail Fig. 7

The phase diagram, 1673 K liquidus (red line) and 1823 K liquidus (blue line) of the Al2O3–SiO2–MgO and Al2O3–SiO2–CaO–5%MgO systems and with experimental data in No. 3 heat.

In the text
thumbnail Fig. 8

Size distribution of the observed inclusions in all melts (parameter A presents AOD end, L-LF start, C-after calcium treatment, T-Tundish, M-Mold).

In the text
thumbnail Fig. 9

Number density (bar) and average size (plot) of the observed inclusions in all melts (parameter A presents AOD end, L-LF start, C-after calcium treatment, T-Tundish, M-Mold).

In the text
thumbnail Fig. 10

Equilibrium precipitation of inclusions for Fe-Cr-Ni-Si-Al-Ca-0.005O in mass pct steel different temperature: (a) Al = 0.003 pct, T = 1823 K; (b) Al = 0.012 pct, T = 1823 K; (c) Al = 0.003 pct, T = 1673 K; (d) Al = 0.012 pct, T = 1673 K.

In the text
thumbnail Fig. 11

Equilibrium precipitation of inclusions during solidification for steel of composition, Fe-Cr-Ni-Si-Al-Ca-0.005O in mass pct: (a) Al = 0.003 pct, Ca = 0.001 pct; (b) Al = 0.003 pct; Ca = 0.0025 pct; (c) Al = 0.012 pct, Ca = 0.003 pct.

In the text

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.