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Influence of phase distribution of converter slag microzones on the occurrence of P

  • Chenxiao Li EMAIL logo , Shuai Tong , Yuekai Xue and Shuhuan Wang
Published/Copyright: March 3, 2021
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High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 40 Issue 1

Abstract

The phase and element distribution of converter slag was analyzed with the backscattered electron (BSE) images of scanning electron microscopy and X-ray energy spectrum. The results show that the Ca and Si are attached in the slag micro-area, while the Fe is present in areas with less Ca and Si. Most of the P appear in areas with more Ca and Si. The content of SiO2 tends to increase with an increase in the CaO content in the slag micro-area. The activity of a CaO increases with an increase in the CaO content in the slag micro-area, while the activity of a FeO increases first and then decreases. In the slag micro-area with an increase in the FeO content, both the mole fraction and the activity coefficient of SiO2 decrease; so, the content of SiO2 decreases gradually.

Keywords: converter slag; phosphorus occurrence; micro-area; calcium oxide; activity

1 Introduction

The converter slagging dephosphorization process is one of the main tasks in the steelmaking process, its importance is self-evident [1,2]. The formation of slag and the distribution of each oxide phase directly affect the slag phosphorus capacity, thereby affecting the slag phosphorus distribution ratio. The formation of slag involves a series of physical and chemical effects. The components of converter slag-making are diverse, and the formation of slag is complex with many influencing factors. However, there are some links in the mineral distribution of slag, because the mineral composition and crystallization state are closely related to the smelting and slagging process. Hence, it is helpful to study the distribution of oxides in the slag micro-area for improving the slagging process. Also, phosphorus enrichment in the slag is more closely related to the distribution of the microregions. It can be seen that the research on the distribution of each oxide phase in the slag micro-area can not only clarify the slag formation process but also further lay the foundation for studying the occurrence of P regularity to optimize converter dephosphorization [3,4,5]. The formation of f-C2S in the slag affects the content of P2O5 in the phosphate-rich phase nC2S-C3P [6,7]. The FeO content in the micro-area affects both the activity coefficient of P2O5 and the enrichment of P elements. It can be seen that the research on the distribution of each oxide phase in the slag micro-area can not only clarify the slag formation process but also further lay the foundation for studying the occurrence of P regularity. In this paper, the slag formation mechanism was analyzed by the backscattered electron image of cold slag, which focuses on CaO, SiO2, FeO oxide distribution behavior.

2 Experimental methods

Under normal smelting conditions, the earlier slag and the final slag are sampled and slowly cooled in a company’s converter double slag process operation, and the treated steel slag is in a gray block shape. The main component of the earlier and final slag was analyzed by XRF. The analysis results are shown in Table 1.

Table 1

Slag composition (wt)/%

TFe CaO SiO2 MgO MnO P2O5 S
Earlier slag 14.4–21.2 25.7–36.9 16.2–23.7 6.0–11.3 4.3–7.8 2.6–5.0 0.03–0.05
Final slag 17.3–26.8 31.6–44.8 8.8–14.7 7.5–16.8 1.9–3.6 1.80–2.91 0.04–0.14

The industry tests are a total of five heats, ten slags. In addition, the phase composition and elemental distribution of earlier and final slag from the different furnaces are observed by electron backscattered diffraction (EBSD). The analysis results show the contents of Ca, Si, Fe, and P in different phases [7]. Then, the content of each element in a different slag phase is summarized.

3 Results and discussion

The EBSD is used to analyze the earlier slag and final slag in converter smelting. The scanning image of the representative phase is shown in Figure 1. According to the principle of backscatter electron imaging, the smaller the atomic number of a substance is, the darker the image is. The atomic number of the major elements in the slag is in turn Fe, Ca, Si, Mg, and O. Hence, the color of the phase can reflect its chemical composition [8,9,10]. According to Figure 1, the type of steel slag is divided into three types: black, gray, and off-white.

Figure 1 Backscattered electron images of each phase in the converter slag.
Figure 1

Backscattered electron images of each phase in the converter slag.

The elemental composition can be obtained by energy spectrum analysis of different color phases in the slag zone. The elements in the microregion of the representative phase are shown in Table 2, which corresponds to Figure 1. The contents of Ca, Fe, Si, and P element are analyzed and studied emphatically. According to the results of energy spectrum analysis, the gray-white phase is mostly ferrite phase, namely ferrite phase and ferric acid dihydrate, the gray matter is mainly silicate phase, and the black matter is RO phase.

Table 2

EDS of each phase in converter slag

Spectrum O Mg Si P Ca Fe CaO/SiO2
Spectrum 1 42.52 30.84 1.12 — 6.10 17.00 3.56
Spectrum 2 42.60 28.52 1.10 — 6.54 18.88 3.88
Spectrum 3 41.98 30.84 1.10 — 5.81 17.54 3.45
Spectrum 4 44.54 1.24 10.21 2.36 33.30 7.22 2.13
Spectrum 5 45.29 1.51 10.29 2.58 32.85 7.09 2.09
Spectrum 6 39.46 2.60 2.20 — 20.58 30.96 6.11
Spectrum 7 39.49 3.10 2.85 0.41 21.32 28.94 4.89

In this paper, phase analysis of different microregions of 10 slags was performed, and more than 130 sets of data similar to Table 2 were obtained. According to the content of Ca, Fe, and Si in the slag microregion, element content was converted into the corresponding oxide content ratio, and then the distribution characteristics between the three oxides in the micro-region were researched.

3.1 Elemental distribution of slag microzone

Figure 2 shows the backscatter images and elemental distributions of 1# converter slag.

Figure 2 Backscattered electron image and elements distribution of 1# converter slag.
Figure 2

Backscattered electron image and elements distribution of 1# converter slag.

It can be seen from Figure 2 that in the microscopic area of the slag, the Ca are mostly attached to the Si elements. While Fe is present in areas with less Ca and Si, which presents an alternative trend. Most of P occurs in areas with high Ca and Si contents [8,9].

3.2 Distribution of CaO, FeO, SiO2 in slag micro-area

To quantitatively study the distribution characteristics of Fe, Si, and Ca in the slag micro-area, the analysis data of different microregions are summarized and analyzed. Table 2 is the ratio of the quality score of each element of the management region, while the molar ratio of each element is obtained by dividing the mass fraction with the molar mass. The molar ratio of the element is the molar ratio of its simple oxide. CaO, FeO, and SiO2 are the main compositions of the slag oxide, and the proportion of the three added together is above 60%. Therefore, the slag formation process can be understood by studying the distribution characteristics of CaO, FeO, and SiO2 in the slag micro-area. First, CaO was used as the matrix to study the distribution relationship of CaO, FeO, and SiO2 in earlier slag and final slag. Figure 3 shows the distribution characteristics of CaO and SiO2 in the earlier slag and the final slag.

Figure 3 Distribution characteristics of CaO and SiO2 in the slag micro-area phase.
Figure 3

Distribution characteristics of CaO and SiO2 in the slag micro-area phase.

As can be seen from Figure 3, the content of CaO is small in the micro-area of earlier slag. With an increase in the CaO content, SiO2 becomes larger, and the trend of change is uniform. Compared with the earlier slag, the content of CaO in the final slag is large, and with an increase in the CaO content, SiO2 in the micro-area increases.

According to the slag molecular theory, CaO belongs to basic oxide, SiO2 belongs to acidic oxide, and both can react to form calcium silicate. At the steel-making temperature, silicates may exist in the form of CaSiO3, Ca2SiO4, and Ca3SiO5. Figure 4 shows that the SiO2 content gradually increases with an increase in CaO in the micro-area. Figure 2 shows that the Ca and Si are attached to each other. The steelmaking slag is mainly CaO–SiO2–FeO–MgO four-component slag system; the analysis result indicates that the CaO activity (a CaO) increases with the addition of CaO content, while the activity of SiO2 ( a SiO 2 ) in the micro-area also increases.

Figure 4 Distribution characteristics of CaO and FeO in the slag micro-area phase.
Figure 4

Distribution characteristics of CaO and FeO in the slag micro-area phase.

Figure 4 shows the distribution characteristics of CaO and FeO in the earlier slag and the final slag.

Figure 4 shows that in the earlier slag and final slag micro-areas, although the FeO and CaO contents are different, the changing trends of the two are consistent. With an increase in the CaO content, FeO in the micro-area first increases and then decreases. According to the changing trend, it is known that a CaO increases with an increase of CaO content in the slag micro-area, while the activity of a FeO increases first and then decreases in the micro-area. Because CaO content is small in the slag micro-area, CaO is more alkaline than FeO; hence, CaO is combined with acidic substances such as SiO2 in the slag, which results in an increase of free FeO content in the slag and an increase of a FeO in the slag. However, when the content of CaO is higher than a certain value, the increase of CaO will result in a decrease in the FeO mole fraction. However, the addition of CaO content increases the FeO activity coefficient [10]. But, the combined effect of two is the decrease in a FeO.

Figure 5 shows the distribution characteristics of SiO2 and FeO in the earlier slag and the final slag.

Figure 5 Distribution characteristics of SiO2 and FeO in the slag micro-area phase.
Figure 5

Distribution characteristics of SiO2 and FeO in the slag micro-area phase.

Figure 5 shows that with an increase in the FeO content, the SiO2 gradually decreases in the earlier and final slag. They exhibit anti-correlation properties because FeO is a basic oxide and SiO2 is an acidic oxide, both of which react to form complex compounds. With an increase in the FeO content in the slag micro-area, the melting point and viscosity of the slag are reduced, and the fluidity of the slag becomes better, which is conducive to mass transfer. The mole fraction of SiO2 and the activity coefficient of SiO2 decreased, so that the content of SiO2 in the slag decreased [11,12,13]. Figure 5 shows that both CaO and SiO2 oxides appear to be substitutable in the slag micro-area; that is, the existence of oxide is bound to reduce the activity of another oxide.

4 Conclusions

In the present work, the oxides’ distribution behavior of CaO–SiO2–FeO–P2O5 in converter slag micro-area was investigated. The main conclusions are described as follows:

  1. Most of Ca are attached to the Si in the slag micro-area, while the Fe is present in the areas with less Ca and Si, which shows an alternative trend. The P is mostly found in areas where there are more Ca and Si. And, O shows an average distribution in the micro-area.

  2. With an increase in the CaO content, the a CaO increased and the content of SiO2 in the micro-area increased. In the micro-area, the influence of CaO content on the FeO content is consistent, and the a CaO increases with an increase in the CaO content, while the a FeO first increases and then decreases.

  3. In the earlier and the final slag micro-area, with an increase in the FeO content, the mole fraction and the activity coefficient of SiO2 decrease.

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  1. Funding information: The presented research was supported by the National Natural Science Foundation of China (52004097).

  2. Author contributions: Yuekai Xu contributed to the conception of the study; Shuai Tong performed the experiment; Chenxiao Li performed the data analyses and wrote the manuscript; Shuhuan Wang helped perform the analysis with constructive discussions.

  3. Conflict of interest: The authors have no conflicts of interest to declare.

  4. Data availability statement: All authors follow the data sharing policy, and all research data in the article can be shared and widely available to the research community by the request.

References

[1] Wang, X. H. Steel Metallurgy, Education Press, Beijing, 2007, pp. 13–20.10.1016/S1005-8850(06)60065-0Search in Google Scholar

[2] Qu, Y. Principles of Steelmaking, Metallurgical Industry Press, Beijing, 1980, pp. 53–55.Search in Google Scholar

[3] Aratani, F. Kinetic study of dephosphorization of liquid Fe solid CaO, Tetsu-to-Hagane, Vol. 58, No. 9, 1972, pp. 1217–1224.10.2355/tetsutohagane1955.58.9_1217Search in Google Scholar

[4] Kitamura, S., N. Sato, and K. Okohira. Dephosphorization and desulfurization of hot metal by CaO based fluxes containing Fe-oxide and Mn-oxide as oxidant, Transactions of the Iron and Steel Institute of Japan, Vol. 28, No. 5, 1988, pp. 364–371.10.2355/isijinternational1966.28.364Search in Google Scholar

[5] Swinnerton, M. The influence of slag evolution on BOF dephosphorisation. Master Dissertation, University of Wollongong, Australia, 2005.Search in Google Scholar

[6] Xin, Q. Theoretical and experimental research on the slag formation route of the converter dual dephosphorization process, Chongqing University, China, 2013.Search in Google Scholar

[7] Kitamura, S. and H. Aoki. Dephosphorization reaction of chromium containing molten iron by CaO-based flux, ISIJ International, Vol. 34, No. 5, 1994, pp. 401–407.10.2355/isijinternational.34.401Search in Google Scholar

[8] Sane, W. P., M. Hirasawa, and K. Mori. Kinetics of phosphorus transfer between iron oxide containing slag and molten iron of high carbon concentration under Ar-O2 atmosphere, ISU International, Vol. 33, No. 4, 1993, pp. 479–487.10.2355/isijinternational.33.479Search in Google Scholar

[9] Wang, N., Z. G. Liang, and Z. S. Zou. Phosphorous enrichment in molten adjusted converter slag: part II enrichment behavior of phosphorus in CaO-SiO2-FeOx-P2O5 molten slag, Journal of Iron and Steel Research International, Vol. 18, No. 12, 2011, pp. 22–26.10.1016/S1006-706X(12)60004-1Search in Google Scholar

[10] Zhao, L. H., Y. J. Zhang, H. M. Zhou, P. Xu, and Y. P. Bao. The effects of different P2O5 content and basicity on phosphorus enrichment in the CaO-SiO2-FetO-P2O5 slag system, High Temperature Materials and Processes, Vol. 34, No. 7, 2015, pp. 55–63.10.1515/htmp-2014-0089Search in Google Scholar

[11] Zhou, H. M., Y. P. Bao, and L. Lin. Distribution of P2O5 between phosphorus-enrichment phase and matrix phase in phosphorus slag, Steel Research International, Vol. 84, No. 9, 2013, pp. 78–86.10.1002/srin.201200231Search in Google Scholar

[12] Kim, K. D., W. H. Wan, and J. M. Dong. Effect of FeO and CaO on the sulfide capacity of the ferronickel smelting slag, Metallurgical and Materials Transactions B, Vol. 45, No. 3, 2014, pp. 889–895.10.1007/s11663-013-9994-6Search in Google Scholar

[13] Kojima, Y., M. Inouye, and K. Sano. The activity of the iron oxide in FeO-MgO-SiO2 slag at 1600°C, Archiv Eisenhuttenwesen, Vol. 40, No. 1, 1969, pp. 37–46.10.1002/srin.196901732Search in Google Scholar
Received: 2020-07-17
Revised: 2020-11-23
Accepted: 2021-01-12
Published Online: 2021-03-03

© 2021 Chenxiao Li et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/htmp-2021-0012
Keywords for this article
converter slag; phosphorus occurrence; micro-area; calcium oxide; activity
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Fused deposition modeling of poly(ether ether ketone) scaffolds
  3. Investigation of the microstructure evolution in TP347HFG austenitic steel at 700°C and its characterization method
  4. Hot deformation behavior and processing maps of 9Cr3W3Co oxide dispersion-strengthened steel
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  7. Investigation on ultrasonic assisted friction stir welding of aluminum/steel dissimilar alloys
  8. Analysis of oxide scale thickness and pores position of HCM12A steel in supercritical water
  9. Behavior of MnS inclusions during homogenization process in low-alloyed steel FAS3420H
  10. Preparation and cutting performance of nano-scaled Al2O3-coated micro-textured cutting tool prepared by atomic layer deposition
  11. Prediction of hot metal temperature based on data mining
  12. Effect of TiO2 content in slag on Ti content in molten steel
  13. Performance evaluation of titanium-based metal nitride coatings and die lifetime prediction in a cold extrusion process
  14. Effect of different drilling techniques on high-cycle fatigue behavior of nickel-based single-crystal superalloy with film cooling hole
  15. Effect of CO2 injection into blast furnace tuyeres on the pulverized coal combustion
  16. Microstructure and properties of Co–Al porous intermetallics fabricated by thermal explosion reaction
  17. Evolution regularity of temperature field of active heat insulation roadway considering thermal insulation spraying and grouting: A case study of Zhujidong Coal Mine, China
  18. Evolution of reduction process from tungsten oxide to ultrafine tungsten powder via hydrogen
  19. A thermodynamic assessment of precipitation, growth, and control of MnS inclusion in U75V heavy rail steel
  20. Effect of basicity on the reduction swelling properties of iron ore briquettes
  21. Effect of Cr and Al alloying on the oxidation resistance of a Ti5Si3-incorporated MoSiBTiC alloy
  22. Microstructure and mechanical properties of 2060 Al–Li alloy welded by alternating current cold metal transfer with high-frequency pulse current
  23. Effects of composition and strain rate on hot ductility of Cr–Mo-alloy steel in the two-phase region
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  25. Dephosphorization mechanism and phase change in the reduction of converter slag
  26. Parametric investigation and optimization for CO2 laser cladding of AlFeCoCrNiCu powder on AISI 316
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