Effect of reoxidation on inclusions in Al-killed stainless steel during the casting start process

LING Hai-tao; WU Jin-yuan; CHANG Li-zhong; YANG Shu-feng; QIU Sheng-tao

doi:10.13374/j.issn2095-9389.2022.03.22.002

Volume 45 Issue 5

May 2023

Turn off MathJax

Article Contents

Article Navigation > Chinese Journal of Engineering > 2023 > 45(5): 737-746

LING Hai-tao, WU Jin-yuan, CHANG Li-zhong, YANG Shu-feng, QIU Sheng-tao. Effect of reoxidation on inclusions in Al-killed stainless steel during the casting start process[J]. Chinese Journal of Engineering, 2023, 45(5): 737-746. doi: 10.13374/j.issn2095-9389.2022.03.22.002

Citation:

LING Hai-tao, WU Jin-yuan, CHANG Li-zhong, YANG Shu-feng, QIU Sheng-tao. Effect of reoxidation on inclusions in Al-killed stainless steel during the casting start process[J]. Chinese Journal of Engineering, 2023, 45(5): 737-746. doi: 10.13374/j.issn2095-9389.2022.03.22.002

Citation:

LING Hai-tao, WU Jin-yuan, CHANG Li-zhong, YANG Shu-feng, QIU Sheng-tao. Effect of reoxidation on inclusions in Al-killed stainless steel during the casting start process[J]. Chinese Journal of Engineering, 2023, 45(5): 737-746. doi: 10.13374/j.issn2095-9389.2022.03.22.002

PDF( 4179 KB)

Effect of reoxidation on inclusions in Al-killed stainless steel during the casting start process

doi: 10.13374/j.issn2095-9389.2022.03.22.002

1.
School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan 243002, China
2.
Jiangsu Yonggang Group Co., Ltd., Zhangjiagang 215628, China
3.
State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China
4.
National Engineering and Research Center for Continuous Casting Technology, Central Iron and Steel Research Institute, Beijing 100081, China

More Information

Corresponding author: E-mail: linghaitao@ahut.edu.cn
Received Date: 2022-03-22
Available Online: 2022-06-14
Publish Date: 2023-05-01

Abstract

Abstract

Stainless steels are widely used for corrosion resistance and as construction materials. The existence of harmful inclusions probably deteriorates corrosion resistance and easily causes nozzle clogging, surface defects, and the occurrence of cracks. Reoxidation during the casting start process significantly affects the cleanliness of molten steel, which may result in the downgrading or discarding of the steel. The production route of Al-killed stainless steel in this work is “EAF → AOD → LF → Calcium treatment → Continuous casting of round billet.” At LF departure, steel samples were taken at different moments during the casting start process to investigate the effect of reoxidation on the cleanliness of molten steel and the evolution of inclusions in the steel. It aims to achieve effective control of inclusions in the steel. The morphology, composition, amount, and size of inclusions in Al-killed stainless steel were studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), as well as automated SEM/EDS inclusion analysis (ASPEX). The effects of the oxygen content from reoxidation and the temperature decrease during solidification on the inclusion composition were calculated by the thermodynamic software FactSage 7.2. The evolution behavior and mechanism of inclusions during the casting start process of Al-killed stainless steel were analyzed and discussed. The findings showed that the total oxygen and nitrogen contents, as well as the number density of inclusions in the steel during the casting start process, indicated a similar change trend. They were increased to 7.4×10^?5, 0.0674%, and 17.1 mm^?2, respectively, at casting 20 min, and then gradually decreased. Inclusions in the steel have been well modified by calcium treatment at LF departure, and its composition was primarily CaO?Al₂O₃?SiO₂?MgO. The effects of calcium treatment were mitigated by reoxidation during the casting start process. Inclusions in the round billet were transformed to MnO?Al₂O₃?SiO₂?CaO at casting 20 min. When the pouring time was 60 min, the cleanliness of the molten steel almost reached a steady state during continuous casting. The contents of total oxygen and nitrogen with the number density of inclusions in the steel were 3.2×10^?5, 0.0628%, and 7.1 mm^?2, respectively, and inclusions were transformed back to CaO?Al₂O₃?SiO₂?MgO. Furthermore, reoxidation increases the oxygen content in molten steel and promotes the formation of MnO?Al₂O₃?SiO₂?CaO inclusions. Collision and coalescence among inclusions produce large-sized CaO?Al₂O₃?SiO₂?MnO?(MgO) inclusions in the steel. The decrease of the temperature during solidification promotes the precipitation of the MgO?Al₂O₃ spinel phase and CaO?2MgO?8Al₂O₃ phase. As a result, the Al₂O₃ content in inclusions increases.
- Al-killed stainless steel,
- reoxidation,
- cleanliness,
- inclusions,
- solidification

FullText(HTML)

References(30)

References

[1]	Park J H, Todoroki H. Control of MgO·Al₂O₃ spinel inclusions in stainless steels. ISIJ Int, 2010, 50(10): 1333 doi: 10.2355/isijinternational.50.1333
[2]	Kim W Y, Nam G J, Kim S Y. Evolution of non-metallic inclusions in Al-killed stainless steelmaking. Metall Mater Trans B, 2021, 52(3): 1508 doi: 10.1007/s11663-021-02119-4
[3]	華承健, 王敏, 張孟昀, 等. 浸入式水口內壁特征對邊界層流場結構和氧化鋁夾雜物運動行為的影響. 工程科學學報, 2021, 43(7):925 Hua C J, Wang M, Zhang M Y, et al. Effect of submerged entry nozzle wall surface morphologies on boundary layer structure and alumina inclusions transport. Chin J Eng, 2021, 43(7): 925
[4]	王啟明, 成國光. 含Ti不銹鋼冶金工藝進展. 工程科學學報, 2021, 43(11):1447 Wang Q M, Cheng G G. Metallurgy development of Ti-stabilized stainless steel. Chin J Eng, 2021, 43(11): 1447
[5]	Park J H, Lee S B, Kim D S. Inclusion control of ferritic stainless steel by aluminum deoxidation and calcium treatment. Metall Mater Trans B, 2005, 36(1): 67 doi: 10.1007/s11663-005-0007-2
[6]	Ren Y, Zhang L F, Fang W, et al. Effect of slag composition on inclusions in Si-deoxidized 18Cr–8Ni stainless steels. Metall Mater Trans B, 2016, 47(2): 1024 doi: 10.1007/s11663-015-0554-0
[7]	張樂辰, 包燕平, 王敏, 等. TP347H精煉渣二次氧化控制及夾雜物變性處理. 工程科學學報, 2016, 38(Suppl 1):1 Zhang L C, Bao Y P, Wang M, et al. Reoxidation control of refining slag and inclusion modification in TP347H stainless steel. Chin J Eng, 2016, 38(Suppl 1): 1
[8]	Guo J, Han S W, Chen X R, et al. Control of non-metallic inclusion plasticity and steel cleanliness for ultrathin 18 pct Cr-8 pct Ni stainless steel strip. Metall Mater Trans B, 2020, 51(4): 1813 doi: 10.1007/s11663-020-01862-4
[9]	張一民, 孫彥輝, 白雪峰, 等. 不銹鋼中夾雜物三維形貌及其熱力學計算. 工程科學學報, 2020, 42(Suppl 1):14 Zhang Y M, Sun Y H, Bai X F, et al. Three-dimensional morphology and thermodynamic calculation of inclusions in stainless steel. Chin J Eng, 2020, 42(Suppl 1): 14
[10]	Okuyama G, Yamaguchi K, Takeuchi S, et al. Effect of slag composition on the kinetics of formation of Al₂O₃–MgO inclusions in aluminum killed ferritic stainless steel. ISIJ Int, 2000, 40(2): 121 doi: 10.2355/isijinternational.40.121
[11]	Todoroki H, Mizuno K. Effect of silica in slag on inclusion compositions in 304 stainless steel deoxidized with aluminum. ISIJ Int, 2004, 44(8): 1350 doi: 10.2355/isijinternational.44.1350
[12]	李璟宇, 成國光, 李六一, 等. 202不銹鋼中非金屬夾雜物的形成機理. 工程科學學報, 2019, 41(12):1567 Li J Y, Cheng G G, Li L Y, et al. Formation mechanism of non-metallic inclusions in 202 stainless steel. Chin J Eng, 2019, 41(12): 1567
[13]	任英, 張立峰, 楊文. 不銹鋼中夾雜物控制綜述. 煉鋼, 2014, 30(1):71 doi: 10.3969/j.issn.1002-1043.2014.01.018 Ren Y, Zhang L F, Yang W. Review of control of inclusions in stainless steel. Steelmaking, 2014, 30(1): 71 doi: 10.3969/j.issn.1002-1043.2014.01.018
[14]	Li S S, Zhang L F, Ren Y, et al. Transient behavior of inclusions during reoxidation of Si-killed stainless steels in continuous casting tundish. ISIJ Int, 2016, 56(4): 584 doi: 10.2355/isijinternational.ISIJINT-2015-694
[15]	徐海坤, 黃慶周, 謝明耀, 等. 中間包二次氧化對304不銹鋼潔凈度的影響. 中國冶金, 2018, 28(Suppl 1):76 doi: 10.13228/j.boyuan.issn1006-9356.2018s014 Xu H K, Huang Q Z, Xie M Y, et al. Effect of reoxidation on cleanliness of 304 stainless steel in tundish. China Metall, 2018, 28(Suppl 1): 76 doi: 10.13228/j.boyuan.issn1006-9356.2018s014
[16]	付邦豪, 陳超, 成國光, 等. 430不銹鋼冶煉過程的夾雜物. 鋼鐵, 2012, 47(1):40 doi: 10.13228/j.boyuan.issn0449-749x.2012.01.017 Fu B H, Chen C, Cheng G G, et al. Inclusions in 430 stainless steelmaking during AOD-LF-CC process. Iron Steel, 2012, 47(1): 40 doi: 10.13228/j.boyuan.issn0449-749x.2012.01.017
[17]	Goto H, Miyazawa K I. Reoxidation behavior of molten steel in non-killed and Al-killed steels. ISIJ Int, 1998, 38(3): 256 doi: 10.2355/isijinternational.38.256
[18]	Zhang L F, Thomas B G. State of the art in evaluation and control of steel cleanliness. ISIJ Int, 2003, 43(3): 271 doi: 10.2355/isijinternational.43.271
[19]	王新華. 高品質冷軋薄板鋼中非金屬夾雜物控制技術. 鋼鐵, 2013, 48(9):1 doi: 10.13228/j.boyuan.issn0449-749x.2013.09.004 Wang X H. Non-metallic inclusion control technology for high quality cold rolled steel sheets. Iron Steel, 2013, 48(9): 1 doi: 10.13228/j.boyuan.issn0449-749x.2013.09.004
[20]	Yan P C, van Ende M A, Zinngrebe E, et al. Interaction between steel and distinct gunning materials in the tundish. ISIJ Int, 2014, 54(11): 2551 doi: 10.2355/isijinternational.54.2551
[21]	Kim T S, Chung Y, Holappa L, et al. Effect of rice husk ash insulation powder on the reoxidation behavior of molten steel in continuous casting tundish. Metall Mater Trans B, 2017, 48(3): 1736 doi: 10.1007/s11663-017-0971-3
[22]	Wang F, Liu D X, Liu W, et al. Reoxidation of Al-killed steel by Cr₂O₃ from tundish cover flux. Metals, 2019, 9(5): 554 doi: 10.3390/met9050554
[23]	朱坦華, 周秋月, 任英, 等. 二次氧化過程IF鋼中間包中夾雜物演變行為. 鋼鐵, 2020, 55(3):35 doi: 10.13228/j.boyuan.issn0449-749x.20190242 Zhu T H, Zhou Q Y, Ren Y, et al. Inclusion evolution in IF steel during tundish reoxidation. Iron Steel, 2020, 55(3): 35 doi: 10.13228/j.boyuan.issn0449-749x.20190242
[24]	Yang G W, Wang X H, Huang F X, et al. Influence of reoxidation in tundish on inclusion for Ca-treated Al-killed steel. Steel Res Int, 2014, 85(5): 784 doi: 10.1002/srin.201300243
[25]	許苗苗, 尚正鴻, 凌海濤, 等. 316L不銹鋼精煉過程中夾雜物成分演變. 煉鋼, 2021, 37(2):16 Xu M M, Shang Z H, Ling H T, et al. Composition evolution of inclusions in 316L stainless steel refining process. Steelmaking, 2021, 37(2): 16
[26]	Jiang M, Wang X H, Chen B, et al. Laboratory study on evolution mechanisms of non-metallic inclusions in high strength alloyed steel refined by high basicity slag. ISIJ Int, 2010, 50(1): 95 doi: 10.2355/isijinternational.50.95
[27]	Yang S F, Wang Q Q, Zhang L F, et al. Formation and modification of MgO·Al₂O₃-based inclusions in alloy steels. Metall Mater Trans B, 2012, 43(4): 731 doi: 10.1007/s11663-012-9663-1
[28]	Kim J W, Kim S K, Kim D S, et al. Formation mechanism of Ca?Si?Al?Mg?Ti?O inclusions in type 304 stainless steel. ISIJ Int, 1996, 36(Suppl 1): S140
[29]	Yin X, Sun Y H, Yang Y D, et al. Inclusion evolution during refining and continuous casting of 316L stainless steel. Ironmak Steelmak, 2016, 43(7): 533 doi: 10.1080/03019233.2015.1125599
[30]	Li J Y, Cheng G G, Li L Y, et al. The formation mechanism of Mn?Al?O inclusions in Fe?Cr?Mn stainless steel during continuous casting. Steel Res Int, 2018, 89(5): 1700461 doi: 10.1002/srin.201700461