Effect of reoxidation on inclusions in Al-killed stainless steel during the casting start process
-
摘要: 為了研究鋁脫氧不銹鋼開澆過程中二次氧化對鋼水潔凈度和夾雜物演變的影響，實現鋼中夾雜物的有效控制，分別在LF精煉出站、開澆過程中不同時刻取樣，采用掃描電鏡、ASPEX自動分析儀、熱力學計算等不同方法研究了鋁脫氧不銹鋼中夾雜物的形貌、成分、數量和尺寸分布，確定了鋁脫氧不銹鋼開澆過程中夾雜物的演變行為和對應機理。研究結果表明，開澆過程鋼中氧氮質量分數、夾雜物數密度變化規律類似，20 min時分別增加至7.4×10?5、0.0674%、17.1 mm?2，此后隨著澆鑄過程進行逐漸降低；LF精煉出站時鈣處理改性夾雜物效果較好，其類型主要為CaO?Al2O3?SiO2?MgO，開澆過程中二次氧化降低了鈣處理操作的作用效果，20 min時夾雜物類型轉變為MnO?Al2O3?SiO2?CaO復合夾雜物，澆鑄約60 min時，連鑄過程中鋼水的潔凈度基本達到穩定，此時夾雜物類型重新轉變為CaO?Al2O3?SiO2?MgO；二次氧化使得鋼液中氧質量分數較高，促進了MnO?Al2O3-SiO2?CaO夾雜物的生成，而鋼中大尺寸的CaO?Al2O3?SiO2?MnO?(MgO)夾雜物主要通過夾雜物間的碰撞聚合形成；凝固過程中隨著溫度的降低，促進了MgO?Al2O3尖晶石相和CaO?2MgO?8Al2O3相的析出，提高了夾雜物中Al2O3組分的含量。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.
-
Key words:
- Al-killed stainless steel /
- reoxidation /
- cleanliness /
- inclusions /
- solidification
-
圖 1 取樣示意圖. (a) 提桶樣; (b) 圓坯樣
Figure 1. Schematic diagram of taking samples: (a) bucket-shaped sample; (b) round billet (RB)
圖 2 鋼中氧氮質量分數和夾雜物數密度變化
Figure 2. Variations of the total oxygen and nitrogen contents and number density of inclusions in the steel
圖 3 LF出站時鋼中夾雜物典型形貌和成分
Figure 3. Typical morphology and composition of inclusions in the steel at LF departure
圖 4 LF出站時鋼中夾雜物成分分布
Figure 4. Composition distribution of inclusions in the steel at LF departure
圖 5 LF出站時鋼中典型夾雜物面掃描分布
Figure 5. Element mapping of typical inclusions in the steel at LF departure
圖 6 不同時刻鑄坯內夾雜物成分變化. (a) 開澆20 min; (b) 開澆40 min; (c) 開澆60 min; (d) 正常澆鑄
Figure 6. Variation of the composition of inclusions in the round billet: (a) casting 20 min; (b) casting 40 min; (c) casting 60 min; (d) casting at steady state
圖 7 不同時刻鑄坯內夾雜物典型形貌和成分. (a, b) 開澆20 min; (c, d) 開澆40 min; (e, f) 開澆60 min
Figure 7. Typical morphology and composition of inclusions in the round billet: (a, b) casting 20 min; (c, d) casting 40 min; (e, f) casting 60 min
圖 8 開澆20 min時鑄坯內典型夾雜物線掃描結果
Figure 8. SEM line scanning of typical inclusions in the round billet at casting 20 min
圖 10 鑄坯內CaO?Al2O3?SiO2系夾雜物成分分布. (a) 開澆60 min; (b) 正常澆鑄
Figure 10. Composition distribution of CaO?Al2O3?SiO2 inclusions in the round billet: (a) casting 60 min; (b) casting at steady state
圖 11 鑄坯內CaO?Al2O3?MgO系夾雜物成分分布. (a) 開澆60 min; (b) 正常澆鑄
Figure 11. Composition distribution of CaO?Al2O3?MgO inclusions in the round billet: (a) casting 60 min; (b) casting at steady state
圖 12 1773 K下二次氧化過程鋼中夾雜物成分預測
Figure 12. Predicted composition of inclusions in the steel during reoxidation at 1773 K
圖 13 開澆20 min時鑄坯內夾雜物成分與直徑的關系. (a) Al2O3; (b) CaO; (c) SiO2; (d) MnO
Figure 13. Relationship between composition and diameter of inclusions in the round billet at casting 20 min: (a) Al2O3; (b) CaO; (c) SiO2; (d) MnO
圖 14 開澆20 min時鑄坯內CaO?Al2O3?SiO2?MnO?(MgO)系夾雜物典型形貌和成分
Figure 14. Typical morphology and composition of CaO?Al2O3?SiO2?MnO?(MgO) inclusions in the round billet at casting 20 min
圖 15 凝固過程鋼中氧化物夾雜析出轉變. (a) 相轉變; (b) 組分含量
Figure 15. Transformation of precipitation of oxide inclusions in the steel during solidification: (a) phase transformation; (b) composition
圖 16 開澆過程鋼中夾雜物的演變機理
Figure 16. Evolution mechanism of inclusions in the steel during casting start process
表 1 鋁脫氧不銹鋼典型成分（質量分數）
Table 1. Chemical composition of Al-killed stainless steel
% C Si Mn P S Ni Cr Mo Al Ca Mg N 0.018 0.48 0.98 0.039 0.003 10.07 16.28 2.07 0.006 0.0018 0.0008 0.063 
下載: 導出CSV
表 2 取樣過程和鋼中夾雜物分析
Table 2. Taking samples and inclusion analysis in the steel
Heat No. Sampling Scanning area/mm2 Number of inclusions 1# LF departure 50.0 485 RB at casting 20 min 50.0 855 RB at casting 40 min 50.0 609 RB casting 60 min 48.9 345 2# RB at a steady state 48.9 204
下載: 導出CSV
www.77susu.com<span id="fpn9h"><noframes id="fpn9h"><span id="fpn9h"></span> <span id="fpn9h"><noframes id="fpn9h"> <th id="fpn9h"></th> <strike id="fpn9h"><noframes id="fpn9h"><strike id="fpn9h"></strike> <th id="fpn9h"><noframes id="fpn9h"> <span id="fpn9h"><video id="fpn9h"></video></span> <ruby id="fpn9h"></ruby> <strike id="fpn9h"><noframes id="fpn9h"><span id="fpn9h"></span> -
參考文獻
[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] 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 [4] Wang Q M, Cheng G G. Metallurgy development of Ti-stabilized stainless steel. Chin J Eng, 2021, 43(11): 1447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 [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] 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 [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] 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 [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] 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 [13] 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 [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] 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 [16] 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 [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] 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 [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] 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 [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] 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 [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 -
點擊查看大圖
計量
- 文章訪問數: 488
- HTML全文瀏覽量: 153
- PDF下載量: 105
- 被引次數: 0
