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Inclusion engineering and metallurgy of calcium treatment

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Journal of Iron and Steel Research(International) 2018年第2期25卷 133-145页

作者： Sunday Abraham Rick Bodnar Justin Raines Yufeng Wang SSAB Americas Muscatine IA 52761 USA

Although a great deal of research has been done in the area of inclusion control during steelmaking, a complete description of the process of inclusion modification and shape control cannot be found in literatures. As a result, the terms ＂inclusion modification＂ and ＂shape control＂ are often used loosely in the technical community. To utilize the full potential offered by a calcium treatment, it is important to understand why an inclusion whose composition has been modified may not necessarily have its shape modified. With the purpose of decoupling the process of inclusion phase change from inclusion shape control, and to provide a complete description of the metallurgy of calcium treatment, a detailed literature survey has been performed on the subject. By coupling the survey with a new concept developed to tailor the cleanliness of steels to the intended applications, the hope is to provide the reader with valuable information on calcium treatment for inclusion modification and shape control.

关键词： Nonmetallic inclusion Cleanliness calcium treatment Inclusion modification Inclusion shape control

Inclusion variations and calcium treatment optimization in pipeline steel production

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International Journal of Minerals,Metallurgy and Materials 2011年第5期18卷 527-534页

作者： Jian-hua Liu Hua-jie Wu Yan-ping Bao Min Wang Research Institute of Metallurgy Engineering University of Science and Technology Beijing Beijing 100083 China School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China

SiCa line and SiCaBaFe alloy were injected into liquid pipeline steel at the end of LF refining as calcium treatment, and samples were taken from the ladles, mould, and slabs. Analysis of Ca content and inclusions shows that Ca content in steel decreases obviously in the following process after calcium treatment; the compositions, morphology, and sizes of inclusions also vary much in the production; primary inclusions in the ladles prior to calcium treatment are mainly Al2O3 inclusions, but they turn to fine irregular CaS-CaO-Al2O3 compound inclusions after the treatment, then become fine globular CaO-Al2O3 inclusions in the mould, and finally change to a few larger irregular CaS-CaO-Al2O3 complex inclusions in the slabs. Thermodynamic study reveals that inclusion variations are related with the preferential reactions among Ca, Al2O3, and S and the precipitation of S in CaO-Al2O3 inclusions with high sulfur capacity. New evaluation standards for calcium treatment in high-grade pipeline steel were put forward according to the inclusion variations and requirements of pipeline steel on inclusion controlling, and the calcium process was studied and optimized.

关键词： pipeline steel refining inclusions calcium treatment thermodynamics precipitation

Effect of calcium treatment on Non-Metallic Inclusions in Ultra-Low Oxygen Steel Refined by High Basicity High Al_2O_3 Slag

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Journal of Iron and Steel Research(International) 2011年第7期18卷 8-14页

作者： YANG Jun WANG Xin-hua JIANG Min WANG Wan-jun School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China

The influence of calcium treatment on non-metallic inclusions had been studied when control technology of refining top slag in ladle furnace was used in ultra-low oxygen steelmaking. A sufficient amount aluminium was added to experimental heats for final deoxidizing during BOF tapping, and the refining top slag with strong reducibility, high basicity and high Al2O3 in ladle furnace was used to produce ultra-low oxygen steel and the transformation of nonmetallic inclusions in molten steel was compared by calcium treatment and no calcium treatment. The results show that the transformation of Al2O3--MgO - Al2O3 spinel-CaO-MgO-Al2O3 complex inclusions has been completed for aluminum deoxidation products and calcium treatment to molten steel is unnecessary when using the control technology of ladle furnace refining top slag to produce ultra-low oxygen steel, and the complex inclusions are liquid at the temperature of steelmaking and easily removable to obtain very high cleanliness steel by flotation. Further- more, the problems of nozzle clogging in casting operations do not happen and the remaining oxide inclusions in steel are the relatively lower melting point complex inclusions.

关键词： ultra low oxygen top slag deoxidization aluminium oxide inclusion calcium treatment

Effects of calcium treatment on non-metallic inclusions and magnetic properties of non-oriented silicon steel sheets

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Baosteel Technical Research 2013年第1期7卷 12-19页

作者： ZHANG Feng MIAO Lede ZONG Zhenyu WANG Bo ZHANG Yi MA Zhigang Silicon Steel Department Baoshan Iron & Steel Co.Ltd. Center of Analysis and Test Research InstituteBaoshan Iron & Steel Co.Ltd. Steelmaking Plant Baoshan Iron & Steel Co.Ltd.

Based on the industrial production of non-oriented silicon steel,calcium treatment by CaSi wire feeding during the RH refining process was studied. The thermodynamics of CaS inclusion formation was analyzed, and the morphology and the size distribution were observed. Furthermore, the change in inclusion characteristics after calcium treatment and the effect of calcium treatment on magnetic properties were discussed. The results show that the formation of MnS and A1N inclusions were restrained, and the aggregating, floating and removing of microinclusions after calcium treatment were effectively promoted. The cleanliness of liquid steel was obviously increased. The main type of inclusions was single phase of CaO, with some complex inclusions composed of CaO, SiO2 and MgO. No CaS inclusion was observed after an appropriate calcium treatment. The size of all inclusions was distributed in the range of 2 - 20 μm, and the number was about 1.8 × 10^5/mm3. In addition, as an increasing amount of calcium was added,the core loss gradually decreased to a stable level, and the magnetic induction decreased quickly after a slow increase. The optimal calcium treatment mode depends on the chemical composition of steel.

关键词： non-oriented silicon steel RH refining calcium treatment inclusion magnetic property

Effect of Ca and Ti contents on characteristics of inclusions in Fe-Si-Cr-Mn-Al-Ti-Ca-O melts

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Journal of Iron and Steel Research(International) 2023年第10期30卷 1952-1962页

作者： Ren-sheng Li Meng-chuan Li Tong-sheng Zhang Wan-lin Wang School of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina International Union Research Center for Clean Metallurgy Central South UniversityChangsha 410083HunanChina WMG University of WarwickCoventry CV47ALUK

The inclusion characteristics in 55SiCr spring steel with different contents of titanium and calcium were investigated.The chemical compositions of steel samples were detected by inductively coupled plasma optical emission spectrometer,and the inclusion characteristics was determined by field emission scanning electron microscopy(FE-SEM)and energy-dispersive spectroscopy.The results show that the Ti/Al ratio should be kept at less than 1,and the content of calcium should be controlled between 0.0015 and 0.0025 wt.%in Si-Mn-Al deoxidized steel,so that more solid inclusions can be converted to liquid inclusions.Moreover,the high Ti content in melts is the direct cause of the high proportion of Ti_(3)O_(5) in the inclusions,which involves[Ti]to reduce SiO_(2) and A1_(2)O_(3) in inclusions.In addition,calcium treatment can reduce the content of Ti_(3)O_(5) in inclusions,and the degree of reduction is closely related to the content of[O].The thermodynamic calculation of Fe-Si-Mn-Cr-Al-Ti-Ca-O molten steel system during solidification process was performed by FactSage software,taking all types of inclusions into account,such as titanium oxide,calcium oxide,aluminum oxide,silicon oxide,manganese oxide,calcium titanate,mullite,calcium aluminate,and liquid inclusion.The inclusion type of calculation results was in accordance with the experimental results at 1550℃,and TiO_(x) aggregation behavior was consistent with the Ti_(2)O_(3)-containing precipitation phase.

关键词： Spring steel Inclusion Titanium treatment calcium treatment Thermodynamic calculation

Effect of calcium content on inclusions during the ladle furnace refining process of AISI 321 stainless steel

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International Journal of Minerals,Metallurgy and Materials 2020年第11期27卷 1499-1507页

作者： Chao Pan Xiao-jun Hu Jian-chao Zheng Ping Lin Kuo-chih Chou State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China School of Metallurgy Northeastern UniversityShenyang 110819China Ruipu Technology Group Co. Ltd.Qingtian 323903China

The effect of three heat processes with different calcium contents on the evolution of inclusions during the ladle furnace refining process of AISI 321 stainless steel was investigated.The size,morphology,and composition of the inclusions were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy.After the addition of aluminum and titanium,the primary oxide in the AISI 321 stainless steel was an AbOs—MgO—TiOx complex oxide,in which the mass ratio of AbOs/MgO was highly consistent with spinel(MgO・AbO3).After calcium treatment,the calcium content in the oxide increased significantly.Thermodynamic calculations show that when the Ti content was 0.2wt%,the Al and Ca contents were less than 0.10wt%and 0.0005wt%,respectively,which was beneficial for the formation of liquid inclusions in molten steel.Moreover,the modification mechanism of calcium on TiN-wrapped oxides in combination with temperature changes was discussed.

关键词： inclusions stainless steel calcium treatment thermodynamic calculation

Effect of Sulfur Content and Sulfide Shape on Fracture Ductility in Case Hardening Steel

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Journal of Iron and Steel Research(International) 2011年第8期18卷 58-64页

作者： XIAO Guo-hua DONG Han WANG Mao-qiu HUI Wei-jun National Engineering Research Center of Advanced Steel Technology Central Iron andSteel Research Institute Beijing 100081 China

The effects of sulfur content and calcium addition on smooth axisymmetric tensile fracture ductility of case hardening steel DIN 18CrNiMo7-6 have been investigated. The quantitative metallographic analysis of sulfide inclusions and the correlations between sulfide inclusions and fracture ductility were examined. Sulfide inclusions were found to have deleterious effect on fracture ductility, whereas the effect can be offset to some extent by calcium-treat- ment due to less easily deforming of sulfides during hot-working. The product （AA·λAW） of sulfide inclusion area fraction （An） and its area-weighted aspect ratio （λAW） can be used as a parameter to describe the effect of sulfide inclusions on fracture true strain.

关键词： case hardening steel calcium treatment sulfide fracture ductility

Influence of calcium content on solid ratio of inclusions in Ca-treated liquid steel

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Journal of University of Science and Technology Beijing 2006年第6期13卷 486-489页

作者： Fangming Yuan Xinhua Wang Xuefu Yang Metallurgical and Ecological Engineering School University of Science and Technology Beijing Beijing 100083 China Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China

It has been found that Ca-treated liquid steel can be cast at a lower superheat. To ascertain the reason for the improved castability of Ca-treated liquid steel and to find the optimal range of calcium content, the behavior of calcium in liquid steel was studied in terms of the relationship between the calcium content and solid ratio of inclusions. The relationship between the calcium content and solid ratio of inclusions was obtained by means of the classification of nonmetallic inclusions in solid and liquid steels at casting temperature according to the Al 2 O 3 -CaO-SiO 2 phase diagram. The optimum calcium content should be 17–23 ppm.

关键词： steel calcium treatment solid ratio nonmetallic inclusions fluidity

Evolution of Nonmetallic Inclusion during Steelmaking Process of Cold Heading Steel SWRCH35K

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Journal of Minerals and Materials Characterization and Engineering 2022年第5期10卷 438-445页

作者： Mengxiong Li Qi Xu Jianli Li No. 2 Steel-Making Plant Jiangsu Yonggang Group Co. Ltd. Zhangjiagang China Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and Technology Wuhan China

In order to analyze the evolution of the inclusions in the cold heading steel SWRCH35K during the steelmaking process, a systematic sampling of the steelmaking processes in a steel plant was carried out. Both SEM-EDS and the image processing software Image-Pro-Plus6.0 were employed to analyze the chemical composition, morphology, quantity and size of non-metal inclusions in the steel samples. The results show that from BOF tapping to continuous casting tundish, the composition of inclusions in SWRCH35K steel changes from Al2O3 →MgO·Al2O3 →CaO-MgO-Al2O3-CaS, and the typical morphology of the inclusions in the steel gradually changes from irregular blocks and clusters to spherical. The number of inclusions in the BOF argon blowing station is the largest, 213#/mm2, while the number of inclusions at the end of LF refining is the least, about 12#/mm2, and there are basically no inclusions above 5 μm. In addition, LF calcium treatment will adversely affect the size and quantity control of inclusions in steel. In order to effectively reduce the large-size calcium-containing spherical oxide inclusions in cold heading steel, it is necessary to find a technical method that can replace LF calcium treatment to solve the problem of molten steel continuous casting.

关键词： Cold Heading Steel Inclusions LF Refining calcium treatment