Transformation of inclusions during the solidification and cooling process of Al-killed Ca treated structural steels
GAO Jiang1,2, WANG Leyao3, YANG Wen3, ZHANG Lifeng4, LI Quanhui1, LI Ming1
1. Nangang Research Institute, Nanjing Iron and Steel Co., Ltd., Nanjing 210044,Jiangsu,China; 2. School of Materials Science and Engineering,Yanshan University, Qinhuangdao 066004,Hebei,China; 3. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083,China; 4. School of Mechanical and Materials Engineering, North China University of Technology,Beijing 100144,China
Abstract:In order to study the transformation mechanism and influencing factors of inclusions during the solidification and cooling process of aluminum deoxidized calcium treated steel, the transformation phenomenon of inclusions in steel with different cleanliness levels was analyzed by taking molten steel samples in tundish and continuous casting slab samples of S335 structural steel. It was found that during the production process of Al-killed Ca treated S335 structural steels, inclusions underwent a transformation from homogeneous CaO-Al2O3 to multiphase Al2O3+CaS from the molten steel in tundish to the continuous casting slab, accompanied by an increase in the number density and size of inclusions. The transformation mechanism of inclusions during the solidification and cooling process of steel was revealed through thermodynamic calculations. It was found that with the decrease of w(T.[Ca])/w(T.[O]) and the increase of w(T.[O])/w(T.[S]) in the steel, the weight percent of CaO in inclusions in the molten steel decreased. At the same time, the precipitation temperature and precipitation amount of CaS in inclusions decreased during the solidification and cooling process. Based on the transformation phenomenon of inclusions during the solidification and cooling of steels, it could be concluded that when analyzing the composition of inclusions in molten steel, rapid cooling must be carried out after taking out the molten steel sample to avoid the transformation of inclusions during the solidification and cooling process and improve the accuracy of detection.
高江, 王乐瑶, 杨文, 张立峰, 李权辉, 李明. 铝脱氧钙处理结构钢凝固冷却过程夹杂物的转变[J]. 连铸, 2024, 43(1): 26-31.
GAO Jiang, WANG Leyao, YANG Wen, ZHANG Lifeng, LI Quanhui, LI Ming. Transformation of inclusions during the solidification and cooling process of Al-killed Ca treated structural steels. CONTINUOUS CASTING, 2024, 43(1): 26-31.
BESKOW K, TRIPATHI N N, NZOTTA M, et al. Impact of slag-refractory lining reactions on the formation of inclusions in steel[J]. Ironmaking and Steelmaking, 2004, 31(6): 514.
REN Y, WANG Y F, LI S S, et al. Detection of non-metallic inclusions in steel continuous casting billets[J]. Metallurgical and Materials Transactions B, 2014, 45(4): 1291.
[11]
ZHANG L F, LIU Y, ZHANG Y, et al. Transient evolution of nonmetallic inclusions during calcium treatment of molten steel[J]. Metallurgical and Materials Transactions B, 2018, 49(4): 1841.
CHU Y P, LI W F, REN Y, et al. Transformation of inclusions in linepipe steels during heat treatment[J]. Metallurgical and Materials Transactions B, 2019, 50(4): 2047.
[20]
WANG Y, SRIDHAR S, VALDEA M. Formation of CaS on Al2O3-CaO inclusions during solidification of steels[J]. Metallurgical and Materials Transactions B, 2002, 33(4): 625.
[21]
YANG W,GUO C B,LI C, et al. Transformation of inclusions in pipeline steels during solidification and cooling[J]. Metallurgical and Materials Transactions B, 2017, 48(5): 2267.