Influence of tundish structure on behavior of tundish slag and inclusions during ladle changeover process

SONG Jintao; CHEN Chao; WANG Tianyang; GENG Mengjiao; RONG Zhiren; REN Dekang; WANG Jia; FAN Jinping

doi:10.13228/j.boyuan.issn0449-749x.20240538

Iron and Steel ›› 2025, Vol. 60 ›› Issue (3) : 66-77. DOI: 10.13228/j.boyuan.issn0449-749x.20240538

Steelmaking

Influence of tundish structure on behavior of tundish slag and inclusions during ladle changeover process

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Abstract

Two types of turbulence inhibitors, namely cylindrical turbulence inhibitor and impact pad, were used in a 6-strand tundish with side-arranged inlet of a steelmaking plant. In order to evaluate the metallurgical effect of the two types of tundish during the ladle changeover process, the flow field distribution of the two type of tundishes and the slag entrapment situation in the water model, evolution of inclusions during the ladle changeover process were studied by industrial sampling, physical model, and numerical simulation methods. Particle image velocimetry （PIV） was applied to measure the flow field distribution and velocities at the water oil interface. The morphology, size, and composition of inclusions in the two type of tundishes during the ladle changeover process were explored by industrial sampling and Scanning Electron Microscopy-Energy Dispersion Spectrometer （SEM-EDS）. The results show that the velocity spatial distribution inside the tundish is uneven, with higher velocity in the impact zone and lower velocity at the edge strand. There is an upward backflow in the tundish with a cylindrical turbulence inhibitor. At a normal casting rate of 2.65 t/min, the maximum fluid velocity at the water oil interface of both types of tundish is around 50 mm/s, indicating a relatively stable water oil interface. When rapidly refilling （5 t/min） after ladle change, a circulation is formed near the wall in the impact zone of the tundish with a cylindrical turbulence inhibitor, and a strong horizontal flow that paralleling to the liquid surface towards the outlet is formed. The maximum velocity at the water oil interface is 285.16 mm/s, and the slag eye area is 735.42 cm². A large number of large-sized oil droplets are entrained in the impact zone. For the tundish with an impact pad, the impact zone forms an upward flow field along the wall, with a maximum velocity of 186.54 mm/s at the water oil interface and a slag eye area of 399.27 cm². Small oil droplets are entrained in the impact zone, forming a water oil mixture. The sampling results before and after the ladle change show that no large-sized （≥50 μm） inclusions are found in both types of tundish at the end of casting of the previous heat. After the liquid level rise to the normal working level, a large-sized inclusion with a size of 240.32 μm is found in the tundish with a cylindrical turbulence inhibitor. The average size of the inclusion increases from 13.18 μm to 29.88 μm, and the proportion of large-sized （≥50 μm） inclusions is 24%. The mass fraction of CaO in the inclusion increases significantly. However, no inclusions with a size larger than 100 μm are found in the tundish with an impact pad, and the average size of inclusions remains basically unchanged. The proportion of large-sized （≥50 μm） inclusions is 6.7%. Overall, the metallurgical effect of the impact pad is superior to that of the cylindrical turbulence inhibitor.

Key words

tundish with side-arranged inlet / turbulence inhibitor / ladle changeover process / particle image velocimetry / velocity at water-oil interface / slag entrapment / inclusions / slag open eye area

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SONG Jintao, CHEN Chao, WANG Tianyang, et al. Influence of tundish structure on behavior of tundish slag and inclusions during ladle changeover process[J]. Iron and Steel, 2025, 60(3): 66-77 https://doi.org/10.13228/j.boyuan.issn0449-749x.20240538

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