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Inclusion Motion in the Mold and Pencil Pipe Defects

Alexander Denissov, Yuji Miki and Brian Thomas

Continuous Casting Consortium

Flow of the molten steel contained within the solidifying shell is very influential on the distribution of inclusion particles, which are important to the internal cleanliness and quality of steel. The mold is the last chance to remove inclusions by floating them into the mold slag. The movement of inclusion particles is mathematically traced by the model, including the competing effects of convection and buoyancy. The model trajectories confirm industrial experience that curvature of the mold makes particle entrapment more likely on the inside radius.

Inclusion Trajectories
Flow Pattern in the Mold


The steel companies are encountering a great amount of surface defects they call "pencil pipes." Experimental investigation revealed presence of Argon gas and alumina inclusions inside those defects. To understand pencil pipe formation and suggest operating practice improvements the research is conducted in the following important areas:

Inclusion Formation

  • Different shapes of alumina inclusions are considered.
  • Inclusion attachment rate on gas bubbles is studied.
  • Terminal velocities of different inclusions are determined.

Inclusion Movement

  • 3D Finite Difference model is used to obtain flow pattern changed by Argon injection.
  • Computational domain changed to account for shell growth.

Inclusion Entrapment

  • Particle trajectories are calculated for each flow pattern.
  • Particle is considered captured when it crosses the computational boundary.
  • Statistics for entrapment positions are performed for different types of particles.

Models are being developed for each of these directions. After the mechanisms for inclusion formation, transport and entrapment are modeled separately, we plan to combine them into one complex model to study effects of casting conditions on inclusion distribution in slabs.


Miki, Y., B.G. Thomas, A. Dennisov, and Y. Shimada, "Model of Inclusion Removal During RH Degassing of Steel," Iron and Steelmaker, Vol. 24, No. 8, Iron and Steel Society, Warrendale, PA, 1997, pp. 31-38.

Miki, Y., B.G. Thomas, A. Dennisov, and Y. Shimada, "Model of Inclusion Removal During RH Degassing of Steel," 80th Steelmaking Conference Proceedings, (Chicago, IL, April 13-16, 1997), Iron and Steel Society, Warrendale, PA, 1997, pp. 37-45; [Frank B. McKune Award, 1997, Iron and Steel Society]. Click here for a PDF version. (295 KB)