Relationship between motion of bubbles and agglomeration of inclusions into clusters during solidification of continuously cast steel

Sammanfattning: The possibility of cluster formation during solidication of steel is explored to explain structures that are seen on the fracture surface of the steel. A hypothesis is built that postulates porosities provide favourable locations for inclusions to agglomerate and form clusters.  A thermodynamic model is constructed to describe precipitation of porosity and inclusions. Formation of inclusions follow a nucleation and growth mechanism. Porosities on the other hand are the product of pressure balance in the liquid.  Motion of pores and inclusions is analysed based on the drag force and  surface  stresses. Gradient of surface tension is also identied as a driving force which acts on the pore surface and would cause motion. It is shown that relative motion of pores and inclusions coupled with  the inclusion tendency to get attached on pore surface makes or a viable mechanism explaining agglomeration of inclusion particles to clusters