| The effect of final stage electro-magnetic stirring on the macrosegregation behavior in CC high carbon steel blooms(C contents:0.71, 0.82 and 1.01wt.%) was examined by using the continuous bloom caster, equipped with an in-strand stirrer(SEMS) and a final stirrer(FEMS). The properties of mushy zone were also examined through white band measurement and calulation of iso-solid fraction line and permeability together with a complimentary permeability measurement using a Tamman furnace. An optimum stirring pool thickness(d_o) at the position of FEMS is then determined for each high carbon steel tested, at which the best centre soundness is obtained. The optimum value of d_o is found to decrease almost linearly with increasing the carbon content, due to a longer solidification time interval(t_c) for higher carbon content. The specific permeability is also found to decrease with the carbon content suggesting that for a higher carbon content, the centre defects are formed at a little later stage of final solidification with the reduced optimum stirring pool thickness at FEMS. The cast structure at the centre region, for the most effective reduction of macrosegregation, is then determined as less developed dendritic equiaxed structure, with finely distributed solute segregation spots through thickness, and having small secondary dendrite arm spacing. |
|
