Abstract: Taking the billet with a section of 160 mm×160 mm as the object of study, the fluid flow bias in the billet was analyzed by using numerical simulation and physical simulation. The results show that, the billet flow bias is due to the existence of the crystallizer radian and the center line alignment. The billet flow bias will make the shell of the inner arc side thin, the liquid flow asymmetric, and the high speed point easy to arrive. Furthermore, slag entrapment is easily occurred. In order to solve this problem, the mould nozzle is offset 6~8 mm outward arc side. After offset, the number of pore defects declined more than 30 %; the arc difference inside and outside was basically eliminated. The statistics show that the billet surface depression and mould slag entrapment rate decreased by 21 %, 56 % respectively.

Key words: square billet, numerical simulation, physical simulation, offset