Distribution of oxide inclusions in H13 castings under super-gravity field with multi-stage rotation speeds

The 42 kg industrial H13 castings were prepared by different super-gravity fields with multi-rotation speeds, and the distribution of oxide inclusions in the castings was studied. In addition, the inward movement Reynolds number and inward movement time of oxide inclusions as well as the solidification time of molten steel at different positions in the castings were calculated to clarify the removal mechanism of oxide inclusions in super-gravity field. The results show that the large size (i.e., greater than 10 mu m) oxide inclusions are mainly concentrated in the inner and outer parts of the super-gravity castings with constant rotation speed (500 r min(-1)) and five-stage rotation speeds (500, 600, 750, 850, and 950 r min(-1)), respectively, while there are no large oxide inclusions in the super-gravity castings with three-stage rotation speeds (500, 600, and 750 r min(-1)). Although an increase in the particle size of inclusion and the rotation speed in super-gravity field is conducive to the increase in the inward movement Reynolds number of oxide inclusions and reduction in the inward movement time of oxide inclusions, it will reduce the local solidification time of molten steel. In the range of the rotation speed studied, the super-gravity field with three-stage rotation speeds has the best effect on the removal of inclusions in H13 molten steel.