For the cast iron surface plate, we take casting process to make the first flow of molten iron overflow, but the effect is not obvious. As the cast iron plate pouring liquid iron flow is short, the first flow of molten iron may cause a defect because of contamination and oxidation.
If the coating is coated with iron or other inclusions, then the distribution of defects should be far away from the end of the gate, and will vary with the different authors. If it is dispersed in molten iron glaze slag, the defect should be distributed to the upper part of the casting position. and will melt with the molten metal fluctuations in the quality of the change.