Shrinkage and porosity defects in steel casting and preventive measures

In the thick section of the casting, at the hot spot or the axis where the final solidification takes place, irregular surface rough holes are formed, where the grains are coarse and often with dendrites. The large and concentrated holes are called shrinkage holes, and the small and scattered holes are called shrinkage porosity. The main reason is that the liquid shrinkage and solidification shrinkage of the casting during cooling and solidification are far greater than the solid shrinkage, and at the end of the casting The solidification place is not caused by the supplement of liquid metal.

Preventive measures for shrinkage cavity and porosity:

1.The pouring temperature and pouring speed shall be reduced as much as possible, and the supplementary pouring at the later stage of pouring shall be fully in place.

2.Reasonable design of pouring and pouring system, the castings with small and uniform wall thickness should be solidified at the same time, and the castings with large and uneven wall thickness should be solidified from thin to thick in order to fully supplement the castings.

3.Place the inner and outer chill reasonably at the thick section of the casting.

4 minimize the hot spot of the casting.