Characteristics, causes and prevention of shrinkage cavity and porosity in casting

Features:

Shrinkage cavity: the hole with large volume, rough wall surface and irregular shape in the casting

Shrinkage porosity: a large number of irregular shaped micro holes or fissured holes are distributed on the casting section

Causes:

A. The location or size of the riser is unreasonable. During the solidification of molten iron, the volume shrinks and cannot be compensated, resulting in volume loss. The volume loss is concentrated in one place to form shrinkage cavity and dispersed locally to form shrinkage cavity

B. The shape or sectional area of the riser neck is unreasonable, and the feeding channel is blocked, so that the riser fails to play a feeding role

C. Low riser temperature, poor early solidification feeding effect

D. Low CE value of liquid metal

Plan improvement measures:

A. Increase riser volume

B. Increase (or decrease) riser neck

C. Increase the inlet water of riser and raise the temperature of riser

D、 Change the riser position or shape, change the solidification order so that the shrinkage part that could not be compensated can be compensated, and eliminate the shrinkage or porosity

E. Place cold iron in place (such as TRW bracket series)

F. Changing the position of water in order to obtain a reasonable temperature field and solidification sequence

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