Causes and Solutions of Blow Hole Defects in Automobile Shell Castings

In the process of casting production, the causes of blow hole defects are:

① The excessive velocity of molten iron during pouring causes local sand mold to be washed;

② The molding sand falls due to carelessness during molding;

③ When running the core, it touches the sand mold and causes the molding sand to fall;

④ The sand core strength is too low due to insufficient sand mixing or too high sand temperature;

⑤ The sand mold is not cleaned after repair;

⑥ The surface stability of sand mold is poor;

⑦ The sand mold is scoured by molten iron for a long time;

⑧ Free sand in the sand mold is not cleaned;

⑨ The sand mold collides with the sand box when the box is closed;

⑩ The design of gating system is unreasonable.

In view of the above causes of blow holes, the preventive measures for their defects are:

① Adjust the settings of sprue, runner and ingate;

② Avoid touching the cavity wall during the molding process;

③ Design the shape of core head for easy placement and adopt correct core laying method;

④ Measures such as increasing binder ratio, cooling molding sand, fully mixing sand and removing sand balls were taken to improve sand mold strength;

⑤ Carefully clean the scraping surface and cutting surface of the sand mold;

⑥ The runner and ingate shall be painted;

⑦ The casting process in which the molten iron does not directly wash the molding sand or the filter screen is used to make the molten iron flow smoothly;

⑧ Thoroughly blow the sand mold inside;

⑨ Adjust the size fit of core head and core seat;

⑩ Fillet the root of the ingate to improve the fluidity of molten iron.

Scroll to Top