Sand Casting Defects Analysis-Open holes

May. 06,2022

Sand casting service is one of our most important businesses. Matson metal has more than 20 years of experience in this field.

And today, we would like to continue the defects sharing and solving solutions in Casting production.


These blowholes appear on the surface of the cast and are easier to detect than subsurface blowholes.


Causes and prevention of gas porosity


There are several causes of cavity defects.

  • Poor venting of mold and cores
  • Insufficient drying of mold and cores

How can we prevent gas porosity?

Scars are shallow blows that appear on a flat surface, while blisters are scars covered with a thin layer of metal.

  • casting defects Excessive moisture content of molding sand
  • Inadequate gas permeability of molding sand
Potential solutions include:

  • Incorporate good fluxing and melting practices: melt metal in a vacuum, in an environment of low-solubility gases or under a flux that prevents contact with the air
  • Increase gas permeability of sand: coarser sands have a higher permeability 
  • Increase permeability of mold and cores. Allow air and gas to escape from the mold cavity
  • Dry out molds and cores before use and store dry
  • Increase rate of solidification by reducing metal temperature during casting