Porosity Fracture 1

[corus]

For cast steels what is the effect of regions of porosity in terms of crack growth?
Are these regions of porosity more likely to cause crack initiation and will these cracks form under compressive loads?
If the fracture toughness of the parent metal is 100, say, then what estimate would be made for the fracture toughness of the region of porosity?

 

[RunnerMan]

The extent of crack growth would be dependant upon the severity of the porous area of the section. These regions are more likely to cause crack initiation. In my own experience, cracks caused during post heat treatment contraction (compressive) stresses always manifested in an area that was subsequently found to have contained porosity of some description.
Again, I would say that it would be difficult to estimate the fracture toughness of a given area as this would be dependant upon the severity and orientation of the defect.