Their size varies greatly and their source can include slag, dross, flux residues, and pieces of the mold.
[2] Non-metallic inclusions arise because of many physical-chemical effects that occur in molten and consolidated metal during production.
Non-metallic inclusions, the presence of which defines purity of steel, are classified by chemical and mineralogical content, by stability and by origin.
However, in general the content of inclusions in different steels varies within wide limits and has a big influence on the metal properties.
Present-day methods of steel and alloy production are unable to attain completely pure metal without any non-metallic inclusions.
During deformation, which occurs from flatting, forging, and stamping, non-metallic inclusions can cause cracks and fatigue failure in steel.
These make it possible to determine content, structure and amount of non-metallic inclusions in steel and alloys with high accuracy.