Inclusions can affect both the mechanical properties of the final steel product and the fabricatability of the steel:

Mechanical Properties:

• they can act as cleavage crack initiation sites;
  
• they can debond easily and produce large voids on the fracture surface.
  

Fabricability:

• Inclusions can be detrimental to forming processes such as hot rolling as they can cause defects / tears in the steel.
• Some inclusions can be detrimental to welding as they can reduce the final toughness of the weld.
• Some inclusions can be beneficial to welding as they can act as acicular ferrite nucleation sites thereby promoting a high toughness microstructure.
• Some inclusions can be beneficial for machining.