Critical size of nonmetallic inclusions in fracture in steel

Abstract

1. It was established by experiment that microc racks originating in nonmetallic inclusions or on the metal—inclusion interface do not pass into the metallic matrix when the dimensions of the inclusions are below particular (critical) values. 2. The critical size of inclusions does not depend upon their physical and mechanical properties and is governed by the conditions of metal loading. 3. In tension, the critical size of the types of inclusion studied (alumina, titanium nitrides, ironmanganese sulfides, and oxide-nitride-sulfide complexes) was 3.6 μ, and 2.0 μ in cyclic plane bending. 4. Reducing the size of nonmetallic inclusions by appropriate inoculation processes may be one way of improving the physical and mechanical properties of cast steel.