 This further reduces the chance of cleavage, because these boundaries impede crack propagation.In C-Mn steel weld metals, it is reported that nucleation of various ferrite morphologies is aided by non-metallic inclusion; in particular oxygen-rich inclusions of a certain type and size are associated with the intragranular nucleation of acicular ferrite, as observed, for example, by.Acicular ferrite is a fine Widmanstätten constituent, which is nucleated by an optimum intragranular dispersion of oxide/sulfide/silicate particles.