EFFECT OF FERRITE SUBSTRUCTURE ON PRECIPITATION OF FE3C AT MNS IN AN ULTRA-LOW CARBON-STEEL

The effect of ferrite substructure on precipitation of Fe3C at MnS in an Al-killed steel was studied. By heat treatment, dislocation density and grain size were varied under the presence of MnS particles. By the subsequent aging at 603K and 703K, the ratio of Fe3C precipitates nucleating on MnS with respect to the total number of Fe3C precipitates was lowered under the presence of a large number of dislocations and grain boundaries. It was considered that a MnS particle is less effective than a dislocation, and is comparably effective with a grain boundary as a heterogeneous nucleation site of Fe3C in ferrite.