Effect of Nitrogen on Crystal Grain Forming of Metastable Austenitic Manganese Steel

Abstract

The effect of nitrogen on crystal grain for metastabl austenitic manganese steel was studied. The result indicated that the attachment of nitrogen element in the interface between the crystal and liquid steel will influence the formation mechanism of crystal, that the existing of nitrogen element hinder the diffusion of atoms, increase the free energy of critical nucleation, raise homogeneous nucleation rate of crystal and lower the growing velocity of crystal accordingly, and refine the crystal grain finally for casting steel. And the effect degree of nitrogen will be influenced by the specialty of nitrogen on critical micelle concentration. During heat treatment, because of covalent bond between nitrogen atom and iron atom and manganese atom, the existing of nitrogen element in the boundary of crystal or the attachment of nitrogen element on the face of crystal will hinder the diffusion of iron atoms and manganese atoms, so that lower the growing velocity of crystal and refine the crystal grain of steel finally after heat treatment.