On the Pearlite Reaction in a Hadfield Steel

Abstract

The precipitation of proeutectoid carbide and the pearlitic transformation in a rehe ated high manganese steel were examined by the isothermal dilatation method, the isothermal magnetization method, and both the optical and the electron microscopic observations. The results obtained were as follows:
1) From the measured interlamellar spacing of pearlite in an isothermally heated steel, it is consideredth at the growth of pearlite in this steel is similar as that in other carbon or low alloy steels, though the trans-formation rate of this steel is extremely small, because of the high alloy content.
2) Pearlite in the isothermally heated steel grows with two time-dependent processes, initial rapid growthf ollowing steady slow growth in thermo-magnetic curves. The excellent correlations between the former and the growth of proeutectoid carbide are observed.
3) Activation energy for pearlitic transformation varies with isothermally heated te mperatures, and increases at temperatures lower than 500°C. Also, the time-dependence of activation energy which varies as the proceeding of growth, is observed.
4) The activation energy value for pearlitic growth in 500-600°C indicates that the initial growth of pearlite in this steel may be dependent upon either the self-diffusion of Fe atom in γ, or the interfacediffusion of Fe atom at the interface between γ and pearlite.
5) In the pearlite reaction of high manganese steel, the partitioning of manganese is considered to be an extremely important factor, and the whole transformation behavior is affected by this factor.