CHARACTERISATION AND MODELLING OF MICROSEGREGATION IN LOW CARBON CONTINUOUSLY CAST STEEL SLAB

摘要

Segregation during casting of microalloyed steels can affect subsequent processing and final properties. In optimising composition - processing combinations an accurate prediction of the composition and distribution of solute-rich and solute-depleted regions is needed. A series of low carbon (0.06 - 0.14 wt % C) as-cast steel slabs have been investigated using statistically significant SEM-EDS mapping to characterise the compositions of solute-rich and solute-depleted regions as well as their size and spacing. A Clyne-Kurz model has been applied to these alloys (which all involve the peritectic formation of austenite during their solidification) using Thermo-Calc predictions of transformation temperatures and compositions. Initial modelling using carbon re-distribution predicted solute-rich fractions within 3 % of experimentally-determined values. Measured composition agreement with Clyne-Kurz and Thermo-Calc predictions was less good. The microalloying elements such as Nb seemed to have little effect on the prediction of solute-rich fractions. This paper will report the progress in modelling and characterisation of segregation in continuously cast steel slabs.