PRECIPITATION DURING THE SOLIDIFICATION AND COOLING OF MICROALLOYED IRON

The precipitation of titanium nitride during the solidification of an Fe-Ti-N-C melt saturated at the solidification temperature with respec t to TiN formation was investigated. On the basis of the Brody-Fleming s model, an approximately threefold enrichment of titanium and nitroge n in the interdendritic melt was calculated, yielding a supersaturatio n at the end of the solidification process exceeding a factor of 10. E xperimentally only a very low precipitation of TiN in interdendritic m elts was detected but a rather complete precipitation occurs during a holding time at 1300 degrees C. Comparing these results with a theoret ical description of the homogeneous nucleation the precipitation in th e interdendritic melt is shown to start at an approximately tenfold su persaturation.