The dissolution process of complex dendritic precipitates of as-cast V-Nb-Ti micro-alloy steel slab was addressed, using scanning electron microscopy, transmission electron microscopy and inductively coupled plasma-optical emission spectrometry. The progress of the dissolution process was followed by re-heating the as-cast sample at 1250°C and 1300°C for 30 and 90 minutes. The as-cast microstructure was comprised by complex Ti-rich (Ti,Nb,V) and Nb-rich (Nb,Ti,V) carbonitrides, as well as nanometric precipitates based on the three micro alloys. The former was found in micrometric sizes with cuboidal, plates and dendritic morphologies. The primary and secondary arms of dendrites were rich in Ti, while the tertiary arms were rich in Nb. During re-heating incomplete dissolution of large dendritic precipitates was observed even at 1300°C, resulting in spherodized (Nb, Ti, V) particles and Ti-based carbonitrides, practically unaffected by the heat treatment. Vanadium did not dissolve completely in austenite at this condition, remaining bound to Ti within Ti-rich precipitates and in less proportion to Nb-rich carbonitrides, being both
the Ti-rich and Nb-rich carbonitrides with vanadium thermodynamically stable at least up to 1300°C. The process of dissolution will be discussed.