An oxidation method has been employed to reveal prior austenite grain
boundaries in C-Mn and interstitial free (IF) steels. The ability of t
his technique to reveal prior austenite gain boundaries is assessed by
comparing its results with those of an etching method applied on the
C-Mn steel. Optimum conditions were established by trial and error. Th
e conditions varied with different steels and with heat treatment temp
erature. In the IF steel vapid grain growth at high temperatures in th
e ferrite range made a significant contribution to the prevention of g
rain refinement through transformation. Attempts to obtain the smalles
t prior austenite gain size in the IF steel to assess the ability of t
he oxidation technique to reveal fine austenite grains led to an avera
ge austenite grain size of 80 mu m in warm rolled samples after the sh
ortest holding time at 950 degrees C.