Intro 上游充道大粤 SHANGHAI JIAO TONG UNIVERSITY Typical processes for eutectoid transformation: Normalizing(正火)： Heating at least 55C above the upper critical temperature-i.e.. above Ac3 for compositions less than the eutectoid (0.76 wt%C),and above Accm for compositions greater than the eutectoid.After sufficient time has been allowed for the alloy to completely transform to austenite-the treatment is terminated by cooling in air Full Annealing(退火： 52 Heating to a temperature of about 50 C above Ac3(to form austenite) for compositions less than the eutectoid,or,for compositions in excess of the eutectoid,50 C above the A line(to form austenite and Fe3C phases);then furnace cooled (for several hours) For increased machinability and formability In both processes,austenitization occurs before eutectoid reactions a+Fe3C→Y K.Chen 5K. Chen Typical processes for eutectoid transformation: Normalizing (正火):  Heating at least 55 ºC above the upper critical temperature – i.e., above Ac3 for compositions less than the eutectoid (0.76 wt% C), and above Accm for compositions greater than the eutectoid. After sufficient time has been allowed for the alloy to completely transform to austenite – the treatment is terminated by cooling in air Full Annealing (退火):  Heating to a temperature of about 50 ºC above Ac3 (to form austenite) for compositions less than the eutectoid, or, for compositions in excess of the eutectoid, 50 ºC above the A1 line (to form austenite and Fe3C phases); then furnace cooled (for several hours)  For increased machinability and formability In both processes, austenitization occurs before eutectoid reactions Intro 5 α+Fe3C→γ