Intro 上帝支通人学 JLAO TONG UNIN Typical processes for eutectoid transformation: 。Normalizing(正火) Heating at least 55C above the upper critical temperature-i.e., above A 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： Heating to a temperature of about 50C above Ac3(to form austenite) for compositions less than the eutectoid,or,for compositions in excess of the eutectoid.50C 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 55