GRAPHITIZATION IN HIGH-CARBON COMMERCIAL STEELS

Graphitization kinetics in two commercial high carbon steels, AISI typ es 1075 and 1095, are studied by conducting a series of isothermal ann ealing treatments in the temperature range of 560 to 680 degrees C for periods of time ranging from 20 to 500 h, The samples selected were c ollected along the processing route in a commercial production line de dicated to the fabrication of thin strip. The structures studied were those of hot rolling (consisting of fine pearlite), cold rolling (sphe roidized carbides within a deformed ferritic matrix), and subcritical annealing (spheroidized carbides in undeformed ferrite), The samples o btained from hot rolled coils do not graphitize, whereas those cold ro lled graphitize at a rate that depends on the type of steel and degree of deformation. No graphite was found in samples from the lower carbo n steel, which were subcritically annealed, although they were observe d in specimens from the other steel, which were cold rolled to a reduc tion of 50 % prior to the subcritical annealing.