EFFECT OF DEFORMATION ON GRAPHITIZATION KINETICS IN HIGH-CARBON STEELS

Transformation of iron carbide into graphite (graphitization) was obse rved to occur during industrial processing of high carbon thin strip s teel. Samples of cold rolled and isothermally annealed steels (AISI ty pes 1075 and 1095) were taken along their processing route and were su bjected to a series of isothermal annealing treatments in the temperat ure range of 560-680 degrees C for periods of time ranging from 20 to 500 h. The structures of the different samples were those of cold roll ing (spheroidized carbides within a deformed ferritic matrix) and subc ritical annealing (spheroidized carbides in undeformed ferrite). Tt wa s found that the rate of graphitization depends on the type of steel a nd degree of deformation. No graphite was found in samples from the lo wer carbon steel which were subcritically annealed, although they were observed in specimens from the other steel which were cold rolled to a reduction of 50% prior to the subcritical annealing. (C) 1998 Elsevi er Science S.A. All rights reserved.