HOT DEFORMATION STUDY BY PROCESSING MAPS OF N CONTAINING MICROALLOYED STEEL

The hot formability of a microalloyed steel with 0.16 wt-%C modified with N is studied by using processing maps. Compression tests of cylindrical samples are carried out using a Gleeble (R) 3800 simulator in the range of temperature between 750 - 1000 degrees C and strain rates between 0.01-100 s(-1). For this alloy, an A(r3)-temperature about 740 degrees C is determined by means of dilatometry. Processing maps are calculated using the modified dynamic material model developed by Murty and Rao for different logarithmic strains. For the instability map, the parameter kappa(j) developed by the authors in previous works is used and compared with other instability values. Softening in the flow curves provoked by induced ferrite during deformation at low temperatures and low strain rates is reflected in the eta-value. Light optical microscopy (LOM) and electron back scattered diffraction (EBSD) measurements are used to study the microstructure of the hot deformed samples to determine the deformation mechanisms active and to verify the processing maps.