Development of microstructure and texture of medium carbon steel during heavy warm deformation

The microstructure and texture development of a medium-carbon steel (0.36% C) during heavy warm deformation (HWD) was studied using scanning electron microscopy and electron back scattering diffraction. The spheroidization of pearlite is accelerated due to the HWD, which leads to the formation of completely spheroidized cementite already after the deformation and coiling at 873 K (600 deg. C). The homogeneity of the cementite distribution depends on the cooling rate and the coiling temperature. The cooling rate of about 10 K/s (ferrite-pearlite prior to HWD) and deformation/coiling at 943-973 K (670-700 deg. C) lead to a homogeneous cementite distribution with a cementite particle size of less than 1 μm. The ferrite softening can be attributed to continuous recrystallization. Even up to fairly high deformation/coiling temperatures of 983 K (710 deg. C) the texture consists of typical deformation components. During the continuous recrystallization the amount of high angle grain boundaries can increase up to 70% with a ferrite grain size of 1-3 μm. An increase of the cooling rate up to 20 K/s (ferrite-pearlite-bainite prior to HWD) deteriorates the homogeneity of the cementite distribution and the softening of ferrite in the final microstructure