Characterization of Parent Austenite of Martensitic and Bainitic Steels Based on Their Texture Developed during Phase Transformation

The crystallographic texture of bainitic and martensitic steels determined at room temperature is related to the texture of the prior austenite owing to the orientation relationship between the parent and daughter phases. This allows, in particular, to judge about the deformation or recrystallization of austenite. It becomes possible to analyze the effect of hot rolling on the austenite structural state, which precedes quenching. The structures and textures of bainitic and martensitic steels have been analyzed using electron backscatter diffraction. In the case of single-pass rolling, the state of prior austenite can be estimated based on the morphology of austenite grains reconstructed on the basis of the electron diffraction data. In the case of multi-pass hot rolling, which proceeds with a gradual decrease in temperature, such an estimate is difficult due to peculiarities of structure development. At the same time, this can be performed based on of the analysis of crystallographic texture of steel. As a quantitative characteristic of the structural state of austenite, a scalar parameter is proposed that depends on the relative intensity of texture components formed during the phase transformation.