Peter the Great St. Petersburg State Polytechnic University (St. Petersburg, Russia):

A. A. Kazakov, Dr. Eng., Prof., Head of the Metallurgical Expertise Laboratory, e-mail: kazakov@thixomet.ru
D. V. Kiselev, 1^st Category Engineer
O. V. Pakhomova, Chief Engineer

National Research Centre “Kurchatov Institute” - Central Research Institute of Structural Materials “Prometey” (St. Petersburg, Russia):
O. V. Sych, Cand. Eng., Head of the Sector

The relationships of the anisotropy behavior and other characteristics of structural heterogeneity over the thickness of the plate have been established and their microstructural interpretation has been presented using the example of low-alloy plate steel. The features of structure formation from the surface to the center of 100 mm thick plate metal have been considered with a detailed description of the structure evolution and the processes that caused these changes. It was found that a fine quasi-homogeneous structure consisting of lath bainite and granular bainite provides anisotropy K_a100 <1 and occupies a narrow layer from 5 to 17 mm from the plate surface. In the near-surface layer, due to the abnormal structure consisting of large austenite grains elongated along the rolling direction and decorated with allotriomorphic ferrite, the anisotropy is K_a100 > 1. In a quarter of the plate thickness, due to weak fragmentation of the structure, the anisotropy is K_a100 > 1. In the center of the plate, quasi-polygonal and polygonal ferrite absorbs all extended boundaries of the former austenite grains; therefore, K_a100 becomes again less than unity.

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