Quantitative assessment of microstructural inhomogeneity by thickness of hot-rolled plates made of cold-resistant low-alloy steel for Arctic applications

Abstract

A technique to assess microstructural anisotropy assessing by the thickness of the plate steel based on the texture analysis of the image has been developed. This technique provides for the anisotropy assessment at two dimensional levels: in the short-distance and long-distance neighborhoods, which characterize the elongation along the rolling direction of fine and coarse structural constituents, respectively. The practical approval results of this technique in the study of the microstructural heterogeneity of ferritic-bainitic steels over the thickness of 25–70 mm hot-rolled plates have been presented. It has been shown that the proposed anisotropy criteria in combination with the volume fraction of coarse packet-block regions of lath bainite as well as regions of bainite without an internal developed subgrain structure adequately estimate the microstructural heterogeneity over the thickness of plate steel and can be used for a detailed interpretation of the two-stage thermomechanical processing technology with accelerated cooling including taking into account the metallurgical inheritance of the slab.