EVALUATION OF FRACTURES AND STRUCTURES MORPHOLOGY IN CONSTRUCTION STEELS USING THE COMPUTERIZED PROCEDURES

The absence of fast-acting, documented, objective procedures for structures and fractures measurement makes it difficult to compare inhomogeneity of their structure for identifying structure critical factors limiting the destruction. Therefore, the administrative decisions taken to improve the quality of metal products are often subjective what makes them ineffective, limiting their applying by the narrow circle of tasks. The application of suggested computerized procedures made it possible to perform bulk documented measurements of the construction steels structures and fractures images made in 2D and 3D examination scales. For more accurate identification of structures, they were observed within the same field using the optical, atomic-powered, scanning electron microscopy and electron backscatter diffraction (EBSD - analysis). The fracture relief was reconstructed from the bulk measurements of 2D and 3D geometry of tough fractures of steels with different types of structures (secondary sorbite, ferrite-perlite banded orientation, the residual portion of the fir-tree structure), testing schemes (drop-weight test, static tension test, and test when trepanning throughout the rolling directions, tangentially in forging). It allowed identifying the relief geometrical parameters determining the differences in the metal viscosity levels (a pit depth and diameter, the web thickness between the adjacent pits). To estimate the inhomogeneity of pits distribution in fracture the authors used the statistics of Voronoi polyhedra (the polyhedra distribution by areas, the number of neighbors and the distance between pits). The statistics of measurement results of the structures and fractures elements may be useful both for their identification and for updating the mechanisms of ductile and brittle fracture in structural steels (during the  direct comparison of structures and fractures) in order to identify the factors limiting the quality of metal. It is essential for the promotion of administrative decisions objectivity and efficiency while improving the consistent quality of multipurpose metal products.