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The paper is devoted to examination of the effect of boron modification and temperature conditions for metal cooling in a mold on phase composition, morphology and chemical composition of structural components of heatand wear-resistant white cast iron of Fe – C– Cr– Mn – Ni – Ti–Al – Nb system. The phase composition of the metallic base changed from the dualphase (α- and γ-phases) to the completely single-phase (γ-phase). Boron modification influenced on the type of secondary carbides, while secondary hardening in a mold occurs through extraction of dispersed niobium carbides (without boron, but with chromium carbides). The structure of modified cast iron is presented by the primary complex carbides (Ti, Nb, Cr, Fe)C, as well as by solid solution dendrites, eutectics and secondary carbides MeC. Boron addition changes the chemical composition of primary carbides with decrease of niobium content from 44 to 2 % and increase of titanium content from 24 to 65 %; content of eutectic carbides rises as well. As for hypereutectic carbides, they are characterized by increase of ferrum content and lowering of chrome content. Parameters of the primary phases (MeC carbides and solid solution dendrites) were investigated using the methods of quantitative metallography. The special technique of Thixomet PRO image analyzer was used for evaluation of the F form factor which is the criterion of compatibility of the primary phases. The following parameters were used in this work as the parameters of dendrite structure: dispersity of the dendrite structure (δ), volumetric part of dendrites (V), distance between the axes of second order dendrites (λ2 ), form factor (F), average dimensions of dendrites – square (S), length (l) and width (β). All the suggested characteristics (parameters) allowed not only to provide quantitative evaluation of the dendrite structure, but also to determine modification degree as relative variation (in %) of each criterion in modified cast iron in comparison with non-modified iron. Quantitative relation between modification degree and crystallization conditions were established as well.

The fraction for forming texture of rolls surface of the training mills is investigated in this work. The fraction from various manufacturers has been estimated by comparing the most important characteristics. Metallographic studies of the steel fraction microstructure were carried out on the MEIJI 2700 optical microscope (Japan). Automated processing of measuring results of various shapes indenters microhardness was conducted. Comparing the obtained results with the characteristics declared by the manufacturers was carried out. The rolling roll surface microstructure with which the texture of the cold-rolled strip surface is formed, is investigated in the paper. Roller steel widely used at present as well as the most common methods of rolling roll surface microrelief forming, such as mechanical and electroerosion ones, are discussed in the work. It was established that with the electroerosion method, a more uniform structure with a smoothly changing microrelief was formed on the surface of the roll as compared with the mechanical action of the abrasive. According to the results of the research, recommendations were formulated on the use of the fraction that has the best performance characteristics and which allows one to obtain surface roughness by transferring it to the surface of a cold-rolled strip in accordance with the requirements of consumers.

The paper presents the data on phase composition and structure forming for the alloys and oxide layers, on distribution of elements among the alloy structural components and oxidation surface through the depth of oxide and sub-oxide layers, on variation of wear resistance, scale resistance, growing stability and mechanical properties of cast iron of Cr-Mn-Ni-Ti-Al-Nb system depending on different aluminium and niobium content and thermal accumulating capacity of a casting mould. Complex carbides (Nb, Ti)C are forming in white cast iron during niobium alloying. Quantitative metallographic analysis of (Nb, Ti)C carbides and (Cr, Fe, Mn) 7 C 3 complex carbides was carried out on the samples with examined composition. The tests for scale resistance were conducted, structure and properties of cast iron were investigated. It was determined that chemical composition and structure of oxide layers depend on distribution of alloying elements among the alloy structural components. It was established that the areas of oxide film surface layer, which were formed on eutectics, contain mainly manganese; its concentration is more than 65 %, while Al is 4 % and Cr is 1 %. Manganese leads to increase of defects amount, such as pores, micro-cracks and vacancies, in oxide film during high-temperature gas oxidation; penetration ability of this film also increases, what has a negative effect on metal resistance to further destruction caused by oxidation. The film becomes porous, its thickness enlarges. Aluminium provides favourable influence on forming of the thin protective spinel-type films (dense substance with good metal adhesion) with minimal amount of defects; diffusion through such oxide film is very difficult. The areas of oxide layer, which were formed on austenite dendrites, contain mainly aluminium; its concentration is more than 24 %, while Mn is 16 % and Cr is 12 %. High aluminium content provides small film thickness. Joint alloying by aluminium and niobium leads to simultaneous increase of heat resistance and wear resistance. Wear resistance increased as a result of enlargement of the part of primary carbides (Nb, Ti)C with high hardness in the structure of cast iron. Composition of oxide films includes aluminium which strengthens their protective properties and rises of the alloy scale resistance. Alloying by niobium leads to secondary hardening during cooling in a casting mould. Dispersion particles of М 7 С 3 carbides are forming in solid state, thereby no structure degradation occurs during testing at increased temperatures, and growing stability rises.

The paper compares the technical characteristics of two thermochemical treatment (TCT) lines for self-tapping screws at OJSC MMK-Metiz. Quenching on TCT line 1 is carried out in the furnace by AUTOMATION SERVICE, while quenching on TCT line 2 is carried out in the furnace by KOHNLE. The authors described quenching and tempering schedules in these two furnaces, studied the microstructure of screws at all process stages, determined technical parameters and properties of finished products after thermochemical treatment. The research showed that the best performance had TCT 2 by KOHNLE. The metallographic analysis indicated more stable parameters of the layer thickness after nitrocarburizing, core and surface hardness, which was in full compliance with regulatory documents. By introducing a better structure of a new TCT line by KOHNLE, a TCT process period became shorter, and a range of self-tapping screws might be extended entailing a higher output of finished products.