OJSC “BSW – Management Company of the Holding “BMC” produces a wide range of carbon, high‑quality, alloyed and high‑carbon steel grades, among which a signifi ant share is peritectic grade steels. Basically, the steel of this group is used to produce rolled products intended for the manufacture of components for the automotive industry. The process of production and casting of these steels is characterized by the greatest instability and is often accompanied by rejects and forced sorting of products. This situation is typical for other metallurgical enterprises. Therefore, the search for technological solutions that ensure an increase in the yield while maintaining the existing productivity of metallurgical units is an urgent aspect of improving the technology of continuous casting of peritectic grade steels. At the same time, the main scientific and technical task is to obtain a stable quality of continuously cast billets, aimed at preventing and eliminating the formation of a number of characteristic defects, primarily cracks on the surface of continuously cast billets and rolled products. The search for methods and technological solutions to improve the quality of products made of peritectic grade steel is the goal of the ongoing research.
Seamless hot – rolled pipes are a popular metal product on the world market. During operation, pipelines are subjected to cyclic loads associated with temperature fluctuations, vibrations near compressor stations, and pressure drops in the transformed medium. One of the ways to ensure high performance properties is to manage the quality of pipe metal, including that laid in the process of metallurgical production. All the basic physical and mechanical properties of metal materials are structurally sensitive and significantly depend on both the grain size and the degree of uniformity of the grain structure, that is, on the different grain sizes. For metallographic research, samples of pipes with the size of 70,0×12,5 mm of S460NH steel were selected with satisfactory (#1) and unsatisfactory (#2) results of the impact. It was found that the inhomogeneous (multi – grained) microstructure in sample #2 was the reason for obtaining unsatisfactory results of the impact. As a result, it was found that one of the most important characteristics that can guarantee stable and satisfactory results of mechanical characteristics, in particular the impact performance, is a homogeneous grain structure.
An actual problem of production bars with increased geometry accuracy at existing mill 370/150 at OJSC “BMZ -management company of Holding “BMC” has been reviewed. The object of research was reducing-sizing mill, composed of three finishing stands. The subject of research was rolling process in finishing stands aiming at achieving highly accurate geometry in the finished profile. In the work, based on empirical data, efficiency of existing methods of sizing by statistical method to produce a profile of regular accuracy and highly accurate profile was assessed. By the method of finite elements the rolling processes were simulated, approximated to real conditions by means of numerical modeling. Empiric and theoretic data revealed drawbacks of existing systems of sizing, as well as let determine further direction of research. Analytical description of key factors of rolling affecting creation of profile enabled to come to conclusion that the basis for achieving geometry sizes of transversal profile depends on pressure of steel on to rolls and the inter-stand tension. On this basis the new method of sizing has been developed. On the basis of the new method of sizing, rolling processes at different frequencies of rolls rotation were simulated. The process of mathematical simulation to the maximum approximated to real conditions of rolling. Thanks to this it became possible to obtain reliable results of research, enabling to achieve highly accurate geometry of transversal profile. Obtained results of research are the basis for further study of inter-stand deformation to be followed by experimental rolling at mill 370/150.
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