ASSESSMENT OF THE EFFECT OF CARBON ON PERFORMANCE PROPERTIES AND THE MICROSTRUCTURE OF ROLL STEEL

This paper concentrates on studying the effect of carbon on performance properties of 150KhNM roll steel grade. The introduction contains a brief literature review on the effect of the roll alloy chemistry on performance and mechanical properties of mill rolls. Besides, it demonstrates the relevance of the presented studies. The paper describes the effect of chemical elements, such as manganese, niobium, vanadium, nickel on the microstructure and mechanical properties of mill rolls. It also classifies alloying elements by their effect on polymorphic transformation temperatures and shows carbide-forming elements increasing such property. We also considered the effect of the carbide phase on hypereutectoid steel. The paper contains carbide compounds that may be formed in steels, and their classification. It describes the mechanism of the effect of the carbide phase on performance properties of steel castings. The second part of the paper presents a research procedure and briefly describes materials used for the research and laboratory and analytical equipment. The third part of the paper presents the research results. It describes the effect of carbon in a broad range on service durability of hypereutectoid roll steel in conditions of wear at room and elevated (400 ºС) temperatures. Besides, we determined the effect of carbon on the roll alloy microstructure and analyzed relations between the microstructure and performance properties of hypereutectoid roll steel. The conclusion of the paper summarizes the results and contains the references used for an analytical review.

STUDING OF ROLL STEEL STRUCTURE FORMATION PROCESS

Roll steel crystallization process, and formation process of it's microstructure during cooling are considered in this article. Presented results are received by conducting of laboratory experiments, metallographic researches of roll steel. Short review of science literature is carried out, data about alloys applied in roll production is showed in first part of the article. Moreover, problems in roll manufacture, with which industry have faced, as well arising due this science obligatoriness for making researches, are considered. Based on performed analysis, the researches' target is formulated. Methodology and equipment used during researches are short considered in second part of the article. Besides, influence of cooling speed on roll steel parameters: actual grain size, carbide phase quantity, and temperature intervals of its formation are reviewed. Quantity characteristics of roll steel microstructure have determined. Data received due researches in laboratory conditions are presented graphical. Conclusions based on obtained results, as well as recommendations for further researches are given in final part of the article.

Development of Modeling Algorithm of the Characteristics of the Steels in the Subsystem of Management of the Production Resources of Steel Production

The article is devoted to the development of an algorithm for modeling the characteristics of steels in accordance with customer requirements. A mathematical model is presented that takes into account the optimal levels of the main factors and their interaction, providing the required values of the characteristics. The next step in the study of the mathematical model was modeling by means of functional modeling methodology IDEF0. Input and output data, as well as normative documents of model management and mechanisms of this management for building a functional model are defined. The control mechanism was the software product OptimalSostav, developed using the object-oriented programming language Delphi. The software product is designed to simulate the characteristics of steels using the specified limits of permissible minimum and maximum values of mechanical properties. The algorithm of realization of the control mechanism, which is based on the fractional factor analysis, is described. The presented algorithm allows to identify the influence of chemical composition on the mechanical properties of steels in the form of mathematical and graphical dependencies and to determine the specified mechanical properties that meet the requirements of the customer. The main possibilities and the scope of the software product, which allows to solve the problem of predicting the optimal chemical composition, providing the required mechanical characteristics, as well as to adjust the process of steel melting within a given chemical composition to achieve the desired set of properties. The application of the software product on the example of the analysis of the influence of chemical elements on the mechanical properties of 75HMF roll steel is shown. The results of modeling in the form of mathematical and graphic dependences are given and the estimation of efficiency of application of the software product is given. The results of solving the problem of approximation of the obtained graphic dependences of the influence of chemical elements on the mechanical properties of the studied steel grade by means of Microsoft Excel are presented. It is established that the developed mathematical and algorithmic software of the software product allows to study the percentage of chemical elements in relation to the total composition of the alloy, based on the obtained pie charts and dependency graphs. The adequacy of the model is confirmed by experimental results.

A Nonlinear Dynamic Switched-Mode Model of Twin-Roll Steel Strip Casting

During twin-roll steel strip casting, molten steel is poured onto the surface of two casting rolls where it solidifies to form a steel strip. The solidification process introduces a two-phase region of steel known as mushy steel which has a significant effect on the resulting quality of the manufactured steel strip. Therefore, an accurate model of the growth of mushy steel within the steel pool is imperative for ultimately improving strip quality. In this paper, we derive a reduced-order model of the twin-roll casting process that captures the dynamics of the mushy region of the steel pool and describes the effect that the casting roll speed and gap distance have on the solidification dynamics. We propose a switched-mode description that leverages a lumped parameter moving boundary approach, coupled with a thermal resistance network analogy, to model both the steel pool and roll dynamics. The integration of these models and simulation of the combined model are nontrivial and discussed in detail. The proposed reduced-order model accurately describes the dominant dynamics of the process while using approximately one-tenth of the number of states used in previously published models.