До питання структуроутворення високоміцного чавуну при використанні діаграм стану систем «Fe-Si», «Mg-Si» та «Fe-Si-Mg»

Abstract

The purpose of the work is to establish the patterns of structural formation of high-strength cast iron using the thermodynamic theory of phase transformations and to analyze state diagrams of the components of Fe-Si-Mg ligatures. The article presents the results of the analysis of patterns of structural formation of high-strength cast iron when using state diagrams of the "Fe-Si", "Mg-Si" and "Fe-Si-Mg" systems. The concept of graphite formation in high-strength cast iron is considered. The structure formation scheme of high-strength cast iron is presented. Disclosure of the mechanism of processes of formation of spherical and vermicular graphite opens wide opportunities for controlling the structure and properties of high-strength cast iron and contributes to the development of effective technological processes for obtaining cast products for various purposes. It has been established that during the modification of cast iron melt, as a result of a significant redistribution of all elements dissolved in it, purification of impurities (sulfur, phosphorus, etc.) takes place, which allows obtaining the structure of cast iron with nodular graphite with the use of modifiers. Diagrams of the "Fe-Si", "Mg-Si" and "Fe-Si-Mg" systems for the development of the composition of high-strength cast iron are given. After analyzing the data of the given state diagrams, it was concluded that in the composition of spheroidizing ligatures, all compounds of elements are low-melting (tpl < 1300 °С) in relation to the melting temperature of cast iron. During the crystallization of cast iron with the release of austenite, a direct microliquation of silicon with a distribution coefficient less than unity is characteristic, manganese is more evenly distributed in the metal, and carbide stabilizing elements are treated in the liquid phase. The regularities of structure formation of modified cast iron under different crystallization conditions have been established. The analysis of the study of the regularities of the process of the formation of spherical and vermicular graphite and the analysis of state diagrams of the "Fe-Si-Mg" liga-tur components were performed.