Аналіз впливу вмісту та співвідношення хімічних елементів на фазовий склад та твердість вуглецевих сталей різного складу

Abstract

The axle resource depends on many indicators that determine its service characteristics. These are the chemical composition of steel, structural condition, level of indicators of strength, plasticity, viscosity, etc. However, the most important technical indicator of axle performance is its fatigue strength. To ensure high reliability of axles, it is necessary to form a homogeneous structure and achieve optimal metal purity, avoiding the formation of coarse non-metallic inclusions and their accumulations. It is known that liquation in most cases is formed during crystallization (solidification of an ingot or continuously cast billet). The hereditary influence of the features of the primary structure formation of BLZ and the factors that determine them on the final microstructure and the set of properties of the finished metal products have not been sufficiently studied. Purpose: study of the influence of the chemical composition of carbon steels with different contents and ratios of basic chemical elements on the features of the formation of the microstructure of carbon steel and its hardness. As part of this work, experimental ingots of carbon steels of different chemical composition were melted. The samples were subjected to hot plastic deformation and heat treatment. Hot plastic deformation was carried out by the method of deposition at a temperature of 1260˚C by 50%. The next heat treatment consisted of normalization from 850˚С. According to the results of the metallographic study, the quantitative ratio of pearlite and ferrite in the test samples in the cast state, after hot plastic deformation and after subsequent heat treatment was calculated. The hardness of the experimental steels in different states was determined by the Brinell method. Phase composition was evaluated using ImageJ software. The fundamental role of carbon in the formation of the amount of the pearlite component and hardness has been confirmed. A fragmentary influence of the manganese content on the amount of pearlite in the experimental samples after heat treatment was established, which increases with the increase in the content of this element. A close relationship between vanadium and the amount of pearlite component in the state after hot plastic deformation and partially after hot plastic deformation with subsequent heat treatment was revealed. Aluminum also has a fragmentary effect - with an increase in the content of this element, the amount of pearlite partially decreases, and for the other part of the melts of experimental steels, on the contrary, the share of pearlite increases with an increase in the content of aluminum.