Uniiat M. Improvement of quality for low-alloy structural steels due to increasing the chemical homogeneity by means of heat treatment and optimization of the chemical compositions

The object of research - processes of formation of structure and properties of low alloy steel. The subject of research - features of the effect of chemical composition and heat treatment on microstructure and properties of low alloy steel. Research methods: optical and scanning electron microscopy, energy dispersive spectroscopy, XRD; methods of mathematical statistics and factorial experiment design. In the dissertation is given a solution of actual scientific and technical task, that is the improvement of operational performance, elimination of the anisotropy of the mechanical and physico-chemical properties by optimizing the chemical composition and a homoge-neous spatial distribution in the microstructure of the main alloying elements. Using the methods of the deep data analysis researching, investigated the effect of production parameters (chemical composition and thickness of rolled metal) on the key in-dicators of the mechanical properties: ultimate strength, yield strength, percent elongation and impact resistance. Examined herein the influence of thermal treatment on the chemical distribution of elements, microstructure, hardness and mechanical properties of the welded manganese steels. It is established that in the process of isothermal soaking in a two-phase re-gion there are intensive processes of grain-boundary diffusion, which lead to redistribution of the alloying elements. For low-carbon steels: 10G2FB, 09G2S homogeneous spatial distribution of the ele-ments is achieved at the temperature 710 оС and exposure for 1.5 and 3 min/mm. E36 Steel, which contains up to 0.18% must be subjected to a more isothermal high tempera-ture exposure (T=810 оС 3 min/mm) to achieve homogeneous distribution of the chemical elements. Using the methods of mathematical analysis, experimented optimization of the chemical composition of the investigated steel E36. Determined the optimal chemical composition and developed the processing mode of a heat treatment (patent of Ukraine No. 83059) of steel E36, which provides high-repeatability indicators of the quality of rolled metal sheet. It is shown that the most sensitive characteristic of mechanical properties: impact resistance, is influenced by such elements: C, Mn, Si, P, H2.