Savchenko V. Optimization of chemical composition and modification technology of graphitized steels with the purpose of mechanical and service properties increase.

The object of research – graphitized steels with changing content of carbon and silicium. The subject of research – processes of modification, structure formation, mechanical and service properties of graphitized steels at room and high temperatures. The purpose of the work is development of such chemical content and modification technology of graphitized steel, which would allow obtaining optimal structure with compact graphite inclusions without heat treatment with minimal casting's wall thickness; and high level of mechanical properties both in cast state and after heat treatment.Research methods are spectral analysis, optical and electron microscopy, static tensile tests at room and high temperatures; hardness, heat resistance and heat conductivity determination, mathematical processing of experimental data with the use of personal computer; regression and correlation analysis.The influence of complex modification with aluminium and ferrosilicium, chemical content and cooling rate on the processes of structure formation, physical, mechanical and service properties of graphitized steels has been studied. Structural diagrams for graphitized steels containing 1.2% and 1.6% of silicium and up to 2% of carbon have been plotted. They represent the dependence of structure on the chemical content and casting's wall thickness. It has been established that due to smaller quantity of graphite inclusions according to tensile strength and plasticity indexes at room and high temperatures, and also according to heat resistance criteria K and C, steel of grade 100СЛ exceeds the indexes of high-strength cast iron ВЧ400 1.5…2.0 times. Implemented at Zaporizhzhya plant of nonferrous alloys with expected economical effect of 200 thousand hrn. per year. Area of application – metallurgy and machinery.