Reduction of harmful effects of nitrogen on the properties of low-carbon steel 08Y by electing a rational amount of nitride-forming elements

Abstract

Based on the thermodynamic analysis of nitride formation reactions, the advantage of titanium nitride formation and the lowest probability of boron nitride formation are established. Based on the analysis of experimental data, an analytical expression was established to calculate the required amount of titanium additives to neutralize the harmful effects of nitrogen, which also takes into account the concentration of aluminum in steel and prevents the formation of harmful aluminum nitrides. Necessary and sufficient concentrations of boron in steel are calculated to start the nitride formation reaction and to provide a strengthening effect associated with the formation of boron nitrides. Thermodynamic calculations and based on the analysis of the results of previous experimental melts of low-carbon steel, it is shown that the activity of oxygen in the intermediate to obtain particularly low-carbon steel should be such as to ensure the removal of carbon from it to a given limit, as well as the amounts of carbon deoxidized steels from ferroalloys and electrodes when heating steel on ladle-furnace installations, as well as from periclase-carbon lining-stalkovsha (carbon content in the area of the slag belt 10-12%, in the lining of the walls and bottom - 6%). The consumption of aluminum at the outlet of the furnace should be correlated with the degree of peroxidation of the metal, which would be desirable to stabilize and reduce the precipitation of silicomanganese and ring-containing ferroalloys. When organizing the evacuation of steel, reducing the pressure in the vacuum chamber to 100 mbar is theoretically sufficient for the predominant oxidation of carbon in comparison with manganese and silicon in the entire temperature range of the process. When evacuating non-deoxidized aluminum metal, the final carbon content in the metal of 0.01% is achieved even at its initial content of 0.074%. Due to the use of vacuum oxygen decarburization reaction without additional introduction of oxygen in gaseous form or in the form of oxides, it is possible to obtain a low-carbon metal with a guaranteed carbon content of 0.01% in the finished metal and a minimum manganese content of 0.12% and silicon up to 0.02 %, which provides high plastic properties of the metal. Keywords: low carbon steel, nitrides, titanium, boron, aluminum, vacuum carbon deoxidation