Improving steel melting intensity in the process of electrosmelting from waste and pellets (HBI)

Abstract

The paper addresses the issue on improving the intensity of melting in the production of steels using hot briquetted iron (HBI) in the charge that mostly consists of metal waste. An analysis has been performed into the features of melting that uses charge of complex composition. To ensure the boiling of metal bath, it is recommended to introduce to the bath carbon-containing raw materials in the form of steel waste in the amount exceeding 80 %. It was established that applying HBI almost does not reduce the yield of usable metal due to a high content of metal waste that makes up the charge.At the same time, the paper analyses the role of silicon and manganese oxidation process in the refining of liquid steel at melting the alloy wastes used as charge materials in an electric arc furnace. The dependences of equilibrium concentrations of oxygen and silicon at different temperatures in the system Fe‒Si‒O have been given. In addition, the dependence diagram of manganese oxidation products in a liquid iron on the temperature and concentration of manganese in the alloy MnO‒FeO has been constructed. The equilibrium concentrations of oxygen and silicon with carbon deoxidizing capability have been defined, in the field of liquid silicates and in the field of solid SiO2.The high-quality silicon and manganese oxidation when smelting steel made from metal waste and hot briquetted iron (HBI) contributes to the fullest refining of liquid steel through the phases metal-slag or metal-gas.It has been shown that the content of silicon during electrical steel refining drops to traces. Thus, when using metal waste and pellets as charge in the steel-making process, a silicon oxidation reaction does not reach equilibrium. If a sour process is performed, then the oxidation of silicon reaches equilibrium and, under certain conditions for melting the charge under the influence of heat from an electric arc, there may occur a significant reduction of silicon that takes place at a higher temperature (a silicon-reducing process). The basic process of melting the charge from metal waste and hot briquetted iron in an electric arc furnace has been recommended. In this case, the reducing period of melting is aimed at metal deoxidation, sulphur removal, at bringing the chemical composition of steel to the preset composition, at controlling the process temperature. All these tasks are solved in parallel throughout the entire reduction period. The complete removal of oxidative slag was followed by adding to the furnace of slag-forming mixes together with deoxidizing agents, that is the new slag (carbide or white) was introduced.A rise in the furnace bath temperature decreases the equilibrium constant of manganese. Therefore, in the absence of ferromanganese additives in the bath in the process of melting refinement, the behavior of manganese in the bath can be an indicator for the metal temperature.