A new technological approach to the granulation of slag melts of ferrous metallurgy: obtaining glassy fine-grained granules of improved quality

The technological factors required to improve the operational properties of granulated metallurgical slags demanded in the building industry have been analyzed. In order to satisfy these factors, a new technology for hydro-vacuum granulation of slag melts (HVG) has been developed. It is shown that the main advantage of the proposed HVG process is the provision of forced high-speed vortex convection of water, with the effect of vertical suction, crushing, and degassing of the three-phase (water–slag granules–water vapor) heterogeneous medium formed during the overcooling and solidification of slag. It is proved that the high-speed volumetric disintegration and overcooling with the degassing effect sharply reduces a degree of aggressive gas/vapor impact on the being cooled particles of slag, which, in turn, leads to the reduction of the perforation degree of the granules. The obtained granules are distinguished by stable fractionation and improved, well-defined dense amorphous glassy structure, the water-holding capacity of which has reduced from 45–50% to 25–13%, the actual moisture content from 24–20% to 6–4%, while the hydraulic activity in terms of CaO-uptake increased from the conventional 320–360 mg/g to 610–650 mg/g. Pilot scale research demonstrated that the designed equipment for the HVG technology allows sustainable control of the quality of granules, and it has the potential for further development and implementation.

FORECASTING OF PHYSICO-CHEMICAL PROPERTIES OF LADLE’S SLAGS ON THE BASIS OF THE CONCEPT OF THE DIRECTED CHEMICAL COMMUNICATION

The work is devoted to the development of a methodology for the operational forecast of the properties of the final blast furnace slag by its chemical composition and temperature to improve the quality of hot metal in terms of sulfur content.The analysis of the accumulated experimental data on the properties of modern blast furnace slags is performed, using the criteria of the theory of directed chemical bonding the dependences of liquidus temperature on model parameters are established and an adequate forecast model of bucket slag liquid temperature on its model parameters is obtained.The created technique allows to obtain temperature dependences of density, surface tension, viscosity and electrical conductivity of real blast furnace slags in the temperature range 1200-1400 ° С.The approach to modeling of slag melts at the level of interatomic interaction used in the article can be used to develop predictive models of different technological properties of furnace slags in a wide range of temperatures. The obtained results are of practical importance and can be used for rapid prediction of the liquidity temperature of furnace slags and adjustment of their chemical composition in accordance with technological requirements.

MOLECULAR DYNAMIC SIMULATION OF THE MELT OF OXIDE-FLUORIDE INDUSTRIAL SLAG-FORMING MIXTURE

The paper discusses the results of molecular dynamic simulation of a melt of the multicomponent oxide-fluoride system CaO – SiO2 – – Al2O3 – MgO – Na2O – K2O – CaF2 – FeO, corresponding to composition of industrial slag-forming mixture (SFM) used in steel casting for slag targeting in the mold of a continuous casting machine (in wt %: 35.35 % SiO2 , 30.79 % CaO, 8.58 % Al2O3 , 1.26 % MgO, 13.73 % CaF2 , 7.57 % Na2O, 0.88 % K2O, and 1.82 % FeO). These concentrations were converted to mole fractions, and the number of ions was calculated for each of the components in the model. An eightcomponent oxide-fluoride melt containing 2003 ions in the main cube with a side length of 31.01 Å was simulated under periodic boundary conditions at an experimentally determined solidification onset temperature of 1257 K at constant volume. Coulomb interaction was taken into account by the Ewald–Hansen method. The time step was 0.05t0, where t0 = 7,608·10–14 s is the internal unit of time. The melt density was taken to be 3.04 g/cm3 based on our experimental data. The interparticle interaction potentials were chosen in the Born–Mayer form. Based on the simulation results, the structure of subcrystalline groups of atoms present in the melt at the temperature of solidification onset was determined. A discussion of the simulation results and their comparison with the literature data was held. It is shown that the computer model allows one to obtain a fairly realistic picture of atomic structure of the slag melt, indicating that the main structural component of all silicate systems is silicon-oxygen tetrahedron. Tetrahedra in silicates are either in the form of structural units isolated from each other, or, connecting together through peaks, they form complex anions. It is consistent with the theory of slag melts. Molecular-dynamic simulation allows one to obtain adequate information on structure of the melt of a certain chemical composition.

Viscivity of the B2O3-CaO-NiO (FeO) systems melts

Structure of the B2O3 melt was analyzed as well as CaO modifier additives (25, 34, and 45 mass %) effect to it. As was proved, non-ring groups of associated rings proper to pure B2O3 are transformed into BO2O – metaborate triangles. The released oxide ions increase the coordination number of modifying ions, which occupy cationic vacancies place in the most disordered part of the melt greed. The B2O3–CaO–NiO and B2O3–CaO–FeO melts viscosity were measured by the method of vibration viscometry. Ratio of Boron to Calcium oxide mass fractions was taken as 3/1 and content of Nickel and Iron oxides in the range up to 5 and 20 % mass respectively. The experiments had been carried out using vibration viscometer operating in the mode of forced oscillations. The melt temperature was measured by Platinum –Platinum – Rhodium thermocouple. The measurements were carried out in cooling mode of the melt from 1800 K at 7-10 K/min speed. The viscosity temperature dependencies as well as its dependence on Nickel and Iron oxides were determined. Data processing was performed using the Table curve application software. Viscosity experimental data of the B2O3-CaO-NiO system melts for 1373, 1423, 1473, 1523, 1573 K temperatures have been described by the equation: η = a + b·exp(-cx), and for B2O3 – CaO – FeO melts by equation: η = a + b·x2 + c·exp (x) + d·exp(-x). Experimental data and calculations results show good convergence. The results are supposed to be used for describing the kinetics of metal reduction in bubbling processes, accompanied by the concentrations change of the oxides under reduction. The obtained information is useful for correction the slag melts properties in non-ferrous metal production.

Mathematic simulation of atomic structure of multicomponent oxide-fluoride melt for continuous casting machines

Determination of relation between oxides melts properties, based on silicates and calcium alum-silicates and magnesium and their chemical composition and structure is an important condition to provide a rational slag mode in a continuous casting machines mold. A mathematical simulation of slag melts and casting powders accomplished. The oxide-fluoride system was chosen for the simulation, for which the structure after solidification was determined by experiment. Results of molecular-dynamic simulation of CaO–SiO2–Al2O3–MgO–Na2O–K2O–CaF2–FeO system, correspondent to industrial casting powders composition, used during steel casting for slag formation in a CCM mold (35.35 % SiO2; 30.79 % CaO; 8.58 % Al2O3; 1.26 % MgO; 13.73 % CaF2; 7.57 % Na2O; 0.88 % K2O; 1.82 % FeO). Taking into account the concentration, a re-calculation was accomplished to mole shares and correspondent number of ions in the model for each component calculated. Simulation of the 8-component oxide-fluoride melt with 2003 ions size in the main cube (a side length of 31.01 Å) was accomplished at the experimentally determined temperature of solidification onset (1257 K) under periodic boundary conditions and fixed volume. The Coulomb interaction was taken into account by the Ewald–Hansen method. The time step was 0.05t0, where t0 = 7,608×10–14 sec is the internal unit of time. The melt density was taken as 3.04 g/cm3 based on the experimental data. The inter-particle interaction potentials were chosen in the Born–Mayer form. According to the simulation results, the structure of sub-crystalline groups of atoms present in the melt at the temperature of the onset of solidification was determined. A discussion of the simulation results and their comparison with the literature data presented.

Development of a knowledge base for modeling the physicochemical properties of metallurgical systems and processes

The Institute of Ferrous Metallurgy created the Knowledge Base “Metallurgy” (BDMet). It can be used to model the physicochemical properties of metallurgical systems and processes based on modern computer information technology. The aim of the work is to develop the fundamental foundations and identify the main directions of development of PMD, expand the presentation of fundamental, technological and regulatory reference information for analysis and multi-criteria optimization of technological processes. A component of BDMet is also the Base of models of metallurgical systems and technological processes, applied and theoretical research software. The database contains experimental data on the physicochemical properties of metal and slag melts formed from the corresponding charge materials in reducing and oxidizing conditions. The results of relevant scientific and applied developments of the department of physicochemical problems of metallurgical processes are shown. It is noted that the presence in the BDMet of the stock of models according to redistribution and a unified methodology for their creation on a modular basis allows the generation of models into a single end-to-end model. It also allows you to identify the optimal scheme of metallurgical processes and ensure the production of metal of a given quality in the framework of end-to-end technology. It is shown that the use allows us to solve the problems of optimization of technological processes for the production of iron and steel. The prospects for the development of further studies for systemic accumulation in the databases of documentary factual data and experimental information on the properties of metal and slag melts, as well as their further use in reduction and oxidation processes of metallurgical production, are determined.