The electric arc furnace operation at the Štore Steel company, one of the largest flat spring steel producers in Europe, consists of charging, melting, refining the chemical composition, adjusting the temperature, and tapping. Knowledge of the consumed energy within the individual electric arc operation steps is essential. The electric energy consumption during melting and refining was analyzed including the maintenance and technological delays. In modeling the electric energy consumption, 25 parameters were considered during melting (e.g., coke, dolomite, quantity), refining and tapping (e.g., injected oxygen, carbon, and limestone quantity) that were selected from 3248 consecutively produced batches in 2018. Two approaches were employed for the data analysis: linear regression and genetic programming model. The linear regression model was used in the first randomly generated generations of each of the 100 independent developed civilizations. More accurate models were subsequently obtained during the simulated evolution. The average relative deviation of the linear regression and the genetic programming model predictions from the experimental data were 3.60% and 3.31%, respectively. Both models were subsequently validated by using data from 278 batches produced in 2019, where the maintenance and the technological delays were below 20 minutes per batch. It was possible, based on the linear regression and the genetically developed model, to calculate that the average electric energy consumption could be reduced by up to 1.04% and 1.16%, respectively, in the case of maintenance and other technological delays. REMARK: open access publication.

F.10 Improvements to an existing technological process or technology

COBISS.SI-ID: 16647451In this work, a rolling simulation system for the hot rolling of steel is elaborated. The system is capable of simulating rolling of slabs and blooms, as well as round or square billets, in different symmetric or asymmetric forms in continuous, reversing, or combined rolling. Groove geometries are user-defined and an arbitrary number of rolling stands and distances between them may be used. A slice model assumption is considered, which allows the problem to be efficiently coped with. The related large-deformation thermomechanical problem is solved by the novel meshless Local Radial Basis Function Collocation Method. A compression test is used to compare the simulation results with the Finite Element Method. A user-friendly rolling simulation application has been created for the industrial use based on C# and .NET framework. Results of the simulation, directly taken from the system, are shown for each type of the rolling mill configurations. REMARK: open access publication.

F.10 Improvements to an existing technological process or technology

COBISS.SI-ID: 16723995A simple Lagrange-an traveling slice model has been successfully used in the past for prediction of the relations between the process parameters and the temperature field as well as grain structure, macrosegregation assessment, optimization of process parameters and calculation of caster regulation coefficients. It is the purpose of the present paper to include also the mechanical stress and deformation model into the slice framework. The basis of all the mentioned models is the slice heat-conduction model that takes into account the complex heat extraction mechanisms in the mould, with the sprays, rolls and through the radiation. Its main advantage is very fast calculation time, amenable for use also in the on-line control of the caster. The macroscopic model used in this study is based on the continuum mixture theory, calculating enthalpy and mixture composition as input parameters for microscopic calculations. The grain structure model is based on the cellular automaton concept, replaced by a random node point automata concept. The macrosegregation model is based on the lever rule microsegregation model. The thermal conductivity and species diffusivity of the liquid phase are artificially enhanced for considering the convection of the melt. The calculated thermal field is used to estimate the thermal contraction of the solid shell, which, in combination with the metallostatic pressure, drives the elastic-viscoplastic model of solid mechanics. The results of the model are used to estimate the areas susceptible to crack nucleation using several hot-tearing and damage models. The solution procedure of all the models is based on the meshless local radial basis function collocation method on the macroscopic scale and on the point automata concept on the grain structure scale. A sensitivity study on the recently introduced standard continuous casting geometry is performed as well as on the realistic conditions in Štore-Steel billet caster. Possible additional refinements of the model are discussed.

F.10 Improvements to an existing technological process or technology