Impingement Density Analysis on Heat Transfer and the Appearance of Edge Cracks in Conventional Slab Using Hydraulic Nozzles

In this work, the fluid dynamics and heat transfer of two hydraulic nozzles used in the secondary cooling of the conventional slab continuous casting machine were analyzed. Impingement density maps, the jet opening angle and heat flux associated with different operating conditions (impingement distance, pressure) were experimentally determined. The opening angle and impingement density footprint were found to vary considerably in shape and magnitude with varying operating pressure and distances. Finally, it was found that when short operating distances are used, a greater heat extraction gradient occurs in the major axis of the impingement footprint, which promotes edge-cracks in the slab in plant.

An automated system development to control the device for supplying slag-forming mixture into mould of CCM

The mechanism of feeding slag-forming mixture (SFM) with a pneumatic drive has a number of disadvantages associated, in particular, with the uneven supply of the mixture into mould. To eliminate the drawbacks, mixture feeding device with an electric drive was designed to eliminate them. In order to ensure control of the SFM feeding process, an automated system has been developed that provides real-time information on the technological process of feeding the mixture into the mould of continuous casting machine, including speed of rotation of screw drive motors and movement of carriage, the level of the mixture in the bunkers and its consumption, temperature of the metal and slag. A software and hardware complex (SCADA-system) has been developed, which makes it possible to analyze the components of the mixture in the “online” mode and take into account the effect of changes in the supply of each of them on its composition. The dependence of the mixture consumption rate on the casting rate has been established, which can be displayed on the screen in the current mode. Application of the SCADA-system made it possible to control the developed SFM feeder both in manual and automatic modes. It was shown that the implementation of the developed automated SFM feeding device in the steelmaking production of Ural Steel, JSC will secure decreasing the SFM consumption by 2.8% and decreasing downtime by 5% due to increasing efficiency of fault detection with a total implementation cost of 200 thous. rubles.

Improvement the Round Bloom Continuous Casting Technology at JSC “Ural Steel”

The results of assessment of macrostructure and surface quality of round blooms 455 mm in diameter, cast on 4-strand continuous casting machine (CCM) at JSC “Ural Steel” are presented. The analysis of technological casting parameters of round blooms 455 mm in diameter (from steel grade “2”) at bloom caster of JSC “Ural Steel” are completed. Violations in casting temperature and rate parameters, which deteriorate thermal conditions of solidification and quality of continuous casting blooms, have been revealed. The main causes of unsatisfactory bloom quality have been determined, which are the increased overheating of cast metal and irrational secondary cooling mode. The results of the experiment to evaluate the surface temperature dynamics of a round bloom in the secondary cooling zone are presented, which confirmed the inefficiency of the secondary cooling mode for the defect-free bloom formation. As a result of thermal calculations of round blooms solidification of 455 mm in diameter, rational coolant flow rates by secondary cooling sections for bloom caster of JSC “Ural Steel” have been proposed. Optimized secondary cooling parameters provide a softer secondary cooling of the round bloom, which reduces the probability of the surface and internal defects development.

Optimization of the Continuous Casting Process of Hypoeutectoid Steel Grades Using Multiple Linear Regression and Genetic Programming—An Industrial Study

Štore Steel Ltd. is one of the major flat spring steel producers in Europe. Until 2016 the company used a three-strand continuous casting machine with 6 m radius, when it was replaced by a completely new two-strand continuous caster with 9 m radius. For the comparison of the tensile strength of 41 hypoeutectoid steel grades, we conducted 1847 tensile strength tests during the first period of testing using the old continuous caster, and 713 tensile strength tests during the second period of testing using the new continuous caster. It was found that for 11 steel grades the tensile strength of the rolled material was statistically significantly lower (t-test method) in the period of using the new continuous caster, whereas all other steel grades remained the same. To improve the new continuous casting process, we decided to study the process in more detail using the Multiple Linear Regression method and the Genetic Programming approach based on 713 items of empirical data obtained on the new continuous casting machine. Based on the obtained models of the new continuous casting process, we determined the most influential parameters on the tensile strength of a product. According to the model’s analysis, the secondary cooling at the new continuous caster was improved with the installation of a self-cleaning filter in 2019. After implementing this modification, we performed an additional 794 tensile tests during the third period of testing. It was found out that, after installation of the self-cleaning filter, in 6 steel grades out of 19, the tensile strength in rolled condition improved statistically significantly, whereas all the other steel grades remained the same.

Ladle Intelligent Re-scheduling Method in Steelmaking–Refining–Continuous Casting Production Process based on BP Neural Network Working Condition Estimation

The ladle re-scheduling of steelmaking and continuous casting production aims at continuously casting many charges with the same cast and avoiding conflicts of adjacent charges on the same machine. It proposes a method of ladle re-scheduling in the production process of steelmaking–refining–continuous casting, including two parts: plan re-scheduling and ladle optimisation scheduling. Firstly, a re-scheduling optimisation model of the steelmaking and continuous casting production is built, which aims at minimising the waiting time of all charges. The re-scheduling strategy of steelmaking and continuous casting production is proposed by interval processing time of charges and scheduling expert experience. The re-scheduling strategy is composed of two parts: re-scheduling charge decision and charge processing machine decision. Then, the first-order rule learning is used to select the optimisation target to establish the ladle optimal scheduling model. The ladle matching rules are extracted by the rule reasoning of the minimum general generalisation. The ladle optimisation scheduling method consisting of the optimal selection of the ladle and the preparation of the optimal path of the ladle is proposed. Ladle selection is based on the production process and adopts rule-based reasoning to select decarburised ladle after choosing dephosphorised ladle. Ladle path preparation, a multi-priority heuristic method, is designed to decide the path of the ladle from the converter to the refining furnace to the continuous casting machine. Finally, it was actually verified based on a large-scale steel company in Shanghai, China. Results showed that the production efficiency of steelmaking-refining-continuous casting was improved.

Interrelation of CCM (Steel Billet Continuous Casting Machine) Tube Steel Casting Parameters and Hot-Rolled Plate Quality

The quality of the hot-rolled plate up to 36 mm thick was estimated by the percentage of rolled products, sorted due to the presence of a surface defect "Non-metallic inclusions", and internal defects, detected by ultrasonic plate control. The analysis of the data on the total sorting of hot-rolled plates demonstrated that the amount of sorting differs significantly on the melting from which each series of tubular metal casting commenced, compared to all the other melting in the series. The sorting of the sheets rolled from the metal of the first in a series of melting proved to be 1.9 times higher than that of the metal of all other melts. The main reason (in 68% of cases) of sorting is the presence of non-metallic inclusions on the surface of the plates. The effect of sorting of hot-rolled plates on non-metallic inclusions of various parameters has been studied: the duration of the intermediate ladle-heating; the length of time from the end of the heating of the intermediate ladle, prior to the beginning of the casting; lining temperatures of the intermediate ladle before the beginning of casting; duration of filling the intermediate ladle; the filling rate of the intermediate ladle with metal; mass of metal in the intermediate ladle before the beginning of casting into the crystallizer; chemical composition of metal; overheating of the metal over the liquidus point at the beginning, middle and end of the casting. On the sorting of flat products for non-metallic inclusions, of all the parameters considered, a statistically significant effect is due only to the overheating of the metal above the liquidus point, which varies in the range from 19 to 35 ° C. In order to obtain an acceptable quality of both the surface of slabs and the surface of hot-rolled plates for non-metallic inclusions, the first in a series of melts recommends overheating of the metal in the intermediate ladle above the liquidus temperature of 30-35 ° C.