Search

The research is aimed at increasing the quality of a concast billet macrostructure by limiting static and dynamic longitudinal forces created in billets by electrical drives of withdrawal rolls during wear and bending of the withdrawal roll body and random and periodic slips of drives. The paper analyzes process requirements for electrical drives of withdrawal rolls: contains a procedure for calculating dynamic longitudinal forces created in billets by drives of withdrawal rolls, determines whether influence of operating modes of the said drives on changes in billet withdrawal force is relevant, contains developed techniques and algorithms of withdrawal roll drive automated control limiting static and dynamic longitudinal forces in billets, and includes the experimental analysis of efficiency of methods and technical solutions on operating drives. Research was carried out at the Russian large iron and steel works. When performing the research, the authors applied analytical and numerical methods of solving algebraic and differential equations and systems, methods for structural modeling. As a result of the research, the authors developed and experimentally confirmed methods for "soft" restoring of the contact between the withdrawal roll and the billet and adjusting phases of fluctuating changes in load currents of motor groups. The obtained results are transferred as technical specifications and taken for introduction, when revamping electrical equipment of existing continuous casting machines. Results of mathematical simulation and experimental research are used to design automated electrical drives of withdrawal rolls in the secondary cooling zone of the bow-type continuous casting machine. Impact dynamic loads were decreased by 3 times, resulting in an average increase of 8% in the quality of the billet center with regard to all types of defects. [ABSTRACT FROM AUTHOR]

The aim of this research is to help reduce the share of cast slabs with extensive macrostructural defects by changing the structure and the control system of the straightener drive. The article describes the results of a passive experiment. On the basis of these results, requirements have been formulated to the structure and the control system of the straightener drive, a control philosophy developed and a new functional block diagram proposed. The study has been carried out for the curve-type continuous caster operated by one of the major Russian steel producers. The experimental study involved a statistical analysis of the pinch roll drive load sharing data registered by the current monitoring system, as well as the data provided by the sample testing laboratory on the main internal defects found in slabs. The theoretical study included the application of analytical and numerical solutions to algebraic equations, as well as structural modelling. The results of this research were tested on a prototype electric drive for the continuous caster pinch rolls. The authors offer some recommendations on the design of the automatic drive for the pinch rolls installed in the horizontal section of the secondary cooling zone, which also include a technique for calculating the load torques on the straightener pinch rolls, a functional block diagram and a control algorithm for the pinch roll drive installed in the horizontal section of the secondary cooling zone. An average of 50% improvement has been seen in load sharing between the pinch roll drives of the secondary cooling zone. The maximum axial stresses in the slab have reduced four times. There has been an average of 16% improvement in the slab macrostructure for all types of defects and a 13% improvement in terms of axial defects. [ABSTRACT FROM AUTHOR]