Electrical drives of continuous casting machine withdrawal rolls: a model and practical implementation of limitations on longitudinal forces in billets

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.