Improving the quality of continuously cast slabs: by means of the pinch roll drive of the horizontal part of a continuous casting machine

Abstract

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.