Optimization of machine parameters to improve the quality of continuously cast slab

Abstract

Industries in general target to produce high quality tonnage steel at a lowest possible cost. On this count the technology of continuous casting (con-cast) is very promising. However, one of the serious quality problems that may arise in the con-cast slabs is the formation of cracks, on the surface and/or in the interior of the slabs. The cracks appearing on the surface get oxidized in air and therefore cannot be re-welded during rolling of the slab resulting into defective rolled plates. In this work, carried out at Bhilai Steel plant Bhilai (MP), machine parameters responsible for the formation of longitudinal surface cracks are studied. The objective of doing this exercise is to optimize these parameters to reduce the frequency of crack formation. Mould taper, age of the mould, pinch roll conditions and rigidity in fixing the pinch rolls are some of the parameters studied. The study concludes that, the existing level of 1.3% of mould taper is excessive and the optimum value is found to be 1.13%. From this study, the history of the machine after maintenance is optimized to 140 heats and the rigidity maintenance period for pinch rolls to 80 heats. It is proposed that the roll gap of the pinch rolls should be checked and rectified for every 65 heats.