Effect of Coiling Operation on Strip Quality of 4.5% Si Steel in Twin-roll Casting Process.

Rapid solidification in the twin-roll casting process allows the production of thin strip with a unique combination of properties, directly from the melt. However, the production of the thin strip without any intermediate technological processing, is accompanied by strong demands on quality of the as-cast strip and requires full understanding of all aspects of twin-roll casting technology. The present study was aimed at an experimental analysis of the influence of continuous coiling in the twin-roll casting process on structure, properties and the shape of as-cast high silicon electrical steel strip. It was found that solidification, cooling and plastic deformation produce high residual stress heterogeneity in the as-cast strip which exists in a non-equilibrium state. When the compressive residual stress, attains a critical value the strip loses its flatness and waviness of a sinusoidal shape appears on the surface in the casting direction. When the tensile residual stress reaches the yield strength of the casting materials, cracks may be appear in the strip. The use of continuous coiling at elevated temperatures and with the as-cast strip under tension, leads to a change in structure, properties, geometry and shape of the as-cast strip. The structure and properties can be effectively controlled by regulating the temperature of the coiled strip and the shape can be controlled by regulation of the strip tension. The use of optimal temperature and strip tension during the continuous coiling operation are effective control strategies for stabilising structure, properties, and shape of the as-cast strip, reducing the residual stresses in the strip and improving its quality.