Investigation of Friction Force between Mould and Strand Shell under Sinusoidal and Non‐sinusoidal Oscillation in Continuous Slab Casting

Abstract

Friction force is an important parameter to evaluate powder lubrication and reflect the interaction between mould and strand shell. A non‐sinusoidal oscillation pattern emerges under high speed continuous casting, the characteristic of which is that the time of upward motion is longer than that of the downward motion within one cycle. In the present research experiments were performed on a slab continuous caster with a strand size of 1000 mm ×120 mm. The friction forces of sinusoidal and non‐sinusoidal oscillation under the same parameters were calculated and comparatively analysed. The results show that the friction forces of both oscillation patterns approximately change along with velocity, and present a trend to a trapezoid wave, but there is a phase difference between the friction force and relative velocity. Compared with sinusoidal oscillation, the non‐sinusoidal oscillation pattern exhibits some important advantages as follows; the maximal and average compressive forces and the compressive force work acting on the strand shell are all higher, the maximal tension is lower, and the actual amount of negative strip is higher. These advantages effect better healing of surface cracks and strand demoulds, and reduce the generation and expansion of cracks, consequently improve the surface quality.

Dynamic pressure in mould flux channel during mould non-sinusoidal oscillation

“…This indicates that the increase in oscillation frequency has important effects on strand demoulding and welding the cracked shell, but it must be noted that an excessive positive pressure has adverse effect on the strand surface quality. The use of high frequency oscillation and small amplitude is adopted widely in high speed continuous casting 15 because it is effective in strand demoulding, eliminating cracks in tension and avoiding breakouts. However, the oscillation frequency should not be too high because flux consumption, and hence mould lubrication, is decreased.…”