The arc continuous casting machine takes the mode of mould oscillation to draw billet. The mould oscillates sinusoidally and the billet is drawn at the same speed. When the downward oscillation speed is greater than the drawing speed, the negative slippage occurs.
The horizontal continuous caster adopts the mode of slab oscillation, that is, the mould is fixed and the drawing roll is pulled, pulled, pushed and stopped. The difference between them is as follows: (1) The “stop” in drawing billet of the arc-shaped continuous caster is very short or not, there is no relative static stage between the inner surface of billet and copper sleeve of mould, and the heat conduction performance is poor.
When negative slippage occurs in arc continuous casting machine, only the surface of the billet shell in mould is compressed, and the compression force is surface friction resistance, which is also limited. Similar horizontal continuous casting “backstepping” is to compress the billet on the whole metallurgical length, the compression force is supplied by the billet drawing machine, and the compression force can be larger.
The negative slip of arc continuous casting machine is different from the reverse slip of horizontal continuous casting. The former has no stirring effect on the liquid core of slab while the reverse slip of horizontal continuous casting makes the slab compressed, so as to fully compensate the cold shrinkage and tensile stress of slab, and the surface of the slab is not easy to crack. Because of the periodic back-push, the molten steel produces intense eddy current at the mold mouth, which enhances the thermal conductivity of the mold. Moreover, when the back-push is large, the bonding point of the slab on the inner surface of the copper sleeve is loosened, so as to reduce the drawing resistance.
It can be seen that the content of drawing technology of horizontal continuous casting is much richer than that of arc continuous casting, and the effect of improving slab quality and reducing drawing resistance is much more obvious.
