Method for continuous-casting slab

A method for continuous-casting a slab while reduction is carried out on the slab using a continuous casting machine with two stages of reduction rolls, each of the two stages consisting of a pair of the reduction rolls, and being arranged along a casting direction, a diameter of each of the reduction rolls being 1.2 to 2.0 times as much as thickness of the slab just before reduction with corresponding reduction rolls, the continuous casting machine including the reduction rolls and support rolls, the support rolls being arranged between said two stages of the reduction rolls, the method comprising;

• reducing a casting speed compared to a first state where the slab is cast at a constant speed while reduction is carried out on the slab with reduction rolls at a second stage, and
• switching the reduction with the reduction rolls at the second stage to reduction with reduction rolls at a first stage, the reduction rolls at the first stage being arranged more upstream than the reduction rolls at the second stage in a casting direction, in such a manner that a reduction amount of the reduction rolls at the first stage is same as that of the reduction rolls at the second stage, which are used for the reduction on the slab in the first state, accompanying movement of a place of the slab where solidification is ended upstream in the casting direction due to the reduction of the casting speed.