METHOD AND APPARATUS FOR CONTINUOUSLY CASTING STEEL

An improvement is provided in a method for continuously casting steel which includes the following steps: continuously teeming molten steel into a straight mold; guiding an unsolidified cast strand with a solidified shell formed on it substantially vertically downward along a vertical guide section; then, guiding the unsolidified cast strand in the vertical position along a curved multiple-point bending guide section comprising plural pairs of bending rollers while bending the unsolidified cast strand at multiple points by successively decreasing the radius of curvature of the unsolidified cast strand for each pair of the bending rollers; then, further guiding the unsolidified cast strand thus bent at multiple points along a constant curvature guide section comprising plural pairs of guide rollers, the radius of curvature of the constant curvature guide section being the same as that of the tail end of the multiple-point bending guide section; then, reducing the cast strand near the solidification completing point thereof by at least a pair of reduction rolls at a draft of 0.1 to 2.0% per pair of reduction rolls; and then, straightening the cast strand thus reduced in a substantially horizontal direction at a single point at a spot-straightening point. The improvement comprises setting the track length of the vertical guide within a range of from 3 to 7 m from the menisous of molten steel in said straight mold; setting the track length of the multiple-point bending guide within a range of from 1 to 4 m; locating the at least one pair of reduction rolls to form the tail end of the constant curvature guide section, and the track length of the constant curvature guide being within a range of from 35 to 85% of the length from the meniscus of molten steel in the straight mold up to the spot-straightening point provided in succession to the constant curvature guide section; and completing the solidification of the unsolidified cast strand within the constant curvature guide section. By such series of steps a continuously cast strand, substantially free from, or with remarkably decreased, inner and outer defects is obtained.