Continuous casting method of steel

Abstract

The present invention reduces the overall segregation level of the center segregation of a continuous cast slab in a slab width direction, and also reduces the variation in the segregation degree in the slab width direction. The continuous casting method of steel according to the present invention comprises: increasing stepwise the roll opening degree of a plurality of pairs of slab support rolls,which is arranged in a continuous casting machine, toward the downstream side in the casting direction, bulging a long side surface of the slab having inside an unsolidified layer with an intentionaltotal bulging amount of 3-10 mm, and then squeezing the long side surface of the slab in a light squeezing zone in which the roll opening degree of a plurality of pairs of slab support rolls is gradually reduced toward the downstream side in the casting direction, wherein in the light squeezing zone, the long side surface of the slab is squeezed at a squeezing speed of 0.3-2.0 mm / min and a totalsqueezing amount equal to or less than the intended total bulging amount, and a solid phase ratio at the thickness center of the slab in a straightening zone where the casting direction shape of the slab is corrected from an arc shape to a straight line shape is less than 0.2 or is equal to or greater than the flow limit solid phase ratio and equal to or less than 1.0.

Description

technical field [0001] The present invention relates to a continuous casting method for steel capable of suppressing component segregation, that is, center segregation, which occurs in the center of the thickness of a continuously cast slab, and obtaining a slab having good results in a hydrogen-induced cracking resistance test and having no internal cracks. Background technique [0002] During the solidification process of steel, solute elements such as carbon (C), phosphorus (P), sulfur (S), and manganese (Mn) concentrate on the unsolidified liquid side due to redistribution during solidification. These are microscopic segregations that form between dendritic trees. Due to the solidification shrinkage and heat shrinkage of the cast slab, and the swelling of the solidified shell generated between the rolls of the continuous casting machine, voids or negative pressures are generated in the center of the thickness of the cast slab during continuous casting. [0003] When a v...

AI Technical Summary

Problems solved by technology

This technology is a technology that can prevent the following situation: in the case where the solidification completion position is different in the slab width direction, the reduction amount in the light reduction zone is different at each position in the slab width direction, and the solidification completion position extends to the casting At the position on the downstream side of the direction, the amount of reduction decreases, and a sufficient effect of improving center segregation cannot be obtained.

[0010] In addition, it is known that the swelling of the cast sheet between the rolls will also affect the center segregation

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