Continuous casting method for steel

Abstract

The present invention makes it possible to set soft reduction conditions according to the thickness of a slab casting piece and thereby prevent occurrences of center segregation in the casting piece because of insufficient amounts of reduction and occurrences of internal casting piece cracking because of excessive amounts of reduction. Provided is a continuous casting method for steel that continuously casts a region of a casting piece (10) with a thickness of 160-350 mm and a width of 1600-2400 mm from a point in time equivalent to a solid phase rate of 0.1 at the middle part of the thickness to a point in time equivalent to the solid phase rate at the middle part of the thickness being the flow limit solid phase rate while performing reduction at a soft reduction zone (14) in which a plurality of pairs of casting piece support rolls are installed, wherein the thickness (D) of the casting piece, the reduction gradient (Z) of the soft reduction zone, and the drawing speed (V) for the casting piece satisfy the relationship in the following Equation (1) and Equation (2), where [alpha] is the coefficient (non-dimensional) of thickness, Do the thickness (mm) of a reference casting piece directly below a casting mold, and [beta] and [gamma] coefficients determined by the width W (mm) of the casting piece. 0.3 / (V * [alpha]) < Z < 1.5 / (V * [alpha]) ... (1) [alpha] = [beta] * (D / Do) + [gamma] ... (2).

Description

technical field [0001] The present invention relates to a continuous casting method for steel that suppresses component segregation, that is, center segregation, that occurs in the thickness center portion of a continuously cast slab. Background technique [0002] In the continuous casting of steel, in the final process of solidification, unsolidified molten steel (called "unsolidified layer") is attracted as it solidifies and shrinks, resulting in a flow of unsolidified molten steel toward the drawing direction of the strand . In this unsolidified layer, solute elements such as carbon (C), phosphorus (P), sulfur (S), and manganese (Mn) are concentrated, and if the concentrated molten steel flows to the center of the slab and solidifies there, So-called central segregation then occurs. As an important cause of the flow of concentrated molten steel at the end of solidification, in addition to the above-mentioned solidification shrinkage, the expansion of the cast slab betwe...

AI Technical Summary

Problems solved by technology

In addition, the same problem occurs in marine structures, storage tanks, oil tanks, etc.

In addition, in recent years, the use environment of steel products is often required to be used in a severe environment such as a lower temperature or a stronger corrosive environment, and the importance of reducing the center segregation of the slab is increasing.

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