continuous casting method for steel

Abstract

The invention reduces the overall segregation level of central segregation in the width direction of the cast slab of the continuous casting cast slab, and also reduces the deviation of the segregation degree in the width direction of the cast slab. In the continuous casting method of steel according to the present invention, the roll opening of the plurality of pairs of slab support rolls arranged in the continuous casting machine is gradually increased toward the downstream side of the casting direction, so that the long side surface of the slab having an unsolidified layer inside is Swell with a total amount of intentional swelling of 3 to 10mm, and then press down the long side surface of the cast slab in a light reduction belt that gradually reduces the roll opening of a plurality of pairs of slab backup rolls toward the downstream side of the casting direction , in the soft reduction zone, the long side surface of the cast sheet is pressed at a reduction speed of 0.3 to 2.0 mm / min, and the total reduction amount is less than the total amount of intentional swelling, and the cast The solid fraction at the center of the thickness of the cast slab in the rectified zone in which the casting direction shape of the slab is corrected from an arcuate shape to a straight line is less than 0.2 or a flow limit solid fraction to 1.0 or less.

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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