High-strength steel sheet having excellent ductility and low-temperature toughness and method for manufacturing thereof

Abstract

The present invention relates to a structural steel sheet suitable for ships or steel structures and, more particularly, to a high-strength steel sheet having excellent ductility and low-temperature toughness and a method for manufacturing same.

Description

TECHNICAL FIELD[0001]The present disclosure relates to a structural steel sheet suitable for ships or steel structures and, more particularly, to a high-strength steel sheet having excellent ductility and low-temperature toughness and a method for manufacturing the same.BACKGROUND ART[0002]A ship, a steel structure, or the like may experience accidents such as flooding or sinking as a steel plate is fractured by external impacts such as a collision. In addition, cracks may occur due to forming processes during the manufacture of the ship or steel structure. In this case, there may be a problem such as the increase in a construction period or manufacturing costs.[0003]In order to solve the above problems, it is necessary to increase an elongation while maintaining the strength of the steel sheet used in ships or steel structures at the required level. The higher the elongation of the steel, the more deformation may be accommodated until the steel is fractured even if the steel is def...

AI Technical Summary

Benefits of technology

[0019]As set forth above, it is possible to provide a steel sheet having excellent low-temperature toughness as well as high strength and high ductility.

[0020]In addition, the steel sheet of the present disclosure has an effect that may be advantageously applied as a structural steel sheet.

[0021]In general, as the strength of steel increases, the ductility of the steel is relatively reduced. Accordingly, it is not easy to manufacture steel having high strength and excellent elongation. In addition, the high elongation of steel does not necessarily mean that the steel has excellent low-temperature toughness, so it is more difficult to secure excellent low-temperature toughness as well as high strength and high ductility.

[0022]However, as the present inventors have deeply researched the development of a steel sheet capable of securing the low-temperature toughness as well as the high strength and high ductility, the present inventors found that it is possible to provide a steel sheet having target mechanical properties by defining alloy compositions and manufacturing conditions as follows, and reached the completion of the present disclosure.

[0023]Hereinafter, the present disclosure will be described in detail.

[0024]According to an aspect of the present disclosure, a high-strength steel sheet having excellent ductility and low-temperature toughness may contain, by wt %, 0.05 to 0.12% of carbon (C), 0.2 to 0.5% of silicon (Si), 1.2 to 1.8% of manganese (Mn), 0.012% or less of phosphorus (P), 0.005% or less of sulfur (S), 0.01 to 0.06% of aluminum (Al), 0.005 to 0.02% of titanium (Ti), 0.01 to 0.03% of niobium (Nb), 0.002 to 0.006% of nitrogen (N), and 0.5% or less of nickel (Ni).

Problems solved by technology

A ship, a steel structure, or the like may experience accidents such as flooding or sinking as a steel plate is fractured by external impacts such as a collision.

In addition, cracks may occur due to forming processes during the manufacture of the ship or steel structure.

In this case, there may be a problem such as the increase in a construction period or manufacturing costs.

In general, since the strength and elongation of steel have an inverse relationship, it is very hard to increase the elongation while maintaining the strength.

However, it may be found that the above-described techniques have several problems.

Specifically, although the fracture of the steel plate is more related to total elongation (or fracture elongation) than uniform elongation, Patent Document 1 discloses only uniform elongation, and but does not substantially disclose the effect of suppressing defects such as the fracture due to external impacts or the like.

On the other hand, Patent Document 3 discloses the total elongation, but does not disclose securing the toughness at all, which is a very important property of the structural steel sheet.