H-section steel and method of producing the same

Abstract

An H-section steel has a predetermined chemical composition, an Nb content and a B content satisfy Nb+125×B≧0.075%, a thickness of a flange is 12 mm to 40 mm, and in a thickness center portion and ¼ flange width portion of the flange, a metallographic structure of a cross-section perpendicular to a rolling direction contains pearlite having a distribution density of 3.2×10⁻³ units/μm² or lower and the remainder is formed of ferrite and bainite.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates to an H-section steel which is used in a structural member of a building used in a low temperature environment and a method of producing the same, and more particularly to an H-section steel for low temperature use having high strength and excellent toughness in a heat affected zone and a method of producing the same.[0002]Priority is claimed on Japanese Patent Application No. 2013-094589, filed on Apr. 26, 2013, the content or which is incorporated herein by reference.RELATED ART[0003]Recently, due to increasing worldwide energy demand, the demand for structures for use in energy-related facilities in cold regions has rapidly increased. As such a facility, for example, there is a Floating Production, Storage and Offloading System (FPSO), that is, a facility which produces offshore oil and gas, stores the oil and gas in a tank in the facility, and directly offloads the oil and gas onto a transport tanker. H-section ...

AI Technical Summary

Benefits of technology

[0019]According to the above aspects of the present invention, the H-section steel for low temperature use having high strength and excellent low temperature toughness can be produced by rolling without performing accelerated cooling. As a result, a significant cost reduction due to a reduction in construction cost and a reduction of a construction period can be achieved. Furthermore, even when welding is performed on the H-section steel of the present invention, a reduction in the toughness of the heat affected zone is small and excellent low temperature toughness is provided. Therefore, the reliability of a large building used in cold regions can be enhanced without damage to the economic efficiency. Therefore, the present invention makes a significant contribution to industry.

Problems solved by technology

In a case where H-section steel is produced by performing hot rolling on a cast slab obtained by continuous casting, it is difficult to ensure toughness by refining grains.

This is because there is a limit to the maximum thickness of the cast slab that can be produced by a continuous casting facility and thus a rolling reduction ratio (the ratio of product thickness and cast slab thickness) cannot be sufficiently ensured.

However, high cost is required to introduce a cooling facility after rolling.

Images