Structural steel having excellent brittle crack propagation resistance, and manufacturing method therefor

Abstract

A structural steel having excellent brittle crack propagation resistance, according to one aspect of the present invention, comprises, by wt%, 0.02-0.12% of C, 0.01-0.8% of Si, 1.7-2.5% of Mn, 0.005-0.5% of Al and the balance of Fe and inevitable impurities, wherein an outer surface part and an inner center part thereof are microstructurally distinguished in the thickness direction, and the surface part comprises tempered bainite as a base structure, comprises fresh martensite as a second structure and can comprise austenite as a remaining structure.

Description

technical field [0001] The present invention relates to structural steel materials used in structures such as shipbuilding, construction, marine structures, and line pipes, and a manufacturing method thereof. Specifically, it relates to a method for effectively ensuring the propagation of brittle cracks by optimizing steel composition, microstructure, and manufacturing processes. Resistant structural steel and method of manufacture thereof. Background technique [0002] Various structural materials used in shipbuilding, construction, marine structures, line pipes, etc. are used in coastal and polar regions, and actually require high strength, thickening, and high toughness. However, in general, as the thickness of the steel plate increases, the brittle crack growth arrest performance decreases, and a technique for improving the brittle crack growth arrest performance of high-strength thick steel plates used in extreme environments is required. [0003] When the brittle crac...

AI Technical Summary

Problems solved by technology

When a fine structure is formed in the steel plate, although the occurrence and propagation speed of brittle cracks can be reduced, in the case of a thick plate, due to the large thickness of the steel plate, it cannot be expected that there will be no improvement in the densification of the structure by cooling and rolling. have full effect

[0004] Patent Document 1 provides a technology for fine-graining the surface layer of steel to suppress the propagation of brittle cracks, but the surface layer is mainly composed of equiaxed ferrite grains and elongated ferrite grains, and exists at a tensile strength of 570Mpa. Problems that cannot be applied to high-strength steel above grade

In addition, in Patent Document 1, the rolling process must be performed during the reheating treatment of the surface layer in order to refine the grain of the surface layer, so the control of the rolling process is difficult.

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