Welded structure excellent in brittle-cracking propagation stopping characteristics

Abstract

Provided is a welded structure suitable for a hull structure and excellent in brittle-cracking propagation stopping characteristics. The welded structure is provided with a fillet welded joint having an unwelded portion (4) left on the abutting face of a web (1) against a flange (2). A percentage (X) (= 100 / L) (%) to the sum (L) of the width (n) of the unwelded portion (4) and the leg length (3 (3a and 3b)) of the left and right fillet welded joints in the joint section of the fillet welded joint, and the brittle-cracking propagation stopping toughness (Kca (N / mm3 / 2)) at the using temperature of the flange satisfy X (%) >= {5900 - Kca(N / mm3 / 2 / 85. The unwelded portion (4) in the fillet-welded joints is given a width of 15 to 90 % of the sum of the thickness (t) of the web (1) and the leg length (3 (3a and 3b)) of the left and right fillet welded joints. In case the web has the butt-welded joint portion of the thickness (t), the percentage (X) (%) and the brittle-cracking propagation stopping toughness (Kca)(N / mm3 / 2) satisfy the aforementioned formula.

Description

technical field [0001] The present invention relates to a base metal and welding of a welded structure that may occur in, for example, a mega-container carrier and a bulk carrier using a steel plate. A welded structure having excellent brittle crack arrestability (brittle crack arrestability) in which the propagation of brittle cracks on weld joints stops before large-scale failure, specifically, a fillet welded joint (fillet welded joint) A welded structure with excellent brittle crack stop characteristics that generates brittle cracks on the joined member (web) of the joint and stops the propagation of the brittle crack to the joined member (flange). Background technique [0002] The structure of the container ship and the bulk carrier which are welded structures has an enlarged upper aperture in order to increase the carrying capacity and improve the handling efficiency. Therefore, in order to secure the rigidity and longitudinal strength of the hull, it is necessary to ...

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Problems solved by technology

[0008] However, in recent large container ships exceeding 6,000 TEU, the plate thickness of the steel plate exceeds 50 mm. In addition to the decrease in the fracture toughness due to the effect of the plate thickness, the welding heat input also becomes larger. Therefore, the fracture toughness of the welded part (fracture toughness) has a tendency to further decrease

[0009] Recently, tests have shown that in such thick heat input weld joints (large heat input weld joint of heavy gauge steel plate), the brittle cracks generated from the welded part do not extend to the base metal side but go straight, and it is possible to Steel plate base materials such as aggregates (or also called reinforcement materials, stiffeners) are not stopped (Yamaguchi et al.: "Development of Mega-container carrier - new high strength heavy gauge steel plate practicality of steel plate)-"), Journal of the Japanese Society of Ship and Ocean Engineering, 3, (2005), p70.), which has become a major issue in the safety of hull structures using steel plates with a plate thickness of 50 mm or more

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