Welded joint ctod greater than 0.5 mm marine engineering steel and preparation method

Abstract

The invention discloses ocean engineering steel with welded joint CTOD (crack tip opening displacement) greater than 0.5mm and a preparation method, belonging to the technical field of ocean engineering steel. The ocean engineering steel comprises the following chemical components in percentage by weight: 0.05-0.12% of C, 0.10-0.40% of Si, 1.0-1.50% of Mn, 0.03-0.04% of Alt, 0.02-0.06% of Nb, 0.010-0.02% of Ti, 0.1-0.5% of Ni, less than 0.01% of P, less than 0.005% of S and the balance of Fe and unavoidable impurities. The alloy content is adjusted according to the effect of the alloy element in the steel, the parameters of the controlled-rolling and controlled-cooling process are strictly controlled, and the obtained 10-80mm steel plate has comprehensive mechanical properties that the welded joint CTOD is greater than 0.5mm at -10 DEG C under 420MPa and the lamellar tearing resistance is greater than 35% and the like. The ocean engineering steel disclosed by the invention has excellent comprehensive properties and can be widely applied to the key parts of the stationary, semi-submersible and self-elevating platforms.

Description

technical field [0001] The invention belongs to the technical field of marine engineering, and in particular relates to a steel for marine engineering with -10°C welded joint CTOD (crack tip opening displacement)>0.5mm and its preparation method, specifically a -60°C 1 / The average value of conventional impact energy at 4 places and the center is ≥100J; the CTOD value at different positions of the welded joint at -10°C is higher than 0.5mm, the steel for marine engineering does not break when the drop hammer falls at -35°C, and the lamellar tear resistance is ≥35% . Background technique [0002] As my country's demand for non-renewable resources such as oil continues to grow, the ocean has become the hope of meeting oil demand. The process of marine development has been accelerating, and the offshore oil and gas industry has sprung up, with an average annual growth rate of 32.3%, rapidly growing into a pillar industry of China's marine economy. Offshore oil is the focus...

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Problems solved by technology

[0003] The publication number is CN102732781A invention patent, which proposes a steel for offshore platforms with a CTOD ≥ 2mm at -40°C and its production method. The CTOD ≥ 2mm does not add elements such as Nb and Mn. The S that cannot be removed in the medium reacts to form inclusions MnS, which reduces the fracture toughness of the steel. At the same time, it is considered that the low alloy of Nb does not melt the Nb block, which leads to poor quality of the steel plate and deteriorates the fracture toughness of the steel plate.

In addition, B and Ca are added to the steel, only the CTOD performance of the base metal is tested, and the CTOD performance of each welding part, as well as the strength and drop weight performance are not explained.

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