Pipeline steel with thickness more than or equal to 25mm for deep sea and production method thereof

Abstract

The invention relates to a pipeline steel for deep sea and a production method thereof. The pipeline steel for deep sea comprises the following components in percentage by weight: 0.025-0.080% of C, 0.05-0.50% of Si, 1.20-1.60% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 0.05-0.30% of Mo, 0.03-0.06% of Nb, 0.005-0.025% of Ti, 0.01-0.04% of Al, less than or equal to 0.010% of N and 0.0010-0.0050% of Ca used as main components, and less than or equal to 0.03% of As, less than or equal to 0.01% of Sb, less than or equal to 0.02% of Sn, less than or equal to 0.01%of Pb, less than or equal to 0.01% of Bi and less than or equal to 0.0005% of B used as residual elements. The production method comprises the following production steps: smelting according to clean steel, and carrying out continuous casting to obtain a blank; heating the cast blank; carrying out rough rolling; carrying out fine rolling; relaxing; cooling; relaxing again; straightening; and carrying out air cooling to room temperature. The pipeline steel has simple ingredient and technology, the thickness of the pipeline steel is more than or equal to 25mm, and the pipeline steel is used for deep sea pipelines. The Rt05 of the pipeline steel is more than or equal to 450MPa, Rm is more than or equal to 550MPa, Rt05 / Rm is less than or equal to 0.85, A50mm is more than or equal to 40%, Agt is more than or equal to 10%, -40DEG C KV2 is more than or equal to 200J, and -20DEG C DWTT (Drop-Weight Tear Test) SA is more than or equal to 85%.

Description

technical field [0001] The invention relates to steel for pipelines and a production method thereof, in particular to pipeline steel for deep sea use and a production method thereof. Background technique [0002] With the gradual depletion of land oil and gas resources, new resource exploitation extends to areas with harsh geological conditions such as oceans and polar regions. At present, it has been proven that the world's offshore oil resources account for 34% of the world's total oil resources, and the annual production of offshore natural gas has reached 32% of the world's total annual natural gas production. More than 100 countries around the world are conducting offshore oil exploration, of which More than half of the oil exploration has been carried out in the deep sea. Therefore, the importance of the development and application of steel for submarine pipelines, especially steel for deep-sea pipelines, has become increasingly prominent. At present, domestic steel f...

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Problems solved by technology

[0007] The object of the present invention is to provide a yield strength R t0.5 ≥450MPa, -40℃KV 2 ≥200J, -20℃ DWTT SA≥85%, and yield strength ratio R t0.5 / R m ≤0.85, elongation A 50mm ≥40%, uniform elongation A gt ≥10% deep-sea use ≥25mm thick pipeline steel and its production method

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