Steel plate for thick steel pipe, method for manufacturing same, and high strength thick steel pipe
A high-strength, steel pipe technology, applied in the direction of manufacturing tools, pipes/pipe joints/fittings, pipes, etc., can solve the problems of toughness deterioration, easy transformation of the welding point into the upper bainite structure, etc.
Active Publication Date: 2015-11-25
JFE STEEL CORP
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[0078] Steel slabs adjusted to the various component compositions shown in Table 1 were used as raw materials, and thick steel plates with a plate thickness of 27 to 101 mm were produced under the production conditions shown in Table 2. A tensile test, a Charpy test, and a CTOD test were performed on each of the obtained thick steel plates. In addition, although not described in Table 2, in hot rolling, the rolling reduction in the non-recrystallization temperature range (900 degreeC or less) was made into 40 % or more. In addition, the cooling rate in accelerated cooling is set to 5° C. / s or more.
[0079]Tensile test pieces were taken from the central portion of each steel plate in the rolling width direction, and subjected to a tensile test to determine the tensile strength (TS). The Charpy test was performed at a test temperature of -40° C. using a 2 mm V-notch test piece, and the Charpy impact value (average value of 3 pieces) was obtained.
[0080] In addition, "レ"-sha...
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Abstract
Provided are a steel plate for thick steel pipe having superior CTOD characteristics in parts thermally affected by circumferential welds, a manufacturing method for the same, and a thick steel pipe. A steel plate is formed from 0.03 - 0.10% C, 0.05 - 0.50% Si, 1.00 - 2.00% Mn, 0.015% or less P, 0.005% or less S, 0.20% or less (including 0%) Mo, 0.01 - 0.05% Nb, and if necessary, one or two or more of 0.005 - 0.1% Al, 1.00% or less Cu, 1.00% or less Ni, 0.50% or less Cr, and 0.05% or less V, Pcm* (%) (= C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 2 + V / 10) ≤ 0.20, with the remainder being Fe and inevitable impurities. The bainite fraction of the parent material is 50% or greater and the island shaped martensite (MA) fraction in a two-phase reheated granular region is 5.0% or less. After a continuous cast slab of the component system above is reheated to a specific temperature, the same is hot rolled and thereafter undergoes accelerated cooling to 550 - 250°.
Description
technical field [0001] The present invention relates to a steel plate for a thick-walled steel pipe, a manufacturing method thereof, and a thick-walled high-strength steel pipe. The thick-walled high-strength steel pipe of the present invention is preferably used for marine structures and pipelines with a TS of 500 MPa or more. In addition, among the steel sheets for thick-walled steel pipes of the present invention, especially steel sheets for thick-walled steel pipes having a plate thickness of 25 mm or more are excellent in CTOD characteristics of the heat-affected zone of girth welding that becomes multi-pass welding when connecting steel pipes. Background technique [0002] Steel pipes used for marine structures and pipelines are girth welded in order to join steel pipes together during the formation of structures. Circular seam welding refers to welding in the circumferential direction of the pipe, and circular seam welding is an indispensable process in the formation...
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IPC IPC(8): C22C38/00B21C37/08C21D8/00C22C38/12C22C38/58
CPCC21D9/14B21C37/08C21D8/00C21D8/0226C21D8/0263C21D2211/002C22C38/00C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/16C22C38/42C22C38/44C22C38/46C22C38/48C22C38/58C21D6/001C21D6/004C21D6/005C21D6/008C21D8/021C21D9/46F16L9/02F16L9/17
Inventor 太田周作嶋村纯二石川信行远藤茂津山青史
Owner JFE STEEL CORP