High-strength welded steel pipe and method for producing the same

A technology for welding steel pipes and manufacturing methods, applied in welding media, manufacturing tools, welding equipment, etc., can solve problems such as difficulties, and achieve the effect of significant contribution, excellent low temperature toughness, and improved toughness

Inactive Publication Date: 2012-10-17
NIPPON STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, meeting these requirements is difficult in previous methods

Method used

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  • High-strength welded steel pipe and method for producing the same
  • High-strength welded steel pipe and method for producing the same
  • High-strength welded steel pipe and method for producing the same

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Experimental program
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Embodiment

[0092] Through weak deoxidation, the oxygen concentration when adding Ti is adjusted to the range of 0.001 to 0.003%. After the steel with the composition shown in Table 1 is smelted in the steelmaking process, it is continuously cast to produce a 240mm thick steel sheet. billet. These slabs were reheated to 950° C. or higher, rolled to the thicknesses shown in Table 2, and water cooling was started and stopped at various temperatures to produce steel sheets.

[0093] Next, after each steel plate is formed into a tubular shape by the UO process, seam welding is performed from the front and back of the steel plate by submerged arc welding with a welding input energy of 3.5 to 10.0 kJ / mm to manufacture a steel pipe.

[0094]In addition, as the welding wire used for welding, the welding wire of the following composition was used in consideration of the dilution of components by a steel plate. That is to say, the welding wire contains 0.010-0.120 C, 0.05-0.50% Si, 1.0-2.5% Mn, 2....

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Abstract

Provided is a high-strength welded steel pipe obtained by butt welding a steel sheet formed into the shape of a pipe. The base metal portion of the steel sheet comprises, by mass%, C: 0.010% - 0.080%, Si: 0.01% - 0.50%, Mn: 0.50% - 2.00%, S: 0.0001% - 0.0050%, Ti: 0.003% - 0.030%, Mo: 0.05% - 1.00%, B: 0.0003% - 0.0100%, O: 0.0001% - 0.0080%, and N: 0.006% - 0.0118% with the remainder being iron and inevitable impurities, P being limited to 0.050% or less, and Al being limited to 0.008% or less. Ceq is 0.30 to 0.53, Pcm is 0.10 to 0.20, [N]-[Ti] / 3.4 is less than 0.003, the average crystal grain size of the austenite particles of the welding heat-affected section of the steel sheet is 250 [mu]m or less, and the austenite particles include bainite and intragranular bainite.

Description

technical field [0001] The present invention relates to a high-strength welded steel pipe with excellent low-temperature toughness preferably suitable for trunk pipes for crude oil and natural gas transportation, and a manufacturing method thereof. [0002] This application is based on Japanese Patent Application Japanese Patent Application No. 2010-22831 for which it applied on February 4, 2010, the priority is claimed, and the content is used here. Background technique [0003] Currently, as raw materials for long-distance transportation of crude oil and natural gas, trunk steel pipes ranging from X70 (tensile strength of 570 MPa or more) to X80 (tensile strength of 625 MPa or more) according to the American Petroleum Institute (API) standard are in practical use. change. In recent years, in order to further improve the transmission efficiency, research has been conducted on increasing the internal pressure of line pipes. In order to withstand high internal pressures, thi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00B21C37/08B23K9/025B23K9/18B23K9/23B23K31/00C21D8/10C21D9/08C21D9/50C22C38/14C22C38/58B23K35/30
CPCC22C38/14B23K2203/04C22C38/002C21D9/50C22C38/02B23K31/027C22C38/12C21D9/08C21D8/105C22C38/04B23K2201/06B23K35/3053C21D2211/002C22C38/001B23K2101/06B23K2103/04Y10S148/909
Inventor 藤城泰志原卓也寺田好男坂本真也朝日均
Owner NIPPON STEEL CORP
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