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Low Alloy Steel

A low-alloy steel, post-welding heat treatment technology, applied in the direction of furnace type, furnace, heat treatment furnace, etc., can solve the problem of insufficient performance, and achieve the effect of excellent hydrogen embrittlement resistance

Inactive Publication Date: 2014-09-10
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

As a result, no matter how the HIC resistance and SSC resistance of the steel itself are improved, in many cases, sufficient performance cannot be obtained as a welded structure for practical use.

Method used

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  • Low Alloy Steel
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Comparison scheme
Effect test

Embodiment 1

[0084] In order to confirm the effects of the present invention, the following experiments were conducted. That is, a low-alloy steel plate with a thickness of 12 mm having the chemical composition shown in Table 1 was machined into a 12 mm square and 100 mm long to produce a test material. The test material was subjected to a HAZ simulated welding thermal cycle, that is, heating by high-frequency induction heating to a temperature of 1350° C. at which the HAZ hardens significantly, followed by rapid cooling for 3 seconds. The following test was performed using this test material.

[0085]

[0086] According to JIS Z2241, a round bar tensile test piece having a parallel portion diameter of 6 mm and a parallel portion length of 10 mm was collected from the obtained test material, and a tensile test at normal temperature was performed.

[0087]

[0088] A test piece having a thickness of 2 mm, a width of 10 mm, and a length of 75 mm was collected from the obtained test mate...

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Abstract

A low alloy steel subjected to thermal treatment after welding, the low alloy steel containing, in mass%, 0.01 to 0.15% C, 3% or less Si, 3% or less Mn, 0.08% or less Al, and one or more element selected from among Ti, V and Nb in a range satisfying equation (1), the remainder being Fe and impurities, wherein the impurities contain 0.01% or less N, 0.05% or less P, 0.03% or less S, and 0.03% or less O. Said low alloy steel exhibits excellent resistance to embrittlement caused by hydrogen such as stress corrosion cracking in a wet hydrogen sulfide environment in a HAZ. Equation (1): 0.1[C(%)]<=[Ti(%)]+[V(%)]+0.5[Nb(%)]<=0.2. (Each element symbol in the equation represents the content (mass%) of each element}.

Description

technical field [0001] The present invention relates to low alloy steels. In particular, it relates to a low-alloy steel having excellent resistance to hydrogen-induced embrittlement such as stress corrosion cracking in a wet hydrogen sulfide environment in a welded heat-affected zone after post-welding heat treatment. Background technique [0002] In the development of subsea oil fields, in order to transport crude oil or natural gas from the oil well or natural gas well on the seabed to the offshore platform, or from the platform to the refining base on land, a so-called riser or oil flow pipe is used. , dry pipe and other steel pipes. On the other hand, along with the depletion of fossil fuels worldwide, the development of oil fields containing a large amount of corrosive hydrogen sulfide has been gradually promoted. Regarding steel pipes used to transport crude oil or natural gas extracted from oil fields containing such corrosive gases, there are problems caused by wh...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/08C21D9/50C22C38/14C22C38/58
CPCC22C38/54C22C38/14C22C38/04C22C38/001C22C38/002C22C38/22C22C38/44C22C38/18C21D9/50C22C38/02C22C38/12C22C38/42C22C38/26C22C38/48C22C38/06C21D9/08C22C38/28C22C38/08C22C38/32C22C38/24C22C38/38C22C38/00
Inventor 平田弘征大村朋彦小林宪司河野佳织富松宏太小川和博
Owner NIPPON STEEL CORP
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