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Thick steel sheet having excellent HAZ toughness for super high input heat and parent material toughness for low temperature

A technology of thick steel plate and toughness, which is applied in the field of thick steel plate with excellent toughness of low temperature base material, and can solve the problems of HAZ toughness deterioration and coarse structure

Inactive Publication Date: 2009-12-30
KOBE STEEL LTD
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  • Abstract
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  • Claims
  • Application Information

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Problems solved by technology

[0003] However, if welding is performed with a large heat input, since the HAZ is slowly cooled from the austenite region heated to a high temperature, there is a problem that the structure of the HAZ is coarsened, and the toughness of the HAZ is significantly deteriorated.
So all the time, had to carry out welding heat input limitation

Method used

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  • Thick steel sheet having excellent HAZ toughness for super high input heat and parent material toughness for low temperature
  • Thick steel sheet having excellent HAZ toughness for super high input heat and parent material toughness for low temperature
  • Thick steel sheet having excellent HAZ toughness for super high input heat and parent material toughness for low temperature

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Embodiment Construction

[0029] The inventors of the present invention attempted to achieve good HAZ toughness even in ultra-high heat input welding by making Ti-based carbonitrides finer. It is considered that the dispersion state of conventional Ti-based carbonitrides can be determined only by the addition balance of Ti and N if the cooling rate at the time of solidification of molten steel is constant. However, as a result of intense research by the present inventors, it has been revealed that Ti-based carbonitrides can be finely dispersed even with the same Ti and N additions by narrowing the temperature range of the δ region shown in the steel state diagram.

[0030] The so-called "delta region" here means the region containing delta iron in the state diagram of steel. The "region containing δ iron" includes not only a region of δ iron but also a region of a state different from δ iron, such as a δ+γ two-phase region. Then, the "delta domain temperature range" refers to the temperature range inc...

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Abstract

The invention provides a thick steel plate, which has excellent HAZ toughness even in extra large heat input welding and excellent low temperature base metal toughness. The steel contains: C, 0.030-0.10%; Si, less than 1.0%; Mn, 0.8-2.0%; P, less than 0.03%; S, less than 0.01%; Al, 0.01-0.10%; Nb, 0.015-0.035%; Ti, 0.015-0.03%; B, 0.0015-0.0035%; N, 0.0055-0.01%; Cu, less than 2.0%; Ni, less than 2.0%; Cr, less than 1%; Mo, less than 0.5%; V, less than 0.1%; and other component is Fe and inevitable impurities. The components meet the requirement of: [Ti] / [N] is 2-4, and 500[C]+32[Si]+8[Mn]-9[Nb]+14[Cu]+17[Ni]-5[Cr]-25[Mo]-34[V] not less than 40.

Description

technical field [0001] The present invention relates to a thick steel plate suitable for welded structures such as ships and marine structures, and in particular to a heat-affected zone (Heat Affected Zone, HAZ) with excellent toughness and low temperature A thick steel plate with excellent base material toughness. Background technique [0002] In recent years, for example, container ships and the like have been increased in size, and thick steel plates having a plate thickness of 60 mm or more have been used. In order to efficiently weld such a thick steel plate, it is required to perform ultra-high heat input welding with an input heat amount of 50 kJ / mm or more. [0003] However, when welding with an extremely large heat input, since the HAZ is slowly cooled from the heated austenite region to a high temperature, there is a problem that the structure of the HAZ is coarsened, and the toughness of the HAZ is significantly deteriorated. Therefore, there has always been a l...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/50C21D11/00B23K35/22
Inventor 高冈宏行冈崎喜臣
Owner KOBE STEEL LTD
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