High-strength thick steel plate with excellent haz toughness

A technology for high-strength, thick steel plates, applied in the field of high-strength thick steel plates, can solve problems such as increased manufacturing costs, and achieve the effect of excellent toughness

Inactive Publication Date: 2012-09-19
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, in order to obtain a predetermined shape of island-shaped martensite, reheating during cooling is required, and there is a problem of causing an increase in production cost.

Method used

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  • High-strength thick steel plate with excellent haz toughness
  • High-strength thick steel plate with excellent haz toughness
  • High-strength thick steel plate with excellent haz toughness

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Embodiment Construction

[0031] The present inventors investigated the strength-improving effect of adding Nb as a microalloying element and the adverse effect on HAZ toughness from the viewpoint of the action process. As a result, it was found that most of the microalloying elements exist in a solid solution state in the HAZ, which coarsens the bainite structure formed in the HAZ and lowers the toughness. On the other hand, it plays the following two roles in the base metal : It exists in a solid solution state to improve hardenability and inhibit the formation of ferrite; and forms extremely fine atomic aggregates with C atoms, thereby hindering the movement of dislocations, thereby improving strength .

[0032] Based on the above knowledge, the present inventors found that the HAZ toughness can be ensured by specifying the total amount of microalloying elements, and that the HAZ toughness can be improved by studying the form of fine clusters effective for securing the strength of the base metal by ...

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Abstract

The present invention provides a high-strength thick steel plate capable of ensuring a tensile strength to be more than 570MPa and realizing an excellent HAZ (Heat Affect Zone) toughness. The high-strength thick steel plate consists of specified chemical compositions, KV obtained by the following formula (1) is lower than 0.060, more than 90% of the area of a steel structure is bainite, in addition, an Nb atom or C atom having other Nb atoms or other C atoms within a distance of 1.7nm combines with the other Nb atoms or the other C atoms to form an aggregate having more than 5 atoms, by using a 3D atom probe field ion microscope to measure, the aggregate has a number density of more than 1.0*10<22> per cubic meter. KV = [V] + [Nb] ... (1) (wherein, [V] and [Nb] respectively represent V content and Nb content (mass%)).

Description

technical field [0001] The present invention relates to a high-strength thick steel plate with a tensile strength of 570 MPa or more (hereinafter referred to as "570 MPa thick steel plate") suitable for large structures such as building structures and bridges. High-strength thick steel plate with excellent toughness in the HAZ. Background technique [0002] Thick steel plates used in fields such as construction, shipbuilding, and bridges are joined by welding, so it is necessary to ensure the toughness of the welded heat affected zone (HAZ: Heat Affect Zone). In recent years, with the increase in size of welded structures, high-strength thick steel plates with a tensile strength of 570 MPa have been widely used, but the addition of alloying elements for the purpose of improving strength generally has a negative impact on HAZ toughness, so it is necessary to A technology that combines HAZ toughness and steel plate strength (base metal strength) at a high level. In particula...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/58C22C38/54C22C38/38C22C38/32C22C38/14
CPCC22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/12C22C38/14C22C38/42C22C38/44
Inventor 名古秀德长谷川夕起伊庭野朗今村弘树山口彻雄
Owner KOBE STEEL LTD
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