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Tenacity excellent high intensity steel for welding heat influenced part

A welding heat-affected, high-strength technology, applied in the field of high-strength steel, to achieve the effect of excellent base metal toughness and excellent HAZ toughness

Inactive Publication Date: 2006-04-26
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this need cannot be met in the existing technologies for improving the toughness of the HAZ

Method used

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  • Tenacity excellent high intensity steel for welding heat influenced part
  • Tenacity excellent high intensity steel for welding heat influenced part

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Embodiment Construction

[0034] The first point of the composition of the steel sheet of the present invention is that on the basis of extremely low C content, the elements Mn, Ni, and Cu that improve the hardenability are actively added in accordance with AS≥3.60 that can ensure the predetermined base metal strength, and the other On the one hand, Nb, V, and Mo are actively suppressed so that DL ≤ 2.80 can ensure the toughness of the base material. First, the steel composition of the steel sheet according to the present invention, the resulting structure and properties after hot rolling will be described with reference to the CCT diagram.

[0035] figure 1 Shown are the CCT diagrams of the ultra-low C-series steel (A) to which Mn, Ni, and Cu are actively added in the present invention, and the conventional high-C-series steel (B1) and low-C-series steel (B2). The figure shows that BF is carbon-free bainite, GBF is granular carbon-free bainite, M is martensite, B is bainite, and F is ferrite. Accord...

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Abstract

PROBLEM TO BE SOLVED: To provide a high strength steel and a high strength steel sheet capable of obtaining excellent HAZ toughness at the time of big heat input welding under the securance of base metal toughness and low temperature cracking resistance while maintaining a high strength in a 780 MPa class. SOLUTION: The invention has a composition comprising, by mass, 0.010 to 0.080% C, 0.02 to 1.00% Si, 1.10 to 2.90% Mn, 0 to 0.030% P, 0 to 0.010% S, ≤0.20% Al, 0.40 to 2.40% Ni, 0.50 to 1.95% Cr, 0.16 to 1.10% Mo, 0.002 to 0.030% Ti and 0.0058 to 0.0120% N also so as to satisfy 1.0≤[Ti] / [N]<4.0, and the balance Fe with inevitable impurities, and in which AS value and DL value defined by the following formulae satisfy AS≥3.60 and DL≤2.80, and has a structure mainly composed of bainitic ferrite: AS=[Mn]+[Ni]+2×[Cu], and DL=2.5×[Mo]+30×[Nb]+10×[V]; wherein, [X] denotes the content (mass%) of the element X.

Description

technical field [0001] The present invention relates to a high-strength steel with a tensile strength above 780MPa used in bridges, buildings, ships, penstocks, tanks, and other large structures, in particular to a large A material excellent in toughness of the welded heat-affected zone (hereinafter referred to as "HAZ") after heat input welding. Background technique [0002] In the high-strength steel plate above 780MPa, from the viewpoint of ensuring the strength of the base metal, since a large amount of alloy components are added, when the cooling rate is fast under low heat input welding conditions, the HAZ is hardened, and welding cracking (low temperature cracking) is likely to occur. In order to prevent this from happening, preheat above 100°C during welding construction. If such preheating can be omitted, construction efficiency can be greatly improved and cost reduction can be achieved. Therefore, a high-tensile steel sheet of 780 MPa class or higher having excel...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/50
CPCC21D8/0205C22C38/001C22C38/02C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/54C22C38/58
Inventor 高冈宏行冈崎喜臣畑野等
Owner KOBE STEEL LTD