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

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 welding structures such as ships and marine structures, in particular to a heat affected zone (Heat Affected Zone, HAZ) with an ultra-large heat input of 50 kJ / mm or more, which is excellent in toughness after welding and has a low temperature Thick steel plate with excellent base metal toughness. Background technique [0002] In recent years, for example, the increase in size of container ships and the like has been promoted, and thick steel plates having a thickness of 60 mm or more are used. In order to efficiently weld such a thick steel plate, it is required to perform super-large heat input welding with a heat input of 50 kJ / mm or more. [0003] However, when welding with a large heat input is performed, since the HAZ is gradually 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 HA...

AI Technical Summary

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

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