High tension steel plate with excellent weldability

Abstract

The invention provides a Bainite high-tension steel plate with excellent weldability over than 590 MPa grade capable of ensuring excellent HAZ toughness even welding in the wide heat energy input range from low heat energy input welding to high heat energy input welding. The high tensile strength steel plate has a prescribed chemical componential composition, and in which BP value and Pcm prescribed by prescribed relational formulae satisfy 120 to 300 (mass%) and <=0.20 (mass%), respectively, also, Ti-containing nitrides with the circle equivalent diameter of <=0.05 [mu]m are present by >=5.0*10<6> pieces per 1 mm<2>, and, therein, the number of the Ti-containing nitrides with the circle equivalent diameter of 0.01 to 0.03 [mu]m occupies >=75% to the number of all the Ti-containing nitrides.

Description

technical field [0001] The present invention relates to a high-tensile steel plate suitable for welded structures such as bridges, high-rise buildings, and shipbuilding, and particularly relates to the toughness of the heat-affected zone (hereinafter referred to as "HAZ") after welding from low heat input to high heat input welding Excellent high tensile steel plate. Background technique [0002] In recent years, with the increase in size of the various welded structures described above, welding of thick steel plates having a plate thickness of 50 mm or more is unavoidable. Therefore, the situation in this field is directed to high heat input welding of 25 kJ / mm or more from the viewpoint of improving welding work efficiency. [0003] However, if high heat energy input welding is performed, the HAZ will be heated to the high-temperature austenite region and then gradually cooled, so the structure of the HAZ (especially near the fusion zone of the HAZ) will be coarsened, and...

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Problems solved by technology

[0012] However, in the techniques proposed so far, it is the fact that in bainite steels whose strength exceeds the 590 MPa class, stably ensuring good HAZ toughness across a wide range of heat input from low heat input welding to high heat input welding has not yet been achieved. achieve

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