High tension thick steel plate with excellent toughness at welding heat affected zone

Abstract

The invention provides a high-tension hick steel plate for welding having excellent toughness for welding heat affected zone in high heat input welding. The hick steel plate comprises 0.02-0.12% of C, 0-0.40% OF Si, 1.0-2.0% of Mn, 0-0.03% of P, 0-0.015% of S, 0-0.050% of Al, 0.005-0.100% of Ti, 0.0002-0.0500% of REM and / or 0.0003-0.0100% of Zr, 0.0020-0.0300% of Nm 0.0005-0.0100% of O, the rest being Fe and unavoidable impurity. There are more than 500 mm<2> of oxide with diameter of equivalent circle being less than 2 um existed in steel, and there are 5 mm<2> of oxide with diameter of equivalent circle being more than 5 um; according to the viscosity of Mn, REM, Ca forming compounds in steel, the value of X defined by formula (1) is less than 10.0; wherein, [insol Mn], [insol REM], [insol Ca] respectively expresses viscosity (5) of Mn, REM, Ca forming compounds in steel; wherein, X=100 x[insol Mn] / ([insol REM]+[insol Ca]+0.

Description

technical field [0001] The present invention relates to a high-tensile high-tensile thick steel plate for welding that is used as a structural material in the fields of shipbuilding, construction, etc., and has excellent toughness in the welding heat-affected zone (hereinafter referred to as "HAZ") for the application of high-energy-input welding. Background technique [0002] In general, steel materials used as structural materials in the fields of shipbuilding and construction are mostly joined by welding, and must have excellent HAZ toughness in addition to the toughness of the base metal. [0003] In recent years, with the increase in size of welded structures in the construction and shipbuilding fields, the application range of thick steel plates with a plate thickness of 50 mm or more is also expanding. From the perspective of reducing welding construction costs, high heat input welding is desired. However, the HAZ of general thick steel plates is likely to cause tough...

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Problems solved by technology

[0015] However, the increase in the maximum heating temperature and the long time of high temperature retention due to the increase in welding heat energy in recent years have promoted the coarsening of the structure, and at the same time brought about the melting of Mn sulfide in the HAZ during welding, and the subsequent cooling The fine particles of Mn sulfide re-precipitated during the process increase the hardness of the HAZ due to precipitation strengthening, which is the cause of the decrease in the toughness of the HAZ

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