Method of manufacturing steel plate for high-heat input welding

Abstract

Provided is a method of manufacturing a steel plate for high-heat input welding, the plate being made of a high-tensile alloyed steel plate of medium thickness having a yield strength of at least 460 MPa, and having exceptional joining characteristics, such as toughness, even under high-heat input welding conditions. A steel material containing, by mass percentage, C: 0.03-0.1%, Si: 0.01-0.1%, Mn: 0.8-2%, P: no more than 0.02%, S: 0.0005-0.005%, Al: 0.005-0.1%, Nb: 0.003-0.03%, Ti: 0.005-0.05%, Cu: 0.1-0.5%, Ni: 0.3-2%, N: 0.003-0.01%, B: 0.0003-0.0025%, Ca: 0.0005-0.003%, and O: less than 0.004%, and satisfying the conditions Ceq: 0.38-0.43, ACR: 0-1, is heated to 1,050-1,200 DEG C, inclusive, hot rolled such that the temperature at completion of rolling is at or above the Ar3 transformation point temperature, and water-cooled until the surface temperature reaches between (-t*1.5)+400 DEG C and (-t*1.5)+620 DEG C, inclusive.

Description

technical field [0001] The present invention relates to a non-quenched and tempered high tensile strength steel used in various steel structures in the fields of ships, construction, civil engineering, etc., having a yield stress of 460 MPa or more and a plate thickness of 25 mm or more and 50 mm or less, and particularly relates to even if A method for producing a steel sheet for high thermal energy welding that has excellent joint properties even when performing high thermal energy welding with a heat input amount of more than 200 kJ / cm. Background technique [0002] Steel materials used in various steel structures in the fields of ships, construction, and civil engineering are being increased in strength and thickness. With the increase in strength and thickness of such steel materials, there are increasing opportunities to use high-energy-energy welding with excellent productivity, such as submerged arc welding, electric welding, and electroslag welding, when welding ste...

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Problems solved by technology

[0007] However, with regard to the techniques described in Patent Documents 1 to 4, it is difficult to sufficiently suppress the grain growth of austenite in the HAZ and prevent the toughness of the HAZ from decreasing for large heat input welding with a heat input of more than 200 kJ / cm. of

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