Weldability of Advanced Extremely–low Carbon Bainitic Steel for Thick Plates of 570 Mpa Grade through As-Rolled process

摘要

An extremely-low carbon binitic steel with about0.02 mass% or less carbon content can be applied to themanufacture of high strength heavy gauge steel plates becauseof the unique features such as a granular bainitic ferritemicrostructure independent of cooling rate after plate rolling .Being free from martensite transformation due to the decrease incarbon minimizes the hardening of heat-affected zone (HAZ)and the deterioration HAZ toughness at an increase in thewelding heat input .A design to control the microstructure forextremely-low carbon bainite was applied to develop the newhigh trength steel plate which can be manufactured with no heattreatments . TS 570 Mpa grade steel plated of 38 and 75 mmthickness were produced and the weldability was evaluated. Themaximum HAZ hardness value was under 280 in Vickersnumber even under an arc-strike condition. The HAZ toughnessat a heat input of up to 20kJ/mm showed high Charpy impact energy.