Development of Large Heat Input Welding High Strength Steel Plate for Polar Ship

The steel with low C content and carbon equivalent, was added in a small amount of Nb, Ti and large amount of Mn had been designed in micro-alloyed route. The technology of oxide metallurgy was adopted during the smelting process of the steel. The rolling technology of TMCP was controlled at a low rolling temperature and ultra-fast cooling technology was used, for the purpose of controlling the transformation of the microstructure. The microstructure of the steel plate was controlled to be the mixed microstructure of low carbon bainite and ferrite. The mechanical property of the steel plate was excellent and the value of longitudinal KV₂ at-60℃ was more than 200 J. The toughness of WM and HAZ were excellent after the steel plate was welded with a large heat input of 100~250 kJ/cm. The steel plate processed by mentioned process could meet the requirement of large heat input welding.