Uniform-performance low-temperature-resistant easy-to-weld extra-thick steel plate for wind tower door frame and manufacturing method thereof

The invention relates to a low-temperature-resistant easy-to-weld super-thick steel plate with uniform performance for a wind tower door frame and a manufacturing method thereof. The low-temperature-resistant easy-to-weld super-thick steel plate comprises the following chemical components in percentage by mass: 0.12-0.14% of C, 0.10-0.20% of Si, 1.48-1.60% of Mn, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.20-0.25% of Ni, 0.20-0.25% of Cu, 0.040-0.050% of Nb, 0.010-0.020% of Ti, 0.020-0.050% of Alt, 0.0005-0.0020% of Ca and the balance of Fe and inevitable impurities. Through the working procedures of KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing-Ca treatment, continuous casting, slow cooling, blank heating, rolling, normalizing and the like, a continuous casting blank with the thickness of 370-450 mm is used for producing the ultra-thick steel plate for the wind tower door frame with the thickness of 130-150 mm, the product has good internal qua