Large-wall-thickness X65M pipeline steel plate and manufacturing method thereof

The invention relates to a large-wall-thickness X65M pipeline steel plate and a manufacturing method thereof. The large-wall-thickness X65M pipeline steel plate is prepared from, by weight, 0.08%-0.15% of carbon, 0.25%-0.40% of silicon, 1.40%-1.50% of manganese, not larger than 0.008% of phosphorus, not larger than 0.003% of sulphur, 0.06%-0.11% of molybdenum, 0.030%-0.040% of niobium, 0.012%-0.023% of titanium, 0.015%-0.025% of aluminum, not larger than 0.004% of nitrogen and the balance iron and inevitable impurities. The large-reduction-rate rolling at the rough rolling stage is adopted, rough mill scale removal water is innovatively adopted for cooling intermediate billets, pre-forming is not used, and milling is conducted after direct broadening is conducted. The temper pass is adopted as the finish milling last pass, the head and the tail of the steel plate are shielded in the cooling process, the reasonable water convexity is set, and the good strip shape and the performance uniformity of the steel plate are ensured. Transition material milling is conducted, the steel plate is milled through a single-fold ruler, and the temperature difference of the steel plate is reduced.