High strength steel for thick wall water pipe and manufacturing method thereof

The invention provides a high strength steel for a thick wall water pipe. The steel comprises the following components: 0.040%-0.070% of C, 0.10%-0.40% of Si, 1.50%-1.65% of Mn, 0.050%-0.080% of Nb, 0.030%-0.050% of V, 0.20%-0.30% of Cr, 0.005%-0.025% of Ti, 0.015%-0.050% of Als, less than or equal to 0.020% of P, less than or equal to 0.008% of S, less than or equal to 0.008% of N, less than or equal to 0.002% of O, and the balance Fe and inevitable impurities. The manufacturing method of the steel includes: conducting continuous casting to make a continuous casting plate blank, subjecting the continuous casting plate blank directly to hot charging furnace heating at 500-850DEG C, heating the continuous casting plate blank by a reheating furnace to 1150-1230DEG C, discharging it, then carrying out two-stage controlled rolling by roughing rolling and finish rolling units, controlling the initial rolling temperature of rough rolling at 1180-1100DEG C and the final rolling temperature of rough rolling at 1010-960DEG C, keeping the initial rolling temperature of finish rolling at 980-920DEG C and the final rolling temperature of finish rolling at 780-850DEG C, and maintaining the compression ratio of finishing rolling greater than 60%; then subjecting a steel strip to rapid cooling by means of laminar cooling at a speed of 10-20DEG C/s; and performing reeling at 500-580DEG C.