The invention provides a high-intensity and high-
toughness X70 thick-walled seamless pipeline steel. The steel comprises the following elements, in weight percentage: 0.04 to 0.12 percent of C, 0.17 to 0.35 percent of Si, 1.20 to 1.60 percent of Mn, 0.015 percent or less than 0.015 percent of P, 0.010 percent or less than 0.010 percent of S, 0.10 to 0.30 percent or less than 0.10 to 0.30 percent of Mo, 0.005 to 0.045 percent of Al, 0.02 to 0.06 percent of Nb, 0.02 to 0.10 percent of V, 0.10 to 0.25 percent of Cu, 0.10 to 0.30 percent of Ni, 0.010 to 0.030 percent of Ti, 0.20 percent or less than 0.20 percent of Cr, 0.43 percent or less than 0.43 percent of CE, 0.22 percent or less than 0.22 percent of Pcm, balance iron and trace
impurity element. The invention also provides a seamless pipeline steel rolling and manufacturing method. The invention has the advantages that micro-
alloy steel is adopted, the seamless pipeline steel is suitable for the production of the thick-walled pipeline with the wall thickness of less than 36 mm, the overall structure of the
pipe adopts an even
Bainite structure, the carbon equivalent is low, the
welding performance is good, the
impact performance at low temperature is good, the requirements of the thick-walled pipeline used in
deep sea and under other
cold weather are satisfied, the
mechanical property of the pipeline is enhanced, the steel
hardness penetration when in water
quenching is improved, and the difficult problem of thick-walled
pipe machining by a chamfering
machine is solved.