Alloy steel seamless steel tubes for pressure and high temperature (tensile strength, yield strength ≥ 620MPa ≥ 440MPa ≥ 127mm) (boiler tube, the chemical composition (wt%) 0.07 ≤ C ≤ 0.13, 8.5 ≤ Cr ≤ 9.5, 0.3 ≤ Mo ≤ 0.6, 1.5 ≤ W ≤ 2, cold drawn or cold r