A method for manufacturing a
bainite high-strength seamless
steel tube, comprising the following steps:
smelting, manufacturing a billet, heating, perforating, rolling, stretch reducing or
sizing to obtain tube, and cooling. In the cooling step, the
quenching starting temperature is controlled to be at least 20° C. higher than the Ar3 temperature of the steel grade; the finish
cooling temperature is controlled to be within a range between T1 and T2, where T1=519−423C−30.4Mn, T2=780−270C−90Mn, and the units of the T1 and the T2 are ° C.; in the formulas, C and Mn respectively represent the
mass percents of element C and element Mn of the steel grade, the content of the element C is 0.06-0.2%, and the content of the element Mn is 1-2.5%; the
cooling rate is controlled to be 15-80° C. / s; and the finished product of the
bainite high-strength seamless
steel tube is directly obtained after the cooling step. The manufacturing of a
bainite high-strength seamless
steel tube using the method requires neither the addition of precious alloying elements nor the subsequent heat treatment. Therefore the production costs are low.