Abstract: The present disclosure provides a bainite geological drilling pipe, comprising the following chemical elements in percentage by mass: 0.14-0.22% of C, 0.2-0.55% of Si, 2.1-2.9% of Mn, 0.01-0.04% of Nb, 0.015-0.04% of Al, 0.001-0.005% of B, 0<N?0.007%, with the balance being Fe and inevitable impurities, wherein a content ratio of Al to N is Al/N?3. In addition, the present disclosure further provides a manufacturing method for the bainite geological drilling pipe, comprising the following steps: (1) performing smelting and casting on molten steel to obtain a pipe blank; (2) performing heating, piercing, continuous rolling and sizing on the pipe blank to obtain a pipe body; and (3) performing two-stage air cooling on the pipe body; in first-stage air cooling, performing air circular blowing cooling on the outer surface of the pipe body, the temperature before cooling is greater than or equal to Ar/3+50° C., the cooling rate is 5-15° C./s, and cooling to a temperature range from Bs-100° C. to Bs-50° C.

Abstract: An process for the on-line quenching of seamless steel tube using residual heat, a method for manufacturing a seamless steel tube, and a seamless steel tube. The process for the on-line quenching of a seamless steel tube comprises the following steps: when the temperature of a tube is higher than Ar3, evenly spraying water along a circumferential direction of the tube so as to continuously cool the tube to be not higher than T° C., the cooling rate being controlled to be E1° C./s to E2° C./s to obtain a microstructure with martensite as the main composition, wherein T=Ms?95° C., Ms represents the martensitic phase transition temperature, E1=20×(0.5?C)+15×(3.2?Mn)?8×Cr?28×Mo?4×Ni?2800×B, and E2=96×(0.45?C)+12×(4.6?Mn), and the C, Mn, Cr, Ni, B and Mo in the equations each represents the mass percentages of corresponding elements in the seamless steel tube.

Abstract: 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=519-423 C-30.4Mn, T2=780-270 C-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.

Abstract: A seamless steel tube with high strength and toughness, comprising the following chemical elements by mass: 0.1-0.25% of C, 0.1-0.5% of Si, 0.01-0.1% of Al, 0.6-2% of Mn, the balance of Fe and other unavoidable impurities, wherein C+Mn/6?0.35. Also provided is a method for preparing a seamless steel tube.

Abstract: The invention provides a seamless line pipe with excellent resistance against corrosion by CO2—H2S-SRB. The line pipe comprises, by mass fraction, C: 0.03 to 0.10%, Si: 0.1 to 0.5%, Mn: 0.10% to 1.50%, P: 0.02% or less, S: 0.005% or less, Cr: 1.0 to 4.0%, Ni: 0.1 to 1.5%, Cu: 0.15 to 2.0%, Mo: 0.05 to 0.4%, Ti: 0.01 to 0.05%, RE: 0.05 to 0.1%, and balance of Fe. After smelting, rolling into a billet, and piercing and rolling into a pipe, the resultant steel pipe is heated to 920 to 1000° C. and kept for 0.3 to 1 hour depending on the thickness of the steel pipe wall, and then subjected to rapid cooling and tempering heat treatment. The seamless line pipe can be used in the field of oil and gas fluid transportation and the like.

Abstract: An online-control cooling process for seamless steel tube for effectively refining grains, comprising the following steps: when the temperature of a crude tube is higher than Ar3, evenly spraying water along the circumferential direction of the tube so as to continuously cool the tube to T1° C.˜T2° C., the cooling rate being controlled to be N1° C./s˜N2° C./s, wherein T1=810?360C?80(Mn+Cr)?37Ni?83Mo, T2=T1+115° C., N1=55-80×C, N2=168*(0.8?C), and C, Mn, Cr, Ni and Mo in the equations each represent the mass percentage of corresponding elements in the seamless steel tube; then, cooling to the room temperature at cooling rate no more than 10° C./s. Correspondingly, also provided are a method for manufacturing seamless steel tube for effectively refining grains, and a seamless steel tube. The online-control seamless steel tube cooling process does not require adding too many alloying elements, which is simple and can yield seamless steel tubes with good grain refinement and better toughness.

Abstract: 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.

Abstract: A seamless steel tube with high strength and toughness, comprising the following chemical elements by mass: 0.1-0.25% of C, 0.1-0.5% of Si, 0.01-0.1% of Al, 0.6-2% of Mn, the balance of Fe and other unavoidable impurities, wherein C+Mn/6?0.35. Also provided is a method for preparing a seamless steel tube.

Abstract: An process for the on-line quenching of seamless steel tube using residual heat, a method for manufacturing a seamless steel tube, and a seamless steel tube. The process for the on-line quenching of a seamless steel tube comprises the following steps: when the temperature of a tube is higher than Ar3, evenly spraying water along a circumferential direction of the tube so as to continuously cool the tube to be not higher than T° C., the cooling rate being controlled to be E1° C./s to E2° C./s to obtain a microstructure with martensite as the main composition, wherein T=Ms?95° C., Ms represents the martensitic phase transition temperature, E1=20×(0.5?C)+15×(3.2?Mn)?8×Cr?28×Mo?4×Ni?2800×B, and E2=96×(0.45?C)+12×(4.6?Mn), and the C, Mn, Cr, Ni, B and Mo in the equations each represents the mass percentages of corresponding elements in the seamless steel tube.