Baoshan Iron & Steel Co., Ltd.

Yaoheng Liu

Zhonghua Zhang

Ping Hu

Xiaobo Wang

Dongxing Wu

Ke Xu

Wen Sun

Yannan Ma

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.; in second-stage air cooling, performing natural air cooling on the pipe body, the cooling rate is 0.5-4° C./s.

High-strength and high-toughness bainite geological drilling pipe and manufacturing method therefor

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&#xb0; C., the cooling rate being controlled to be E1&#xb0; C./s to E2&#xb0; C./s to obtain a microstructure with martensite as the main composition, wherein T=Ms&#x2212;95&#xb0; C., Ms represents the martensitic phase transition temperature, E1=20&#xd7;(0.5&#x2212;C)+15&#xd7;(3.2&#x2212;Mn)&#x2212;8&#xd7;Cr&#x2212;28&#xd7;Mo&#x2212;4&#xd7;Ni&#x2212;2800&#xd7;B, and E2=96&#xd7;(0.45&#x2212;C)+12&#xd7;(4.6&#x2212;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.

Process for on-line quenching of seamless steel tube using residual heat and manufacturing method

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&#xb0; 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 &#xb0; 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&#xb0; 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.

Method for manufacturing bainite high-strength seamless steel tube, and bainite high-strength seamless steel tube

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&#x2265;0.35. Also provided is a method for preparing a seamless steel tube.

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Shanghai, China

Yaoheng Liu