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

Patent metadata

Field	Value
Publication number	US-11203794-B2
Application number	US-201615762810-A
Country	US
Kind code	B2
Filing date	Sep 21, 2016
Priority date	Sep 24, 2015
Publication date	Dec 21, 2021
Grant date	Dec 21, 2021

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. 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.

First claim

The invention claimed is:

1. A method for manufacturing a bainite seamless steel tube consisting of chemical elements by mass: C, 0.06-0.2%; Si, 0.1-0.6%; Mn, 1-2.5%; Al, 0.01-0.1%; S≤0.005%; P≤0.02%; O≤0.01%, and the balance being Fe and other unavoidable impurities, wherein the mass percentages of the element C and the element Mn satisfy: C+Mn/6≥0.38, the method comprising the following ordered steps:
smelting;
manufacturing a billet;
heating the billet;
piercing, rolling and stretch reducing or sizing to obtain a tube;
cooling the tube, wherein the cooling step comprises a cooling rate of 15-80° C./s and commences once the tube reaches a temperature greater than or equal to the Ar3 temperature of the steel grade +20° C. and ceases once the tube achieves a temperature within a range between T1 and T2, wherein T1=519-423 C-30.4Mn, T2=780-270 C-90Mn, and units of T1 and T2 are ° C. in the formulas, wherein C and Mn respectively represent the mass percent of element C and element Mn of the steel grade;
obtaining a bainite seamless steel tube, wherein the bainite seamless steel tube is directly obtained after the cooling step.

2. The method for manufacturing a bainite seamless steel tube according to claim 1 , wherein the cooling step comprises water cooling.

3. The method for manufacturing a bainite seamless steel tube according to claim 2 , wherein the water cooling comprises spraying water on the outer wall of the tube for cooling.

4. The method for manufacturing a bainite seamless steel tube according to claim 2 , wherein the cooling step comprises placing the tube in a sink for cooling.

5. The method for manufacturing a bainite seamless steel tube according to claim 1 , wherein the heating step comprises heating the billet to 1150-1300° C. and maintained for 1-4 hours.

6. The method for manufacturing a bainite seamless steel tube according to claim 1 , wherein the bainite seamless steel tube manufactured by said method has a yield strength >555 MPa, and an impact energy (full size test piece) at 0° C. of >50 J.

Assignees

• Baoshan Iron & Steel

Inventors

• Liu Yaoheng
• Zhang Zhonghua
• Wang Xiaobo

Classifications

• C21D8/10

  during manufacturing of tubular bodies · CPC title

• C22C38/02 Primary

  containing silicon · CPC title

• C21D11/005

  for cooling · CPC title

• C21D2211/009

  Pearlite · CPC title

• C21D9/48

  deep-drawing sheets · CPC title