Pipeline steel with good and stable low-temperature flexibility and method for rolling hot rolled coils thereof

Abstract

The invention discloses pipeline steel with good and stable low-temperature flexibility and a method for rolling hot rolled coils thereof. The pipeline steel comprises the following compositions in percentage by weight: 0.03 to 0.070 percent of carbon, 0.19 to 0.30 percent of silicon, 1.50 to 1.90 percent of manganese, 0.010 to 0.020 percent of titanium, 0.015 to 0.040 percent of aluminum, less than or equal to 0.30 percent of nickel, less than or equal to 0.02 percent of chromium, less than or equal to 0.0002 percent of boron, less than or equal to 0.018 percent of phosphorus, less than or equal to 0.005 percent of sulfur, 0.002 to 0.003 percent of calcium, 0.20 to 0.40 percent of molybdenum, less than or equal to 0.30 percent of copper, 0.02 to 0.10 percent of niobium, less than or equal to 0.006 percent of nitrogen, less than or equal to 0.004 percent of oxygen, less than or equal to 0.00025 percent of hydrogen, and the balance of iron and impurities. The manufactured pipeline steel has the characteristics that sigma s is equal to be between 565 and 580 MPa; sigma b is equal to be between 665 and 690 MPa; and sigma s / sigma b is less than or equal to 0.85.

Description

technical field [0001] The invention relates to a rolling method of pipeline steel and its hot-rolled coil, in particular to a rolling method of X80 pipeline steel with stable low-temperature toughness and its hot-rolled coil. Background technique [0002] The oil and gas industry is the main energy source for industrial development. In order to improve pipeline transmission efficiency, reduce energy consumption, reduce investment and operating expenses, long-distance transmission pipelines have become a trend towards high pressure and large diameter pipes. The strength, toughness, welding Higher requirements are constantly being put forward for performance and corrosion resistance. At present, X60~X80 steel grade pipeline steel is mostly used for long-distance transportation in the world. X80 pipeline steel has strict requirements on low temperature toughness and welding performance, so it is strictly controlled from three key links of composition design, rolling and smelti...

AI Technical Summary

Problems solved by technology

[0004] Both of the above two pipeline steels are added with vanadium element, which has a high precipitation strengthening effect, but the addition of vanadium element makes the precipitation strengthening effect exceed the required level, and the strength and toughness are gradually unbalanced. After adding more than 0.03% V element, the It will significantly reduce the impact toughness level and toughness value stability of high-grade X80 pipeline steel, and the Charpy impact energy at -20°C will decrease by an average of 95 J, and there will be 10% and 30% -20°C Charpy impact energy in the same furnace pipeline steel strip Significantly below the minimum required by the standard

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