A kind of high-strength and high-toughness n80q petroleum casing and its manufacturing method

Abstract

The invention discloses a high-strength and high-toughness N80Q petroleum casing pipe and a manufacturing method thereof. The high-strength and high-toughness N80Q petroleum casing pipe comprises the following chemical components in percentages by weight: 0.08 percent to 0.22 percent of C, 0.15 percent to 0.30 percent of Si, 0.8 percent to 1.5 percent of Mn, not more than 0.010 percent of P, not more than 0.005 percent of S, 0.5 percent to 1.0 percent of Cr, 0.10 to 0.30 percent of Mo, 0.005 percent to 0.01 percent of Al, 0.03 percent to 0.15 percent of Nb, 0.02 percent to 0.1 percent of Ti, 0.001 percent to 0.003 percent of Ca, 0.001 percent to 0.005 percent of B, 0.0002 percent to 0.001 percent of RE and the balance of Fe and inevitable impurities. The manufacturing method mainly comprises the following steps of longitudinally shearing a hot-rolled coiled plate, making the shorn hot-rolled coiled plate into a pipe blank through forming and welding, then carrying out hot stretch reducing on the pipe blank, quenching the pipe blank on line after the hot stretch reducing, so as to obtain a martensitic structure which is 90 percent or above, and finally, carrying out coupling surface treatment and thread machining on the pipe blank, so as to make the petroleum casing pipe. The sizes of structural crystalline grains of the petroleum casing pipe are not more than 5 microns; the high strength-toughness proportioning of a steel pipe can be realized; according to the high-strength and high-toughness N80Q petroleum casing pipe and the manufacturing method thereof, the on-line quenching is carried out by utilizing high-temperature residual heat; a heat treatment process is reduced; the energy consumption is lowered; and the production cost is decreased.

Description

Technical field: [0001] The invention relates to a petroleum casing, in particular to a high-strength and high-toughness N80Q petroleum casing and a manufacturing method thereof. Background technique: [0002] At present, the exploitation of oil and gas resources requires a significant increase in the strength of the casing, but the toughness of the material is also gradually decreasing, and the sensitivity of the material to surface defects will further increase. A large number of failure analyzes have found that poor structural toughness and low impact toughness are one of the main factors causing oil casing fracture. At the same time, the research also shows that the strength, toughness and plasticity of steel usually show a trade-off relationship, and grain refinement is the only way to improve the strength and toughness. [0003] There are two main production processes for oil casing pipes: seamless rolled steel pipes and straight seam resistance welded steel pipes. B...

AI Technical Summary

Problems solved by technology

At the same time, in order to improve the strength of seamless pipes, higher carbon is generally added, but the problem is the loss of toughness.

In the production of high-strength straight seam resistance welded casings above N80 steel grade, in order to improve the strength, offline quenching and tempering treatment is generally required, which mainly brings about two problems: one is that high temperature and long-term heat preservation are easy to coarsen the structure of the tube blank , so that the advantages of small grains of the original coil cannot be brought into play; the second is that the tube blank is heated at a high temperature above 900°C for a long time in a resistance furnace or a gas furnace, resulting in a large waste of energy, environmental pollution, and increased manufacturing costs.

[0004] A Chinese invention patent with the publication number CN 103147009 A published on June 12, 2013, which discloses an N80Q steel grade oil casing and its manufacturing method, relates to an economical high-strength N80Q steel grade casing and its In the manufacturing method, the content of elements such as Cr and Ti is reduced in the steel composition design, but elements such as Mo and Nb are not used. The heat treatment process still adopts the traditional heat treatment method of quenching + tempering, and its cost reduction is limited, which limits the casing. The performance is improved, so the strength of the casing is lower than the lower limit required by the API standard, and the increase in toughness is also limited

[0005] A Chinese invention patent with the publication number CN 104357756 A published on February 18, 2015, which discloses a hydrogen sulfide stress corrosion resistant straight seam welded petroleum casing and its manufacturing method, relates to a hydrogen sulfide environment. The high-frequency resistance oil casing steel of the company uses Nb, V, Mo and other micro-alloying in its chemical composition. In the manufacturing method of this patent, although the thermal tension reduction waste heat is used to control the cooling of the online pipe, the grain size of the pipe is ≥9. The transverse impact energy of the weld seam is ≥108J, indicating that the refinement of microalloying elements under the hot tension reduction process has not been fully exerted in the high temperature hot rolling process, and there is still room for improving the performance of the pipe and reducing the cost

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