A low-carbon equivalent high-strength hot-rolled seamless line pipe and its manufacturing method

Abstract

The invention discloses a low-carbon equivalent high-strength hot-rolled seamless pipeline tube and a manufacturing method thereof. The low-carbon equivalent high-strength hot-rolled seamless pipeline tube comprises the following components in percentage by weight: 0.08-0.2 percent of C, 0.1-0.45 percent of Si, 0.8-1.6 percent of Mn, less than 0.02% percent of P, less than 0.005 percent of S, not more than 0.5 percent of Cr, not more than 0.5 percent of Ni, not more than 0.5 percent of Cu, not more than 0.05 percent of Mo, not more than 0.01 percent of O, less than 0.15 percent of (Nb+V+Ti), 0.05-0.1 percent of V, not more than 0.05 percent of Nb, not more than 0.04 percent of Ti, 0.38-0.45 percent of Ceq, N% being not less than (V% / 8.6+Ti% / 3.4) and not more than (V% / 3.6+Nb% / 6.6+Ti% / 3.4), and the balance of Fe and unavailable impurities. The seamless pipeline tube disclosed by the invention is low in carbon equivalent (limited below 0.45), also as high as X60 steel grade or higher in strength (the yield strength is as high as 60Ksi / 415MPa or higher), excellent in impact toughness (the full-size charpy V type impact absorbing energy Ak is larger than 100J at 0 DEG C,), also free from quenched-tempered heat treatment, and deliverable in a hot-rolled / normalization state, so that the cost of a pipeline is lowered, and the pipeline tube is applicable to the fields of conveying tubes and structural tubes for oil gas and other fluids, etc.

Description

technical field [0001] The invention relates to a hot-rolled seamless line pipe, in particular to a low-carbon equivalent high-strength hot-rolled seamless line pipe and its manufacturing method, which is characterized in that it has a relatively low C equivalent (Ceq=C+Mn / 6+(Cr +Mo+V) / 5+(Cu+Ni) / 15) is limited to 0.45% and below) to ensure weldability, while the strength can reach X60 steel grade or higher (yield strength 60Ksi / 415MPa and above), It has excellent impact toughness (0°C, full-scale Charpy V-shaped impact absorption energy Ak>100J), and the seamless line pipe does not need quenching and tempering heat treatment, and the above properties can be achieved by hot rolling or normalizing. Background technique [0002] Pipelines are the most economical and efficient way of oil and gas transportation. In recent years, the length of oil and gas pipelines has increased significantly, and the demand for line pipes has also increased accordingly. In addition to requiri...

AI Technical Summary

Problems solved by technology

[0009] The final strength of the above products can reach more than 60Ksi, and the impact performance also meets the standard requirements, but none of them are delivered in a hot-rolled / normalized state, and the final delivery requires quenching and tempering treatment. There are also the above-mentioned high heat treatment costs and the tube body / Weld area structure differences are relatively large, etc.

In addition, the composition of some of the steel grades exceeds the requirements of the API5L standard and does not have general significance

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