Normalized low-yield-ratio UOE welded pipe and manufacturing method thereof

Abstract

The invention discloses a normalized low-yield-ratio UOE welded pipe which comprises the following chemical elements including, by mass, 0.14%-0.18% of C, 0.15%-0.30% of Si, 1.20%-1.50% of Mn, less than or equal to 0.15% of Cu, less than or equal to 0.15% of Ni, less than or equal to 0.15% of Cr, 0.010%-0.030% of Nb, 0.005%-0.020% of Ti, 0.001%-0.005% of Ca, 0.020%-0.050% of Al, less than or equal to 0.0005% of B and the balance Fe and other inevitable impurity elements. In addition, the invention further discloses a manufacturing method of the normalized low-yield-ratio UOE welded pipe. The manufacturing method comprises the following steps of (1) smelting and continuous casting; (2) rolling a steel plate; (3) making a UOE pipe; (4) normalizing the whole pipe; and (5) finishing, specifically, the expanding rate is controlled to be 0.6%-2%.

Description

technical field [0001] The invention relates to a steel pipe and a manufacturing method thereof, in particular to a welded pipe and a manufacturing method thereof. Background technique [0002] Since the high-temperature steam pipelines used in the petroleum refining industry need to serve at high temperatures for a long time, there is a high requirement for the uniformity of the material structure, and heat-treated seamless steel pipes such as normalized state and modulated state are usually used. Steel pipes have good uniformity in structure and performance. However, seamless steel pipes are limited by caliber specifications and cannot meet the large-capacity requirements of some projects. It can only be achieved by increasing the number of pipes, resulting in increased costs. [0003] For example: the publication number is CN105821335A, and the publication date is August 3, 2016. The Chinese patent document titled "A Low-Cost Ultra-Low Temperature Normalized Pipeline Stee...

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Problems solved by technology

[0002] Since the high-temperature steam pipelines used in the petroleum refining industry need to serve at high temperatures for a long time, there is a high requirement for the uniformity of the material structure, and heat-treated seamless steel pipes such as normalized state and modulated state are usually used. Steel pipes have good uniformity in structure and performance. However, seamless steel pipes are limited by caliber specifications and cannot meet the large-capacity requirements of some projects. It can only be achieved by increasing the number of pipes, resulting in an increase in costs

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