Method for improving low-temperature DWTT performance of X70M pipeline steel

Abstract

The invention relates to the technical field of pipeline steel pipe production, in particular to a method for improving the low-temperature DWTT performance of X70M pipeline steel. The method comprises the steps that (1) the heating time and the high-temperature section temperature are limited; (2) rough rolling is conducted in a transverse-longitudinal rolling mode; (3) for a blank smaller than or equal to 250 mm, the thickness of an intermediate blank is 3.0-3.3 times of the thickness of a finished product, and for a blank larger than 250-300 mm, the thickness of the intermediate blank is 4.2-4.5 times of the thickness of the finished product; for the blank smaller than or equal to 250 mm, the number of longitudinal rolling loaded passes is controlled to be 2-4, and the pass reduction rate is larger than or equal to 15%; for the blank larger than 250-300 mm, the number of longitudinal rolling loaded passes is controlled to be 3-5, and the pass reduction rate is larger than or equal to 20%; (4) in the finish rolling stage, the initial rolling temperature ranges from 840 DEG C to 880 DEG C, and the finish rolling temperature ranges from 780 DEG C to 820 DEG C; (5) a semi-automatic controlled cooling mode is adopted, the water feeding amount is 200-500 m<3> / h, and the water discharging amount is 1000-1500 m<3> / h; and (6) one-pass straightening is adopted in the straightening stage. The low-temperature DWTT performance of the X70M pipeline steel is improved, and the performance qualification rate is increased; and performance differences caused by the fact that blanks with different thickness specifications are used for rolling pipeline steel with the same thickness specification without considering the influence of the thickness of the intermediate blank are avoided.

Description

technical field [0001] The invention relates to the technical field of pipeline steel production, in particular to a method for improving the low-temperature DWTT performance of X70M pipeline steel. Background technique [0002] Pipeline transportation has the characteristics of high efficiency, economy, energy saving, environmental protection and pollution-free, so it is used as the first choice for oil and natural gas transportation. In order to ensure the stability and safety of the transportation process, long-distance and high-pressure transmission pipelines usually use thick-gauge pipeline steel. [0003] In order to avoid the potential safety hazards of oil and gas pipelines passing through densely populated areas, the comprehensive performance requirements of steel for oil and gas pipelines are particularly high. They must have high strength, low temperature toughness and good welding performance. Here, it is particularly important to point out that crack arrest Per...

AI Technical Summary

Problems solved by technology

In order to ensure the safety of pipeline steel in the process of transporting high-pressure oil and gas, it is necessary to increase the thickness of pipeline steel while increasing the strength of pipeline steel. However, as the thickness of the steel strip material increases, the performance of the drop hammer will deteriorate and the drop hammer will tear The ductile-brittle transition temperature of the test increases

[0004] Low-temperature DWTT performance is one of the most important properties of pipeline steel. This performance mainly tests the low-temperature toughness of pipeline steel. Traditional control methods do not consider the influence of intermediate billet thickness on this performance In addition, the use of billets with different thickness specifications to roll pipeline steel with the same thickness specification did not consider the influence of the thickness of the intermediate billet, resulting in differences in performance

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