Controlled rolling method implemented by stably controlling low-temperature toughness of large-wall-thickness pipeline steel

Abstract

The invention discloses a controlled rolling method implemented by stably controlling the low-temperature toughness of large-wall-thickness pipeline steel, which belongs to the technical field of low-carbon micro-alloyed steel production. Rolling is divided into two stages, i.e. rough rolling and finish rolling, after the penultimate-pass rolling of the rough rolling is completed, when the temperature of a steel billet is reduced to 975-990 DEG C, the finish-pass rolling of the rough rolling is performed, and the finish-pass rolling is replaced with a rapid and consecutive two-pass rolling mode, the deformation rates of the two passes are respectively controlled at 16-21%, and the time interval of the two passes is controlled at 4-8s so as to ensure that the superimposed deformation ratio of the two passes reaches 32-42%; and a situation that the percentage pass reduction of the two-stage rolling process is arranged in an approximately normal distribution mode is required to be ensured. The controlled rolling method has the advantages that by using the method, the good low-temperature toughness of large-wall-thickness pipeline steel can be stably controlled; charpy impact toughness: when the temperature is minus 20 DEG C, the charpy impact energy of a V-shaped notched specimen, of which the core part in the thickness direction is 10*10*55 mmV, of a steel plate is greater than or equal to 354J; and drop weight toughness: when the temperature is minus 15 DEG C, the drop weight shear area of an all-wall-thickness specimen is greater than or equal to 85%.

Description

technical field [0001] The invention belongs to the technical field of low-carbon micro-alloy steel production, and in particular relates to a controlled rolling method for stably controlling the low-temperature toughness of large-wall-thickness pipeline steel, which is suitable for hot-rolling large-diameter and large-wall-thickness pipeline steel with high requirements on low-temperature toughness Production of steel plates. Background technique [0002] With the rapid development of the oil and natural gas industry, in order to further improve the transmission efficiency, global pipeline engineering construction is developing in the direction of large diameter, large wall thickness and high pressure transmission, such as the use in some areas of my country's West Third Line Pipeline steel, Beixi project ultra-deep sea pipeline use Submarine pipeline steel and Iranian gas pipeline use Acid-resistant pipeline steel, etc. It is well known that for the diameter The pr...

AI Technical Summary

Problems solved by technology

[0003] However, for the pipe diameter High-grade pipeline steel with a thickness specification ≥30mm is produced by hot-rolled steel plate. Under the condition that the actual capacity of the current 4300mm roughing mill is limited, it is difficult to stably realize the low-temperature and high-reduction process in the roughing and longitudinal rolling stage, especially at the end of roughing. The problem of automatic splitting of passes is prone to occur, resulting in a very low deformation rate in the final rough rolling pass, which cannot ensure that the deformation rate of the final rough rolling pass reaches more than 25%, and it is difficult to promote deformation to penetrate into the core of the billet, so the core of the billet The austenite grains cannot be completely recrystallized, so it is impossible to refine the austenite grain structure in the center of the billet uniformly, and finally it will be difficult to realize the fine and uniform grain structure of the thickness section of the steel plate, so it is difficult to stably control the excellent low temperature toughness of the steel plate