Method for improving thick-specification L555M level pipeline steel DWTT property

Abstract

The invention relates to the technical field of pipeline steel pipe production, in particular to a method for improving the thick-specification L555M level pipeline steel DWTT property. The method comprises the steps that firstly, the heating temperature is limited at 1200 to 1250 DEG C, the temperature of a soaking zone is limited at 1190 to 1230 DEG C, the heating main time is limited at 270 to330 minutes, the high-temperature segment time is limited at 120 to 180 minutes, and it is ensured that the tapping temperature is above 1200 DEG C; secondly, the transverse-longitudinal rolling manner is adopted in rough rolling, transverse rolling is carried out for four to six passes, longitudinal rolling is carried out 2 to 4 passes, the initial rolling temperature is not lower than 1150 DEG C, after transverse rolling, after the temperature is 1040 to 1080 DEG C, longitudinal rolling is carried out, meanwhile, it is ensured that the longitudinal rolling accumulative reduction rate is above 55%, the longitudinal rolling single-pass reduction rate is limited as 20%, and the intermediate blank thickness is 80 to 90 mm; thirdly, the initial rolling temperature is 780 to 850 DEG C, the finish rolling and final rolling temperature is 750 to 800 DEG C, and after rolling, the water inlet temperature is 790 to 810 DEG C; and fourthly, the controlled cooling mode is adopted, the water feeding amount is 400 to 500 m<3> / h, the water discharging amount is 1300 to 1400 m<3> / h, 12 to 15 sets are initially rolled, the water ratio is 1 / 3, the cooling speed is 10 to 20 DEG C / s, and it is ensured that the return red temperature is 420 to 480 DEG C. The thick-specification L555M level low-temperature DWTT property is improved, and the property yield is improved.

Description

technical field [0001] The invention relates to the technical field of pipeline steel production, in particular to a method for improving the DWTT performance of thick specification L555M grade pipeline steel. Background technique [0002] With the rise of the energy industry and the continuous growth of energy demand, the transmission volume and transportation distance of oil and gas pipelines continue to increase. Pipeline construction is increasingly using large-diameter, high-strength, and high-toughness pipeline steel pipes. The technological progress of iron and steel metallurgy and pipeline manufacturing industry has greatly improved the quality, level and service performance of high-performance pipeline steel in my country. The production capacity of steel pipe production lines with X80 steel grade and large wall thickness supply capacity in China has reached 5 million tons / year or more. [0003] Although iron and steel and welded pipe enterprises have accumulated c...

AI Technical Summary

Problems solved by technology

[0003] Although iron and steel and welded pipe enterprises have accumulated certain experience in the production of high-performance high-grade, large-diameter, and large-wall-thickness pipeline steel, research and trial production of high-grade pipeline steel with a pipe wall thickness greater than 20 mm have made certain progress. However, the L555M grade pipeline steel with a pipe wall thickness greater than 24mm is not easy to control the low-temperature drop-weight tearing performance due to the thickness limit, and the strength and toughness of the produced L555M cannot meet the technical standards.