Production method of pipeline steel

Abstract

The invention relates to a production method of pipeline steel, which adopts the process route of: smelting in a rotating furnace, ladle furnace (LF) refining, vacuum degassing (VD), continuous casting, heating by a heating furnace, rough rolling, finish rolling, Mulpic cold control and finished product warehousing. The pipeline steel comprises the following alloying elements by mass percent: 0.03-0.06% of C, 0.20-0.35% of Si, 1.60-1.70% of Mn, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.04-0.06% of Nb, 0.008-0.02% of Ti, 0.15-0.25% of Ni, 0.20-0.35% of Cr, 0.10-0.15% of Mo, less than or equal to 0.0003% of H, less than or equal to 0.005% of N, less than or equal to 0.0015% of O and the balance of Fe; and the technical method combining rough rolling, finish rolling and Mulpic cold control are carried out under the following conditions: the heating temperature of a billet is 1180-1230 DEG C, the first-stage blooming temperature is 1180-1220 DEG C, the accumulated deformation is more than or equal to 60% and the finish rolling temperature is 980-1060 DEG C; the second-stage blooming temperature of the billet is 880-900 DEG C, the finish rolling temperature is 780-810 DEG C and the accumulated deformation is more than or equal to 70%; air cooling relaxation is carried out on a rolled steel plate till the temperature is 650-680 DEG C, 40-60% of polygonal ferrite (PF) is separated out before the steel plate is cooled; and then, the steel plate is rapidly cooled by Mulpic, wherein the cooling speed is 30-35 DEG C / min, and the finish cooling temperature is 300-360 DEG C. The pipeline steel produced by the method is better in low strain ageing sensitivity and deformation resistance.

Description

technical field [0001] The invention belongs to a steel rolling method, and relates to a production method of pipeline steel with low strain aging sensitivity and deformation resistance. Background technique [0002] In areas of large-scale ground movement caused by natural disasters such as earthquake permafrost, debris flow, and landslides, pipeline steel will withstand large displacement and strain. At this time, the failure of the pipeline is no longer controlled by stress, but by strain. At this time, the pipeline should not only bear high internal pressure, but also have good resistance to large deformation. Ultra-long-distance pipeline construction often inevitably needs to pass through some cold and earthquake-prone areas or deep-sea and other harsh environments, which requires pipeline transportation to consider the operational safety under special geological conditions. Usually, the traditional pipeline design is based on the principle of stress design, that is, w...

AI Technical Summary

Problems solved by technology

However, due to the complex and changeable operating environment of pipelines, in areas prone to earthquakes and geological disasters, pipelines will suffer large displacements and strains. At this time, the failure of pipelines is no longer controlled by stress, but by strain.

At the same time, in order to improve the corrosion resistance of pipeline steel pipes, it is necessary to heat-coat anti-corrosion coatings. However, high-grade pipeline steels will undergo obvious strain age hardening after heating coating, which will increase the yield strength and yield ratio of steel pipes, while the yield strength Raising the ratio will further reduce the deformation resistance of the steel pipe

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