High-grade large-strain pipeline steel and manufacturing method of steel pipe

Abstract

The invention relates to a high-grade large-strain pipeline steel and a manufacturing method of a steel pipe. The high-grade large-strain pipeline steel comprises the following components in percentage by mass: 0.04-0.08 percent of C, 1.50-1.90 percent of Mn, 0.15-0.30 percent of Si, not more than 0.010 percent of P, not more than 0.003 percent of S, 0.005-0.03 percent of Al, 0.002-0.005 percent of Ca, not more than 0.005 percent of N, and the balance of Fe, wherein the carbon equivalent is not more than 0.55 percent and cold cracking sensitivity coefficient is not more than 0.25. The manufacturing method comprises the following steps of: carrying out smelting, Ca treatment, refining and degassing on the pipeline steel; carrying out continuous casting on the pipeline steel to form a thick plate blank; carrying out finish rolling on the thick plate blank; tempering at low temperature to prepare a hot rolling steel plate; moulding and welding the steel plate; and expanding to manufacture the steel pipe with the yield strength of 485-630MPa, the tensile strength of 570-750MPa, uniform plastic deformation elongation of 8-15 percent, strain ageing sensitivity coefficient of not more than 0.40 and Charpy impact toughness of 220-350J at -20 DEG C.

Description

technical field [0001] The invention relates to a method for manufacturing pipeline steel and steel pipes whose strength level reaches X70 and X80 high steel grade and large strain (strain aging sensitivity coefficient is not more than 0.40). Background technique [0002] my country's oil and gas pipeline projects have developed rapidly, especially the construction of long-distance transmission pipelines has been greatly developed in recent years, and the pipelines must pass through various complex geological and geomorphic conditions. The stress-based design method is used for pipelines in most areas, but the strain-based pipeline design method must be used when the pipeline passes through seismic zones, active faults, subsidence zones, tundra zones, landslide zones, etc. High-grade pipeline steel with large uniform plastic deformation capacity and develop corresponding manufacturing technology. Generally speaking, the uniform plastic deformation capacity is larger when th...

AI Technical Summary

Problems solved by technology

In recent years, with the development of controlled rolling air-cooling technology, the yield ratio of pipeline steel has risen from 0.80 to 0.85 in the past to 0.90 to 0.95. Too high yield ratio limits the deformation capacity of pipeline steel and steel pipe, thus affecting the use of safety impact

At present, high-grade pipeline steel with high strain performance has been developed internationally and has been applied in engineering, but it cannot take into account the strain aging performance well.