Pipeline steel is used to transport oil, natural gas and other large diameter welded steel pipe for hot rolled coil or plate. Pipeline steel in use process, in addition to the compressive strength is high, also requires low temperature toughness is high and excellent welding performance.
Micro alloy modern pipeline steel belongs to low carbon or low carbon steel, high technological content and high added value products, pipeline steel production almost used new technology in metallurgical field all the achievements of the past 20 years. The development trend of pipeline engineering is the thick wall of large diameter, high pressure rich gas transportation, high cold and corrosion service environment, the submarine pipeline. So the modern pipeline steel with high strength, low should be the Bauschinger effect, high toughness and resistance to brittle fracture, low welding carbon amount and good weldability, and anti HIC and anti H2S corrosion. Production optimization is the cleanliness and organization progress steel uniformity, C ≤ 0.09%, S ≤ 0.005%, P ≤ 0.01%, O ≤ 0.002%, and take the micro alloying, light pressure of vacuum degassing +CaSi, continuous casting process, thermo mechanical rolling multi stage and multi function intermittent accelerated cooling process. Domestic pipeline codes do not toughness index of steel pipe, only have specific requirements for pipe:
(1) the lowest temperature (- 5 ℃) DWTT ≥ 85%SA;
(2) the lowest temperature (5 ℃) Charpy impact energy is greater than or equal to 145J.
Technical condition of pipeline steel is widely used in America Petroleum Association standard APISpec5L, but the specific domestic projects or specific user ordering technical condition is often much more stringent API standards.
With rigorous requirements for smelting technology, main difficulties in:
1) controlling the content of impurity elements;
2) inclusion control;
3) narrow composition control.