Microstructure and properties of X100 pipeline
In the transport of oil and gas in the pipeline transportation is an efficient, economical, safe, non-polluting characteristics, it is an effective tool for long-distance transport of oil and gas, and because of its economic, security and continuity and get all the advantages of the developed countries widespread attention.
Research and production pipeline thus become the micro-alloy steel and high-strength low-alloy areas most vibrant an important branch. With the development of the world's oil and gas industry,
long-distance pipeline construction is moving large diameter, large wall thickness, the direction of the development of high-voltage transmission, the transmission medium from oil-based to gas-based changes to the order, which requires pipeline steel with high strength and high toughness. At present, domestic X80 grade pipeline steel has been widely used, X100 and X120 grade steel production experiments constantly improve the process. Senior X100 pipeline steel applications have huge economic benefits, can make long-distance oil and gas pipelines cost savings of 5% to 12%, mainly in material savings, improve the delivery pressure, reducing the amount of construction, reduce maintenance costs, optimize the overall program, etc. . Changes in the organization and performance of X100 pipeline steel under different rolling process is different.
Using Gleeble-1500D thermal simulation machine simulates the X100 pipeline steel rolling process, and through LeicaMEF-4M-based microscope, HITACHIS-4500 scanning electron microscopy and micro-hardness of different processes studied under experimental microstructure of steel and variation of mechanical properties. The results showed that: X100 pipeline steel is mainly composed of granular bainite and lath bainite. Finishing to reduce the amount of deformation increases the stability of austenite transformation start temperature increase, while reducing the hardness, the smaller the amount of deformation of the microstructure by lath bainite transformation to a larger amount of deformation of the The granular bainite. With the amount of deformation and final finishing cold temperature decreases, the number of M / A islands to reduce the distribution becomes more finely dispersed. 25% to 40% deformation under 20 / s cooling rate conditions, the experimental steel phase transformation temperature range of 635 ~ 330 , most of which occurs at phase 550 ~ 400 . At 25% to 40% deformation conditions, the final cooling temperature 600 ~ 350 experimental steel microstructure is substantially granular tissue or granular bainite, but decreased with final cooling temperature, the organization gradually refined, while M / A size and volume fraction decreases; many lath bainite / martensite after the end of the cold temperatures below 350 . By refining granular bainite can get very high hardness values (> 300HV), the translation of strength far greater than 700MPa. At 600 isothermal phase change will occur partially, but with the extension of the isothermal time, not only did not reduce the hardness of steel is also a slight increase, which may be located in an isothermal and deformation of austenite dislocation configuration changes and NbC precipitates etc. precipitation related.
