Engineering Application Research On Domestically Manufactured X80 Pipeline Steel Used For Large Diameter Gas Transportation Pipeline

With the increasing demands for oil and natural gas, the transportation pressureand diameter of pipeline are becoming higher and larger for getting highertransmission efficiency. Now, long distance, large diameter and high transportationpressure have been the main characteristics of oil and gas pipelines, which demandthe steel pipe with higher strength and better toughness in order to guarantee thestructure stability and safety of the pipeline. The first measure to get this goal is to usethe higher strength steel pipe.API 5L X70 steel had been the dominated steel used for gas transportationpipeline in the later of 1990's. API 5L X80, as a higher grade product, has been usedfor more than 500km gas transportation pipelines abroad, and the relevantmanufacturing technologies and QA/QC are now becoming more and more practicaland perfect, which provide the essential condition for large scale adoption of thisgrade steel pipe. The relevant application researches had been carried out in 2000assigned by China National Economy and Trade Committee.This thesis analyzed the application and technical progressing trend of X80 steelpipe, and draw a conclusion that the relevant treatment processes in X80 steel pipemanufacturing are all practical, and the applicable technical demands have been listedin API 5L and GB/T 9711.2.The chemical composition, strength, toughness, micro-structure of domesticmanufactured X80 steel had been tested, analyzed and compared with each other by alarge amount of experiments, and a conclusion has been drawn that the wide and thicksteel plate provided by Anshan Steel Factory and the steel pipe manufactured byJulong Steel Pipe Company have the best quality, and the relevant experiments alsoshown that the quality of domestically manufactured X80 steel, including hot rolledplate coils, steel plates and steel pipes for both SSAW and LSAW, meet the pertinentspecifications by CNPC.Economic analysis has also been done in this thesis. By adoption of higherstrength steel pipe, not only the pipe weight, but also the connected welding, platerolling, pipe manufacturing and transportation cost can be decreased. Especially, thedecrease of pipe weight per meter means much to the economy and feasibility ofpipeline construction.The explosion fracture test has also been done, which proves that the pipelinewill be safe when operated at the designed pressure and tested at the hydraulicpressure during the strength testing.Totally, the adoption of X80 steel pipe in domestic long distance, large diameterand high transportation pressure pipeline project is feasible based on the experimentsand researches above.