Study Of The Behavior Of Stress Corrosion Of X80 Steel In Yingtan Soil Environment

In recent years, with sharply increasing in energy demand in China, the construction of oil-gas pipeline is vigorously developed. By 2004, oil-gas pipelines were built 45777km in China. It is reported that in the future 10 years china petroleum will invest 200 billion for construction of oil-gas pipeline transportation network, all kinds of senior oil-gas pipeline steel will be needed about 10 million ton. The using of X80 steel has researched to application in foreign countries, the existed and building X80 pipeline have 2000km, X100 and X120 steel haVe reached the trial stage. 7.9Km of X80 pipeline has been laid in west-east pipeline project of branch line of Yining, It was filled with signs that rolling X80 steel made in our country and welding technology have reached the practical stage, X80 pipeline steel is also used in natural gas pipeline of west second-line. With the development of localization and energy delivery system of X80 pipeline, it will be more widely applied in energy pipeline in China. Therefore, studying stress corrosion behaVior and mechanism of X80 steel and weld microstructure in typical soils in China (such as saline soil in the western and acid soil northern in the eastern )will be solved scientific problems and necessary precondition to deVelop the large and safe usage of X80 steel oil-gas pipeline .The corrosion process of X80 steel is researched under different conditions in the acidic corrosiVe medium by potentiodynamic scanning technique, electrochemical impedance, cyclic voltammetry, slow strain rate tests, hydrogen permeation, corrosion mechanism of X80 steel in the acidic corrosive medium is analyzed by the experimental results, various gases and corrosions impact on the cathode or the anode reaction is researched. Electrochemical experiments showed that, the polarization curves of X80 pipeline steel and welded joints in simulated Yingtan soil solution have a characteristic of actiVice dissolution.Corrosion resistance of welded joints are better than the base metal. This is likely due to some corrosion-resistant alloy elements, which enhance the corrosion resistance of welded after welding heat .Tensile stress test results show that base metal and weld microstructure of X80 steel can happen SCC in simulated acid soil solution in our environment , in the same conditions,welded is easier to happen SCC than base metal. This paper is able to provide profound insight for the stress corrosion cracking mechanism of X80 steel in acidic solution, it can provide reliable theoretical basis and data support for engineering applications and scientific research of X80 steel .