Cailiao Baohu (Apr 2024)
Hydrogen Embrittlement Sensitivity of X80 Pipeline Steel Welded Joints in Hydrogen Environment
Abstract
In order to explore the changes in fracture mechanical properties of pipeline steel welded joints in hydrogen environment, the notched tensile in-situ hydrogen charging method was used to study the hydrogen embrittlement susceptibility of X80 steel base metal, welds and heat-affected zones under a total pressure of 12 MPa and a hydrogen partial pressure of 0.36 MPa. A high-pressure slow strain rate tensile testing machine was employed to conduct notch tensile test, and a high-pressure fracture toughness testing machine and a high-pressure corrosion fatigue testing machine were used to carry out fracture toughness and fatigue crack growth rate tests on X80 steel, respectively. The crack propagation behavior of X80 steel was studied by combining fracture toughness tests and fatigue crack propagation rate tests. Results showed that under the same conditions, compared with the base metal and heat-affected zone, the reduction of area at the weld position was significantly reduced, showing a higher susceptibility to hydrogen embrittlement. Compared with the original data in air at normal temperature and pressure, the crack tip opening displacement(CTOD) value of the weld position in the hydrogen partial pressure environment of 0.36 MPa changed slightly, and no secondary cracks appeared on the fracture surface. Compared with the air environment, the fatigue crack growth rate of X80 steel welds in a hydrogen partial pressure environment of 0.36 MPa increased by 1 order of magnitude, signifying that hydrogen could increase the fatigue crack growth rate of the material. However, according to the actual pipeline pressure fluctuation, the hydrogen embrittlement sensitivity of X80 steel was smaller under 0.36 MPa hydrogen partial pressure.
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