Strain capacity is an important performance indicator for designing and evaluating high-grade steel pipelines.Due to the inhomogeneity of material properties in welded structures,girth welds are one of the main factor...Strain capacity is an important performance indicator for designing and evaluating high-grade steel pipelines.Due to the inhomogeneity of material properties in welded structures,girth welds are one of the main factors that restrict the strain capacity of pipelines.In this paper,girth-welded pipes with cracks in the inner surface of the weld have been studied,and the ductile crack initiation and propagation behavior have been simulated using the Gurson model.The corresponding nominal strain at the onset of crack initiation was defined as the characteristic value of strain capacity.The influencing factors on the strain concentration area,strain concentration factor,and strain capacity of girth-welded pipes were quantitatively analyzed.A semiempirical calculation formula for the strain capacity of typical girthwelded X80 grade pipes has been proposed as a function of the crack size,mismatch coefficient of the weld,and softening degree of the heat affected zone(HAZ).This study can facilitate the defect assessment of girth-welded pipes.展开更多
The mechanical properties of heat affected zone （HAZ） of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal ...The mechanical properties of heat affected zone （HAZ） of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal simulator. The results showed that the high-Nb steels have excellent weldability. Ernbrittlement regions appear in coarse grain heat affected zone （CGHAZ） and intercritically heat affected zone （ICHAZ） ~ Softening region appears in fine-grain heat affected zone （FGHAZ）, and the strength here was even lower than 555 MPa as required in the standard. Meanwhile, with the increase of heat input, the strength and the toughness of HAZ of steel with high Nb, C and lower alloy decrease notably. Therefore, take into account the welding procedure during manufacture of weld pipe, suitable amount of alloy elements, such as Cr, Ni, Cu, Mo and so on, is necessary for high Nb X80 heavy- thick steel plate.展开更多
基金supported by the grants from the National Natural Science Foundation of China(Grant No.51874324)the Chinese Scholarship Council(CSC)for the financial support。
文摘Strain capacity is an important performance indicator for designing and evaluating high-grade steel pipelines.Due to the inhomogeneity of material properties in welded structures,girth welds are one of the main factors that restrict the strain capacity of pipelines.In this paper,girth-welded pipes with cracks in the inner surface of the weld have been studied,and the ductile crack initiation and propagation behavior have been simulated using the Gurson model.The corresponding nominal strain at the onset of crack initiation was defined as the characteristic value of strain capacity.The influencing factors on the strain concentration area,strain concentration factor,and strain capacity of girth-welded pipes were quantitatively analyzed.A semiempirical calculation formula for the strain capacity of typical girthwelded X80 grade pipes has been proposed as a function of the crack size,mismatch coefficient of the weld,and softening degree of the heat affected zone(HAZ).This study can facilitate the defect assessment of girth-welded pipes.
基金Item Sponsored by National Natural Science Foundation of China(51171162)Natural Science Foundation of Hebei Province of China(E2011203169)The R&D Project of CITIC-CBMM(2011-D056-3)
文摘The mechanical properties of heat affected zone （HAZ） of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal simulator. The results showed that the high-Nb steels have excellent weldability. Ernbrittlement regions appear in coarse grain heat affected zone （CGHAZ） and intercritically heat affected zone （ICHAZ） ~ Softening region appears in fine-grain heat affected zone （FGHAZ）, and the strength here was even lower than 555 MPa as required in the standard. Meanwhile, with the increase of heat input, the strength and the toughness of HAZ of steel with high Nb, C and lower alloy decrease notably. Therefore, take into account the welding procedure during manufacture of weld pipe, suitable amount of alloy elements, such as Cr, Ni, Cu, Mo and so on, is necessary for high Nb X80 heavy- thick steel plate.
