天然气管道在役修补焊接过程的数值模拟

During the in-service welding of natural gas pipeline, large depth of molten pool can result into low strength of the un-melted material at the bottom of the molten pool. The pipeline will fail if it cannot bear the inner gas pressure. To avoid this, this work used MSC∙Marc software to simulate the in-service welding of natural gas pipeline. Tungsten Inert Gas (TIG) Welding was employed. The simulation result of the temperature field showed that the peak temperature of the inner wall of the pipe was 1 131℃ under a welding current of 220 A and did not exceed the melting point of the pipe material. Under this temperature, the yield strength of the material was 19 MPa, which was higher than the gas pressure inside the pipe. Burnthrough easily appeared when the welding currents ranged from 240-260 A. The surrounding of the cover plate was a closed ring weld. The stress field was more complicated than that of the straight weld. The results showed that the residual stress distribution was asymmetrical and its peak value was 212.3 MPa under the welding current of 220 A. The maximum deformation of the cover was 1.79 mm.