Abstract
Glycerol was chosen to simulate the petroleum environment and the welding process and joint’s properties were investigated with a research method referred to underwater wet welding (UWW) in order to study the technology of oil pipeline emergency repair on the inner surface. The droplet transfer process, the molten pool fluctuation behavior and the mechanical properties of the welded joint were studied compared with UWW. Because of the higher viscosity, the bubbles’ volume was larger and rose more slowly in glycerol than that in water. Meanwhile, the droplet transfer process in glycerol was more stable and the welded joints were smoother and more glabrous than those underwater ones. The heat dissipation was slowed down by a low heat dissipation rate of glycerol and the direction was fixed by small scale convection, resulting in a constantly vertical growth of crystal grains in welding seam. Besides, the two welded joints had nearly the same microhardness value except that in the β area, where the fine grains improved the hardness of the welded joint in water. A higher tensile strength (580 MPa) and lower impact toughness (116 J/cm2) welded joint were obtained in glycerol due to the effect of the giant columnar crystal region.
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