Stress corrosion cracks are easily formed at the welding toe
The stress concentration of the docking joints is mainly caused by the height of the weld. The welded joints of the connector are the most stress at their welded toe.
The size of the stress concentration coefficient depends on the height of the welding seam residue, the angle θ at the welding toe, and the corner radius R. The height of the welding seams increases, and the θ angle increases, and the R value decreases, which will increase the concentration coefficient of stress.
The higher the height of the weld, the more severe the concentration of stress, and the intensity of the welding joint will be reduced. After welding, the remaining height is flattened. As long as it is not lower than the mother material, reducing stress concentration, sometimes it can increase the intensity of the welding joint.
The remaining welding seam is tall, which is not conducive to anticorrosive
If you use an epoxy resin glass cloth for anti -corrosion, the remaining welding seams are high, which will make it difficult for the welding toe. At the same time, the higher the weld, the thicker the anti -corrosion layer should be thickened. Because the thickness of the anti -corrosion layer is calculated as the vertex of the welding seams outside the standard, this increases the cost of anticorrosion.
When the spiral buried arc welding, the external welding seam of "fish ridge" is often prone to, which is even more difficult to ensure the quality of anticorrosion. Therefore, it is also important to adjust the spatial position and welding specification of the welding head to reduce or eliminate the outer welding seam of "fish ridge".
The remaining welding seam remains high, which affects the tube shape after the diameter of the water pressure
When the straight seam buried arc welded pipe is expanded in the water pressure, the steel pipe is wrapped through the left and right parts with the same size of the inner cavity and the steel pipe diameter. Therefore, the remaining height of the weld is too large, and the shear stress suffered by the welded seam during the diameter is large, and the "small straight side" phenomenon is prone to appear on both sides of the weld.
However, experience proves that when the remaining high of the external weld is controlled at about 2mm, the "small straight side" phenomenon will not occur when the water pressure diameter is expanded, and the tube shape will not be affected. This is because the remaining height of the outer weld is small, and the shear stress is also small in the welded joint. As long as this shear stress is within the elastic deformation range, after uninstalling, the tube will be restored.
Internal welding seams are high, and energy loss of the transport medium increases
If the surface of the inner surface of the buried arc welding pipe is not treated with coating, the remaining height of the internal weld is large, and the friction resistance of the conveying medium is also large, which will increase the energy consumption of the conveying pipeline.
