1. The joint seam (that is, the forming seam) has no wrong edges or the wrong edges are less than the specified value. Generally, the amount of wrong edges is less than 8% of the plate thickness, and the maximum is not more than 1.5mm.

        2. To ensure that the weld has an appropriate penetration depth and deposition amount, it is necessary to ensure that it does not crack or burn through after welding, and it is also necessary to control the height of the weld so that the weld height of the external weld will not be affected.

        3. The welding bead is continuous and shaped to ensure external welding afterward.

        4. The welding seam does not have defects such as welding deviation, pores, cracks, slag inclusion, burn-through and back welding, and the center deviation from the welding seam is required to be ≤1mm.

        5. No arc burns, little splash, and no influence on the bevel and surface of the pipe end.

        6. The welding seam is matched with the base metal, and the physical and chemical properties of the welding seam metal meet the requirements.