Key points for flux-cored wire welding operations and post-weld inspection

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The welding procedure for flux-cored wires is similar to that of solid wire, but there are some differences. Special attention must be paid during actual operation; otherwise, it will affect the welding quality and lead to defects such as slag inclusions. (1) Arc length requirement: The ideal arc length is as short as possible ； (2) Formation of fusion holes: When using stainless steel cored wire TIG welding, to achieve good formation of the weld bead on the back side of the root, it is essential to have fusion holes during the root pass; this allows sufficient slag to penetrate into the back side of the weld bead, thereby providing complete protection for its surface. If no fusion holes are formed, the molten slag cannot penetrate into the back weld bead to provide protection, which will lead to oxidation of the back weld bead and an unsatisfactory appearance of the weld. On the contrary, if the melting hole is too large, the back bead becomes too wide, the weld metal is too thick, and the high weld temperature makes the bead prone to oxidation, this reduces the welding quality as well as the welding efficiency. Therefore, to obtain a good back weld bead, the size of the fusion hole must be accurately controlled. (3) Key points for wire feeding: When feeding stainless steel cored wire, it is important to do so in small amounts and at a fast pace, with short intervals between movements of the wire tip. During rapid feeding, special attention must be paid to ensuring that the stainless steel cored wire melts fully; generally, the weld pool should remain clear. The tungsten electrode should be moved back and forth to stir the weld pool thoroughly, so that the flux melts completely and rises to the surface, thereby ensuring good weld fusion. Otherwise, slag residues may remain, leading to defects. Experience shows that the presence of slag inclusions within the weld bead can be determined by examining the shape of the inner weld bead; if weld spurs are found on the back side of the weld bead, it is generally indicative of slag inclusions within the weld, and these defects can be removed immediately by grinding. (4) Key points for joint welding: When resuming welding after stopping the arc, it is best to start the arc about 10 mm backward in order to make a lap joint ； If the weld bead temperature remains high, there is no need to remove the slag from the previous weld bead before starting welding. If the temperature of the previous weld bead has already cooled, the slag in the groove must be removed, whereas the slag on the back side of the weld bead cannot be removed, as it helps to prevent oxidation when arcing occurs again on that back side. 1. FCAW – SS cored wire arc welding–self-shielding welding: Advantages: Can be used for outdoor operations, reduces the number of re-ignitions to a minimum, eliminates the need for shielding gas, offers high deposition rates, good mechanical properties, effective smoke suppression, and enables full-position welding on lower-quality steels. Limitations: There is smoke, splashes, and slag; the wire end must be cut before restarting arcing. 2. FCAW-GS flux-cored wire arc welding – gas shielding. Advantages: good weld appearance, little to no spatter, high deposition rate, good mechanical properties, easy re-ignition, welding in all positions, and the ability to form low-hydrogen welds. Limitations: There is smoke; relevant equipment must be carried; welding must be done indoors; there is a possibility of gas scars, so shielding gas is required; there is high radiant heat, and slag is produced. Images: Post-weld inspection of cored wire welding 1. Visual inspection: Defects that can be detected through visual inspection include surface pores, slag inclusions, weld penetration, undercutting, cracks, and other similar surface defects, as well as the surface color of the welded joint. Check using a magnifying glass with a power of 10 or less. Before inspection, the area 20 mm wide on each side of the weld should be cleaned of slag, after which the inspection is carried out along both sides of the weld. 2. Radiographic testing: The radiographic inspection of welds shall comply with the provisions of current industry standards.