The first one is flux-cored wires. When welding out of position on thick-walled welded steel pipe, it is better to choose gas-shielded flux-cored wire to achieve high deposition rates. This kind of filler metal can weld out of position without a special power, and the flux coating on the wire can be considered as a dam which can hold the molten weld pool in place. Therefore, the flux –cored wires are useful for improving productivity. However, there are some disadvantages when using the flux-cored wires in the welded steel pipe. Higher levels of smoke may be produced and a slag may be generated by the wires. Then both between passes and after the cap pass, the welding operators will need to chip or grind in, which in turn leads to greater downtime for cleanup.
The other kind is metal-cored wires. When welding welded steel pipe, the metal-cored wires are accepted more and more widely. The available diameters of the metal-cored wires range from 0.035- to 1/16-inch. In order to weld out of position, the pulsing or advanced short-circuit processes, with which the metal-metal wires can be applied to weld from root to the cap, are needed by stainless steel metal-cored wire. What is more, the welded steel pipe with these kinds of wires can provide greater productivity. One disadvantage to metal-cored wires is their cost. Though the metal-cored wires are more expensive, the productivity and quality improvements outweigh the cost.
The third one is solid wire. When welding thicker-walled welded steel pipe, we usually choose solid wires which must use a special power source to weld out of position. If the welded steel pipe is being rotated, these filler metals can be used to weld fill and cap passes in the flat or horizontal position. In addition, solid wires are useful for welding out of position for root, fill and cap passes. However, for welded steel pipe, it is more difficult to match the chemistry. Then the availability of the filler metals may be influenced.
The last one is SMAW electrodes. SMAW (shielded metal arc welding) electrodes are of great importance for welded steel pipe because of the availability and familiarity of the filler metal. However, compared with other filler metals, the SMAW electrodes are slower and less efficient.