Submerged arc welding - the most practical pipe welding technology!

The submerged arc welding process is ideal for important applications in pipeline, pressure vessel and tank, rail fabrication and major construction, with the simplest single wire forms, double wire construction, tandem double wire construction and multi wire construction.

The submerged arc welding process can benefit users in many welding applications, from increasing productivity to improving the work environment to ensuring consistent quality, and more. Metal fabricators who are considering a change in their submerged arc welding process should be thinking of the many benefits they can get from this process.

Basic knowledge of submerged arc welding

The submerged arc welding process is suited to the requirements of heavy industrial applications such as pipelines, pressure vessels and tanks, locomotive fabrication, and heavy construction/excavation. Ideal for industries requiring high productivity, especially those involving the welding of very thick materials, there are very many benefits to be gained from the submerged arc welding process. Its high deposition rate and travel speed can have a significant impact on worker productivity, efficiency and production costs, which is one of the key benefits of the submerged arc welding process. Other benefits include welds with excellent chemistry and mechanical properties, minimal arc visibility and low welding fume, improved comfort in the work environment, and good weld shape and toe line.

Submerged arc welding is a wire feeding mechanism that uses a granular flux to separate the arc from the air. As the name implies, the arc is buried in the flux, meaning that when the parameters are set, the arc is invisible along with the subsequent layer of flux flow. The wire is fed continuously by a torch that moves along the weld seam. The arc heats up and melts a section of wire, some of the flux and the base material to form a molten pool, which condenses to form a weld covered with a layer of slag. The weld material can be welded in the thickness range of 1/16"-3/4" and can be welded with 100% penetration by a single pass, or in multiple passes if the wall thickness is not limited and the weld is properly pre-treated to select the proper wire-flux combination.

Selection of flux and welding wire

Selecting the right flux and wire for a particular submerged arc welding process is critical to achieving optimal results using that process. While the submerged arc welding process alone is efficient, productivity and efficiency can even be improved based on the wire and flux used. Flux not only protects the weld pool, but also contributes to the mechanical properties and productivity of the weld. The formulation of the flux is a huge influence on these factors, affecting the current-carrying capacity and slag release. Current-carrying capacity means that the highest possible deposition efficiency and high quality weld profile can be obtained. The slag release of a particular flux affects the choice of flux, as some fluxes are better suited for some weld designs than others.

Flux selection options for submerged arc welding include active and neutral types of welds. A basic difference is that reactive fluxes change the chemistry of the weld, while neutral fluxes do not. Active fluxes are characterized by the inclusion of silicon and manganese. These elements help maintain the tensile strength of the weld at higher heat input, help keep the weld smooth at higher travel speeds and provide good slag release. Overall, reactive fluxes can help reduce the risk of poor weld quality, as well as expensive post-weld cleaning and rework. Keep in mind, however, that reactive fluxes are usually best suited for single-pass or two-pass welds. Neutral fluxes are better for large multi-pass welds because they help avoid the formation of brittle, crack-sensitive welds. There are many different wire options for submerged arc welding, each with advantages and disadvantages. Some wires are formulated to weld at higher heat inputs, while others are specifically designed to have fluxes to help clean the alloy for welding. Note that the interaction of wire chemistry and heat input affects the mechanical properties of the weld. Productivity can also be greatly improved by filler metal selection. For example, using metal cored wire with a submerged arc welding process can increase deposition efficiency by 15 to 30 percent while also providing a wider, shallower penetration profile compared to using solid wire. Due to its high travel speed, metal cored wire can also reduce heat input to minimize the risk of weld distortion and burn-through. When in doubt, consult the filler metal manufacturer to determine which wire and flux combinations are best suited for a particular application.