Submerged arc welding is an arc welding process whereby the arc is "submerged" in a layer of granular flux, while the bare welding electrode performs the weld. The layer of flux creates a protective environment from atmospheric contamination while the weld takes place, as well as preventing sparks, and spatter, and suppressing the UV radiation and fumes associated with the arc welding process. The flux becomes conductive when molten, allowing the current from the arc of the electrode through.
Sub-arc welding is normally a mechanised or automatic process, however, it can be done semi-automatically by hand also, by means of a pressurized or gravity flux-fed delivery system. Correct input of parameters is vital to achieve desired results, as the weld pool is not visible. Current, arc voltage and travel speed all affect the quality of the bead, chemical composition and penetration depth so great care is needed to get the parameters right to avoid costly mistakes. Completed with either an AC or DC current, the submerged arc welding process is often a single wire application. However, there are ways to increase productivity by means of increased deposition rate and travel speed, and improved bead quality. These include the use of multiple wire operations (twin wire feed, tandem systems), addition of metal powder and use of tubular wire.
Due to the fluid nature of the weld pool produced, molten slag and loose flux, welding is usually carried out in the flat or horizontal position. Therefore, it is an ideal process for longitudinal butt and fillet welds, as well as circumferential welds when the weld head is fixed with something like a column and boom, and the workpiece is rotated slowly by use of a welding manipulator, like a positioner or pipe rotators. Multiple passes can be carried out using this method, meaning there is virtually no restriction on material thickness if the correct weld preparation techniques have been used.
While the process of arc welding isn't complicated in and of itself, there are aspects of the process requirements that should be addressed before going forward. One of the most important is deciding which type of wire and flux material should be used. An excellent resource for this type of information is almost always the American Welding Society which defines a wide range of classifications and codes, and very clearly lays out the specifications for different materials based on the design and fabrication requirements indicated. Because the combinations of flux and wire pairings available are practically endless, it's extremely important to understand how the wire and flux will interact with not just each other, but the material to be welded. After all, skilled welders don't just know how to weld, but also understand the complex interplay of the many materials that can be involved in welding in order to ensure the desired outcome.
Besides a thorough grasp of the materials involved in SAW, it's also important to understand how and where the finished product will be used, post-welding, and in particular, to what type of load the item will be subjected. For instance, some products will need to be able to handle multiple changes in load, while others will only be required to handle a single, static load type while in use. Other products may be used in extreme temperatures, or those that run the risk of corrosion. All of these use cases require completely different kinds of weldments, which are often the result of different wire and flux combinations. Understanding which combination is best suited for the situation at hand - and acknowledging that price cannot be the only consideration - is essential for ensuring that the end product is able to consistently meet quality and safety standards once in use.
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