Submerged arc welding is a process that uses an electric arc to create a weld between a consumable welding wire and a parent material covered with a granular flux. Submerged arc welding is a process for joining metals. Submerged arc welding is widely used in the shipbuilding industry.
The SAW process was developed in the early 20th century and became popular in the 1940s. The process is used to weld different types of metals such as steel, stainless steel, aluminum, copper, brass, nickel, and other alloys.
The process has been adopted by many industries because it provides high-quality welds with less distortion than other processes such as gas metal arc welding or shielded metal arc welding. It is also more economical than other processes because it can be automated and requires less labor than manual welding methods.
The SAW process has many advantages over other welding processes such as being faster and more economical than gas metal arc welding. It also produces less fumes and slag. The disadvantage of the process is that it requires more skill from the welder than other processes.
The submerged arc welding process stands out due to its unique approach compared to other flux welding methods like MMA or FCAW. Unlike these, submerged arc welding separates its consumables into two parts: the wire and the flux, which are provided separately.
Both the wire and flux significantly influence the composition of the weld metal and subsequently affect its mechanical properties. Therefore, it is crucial for welding engineers to carefully choose the appropriate combination of wire and flux tailored to the specific application. This article explores various characteristics of both the wire and flux. The subsequent article will delve into detailed specifications.
The welding wire's composition is typically matched to the parent metal and serves a versatile role in welding various materials including carbon steels, low-alloy and high-alloy steels, stainless steels, nickel, and copper/nickel alloys. Submerged arc welding is also capable of creating corrosion-resistant or wear-resistant coatings using both wire and flat strip forms. The wire itself can be solid or metal-cored, while the strip can be rolled or sintered.
Wire diameters range widely from 1.2 mm (considered 'fine' or used in twin-wire submerged arc applications) up to 6.4 mm, supporting welding currents ranging from 150 to 1600 amps. To enhance performance, ferritic steel welding wire is often copper plated to extend its life at the contact tip, improve conductivity, and prolong shelf life. In contrast, stainless steel and nickel alloy welding wire is typically bright-drawn and remains uncoated. The wire is supplied either in reels weighing 10 to 50 kg or in larger pay-off packages weighing up to 500 kg. For cladding purposes, strip widths range from 15 to 240 mm with a standard thickness of 0.5 mm, available in various coil weights.
While welding wire primarily focuses on matching parent metal composition and mechanical properties, fluxes are more intricate in their functions. These include assisting with arc starting and stability, forming slag to protect and shape the weld bead, creating a gas shield to protect molten filler metal, reacting with the weld pool to produce clean weld metal with desired properties, removing oxygen, acting as a scavenger, and in some cases, adding alloying elements to the weld pool.
Fluxes can be categorized by their manufacturing method (melting or sintering) or by their activity level (neutral, active, or alloying). They vary widely in composition, containing components like silica, manganese oxide, calcium fluoride, and others. An effective classification method is the flux's "basicity index" (BI), calculated by dividing the sum of basic components by acidic components. This index strongly influences weld metal properties, particularly notch toughness: acid fluxes (BI 0.5-0.8) tolerate rusty surfaces and are suitable for high-speed welding, while basic fluxes (BI 1.2-2.5) produce low-oxygen, high-toughness welds ideal for critical applications.
Melting fluxes, produced via melting and solidifying slag components, are uniform and strong against moisture absorption, suitable for general structural engineering. Agglomerated fluxes, formed from ground mixes baked at lower temperatures, allow for easier addition of deoxidizers and ferroalloys but may require precautions against moisture due to their hygroscopic binders.
Fluxes are typically supplied in plastic bags or drums, with recent innovations including vacuum-packed electrodes for improved hydrogen control and ease of use. This comprehensive approach highlights how submerged arc welding, with its dual consumable system and diverse flux options, remains a versatile and effective method for various welding applications.
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