Making the Case for Metal Cored Wire in Submerged Arc Welding

Productivity is important in many manufacturing and industrial welding applications, but maximizing throughput without sacrificing quality requires careful selection of the process, equipment, and consumables. Submerged arc welding (SAW) is a powerful process that can improve productivity, weld quality, and consistency for the right applications. This mechanized, wire-fed process submerges the arc beneath a layer of granular flux, which shields the weld from atmospheric contamination.

One of the most critical decisions in SAW is wire selection, which directly affects joint penetration, deposition rates, and the mechanical properties of the weld. The two primary wire types for SAW are solid wire and metal cored wire, each of which has distinct advantages and limitations. Transitioning from solid to metal cored wire can further optimize your process and improve net operational efficiencies, making it worth considering if it aligns with your application.

When to Use Solid Wire in SAW

Solid wire is a straightforward and familiar option, and it has long been the standard for SAW. One of the main advantages of solid wire is its ability to achieve significant joint penetration, making it ideal for applications where complete joint penetration is necessary. This is commonly required for square-groove welds where plates are butted together with minimal joint prep. Solid wire is also known for delivering consistent mechanical properties, reliably meeting specific requirements for various welding projects.

However, solid wire has limitations. At a given amperage, it cannot match the higher deposition rates that metal cored wire can achieve, which may impact productivity. Its deep joint penetration profile also makes it more sensitive to openings at the joint, increasing the risk of melt-through on thinner materials or poorly fitted joints. This can ultimately result in defects and rework.

Increase Productivity and Efficiency with Metal Cored Wire

Metal cored wire was designed specifically to achieve higher deposition rates. This tubular wire is filled with metallic powders, alloys, and arc stabilizers, each of which offers distinct benefits, such as helping to manage less-than-ideal base metal conditions and providing higher impact strength.

Metal cored wire is becoming increasingly popular in SAW due to its ability to boost productivity and adapt to a broader range of applications. One of its primary advantages is the significantly higher deposition rates it offers, allowing welders to lay down more weld metal per hour, even when using standard direct current welding machines, eliminating the need for costly alternating current-capable equipment. The broader joint penetration profile and enhanced sidewall fusion of metal cored wire make it especially effective for fillet welds, wide grooves, and situations where joint fitup is less than perfect, as metal cored wire can bridge gaps more effectively than solid wire.

Additionally, because metal cored wire is less intense with its joint penetration, it reduces the risk of melt-through, particularly on thinner materials. In this case, the minimized risk of melt-through means there are situations where using a metal cored wire could eliminate the need for gas metal arc welding a root pass. Or passes could be performed on less-than-optimal conditions while still using high-current welding parameters.

Despite these advantages, metal cored wire is not ideal for applications that require deep, narrow joint penetration; solid wire remains the better choice in those cases. Operators are limited to flat and horizontal positions because of the highly fluid weld pool and the flux that covers the arc, which makes welding out of position difficult.

Choosing between Solid and Metal Cored Wire

The SAW process can provide significant advantages for productivity and quality, and it can be optimized further with the right wire selection. This is a quick look at the important factors to consider when choosing between solid and metal cored wire.

• Mechanical Properties: Ensuring the wire meets the required mechanical specifications for your base material and intended application is paramount. If opting for a metal cored wire for most general-purpose SAW applications, the SubCOR™ EM13K-S MOD wire is a choice. It offers good  mechanical properties, is well suited for multipass work, and is a reliable choice for a broad range of industries.

  While wire selection is crucial, flux also plays a significant role in determining weld properties. Choosing the right flux can further optimize mechanical properties and weld quality. For general fabrication, medium-neutrality fluxes are recommended. High-basicity fluxes are best for critical, low-impact applications, and active fluxes suit high-speed fillet welding. The key is to match flux selection to the desired weld properties and application needs.

• Joint Geometry: Solid wire excels when the joint fitup is tight, material is clean, and deep joint penetration is required. Metal cored wire is better for fillets, wide grooves, the presence of scale, and applications where gap-bridging is needed.
• Material Thickness: Metal cored wire is less likely to cause melt-through on thinner materials due to its broader arc that distributes heat over a wider area. If the joint geometry allows for it, metal cored wire is a good choice for thick materials as well. Otherwise, solid wire is a standard option because the heat input and joint penetration profile meet the standard needs of the base metals typically used for pressure vessels, structural steel and construction, and shipbuilding.
• Workflow: Transitioning to metal cored wire is typically seamless, needing only minor adjustments to travel speed and wire-feed settings to maintain a given weld size. The increased deposition rates allow for faster travel speeds or decrease the number of passes to fill a joint, improving productivity.

Boosting Output and Reliability for Modern Operations

When productivity and weld quality are priorities, SAW combined with metal cored wire offers significant gains in efficiency and weld integrity over welding with a traditional solid wire. This combination boosts throughput and reduces rework, making it a smart choice for demanding production environments.
 

T. J. SNEERINGER (TJ.Sneeringer@hobartbrothers.com) is a welding applications engineer at Hobart Brothers, Troy, Ohio.