Get ready for more SAW output

Good preparation, process control, and equipment choice can increase submerged arc welding productivity

Photo of controllers for two-wire SAW process from ESAB.

PEK process controllers are set up to control a two-wire SAW process that can increase deposition rates and fill large joints faster than a single-wire process.

Like any welding process, maximizing submerged arc welding (SAW) productivity requires examining all the components involved in a system. For those who don’t know what they don’t know, the best first step is to work with a third-party expert, such as an equipment manufacturer. Fortunately, an upgrade in quality and productivity may be as simple as optimizing weld preparation.

To get the best from a SAW process, the goal is to avoid manual root runs and to be able to start welding directly with the robotic system. Since the SAW process requires a zero gap to avoid burn-through, the accuracy of the bevel, including the root face, straightness, and angle, is extremely important.

Cutting and milling are the typical bevel preparation methods. Regardless of the cutting process, achieving the optimal joint geometry for the chosen welding process is important. This includes setting and controlling face or bevel angles and root openings, as well as minimizing gaps and part mismatches. For thermally cut parts, achieving a good joint geometry also involves managing kerf angles and surface roughness and removing oxide or recast deposits.

Selecting an appropriate joint geometry for the chosen welding process can minimize joint volume, achieve desired penetration and fusion, and reduce the overall welding process time.

Additionally, most high-performance welding processes require very good control of joint conditions. Whether we are talking about high-deposition or high-welding-speed processes, they all need consistent part presentation to achieve robust welding performance.

Consistency Matters

The automation of welding processes also forces fabricators to achieve very consistent part and joint presentations. Depending on the component, material grade, thickness, and welding equipment, various types of bevels can be used. Typically for SAW, when welding thicknesses less than 3 inches, the Y and X bevels are used in full or half versions. In thicker plates, various types of machined U-shaped bevels typically are used to reduce the volume to be filled. The more accurate the bevel, the higher the level of automation that can be used to achieve better productivity.

Good choices in part edge preparation and high precision and control of part geometries enable the use of welding automation and help optimize the performance of high-productivity welding processes. Incorrect bevel design or poor preparation can cause weld defects; require manual welding; or cause post-weld corrections, such as grinding or gouging, which will lead to an overall reduction in productivity.

Joints also can be redesigned to reduce bevel complexity and to improve the ability of CNC cutting machines to perform the bevelling rather than forcing the use of mechanical bevelling after cutting.

Find the Right Combination

The level of productivity depends on the application, base material, thickness, and joint preparation. In some welding processes, like in thick plate butt welding, the deposition rate of the welding process drives the overall welding productivity. In these cases, more wire mass per unit of time means more work will get done, which leads to higher productivity.

Choosing the right wire size, wire chemistry, and multiple-wire setup options can dramatically increase productivity in these types of jobs. It is not uncommon to increase productivity by three to four times just by adjusting the wire size and shifting to a twin or tandem process. Often, the limiting factor in these applications becomes the heat input needed to achieve suitable mechanical properties in the weld.

Closeup photo of flux in SAW process from ESAB.

Choosing the correct flux for a SAW process can improve productivity.

Reduce the Heat

Heat input is a byproduct of increasing amperage in welding. It used to be that the only way to increase productivity was to increase amperage and consequently increase heat. ESAB has spent the last decade focused on breaking the connection between productivity and heat input. Reducing the heat starts with improving part cutting accuracy and joint geometry to reduce the size of the gap and the amount of weld metal needed to produce a secure weld. The cheapest pound of welding wire is the pound that didn’t need to be used.

Employing a three-wire process, such as ESAB’s ICE™ (Integrated Cold Electrode) process, can double the productivity of twin or tandem processes without increasing heat input. The process follows the same principles as twin-wire SAW, except a third, electrically insulated wire is located in-between and parallel to the two hot wires in the same contact device. The excess heat generated by the welding process melts an additional non-powered welding electrode—the Integrated Cold Electrode.

Choosing the correct flux also can improve SAW productivity. For example, fluxes with good slag detachability and smooth side-wall blending are especially suited for narrow-gap welding. The narrow running slag allows higher currents in narrow-gap joints, which results in a higher deposition rate and consequently higher productivity.

Special Delivery

Common SAW applications are offshore construction such as drilling rigs and platforms, pressure vessels, wind towers, ships, and barges. Because these applications often require unique access to confined or unusually shaped areas, manufacturers of column and boom (CaB) systems and SAW tractors have become adept at customizing the equipment.

For example, ESAB engineers have designed a CaB system equipped with a compact head for SAW to reach inside pipe with diameters smaller than 20 ins. A tractor mount for an Arcair-Matic® N7500 automatic air-carbon arc gouging head was designed to enable automatic backgouging when a fabricator’s welding procedures call for the process. Other customized systems have been developed to track long seams and increase deposition by using a twin-wire process.

From joint preparation, process selection, filler metal, and flux and customized tractors, the options to improve SAW productivity can be overwhelming. The number of choices available illustrates the importance of working with a supplier that can provide a complete, integrated system. In an era when companies must demonstrate continuous improvement, working with a knowledgeable outside resource is often the easiest, fastest way to increase productivity.

Peter Kjällström is director product management for SAW and FSW at ESAB Welding & Cutting Products, 800-372-2123, www.esabna.com.