High Productivity Welding Process for the Energy Market

Thick-section fabrication is an important part of the energy economy. With the aging pipeline, power, and refining infrastructure it will continue to grow in importance with every passing day. In the recent years, EWI has focused a notable portion of its internal research and development activities on development and optimization of high productivity welding processes. High productivity welding processes are defined as those with the ability to weld thick sections at a high welding travel speed or in a fewer number of passes. These welding processes include technologies such as adaptive automated welding, novel cladding approaches, as well as narrow groove, advanced submerged arc, laser/GMAW hybrid, and friction stir welding. Below is a brief highlight of some of these technologies.

Advanced Submerged Arc Welding: Inverter power sources have advanced arc welding technology beyond open arc, DC polarity by integrating an AC switch with waveform control technology. Submerged arc welding process control has thus gone from pedestrian to state-of-the-art. Machine outputs can be changed in AC polarity that enable the DC+ cycle to be controlled independently from of the DC- cycle. Multiple arc systems are now simpler to use and set up. Integration is made easier giving the operator greater control over the weld. Advances in transformer efficiency, output control, and software now enable companies to increase productivity by 30 to 50%, while maintaining or even decreasing heat input. A marriage of consumables with new equipment has enabled EWI to help its member companies to increase quality and productivity while giving them the ability to monitor production, procedures, and diagnostics.

Narrow Groove Welding: The use of narrow groove joint preparations allow significant reductions in weld metal volume, which can reduce welding time, filler metal usage, and distortion. While not all welding processes are well suited for narrow groove welding, EWI has helped countless members implement narrow groove joint designs into their production process using submerged arc, gas tungsten arc, laser hybrid, and the tandem variants of each. Historically, the base welding processes (GTAW, GMAW, FCAW, and SMAW) were used for applications that demanded out-of-position welding, leaving their high productivity alternates for flat and horizontal welding. One of the key advancements to narrow groove welding has been the ability to use a narrow groove in combination with tandem GMAW and laser hybrid welding. To date, EWI has proven success using both tandem and laser hybrid in all welding positions, including orbital welding with a prototype CRC-Evans laser hybrid pipeline welding system.

High Productivity Cladding Processes: Cladding and surfacing processes are used to deposit corrosion or wear resistant alloys onto structural materials. The productivity of conventional arc cladding techniques are often limited by the need to adhere to specific dilution and surface texture requirements. EWI has spent an appreciable effort evaluating dissimilar material welding to determine where the opportunity for development and growth in the clad market resides.

A specific focus has been made on ID cladding of pipe. In this regard, a new technology is under development for providing continuous cladding of straight pipe segments. This process (termed resistance pipe cladding) has shown the ability to provide corrosion resistant layers up to 3-mm thick with virtually zero dilution. The process provides an alternative to the roll clad and welded or mechanically clad approaches used today.

As part of this evaluation, high productivity arc welding processes, including electroslag strip cladding and submerged arc strip cladding have been identified as cladding processes with opportunity for optimization. New equipment has been added to EWI capability for these two processes by Bohler Welding Group USA, Inc.

Friction Stir Welding: Friction stir welding (FSW) is a solid-state joining process originally developed and applied on soft metals such as aluminum. The technology has advanced rapidly allowing for joining of all grades of aluminum in thicknesses up to 50-mm in a single pass. It has more recently evolved into a method capable of joining hard metals, such as steel, nickel based alloys, and titanium. Current research focuses on the development of tool materials and tool designs capable of welding long lengths of thick-section hard metals. There are two main categories in the development of tool materials; polycrystalline cubic boron nitride (PCBN) and refractory alloys. The design of the tools has progressed from a smooth cylindrical pin and shoulder to include various complex geometries that improve tool life and material processing capability. Using these advanced tool materials and new tool geometries, EWI has helped many of its clients produce repeatable, defect-free thick-section welds over long lengths with minimal tool deformation or wear.

For more information about these technologies, contact Jon Jennings at jjenning@ewi.org or call 614.688.5144.