African Fusion

African Fusion talks to SAIW Technical Services manager, Riaan Loots, about some new services now available from The Institute and the need for the welding industry to be open to modern technology.

Lincoln TrueEnergy Riaan Loots Lincoln Electric“The role of Technical Services at SAIW has not really changed,” begins Loots. “Supported by our Materials testing laboratory, which is accredited by SANAS to ISO 17025, we still offer consultancy services in five key areas, investigating and preventing failure; establishing new and better welding and cutting procedures; quality assurance and quality systems requirements – ISO 3834, EN 15085 and ISO 14731, for example; materials support and testing; and collaborative research and development programmes.

“Our consultants are constantly busy helping companies with welding procedure specifications and welder performance qualifications and advising on all welding related issues that arise: this supported by our laboratory services that do the mechanical and materials testing required for approvals and investigations,” he continues.

According to Loots, new technologies and changes in the way modern welding equipment is able to control and monitor the welding arc, however, are changing the welding industry, while bringing new challenges and opportunities.

“Modern welding machines are now mostly inverter driven and offer sophisticated waveform control: pulsed current; pulse-on-pulse; ac/dc wave balance, cold-metal and surface tension transfer, and more. What people should be looking for is how these machines can be effectively used to improve productivity and weld quality. We can help users of these machines to make the transition – and there are important differences that need to be borne in mind: how to calculate the arc energy/heat input, for example,” he tells African Fusion.

There is a standard dealing with this – ISO/TR 18491: 2015; Welding and allied processes; Guidelines for measuring welding energies – which gives additional formulas for calculating the arc energy/heat input for different types of power sources.

“Power sources featuring fast changing or pulsing current and voltage waveform control are effectively delivering the arc energy in pulses too. So the resulting effective arc energy can no longer be accurately calculated using traditional volts×amps/travel speed formulas,” he suggests.

ISO/TR 18491 describes three different formulas available to help welding engineers and supervisors to get the arc energy calculation right for conventional and waveform-control machines: one for non-waveform controlled machines; a second for non-waveform controlled machines but using instantaneous energy or power; and a third formula for calculating the instantaneous energy or power for waveform-control machines,” Loots explains.

Heat input/arc energy is a critical weld variables stipulated in ISO 15614, the standard for welding procedure specifications (WPSs). It is also increasingly important when using modern high-strength steels, particularly those used in the power and petrochemical industries. With these steels, the weld thermal cycle can alter the condition of the base metal being welded, that is, the microstructure is affected, which directly affects the mechanical properties.

“So if there is a calculation difference for determining arc energy based on the power source being used for welding, then the welding industry needs to become more aware of it. We at Technical Services can help people to better employ this new equipment to give them a competitive edge, particularly when competing with global players,” Loots assures.

“In the laboratory, when we are asked to develop a welding procedure specification, we now need to know which welding technology and, sometimes, which machine will be used to fabricate the product. And this relates also to the increase in complexity of the new materials available for use,” he continues.

“For common structural steels such as S355, the materials are well known and fabrication shops know exactly how to weld them using their existing fleet of machines. But when it comes to the P91/92 type steels used for power stations, much more care has to be adopted to prevent the properties of the steel from being impaired during welding. And this is increasingly true as lightweighting in design becomes more prevalent, which relies on stronger and thinner material sections with more complicated microstructures.

“Duplex stainless steel is another example where arc energy is important, and for joining dissimilar materials. In all these cases, the real heat input values and the associated thermal cycle will play an important role in the quality of the final product,” Loots notes.

The material specifiers may give guidance on how to weld these new materials, and the welding equipment OEMs may offer guidance on how to use their machines and to calculate arc energy. “But to get the best out of both the material and the machine, developing a WPS that properly matches the material and the welding equipment to the quality specifications of the product has got to be the way to go,” Loots advises.

In addition, Loots cites the increasing use of automation technology as influencing change in the welding industry.

In the automotive industry, for example, the trend is to use thinner and thinner plate to keep vehicles as light as possible. So new ‘colder’ welding processes have to be applied to reduce arc energy and minimise distortion.

For higher welding speeds, better quality and tighter heat input control, robot cells are typically used and carmakers will try to use the welding equipment’s waveform control capability to full effect to meet the requirements in the fastest possible time.

“Operators can take advantage of the consistency of the new digital automation technologies to prevent burn through, eliminate distortion and reduce reject rates drastically. But to do so, they also need to develop properly researched welding procedures, which are equipment-specific.

In the past, SAIW has been very focused on arc welding, “but we are now starting to look at different technologies, such as brazing and additive manufacturing (3D printing), which will be increasingly important in the factories of the future.

“Metal additive manufacturing or 3D printing was a big new focus of the IIW Annual Assembly in Bali last month. Industry 4.0 is coming fast and we at SAIW will be moving in that direction, too. By engaging and learning from our international IIW colleagues, we aim to start bringing best-practice modern approaches to shop floors in South Africa,” he says.

Modern welding equipment from OEMs such ESAB, Lincoln Electric and Fronius all now comes with data monitoring capabilities built in. This enables advanced data tracking capabilities, allowing many of the critical parameters specified in welding procedure specifications to be tracked and deviations recorded and time stamped, for example.

The machine OEMs are also currently working on making this data live and connected to the Internet. “So the instantaneous heat input, for example, will soon be able to be tracked while welding proceeds, and alerts sent to the welder and the welding supervisor while the welder is still busy welding,” Loots predicts.
In ten years’ time, these features might be standard on all welding equipment and the data collected may well be shared with the welding inspectors to alert them to likely defect locations.

All of this technology is fast becoming available and, if properly used, it is sure to reduce weld repair rates, improve weld quality and reduce costs.

It could also significantly improve welder skills, because welders can be held accountable for every metre of welding they do through weld maps and traceability.
“All of this is already part of the ISO 3834 quality requirements for fusion welding. Potentially, following research into the practical applications of Industry 4.0 and the Industrial Internet of Things (IIoT), it is not inconceivable that welding data mining may also become incorporated into our welding quality system standards,” Loots argues.

ISO 3834 remains the cornerstone of quality in welding and Loots sees more and more people wanting to get their quality and documentation right. “People are starting to understand that, these days, it is possible to control welding and weld quality if fabricators all look to work within a welding quality management system,” he says, adding that it is no longer acceptable to simply produce good welds. A quality management system such as ISO 3834 is now becoming a requirement for doing business at all levels of complexity.

“Smaller fabricators, however, often struggle to justify employing their own responsible welding coordination personnel. SAIW Technical Services is in a position to provide these services on a contract basis, which means that small component level fabrication shops can also comply with ISO 3834 certification requirements without the burden of employing high-level technical staff. We can offer IWT- or IWE-qualified personnel to take that role, checking that the welding quality management system is being implemented via regular site visits.

“Neither advanced technology nor quality management certification need be a barrier to welding success, no matter how small the fabricator,” Loots concludes.

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