Arc welding has been a major part of our work over the decades, with our experts working to innovate and advance the various processes while also having important input into codes, standards and safety.
Working across all industry sectors, our arc welding experts offer independent and impartial advice to our Industrial Members, helping them to solve their arc welding challenges, improve their existing processes, and integrate new solutions into the manufacturing and production regimes.
Our projects cover work undertaken on behalf of specific Member companies, those completed on behalf of groups of interested Member companies, and those for the wider benefit of industry. Here we present a snapshot of some of the arc welding–related projects and breakthroughs we have been involved in.
- Mechanised Flux Cored Arc Welding for Underwater Wet Welding
This 2000 project investigated the use of mechanised welding with the self-shielded flux cored arc (FCAW) process. The aim was to assess its potential application for remote operation, which would extend the operating depth from around 50m (for manual welding processes) as well as eliminating the safety risks associated with manual wet welding. The work included a review of the equipment, operating characteristics and potential applications of the FCAW system as well as commissioning a mechanised underwater wet welding system to determine its operating characteristics and assess the performance of a range of power sources and alternative consumables.
- Rotating Arc Welding of Thin Section Tubulars
Another core research project from the year 2000, our experts investigated the use of magnetically impelled arc butt (MIAB) welding for aluminium space frames, titanium tubular structures and stainless steel tubes. Although it has been patented in the 1940s and became more widely used during the 1970s, at the time of the project MIAB was underused for aluminium and stainless steel alloys. However, improvements in power source technology, control systems, magnetic coil designs, and gas shielding had opened up new avenues for investigation. To complete this work we took our existing vertical MIAB machine and modified it to improve its operational capabilities.
- Root Passes - A Feasibility Study
In 2004, we launched a feasibility study to investigate alternating current (AC) pulsed metal active gas (MAG) and powder plasma arc welding (PPAW) of positional unbacked root passes. Both processes offer the capability to adjust the arc energy independently of filler metal deposition rate. The study aimed to determine whether the degree of independent control over heat input and metal deposition rate offered by the PPAW and AC pulsed MAG processes is sufficient to make positional unbacked root welds on 7.5-15mm thick carbon-manganese steel material.
- A Low-Cost Camera for Monitoring Arc Welding Processes
Monitoring welding processes is an important part of the industry but arc welding can pose a challenge for remote monitoring as the high intensity of light emitted by the arc prevents good visibility of the metal transfer and weld pool, making automated control of the process difficult.
As high-speed video systems are too expensive for the majority of industrial users, TWI, in cooperation with the University of Liverpool, developed a vision system for monitoring arc welding processes based on a low-cost CMOS camera. The system uses a narrow bandpass filter that is tailored to the illumination source, and control of aperture and exposure settings to limit the amount of arc light reaching the camera sensor.
A 2007 project was launched to evaluate the performance of the low-cost vision system using a continuous wave (CW), high power neodymium-doped yttrium aluminium garnet (Nd:YAG) laser source for illuminating the weld pool. The system was used to observe the tungsten inert gas (TIG) and metal active gas (MAG) arc welding processes.
- A Laser Diode Based Vision System for Monitoring Arc Welding
Also aiming to solve the issue of affordable arc welding monitoring was a core research project created in 2009. Once again working alongside the University of Liverpool, our experts developed a vision system for monitoring arc welding processes based on a low cost system comprising a complimentary metal oxide semiconductor (CMOS) camera and a laser diode array. The system uses a narrow bandpass filter that is tailored to the illumination source, and control of aperture and exposure settings to limit the amount of light reaching the camera sensor. This system was evaluated using tungsten inert gas (TIG) and metal active gas (MAG) arc processes in order to identify applications for the vision system which would lead to improved process control and understanding.
- Process Interactions in Hybrid Nd:YAG Laser-MIG/MAG Welding
Although the potential benefits of hybrid laser-arc welding had been demonstrated for a range of applications in a variety of industry sectors, including automotive, shipbuilding and aerospace, a true understanding of the interaction between both processes during hybrid welding, resulting in the performance advantages over the individual processes, remained outstanding. Optimising the welding conditions required an understanding of both processes and how they function together.
To solve this, TWI initiated a study to gain a better understanding of the interactions between the Nd:YAG laser keyhole and the MIG/MAG arc that determine the stability of the process and maximise the (industrial) potential of the process over Nd:YAG and MIG/MAG welding.
- Melt Profile/Deposition Rates in Thick Section Arc Welding
Arc welding remains the predominant welding process for many fabrication industries, with a wide range of process techniques and consumables, coupled with widely available equipment, which continue to make arc welding an attractive proposition. Whilst higher welding productivity may be possible with alternative processes, for example, power beam welding, the relatively high cost and inflexibility of the equipment precludes its use for many applications. However, improved productivity continues to be a primary goal for most fabricators which has created a need to continue to develop high productivity arc welding process solutions.
High deposition process variants such as AC SAW, twin/tandem SAW, and tandem MAG welding are available. But they are not straightforward in their application as more operating variables need to be optimised compared with conventional processes. To derive the full benefits of these advanced processes, a clear understanding of the influence of each of the parameters on the weld size and penetration was required. To help achieve this, we launched a project to provide general guidance for the practical implementation of some of these advanced arc welding techniques with a view to improving productivity.
- Advancement of Arc Welding Repair of Mar-M247 and Alloy 713C
Arc welding is also widely used to repair existing components, such as cast components made from precipitation-strengthened nickel alloys for the aero-engine and power generation industries. Because these components are of high value, their scrappage can have a significant economic impact. Therefore, it is desirable to be able to perform arc weld repairs on these components, particularly in low stress regions in which post-weld heat treatment might be deemed unnecessary.
Precipitation-strengthened nickel alloys have a range of weldability with weld cracking susceptibility being often well correlated with aluminium and titanium content. Alloys containing more than six atomic percent combined aluminium and titanium are generally considered unweldable. This includes alloys which are widely used, like Mar-M247 and Alloy 713C, in which our Industrial Members expressed an interest.
Previous work on these alloys showed significant difficulty in performing weld repairs without solidification or liquation cracking, so we initiated a body of work to investigate process space not yet explored. A literature review was undertaken, ‘Shaw, 2013: TWI Technical Literature Review 22954: A Review of Weld Repairs of Mar-M247 and Similar Alloys’, which set the direction of this work.
- Technical Literature Review of Telerobotics for Arc Welding 1161/2022
By 2022, robotic welding systems had become well established. However, they were still limited in adaptability due to the existing control systems. To improve this, our experts investigated how to directly translate operator movements to a (potentially hostile) welding environment. Our technical literature review of telerobotics for arc welding demonstrated that direct control methods for welding, such as a ‘joystick’ approach were at a significantly high enough technology readiness level (TRL). However, complex vision and mechanical systems were both deemed to be at a relatively low TRL for welding, with them generally being restricted to research projects, and having significant knowhow and cost/complexity requirements associated with them.
- Automated Process Parameter Optimisation for Robotic Arc Welding and Additive Manufacturing
Multi-axis industrial robots are widely used in arc welding production, providing the benefits of increased productivity and improved quality. These systems have also been introduced for arc process-based additive manufacturing (AM) processes, which have further complicated the application and material requirements. This has led to more complex process parameters to cover weld formation, welding quality, mechanical properties and other key aspects of the joints, as well as directly influencing productivity and cost. To improve this situation, we launched a 2023 project to optimise process parameters using a state-of-the-art numerical modelling approach alongside a real time weld monitoring system linked to an industrial welding robot.
The project developed and demonstrated an approach of combining numerical modelling and weld profile monitoring for parameter development and refinement. This should provide a platform to support future industrial needs related to simplifying and automating parameter development for robotic arc welding for fast changing product designs in high value manufacturing. Furthermore, the concept can be adapted by other robotic welding and material processing processes, e.g. laser beam welding, surfacing, laser wire AM and electron beam wire AM.
To find out more about arc welding at TWI, please email contactus@twi.co.uk.