IIW White Paper

In submerged arc welding one can reach very high deposition rates, 50 kg/h by multiple electrodes ( Figure 5.14 ), which is required for heavy welding such as wind power towers.

Figure 5.14 Submerged arc welding with two tandem-wire heads and cold wire added SCWTM (Reproduced courtesy: ESAB)

Tandem MIG/MAG welding is another process attracting a lot of interest but there are still fairly few in regular production. The automotive industry is increasingly using different forms of brazing such as MIG/MAG, Plasma and Laser brazing for zinc coated sheets to reduce the amount of pores in the weld metal and with acceptable mechanical joint properties. In accordance with modern quality management strategies (ISO 9004), non-destructive inspection (NDI) and evaluation (NDE) are always embedded as continuous tasks into the quality circle conducted during the lifetime of a product, beginning with the design phase of a component and ending with the recycling phase. NDI includes testing, detection, classification and sizing of imperfections (pores, inclusions, shrinkage cavities, cracks, etc.) in material joints and components. Clearly safety-relevant components require NDE to be regulated by technical rules, standards and/or laws throughout their production and operation lifetime. NDI and NDE contribute to the assurance of the product’s integrity by characterising tolerable findings and relevant material degradation (corrosion, fatigue, creep, thermal ageing, and synergies) limiting the lifetime. NDI/NDE techniques developed in the last decade have opened new fields of application. NDI/NDE techniques are integrated in the early phases of product design in the industrial R&D-laboratories and contribute to the quality strategy, i.e. to design the basic safety of components. During the design phase of the component the NDE procedures for testing after production and in service are also designed. Modelling of NDE is a strong tool for technical inspection justification. In the aviation industry this “ concurrent engineering ” approach absolutely is a must when “damage tolerance” principles are to be fulfilled in design. The use of NDI/NDE gives increases in “intelligent processing” in order to assess quality characteristics which can be estimated often only destructively and which are parameters for process diagnosis, monitoring, and control; for instance mechanical properties like hardness, yield or tensile strength or toughness parameters. As part of themaintenance strategy and in combinationwith fracture and fatiguemechanics, NDE contributes to lifetime prediction delivering input parameters for failure assessment by applying “fitness for service” (FFS) approaches. Software based on this state-of-the-art technology taking into account probabilistic features is under development worldwide, mainly for applications in transportation, pipeline servicing, nuclear and aviation industries. The most modern approach in quality management relies however on online monitoring technology of the full structure. Here also, the aviation industry is the front-runner in the technology race of “structural health monitoring” (SHM). The challenge is inspection reliability by developing low-cost but highly durable (40 years in aviation) sensors. Future applications are in civil engineering (bridges, off-shore structures, wind energy mills) and in monitoring of vehicles (air planes, ships, railway, and cars). NDE like other technologies too can benefit from the mainstream microelectronics and computer-science, which have revolutionised the development speed and have enabled the development of new testing technology, with the support of automation and robotics.

44

Through Optimum Use and Innovation of Welding and Joining Technologies

Improving Global Quality of Life