A request for technical support from an offshore gas pipeline customer highlighted the importance of the effect of filler wire selection on weld metal toughness. This triggered OCAS to set up a detailed project to further investigate the topic to be able to advise customers on filler wire selection.
Meanwhile, OCAS has the capability to develop tailor-made solid welding wire of optimum chemistry.
In any pipe welding project, great attention is given to guarantee in-use properties and customer specs. So, it’s also important to select the best filler wire, with the most suitable chemical composition, to prevent the seam weld from becoming the weakest link.
Defining the test set-up
OCAS conducted the double-sided submerged arc welding (SAW) experiments using a two-wire tandem set-up for both the inside and the outside weld on trial coil samples of linepipe grades with different compositions and processing parameters.
To define the test matrix and select the filler wire combinations, results from literature were reviewed, recommendations by consumable suppliers were taken into account, and in-house experience from previous OCAS welding trials was considered.
Welding is much more than joining metals
All experiments were conducted with similar welding parameters. Toughness of each weld was evaluated by means of Charpy V-notch impact and Crack Tip Opening Displacement (CTOD) testing. Results clearly demonstrated the need to select filler wire as a function of the chemical composition of the grade to achieve good CTOD toughness in SAW welding.
This detailed test set-up, and our in-house SAW welding expertise, has provided OCAS with in-depth knowledge concerning the selection of the appropriate filler wire. It’s clear that customers’ common practise of purchasing just one type of filler wire may not be the best way forward. OCAS has developed a strong asset for future technical assistance projects for manufacturers.
Tailor-made welding wire
Combining our expertise on welding wire selection with our metallurgical knowledge, OCAS recently started the development of tailor-made welding wire using chemistries wich are not yet available on the market. OCAS can design, cast, roll wire rod, cold draw and coat solid welding wire of optimum chemistry in small batches for research purposes.
“Helping the customer with recommendations on filler wire selection is a further step in the high-level technical assistance OCAS can provide in the field of welding. On top, OCAS can now even produce tailor-made solid welding wire of optimum chemistry in-house.”
Özlem Esma Ayas Güngör, Senior research engineer welding, Applications & Solutions department at OCAS