DUAL PROCESS WELDING OF STEEL PLATE

摘要

Large scale fabrication and welding industries, such as those involved in offshore construction, are continuously striving to improve productivity, while maintaining quality levels required by the applicable design codes and standards. To achieve this, new improved welding technologies are regularly being evaluated. One area of development is to combine different welding processes to produce a welded joint exhibiting properties and productivity benefits that neither process could achieve individually. One promising combination is the use of both arc and laser beam welding for products such as pipeline. The welding procedure development work described, was carried out in two stages. Stage 1 (discrete dual processing) investigated the production of a welded joint using both arc and laser welding at separate times. The welds produced for this work, demonstrate that significant increases in welding speed are achievable in comparison to using either process individually. Stage 2 (simultaneous dual processing) investigated arc and laser welding of the joint at the same time from opposing plate faces, with the laser weld pool trailing the arc weld pool so that the former was positioned in the area of highest preheat temperature. The use of arc preheat significantly reduced the hardness of the laser welds to more acceptable levels. The main disadvantage identified for both stages of work was that fit up of the laser welded part of the joint needed to be good to accommodate the autogenous laser weld. Both Stages were shown to be capable of producing full penetration welds at higher productivity than using either process individually. It has been demonstrated that for 19 mm thick plate, an overall doubling of welding speed could be achieved using dual process as opposed to submerged arc welding, which is currently widely used to weld fabricated products such as pipeline. Future work to be carried will include extensive destructive testing on the welds to assess the benefits of Stage 1 and 2, which will be reported in another paper.