P 878 - Method development for the evaluation of the effects of hardening and production-related expansion and shrinkage processes of adhesive layers

P 822 - Use of the laser beam-MSG hybrid welding process on longitudinally welded large-diameter pipes of grade API-X80/ -X100 to increase toughness and efficiency A significant proportion of modern oil and gas pipelines are made from longitudinally welded large-diameter pipes in API steel grades X65 (L450, 1.8726) and X70 (L485, 1.8727). Constantly increasing natural gas and crude oil production rates in conjunction with minimising wall thickness or increasing operating pressure will in future require corresponding material substitutions with modern higher-strength materials, such as API-X80 (L555, 1.xxxx), X100 (L690, 1-xxxx) and X120, with sufficient strength and toughness. The submerged arc welding process is used to weld these pipes. The entire pipe length is first welded with a continuous MSG tack weld. To increase economic efficiency, this process step is to be replaced by the laser beam-MSG hybrid welding process. For the safe operation of large-diameter pipes, the required impact strength of the welded joint must be observed in addition to the strength properties. Against this background, the primary research objective of this research project was to define and systematically investigate the achievement of sufficient toughness in the temperature range of -60°C and -40°C with economic process parameters. Suitable filler materials (solid wire and flux-cored wire electrodes) were identified for the laser-MSG hybrid welding of the aforementioned high-strength pipeline materials and systematic studies were carried out on the dependence of toughness on solidification behaviour and the achievable mixing depth. Increased economic efficiency when using laser hybrid technology is seen primarily in the modified seam preparation. A constructive change in the joint shape leads to a reduction in the seam volume and thus to a considerable reduction in production costs, because in this case the amount of filler material required to fill the seam is reduced. Based on demonstrators produced, an approx. 2.7-fold reduction in the seam cross-section and thus the required quantity of filler material is demonstrated. The IGF project 16415 N of FOSTA -Forschungsvereinigung Stahlanwendung e.V., Düsseldorf, was carried out at the Federal Institute for Materials Research and Testing (BAM), Department 9.3 "Welding Manufacturing Processes", Berlin, and funded by the Federal Ministry of Economics and Technology via the AiF as part of the programme for the promotion of joint industrial research and development (IGF) on the basis of a resolution of the German Bundestag. Authors: M. Rethmeier, S. Gook, A. Gumenyuk Publication: 2013