Thick-section laser multi pass welding of austenitic stainless steel joints using defocusing technique

Miikka Karhu, Veli Kujanpää

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    Abstract

    This study introduces an experimental work carried out in multi pass laser welding with cold filler wire and laser-arc hybrid welding of thick section austenitic stainless steel. As it has been demonstrated earlier, hybrid and cold wire welding with a keyhole-mode can offer very efficient way to produce multi pass welds in narrow gap thick section joints. However, when multi-pass welding is applied to one pass per layer method without e.g. scanning or defocusing, the used groove width needs to be very narrow in order to ensure the proper melting of groove side walls and thus to avoid lack of fusion/cold-run defects. As a consequence of the narrow groove, particularly in thick section joints, the accessibility of an arc torch or a wire nozzle into the very bottom of a groove in root pass welding can be considerably restricted. In an alternative approach described in this paper, a power density of a laser beam spot was purposely dispersed by using a defocusing technique. In groove filling experiments, a power density of defocused laser beam was kept in the range, which led the welding process towards to conduction limited regime and thus enabled to achieve broader weld cross-sections. The object was to study the feasibility of defocusing as a way to fill and bridge wider groove geometries than what can be welded with focused keyhole-mode welding with filler addition. The paper covers the results of multi pass welding results of up to 60 mm thick joints with single side preparations. In order to reach final 60 mm joint thickness, it required the preliminary defocusing trials of bead-on plate samples, and tests of joint thicknesses of 10 mm and 20 mm with different groove openings.
    Original languageEnglish
    Title of host publicationCongress proceedings ICALEO
    Subtitle of host publication32nd International Congress on Applications of Lasers & Electro-Optics
    PublisherLaser Institute of America
    Pages472-481
    ISBN (Print)978-194-01680-2-9
    Publication statusPublished - 2014
    MoE publication typeA4 Article in a conference publication
    Event32nd International Congress on Applications of Lasers and Electro-Optics, ICALEO 2013 - Miami, United States
    Duration: 6 Oct 201310 Oct 2013

    Conference

    Conference32nd International Congress on Applications of Lasers and Electro-Optics, ICALEO 2013
    CountryUnited States
    CityMiami
    Period6/10/1310/10/13

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    Cite this

    Karhu, M., & Kujanpää, V. (2014). Thick-section laser multi pass welding of austenitic stainless steel joints using defocusing technique. In Congress proceedings ICALEO: 32nd International Congress on Applications of Lasers & Electro-Optics (pp. 472-481). Laser Institute of America.