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Vol.24, No.1, 2024, pp. 21–27 |
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INFLUENCE OF INCREMENTAL SHEET FORMING AND PWHT ON THE STRUCTURAL INTEGRITY OF VESSEL HEADS MADE OF STEEL P355NL2+H Nedeljko Vukojević1, Zlatan Ištvanić2, Fuad Hadžikadunić1, Amna Bajtarević-Jeleč1 1) University of Zenica, Faculty of Mechanical Engineering, Fakultetska 1, 72000 Zenica, Bosnia and Herzegovina (B&H), *email: nedeljko.vukojevic@unze.ba 2) Metacomm Jajce d.o.o., Bage 5, 70101 Jajce, B&H
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Abstract Incremental sheet forming (ISF) of torispherical vessel heads causes hardening of surface layers. The strengthening of the material can cause formation of initial cracks, and in combination with welding and residual stresses can cause the appearance of brittle fracture. The focus of the research is the heat-affected zone (HAZ) in the welded joint. Post weld heat treatment can reduce but also increase negative effects, as is the subject of analysis in this paper. Experimental research was carried out on a sheet of high-quality steel grade P355NL2+H. Research included determining actual mechanical properties of the welded joint, impact energy testing, hardness testing, measurement of residual stresses, as well as fracture mechanics tests on samples taken from the welded joint zone of finally formed vessel heads. An integrity assessment procedure was carried out for the assumed values of internal pressure and for a hypothetical crack on the outer contour of the vessel head, and the results are presented graphically (failure assessment diagram). Analyses were carried out on samples taken from finished vessel heads, before and after normalisation. Keywords: welded vessel heads, incremental sheet forming (ISF), steel P355NL2+H, structural integrity, post weld heat treatment (PWHT), residual stress |
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full article (883 kB)
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