1. The influence of delta ferrite on the quality assessment of austenitic stainless steel welds for the production of ovensZdravko Praunseis, 2020, izvirni znanstveni članek Opis: Rust-resistant metals, such as the popular stainless steel, often contain some quantities of delta ferrite that lower the mechanical properties of welded joints. The results of the study show that the amount of ferrite influences the quality assessment of austenitic stainless steel welds for the production of ovens using the resistance seam welding process. In this article, the basic device of resistance seam welding for the production of stainless steel welds is described. The device itself will have a significant role in the operation of the line; therefore, it was very precisely constructed and designed. Ključne besede: austenitic stainless steel, delta ferrite, quality assessment, welded joints, production of ovenss Objavljeno v DKUM: 15.11.2023; Ogledov: 55; Prenosov: 2
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2. Quality assessment of single-pass corner steel welded jointsZdravko Praunseis, Bojan Stergar, Iztok Brinovar, 2021, izvirni znanstveni članek Opis: The aim of this paper is to analyse the quality assessment of single-pass corner steel welded joints. The testing revealed the most burdened welded joints, which were cut out of the workpiece and prepared for metallographic macroscopic and microscopic analysis. Thus, for all examinations of single-pass corner steel welded joints, the standard test procedures were used to determine the weldability and quality assessment of base materials and welded joints. Additionally, the effects of various welded defects of single-pass weld material on the bearing strength of corner welded joints will be analysed. Ključne besede: welded joints, microstructure, cracks, undercut, main frame Objavljeno v DKUM: 13.11.2023; Ogledov: 81; Prenosov: 2
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4. Fatigue crack initiation from microstructurally small Vickers indentationsTomaž Vuherer, Andrej Godina, Zijah Burzić, Vladimir Gliha, 2007, izvirni znanstveni članek Opis: The resistivity of coarse grain steel against crack initiation in the presence of micro defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as an artificial micro defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses. Ključne besede: welded joints, micro defect, coarse grain HAZ, crack initiation, crack growth, stress concentration, fatigue limit, Vickers, residual stresses Objavljeno v DKUM: 03.07.2017; Ogledov: 1305; Prenosov: 110
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5. Charpy toughness of vibrated microstructuresBogdan Pučko, Vladimir Gliha, 2005, izvirni znanstveni članek Opis: The aim of this study was to investigate the influence of vibration on impact toughness of weld metal. Studies were carried out on two welds, of which one had been welded with applying vibration during welding. From test plates samples were made to simulate heat affect in combination with or without vibration after solidification. In this way conditions at multi-pass welding were simulated. According to different conditions Charpy toughness on non standard specimens and fracture appearance were observed. Vibration during welding benefits impact energy of weld metal, especially if weld metal undergoes further heatb treatment. Ključne besede: welded joints, impact toughness, vibration, Charpy toughness, SAW Objavljeno v DKUM: 03.07.2017; Ogledov: 871; Prenosov: 103
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6. Factors influencing the yielding constraint by cracked welded componentsDražan Kozak, Jelena Vojvodič-Tuma, Nenad Gubeljak, Damir Semenski, 2005, izvirni znanstveni članek Opis: The effect of strength mismatch for welded joints performed with different geometries on the yielding constraint has been investigated in the context of single-edged fracture-toughness specimens subjected to bending SE(B) using the finite-element method. The crack was located in the centre of the weld. Two geometri cal parameters have been identified as being the most important: the crack-Iength ratio a/W and the sIenderness of the welded joint (W-a)/H. They were systematically varied as follows: a/W = 0.1; 0.2; 0.3; 0.4; 0.5 and W = 2H, 4H, 8H, 16H, 24H. Basic equations and plane-strain finite-element solutions for the overmatched SE(B) specimen with all configuration combinations are given. The results are in good agreement with those in literature. This paper aims to establish yield-Ioad solutions for the same weldment configurations, but with materials dissimilarity present within the weld. This situation is usually encountered during repair welding. For this purpose, a practical combination of filler materials, with the same portion of overmatched part with M = 1.19 and undermatched part with M = 0.86, has been selected. Plane-strain solutions for the heterogeneous weld with the cracklocated in the overmatched half were obtained. The influence of the yielding-constraint key parameters has al so been evaluated. Yield-Ioad results for the specimens performed with different weld widths have the greatest scattering for the a/W = 0.5. The transition from the overmatched to the undermatched solution with increasing H is evident. On the other hand, the behaviour of the specimen with a shallow crack is dictated by the overmatch region ahead of the crack tip and depends very little on the weld slenderness. An approximated 3-D area of the yield-Ioad solutions depending ona/W and (W-a)lH has been proposed. Furthermore, the stress triaxility parameter h has been calculated using 2-D and 3-D finite-element analysis, and given as a field in the spec imen to get an insight into yielding-constraint regions. It was found that the 3-D yield-Ioad solutions are very close to the plane-strain solutions. Also, the effect of a/W on the yielding constraint is more significant than the effect of Mand (W-a)/H. Ključne besede: welded structures, welded joints, fracture mechanics, cracks, SE(B) specimens, yielding load, yielding constraint parameters Objavljeno v DKUM: 06.04.2017; Ogledov: 1283; Prenosov: 113
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8. Microstructural investigation of the heat-affected zone of simulated welded joint of P91 steelTomaž Vuherer, Marko Dunđer, Ljubica Milović, Milorad Zrilić, Ivan Samardžić, 2013, izvirni znanstveni članek Opis: In the process of testing real components exposed to elevated temperature, it is not possible to neglect cracks. The most significant cracks can be induced by welding, which is applied for joining of structural components. Pressure equipment in service is also exposed to high pressure and high stresses. Materials for their manufacturing are designed to resist high stressat elevated temperature, and to meet requirements regarding creep resistance. The objective of this study is to investigate microstructure of different regions of the heat affected zone in T/P91 steels by using thermal simulation instead of welding. Ključne besede: welded joints, microstructures, P91 steel, heat-affected zone, heat treatment Objavljeno v DKUM: 10.07.2015; Ogledov: 1097; Prenosov: 163
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10. The fracture behaviour of global/local mis-matched weld joints provided on HSLA steelsInoslav Rak, Nenad Gubeljak, Zdravko Praunseis, 2001, izvirni znanstveni članek Opis: The fracture behaviour of thick section high strength steel weldments, that contain soft root passes, has been studied. Two different weld consumables with different strength mismatch (1>M>1) and fracture toughness properties in the WM have significantly increased the complexity of the mis-match effect and failure behaviour of weld joints, depending on the crack location and the thickness of the soft root layer. The aim was to explain the effect of strength heterogeneity between BM and WM and between different regions in WM (global/local mismatching). R-curves of WM and HAZ regions were also discussed. The conclusion is that the application of a welding procedure with a two-pass soft root layer, introduced for the purpose of reducing or even omitting preheating, can be recommended in mis-matched weld joints on steel grade HT80. Nevertheless, the alloying from BM, and the tempering effect of subsequent weld passes, have to be taken into account. They can cause reduction of the root region ductility and affect the local mismatch in WM and HAZ. The deterioration by providing a soft root layer can probably be reduced by a selected consumable and proper welding procedure. The final conclusion is that the application of a mismatched weld joint with a soft root layer can be recommended only if high root toughness can be provided. Ključne besede: welding, welded joints, strength mismatching, fracture toughness, CTOD, hardness, impact toughness, HSLA steels Objavljeno v DKUM: 01.06.2012; Ogledov: 1848; Prenosov: 133
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