1. Macro to micro stratigraphic and artefactual evidence from an Early Iron Age smithy at the Pungrt hillfort (Central Slovenia)Luka Gruškovnjak, Agni Prijatelj, Petra Vojaković, Jaka Burja, Barbara Šetina, Rok Brajkovič, Borut Toškan, Tjaša Tolar, Helena Grčman, Matija Črešnar, 2025, drugi znanstveni članki Ključne besede: Early Iron Age, geoarchaeology, micromorphology, microrefuse, archaeometallurgy, smithy, floor construction, floor maintenance, lime plaster, hammerscale
Objavljeno v DiRROS: 13.05.2025; Ogledov: 67; Prenosov: 18
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2. From macro to micro approaches in settlement archaeology : a case study of an Early Iron Age smithy at the Pungrt hillfort (Central Slovenia)Luka Gruškovnjak, Agni Prijatelj, Petra Vojaković, Jaka Burja, Barbara Šetina, Rok Brajkovič, Borut Toškan, Tjaša Tolar, Helena Grčman, Matija Črešnar, 2025, izvirni znanstveni članek Ključne besede: Early Iron Age, geoarchaeology, micromorphology, microrefuse, archaeometallurgy, smithy, floor construction, floor maintenance, lime plaster, hammerscale
Objavljeno v DiRROS: 13.05.2025; Ogledov: 76; Prenosov: 33
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4. Corrosion of household mixer headsJaka Burja, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: Household appliances often utilize polymer-metal bonding, typically achieved through adhesive bonding or press-fitting techniques. Corrosion resistance is a major factor in household appliances, as corrosion can compromise the functionality and aesthetics of household appliances. Stainless steels are a natural choice. However, the nature of polymer-stainless steel bonds can cause susceptibility to crevice corrosion. Crevice corrosion, a localized attack on stainless steel in confined spaces. This study investigates crevice corrosion in mixer heads fabricated with two different grades of stainless steel (1.4016 and 1.4021). Metallographic analysis revealed a ferritic microstructure with higher chromium content for 1.4016, contributing to its superior corrosion resistance compared to the martensitic structure of 1.4021. Both materials exhibited a critical crevice width of 9-10 μm between the plastic head and the steel shaft, facilitating the entrapment of corrosive solutions (confirmed by EDS analysis) and subsequent crevice corrosion. The PREN (pitting resistance equivalent number) calculation further supported the observed behavior, with 1.4016 boasting a higher value (16-18) compared to 1.4021 (12-14). While PREN offers a valuable indicator, it highlights the importance of design considerations to minimize crevice formation. Here, eliminating the gap between plastic and steel through improved design or sealants emerges as a crucial preventive strategy. This study emphasizes the interplay between material selection and design in mitigating crevice corrosion in household appliances. By understanding the factors influencing corrosion susceptibility, manufacturers can optimize material choices and implement design solutions to ensure the longevity and performance of their products.
Ključne besede: crevice corrosion, stainless steel, mixer heads
Objavljeno v DiRROS: 16.01.2025; Ogledov: 257; Prenosov: 146
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5. Optimization of partial stainless steel melt oxidation in the EAFAnže Bajželj, Jaka Burja, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: Stainless steel production typically follows the duplex process, beginning with the electric arc furnace (EAF) and proceeding to the vacuum oxygen decarburizer (VOD) or argon oxygen decarburizer (AOD). The EAF's role is to melt the charge and heat it up for further processing, reducing tap-to-tap times through partial oxidation. However, this partial oxidation in the EAF leads to chromium losses as oxygen interacts with the high chromium steel melt. To address this issue, parameters affecting chromium burn-off have been identified and presented. A primary challenge in EAF steel production with elevated chromium content is to lower carbon levels while maximizing chromium yield in the melt. Unlike VOD and AOD processes, which permit low carbon and high chromium levels through vacuum or argon blowing, the EAF provides limited protection, mainly through silicon. At higher temperatures, carbon oxidation predominates, hence it is important to limit oxygen input into the system in the initial stages, while “protecting” the chromium with silicon. During the oxidation phase of the steel melt, carbon content decreases; however, attention must be paid to ensure that the concentration is not too low, as this increases chromium activity in the melt, leading to more intense oxidation. A practical model, derived from thermodynamic calculations, has been developed to guide carbon, chromium, and other element oxidation during scrap melting. This model, validated through industrial trials, aids in optimizing steel melt oxidation to minimize chromium losses effectively.
Ključne besede: EAF, stainless steel scrap, carbon oxidation, chromium oxidation, thermodynamics
Objavljeno v DiRROS: 16.01.2025; Ogledov: 266; Prenosov: 118
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6. Magnetic properties of as-cast iron-cobalt alloysMario Vukotić, Alen Alić, Urban Rupnik, Damijan Miljavec, Jaka Burja, 2024, izvirni znanstveni članek Povzetek: The structural and magnetic properties of iron-cobalt alloys (FeCoV) were compared to those of electrical steel alloys. The latter are widely used for the ferromagnetic cores of electric motors. However, the as-cast and rolled FeCoV alloys, which were ana lysed, showed enhanced magnetic properties compared to electrical steel alloys. Moreover, since they can be cast directly into the final shape of the rotor’s main structure (excluding the pole shoes, which must be laminated) for a wound-rotor synchronous electric motor, the production becomes more cost-effective and energy-efficient. In addition, the performance of the electric motor is improved in terms of mechanical output power and energy efficiency
Ključne besede: iron-cobalt alloys, ferromagnetic materials, electromagnetic energy conversion
Objavljeno v DiRROS: 25.11.2024; Ogledov: 313; Prenosov: 166
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7. Effect of Nb, Ta, and Ti microalloying on the secondary hardening of Mo-W tool steelJaka Burja, Aleš Nagode, Klemen Grabnar, Jože Medved, Tilen Balaško, 2024, izvirni znanstveni članek Ključne besede: hot work tool steel, microalloying, tempering, heat treatment, carbides
Objavljeno v DiRROS: 25.11.2024; Ogledov: 290; Prenosov: 806
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8. Degradation processes of two compound layers on nitrided surfaces during the wear test by ‘‘block on hot al cylinder’’Martin Lamut, Jaka Burja, Milan Terčelj, Goran Kugler, David Bombač, 2024, izvirni znanstveni članek Ključne besede: wear, nitrided steel, hot-work tool steel, thermal fatigue, aluminium extrusion, tool surface degradation
Objavljeno v DiRROS: 30.08.2024; Ogledov: 530; Prenosov: 348
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9. In vitro corrosion-fatigue behaviour of rare-earth containing magnesium WE43 in sterile complex cell culture mediumJulia Nachtsheim, Songyun Ma, Jaka Burja, Alexander Köppl, Jan-Marten Seitz, Bernd Markert, 2024, izvirni znanstveni članek Povzetek: Rare-earth containing magnesium alloys are promising biomedical materials for a new generation of biodegradable orthopaedic implant systems due to their excellent biocompatibility, mechanical and biodegradation properties. However, chemo-mechanical interactions in aggressive physiological corrosion environments result in rapid degradation and early loss of mechanical integrity, limiting its broader application for orthopaedic implants. To date, only few studies have assessed the corrosion-fatigue behaviour of medical-grade magnesium alloys in an organic physiological corrosion environment, especially under sterile test conditions. In the present work, the corrosion-fatigue behaviour of fine-grained medical-grade magnesium alloy WE43MEO was systematically analysed under in vitro conditions using an organic physiological fluid DMEM. The experimental results showed that the fatigue strength of the alloy is nearly unaffected by a 1-day precorrosion, while a 7-day precorrosion resulted in a significant deterioration of mechanical integrity. In corrosion-fatigue experiments, the fatigue life was considerably reduced by interactions between corrosion and fatigue damages. The SEM analysis revealed that the mixed mode of intergranular and transgranular fracture in the crack propagation zone transits to intergranular cracking dominant mode under the corrosion-fatigue conditions due to hydrogen embrittlement.
Ključne besede: corrosion-fatigue behaviour, stress corrosion mechanisms, biodegradable magnesium alloys, WE43, DMEM
Objavljeno v DiRROS: 02.08.2024; Ogledov: 600; Prenosov: 394
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10. Characterization of bloom iron smelting site remains in Pržanj, SloveniaJaka Burja, Barbara Šetina, Daša Pavlovič, 2024, izvirni znanstveni članek Povzetek: This paper gives an overview of findings, connected with metallurgical activity, at the Pržanj archeological site near Ljubljana, Slovenia. More than 230 kg of slag and other remains connected with early medieval (from the 5th to the 12th century AD) metallurgical activities was found at the excavation site. The remains were grouped into four categories, i.e., furnace remains, ore, slag and a ferrous product, and analyzed in detail to obtain their chemical composition, microstructural characteristics, and mineral phase composition. The furnace wall remains, identified by their morphology and chemical composition, revealed an intensive iron processing activity at the site. The iron ore at the site was identified as goethite (FeO(OH)), a surprising find in Slovenia where limonite is typically used, and its presence suggests the potential exploitation of local bog iron ore, given the site’s geological context. Abundant slag remains at the site, identified by their shape, molten microstructure, and mineral components like wuestite, fayalite, and hercynite, indicated sophisticated smelting practices, including the use of CaO-rich materials to lower the melting temperature, a technique likely preserved from antiquity. Findings of ferrous products at ancient metallurgical sites are rare due to their value, but the discovery of a corroded iron bloom conglomerate at this site, initially mistaken for furnace remains, highlights the challenges in identifying small, corroded ferrous fragments that are often misidentified as ore. The results indicate extensive metallurgical activity at the excavation site, marking it as the first documented early medieval iron smelting production site in Slovenia.
Ključne besede: bloom iron, bloomery slag, archaeometallurgy, microstructure
Objavljeno v DiRROS: 29.07.2024; Ogledov: 613; Prenosov: 382
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