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1.
Application of semantic technology for calculation of welding time in the development of new products
Ambrož Stropnik, Tomaž Vuherer, Ivan Samardžić, Milan Zorman, 2017, original scientific article

Abstract: Determining the time of execution is very important in the early stages of each project (e.g. making offers, design phase etc.), especially in the stage of planning. This paper presents our approach to estimating the welding time for the purposes of planning the manufacturing processes. The approach is based on the knowledge of welding experts from the Nieros metal d.o.o. company and standards of welding (international and internal). An expert system was developed based on semantic web technologies for calculating the welding time in the product design phase and it is strongly integrated with the main ERP system of the Nieros metal d.o.o. company. Test results are presented at the end of this article.
Keywords: expert systems, new product development, ontology, welding of steels
Published: 23.08.2017; Views: 542; Downloads: 322
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2.
Weldability prediction of high strength steel S960QL after weld thermal cycle simulation
Marko Dunđer, Tomaž Vuherer, Ivan Samardžić, 2014, original scientific article

Abstract: This paper presents weld thermal cycle simulation of high strength steel S960QL, and describes influence of cooling time t8/5 on hardness and impact toughness of weld thermal cycle simulated specimens. Furthermore, it presents analysis of characteristic fractions done by electron scanning microscope which can contribute to determination of welding parameters for S960QL steel.
Keywords: high strength steels, S960QL steel, weldability, weld thermal cycle simulation, hardness, toughness
Published: 03.07.2017; Views: 2102; Downloads: 105
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3.
Weldability of microalloyed high strength steels TStE 420 and S960QL
Marko Dunđer, Tomaž Vuherer, Ivan Samardžić, 2014, original scientific article

Abstract: The paper presents research of weldability of microalloyed high strength steels TStE 420 and S960QL after weld thermal cycle simulation. Beside mechanical properties hardness and impact strength, the microstructures of characteristic weld thermal cycled structures for both steels are given. The results will contribure to determination of weakest points in Heat Affected Zone of both steels.
Keywords: weldabilty, high strength steels, mechanical properties, TStE 420, S960QL
Published: 03.07.2017; Views: 1584; Downloads: 91
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4.
Weld joint fracture behaviour of HSLA steels dissimilar in strength
Inoslav Rak, Arpad Treiber, 1998, original scientific article

Abstract: The effect of strength differences (mismatch) between weld metal and two base metals as well as local variations of strength within weld metal/HAZ zones on the toughness properties were discussed. The significance of local fracture toughness measurement technique was also discussed by comparing the CTOD results of [delta]5 and British Standard [delta]BS. Some differences between the two techniqes were discussed in particular for CGHAZ toughness of similar and dissimilar joints.
Keywords: welding, welded joints, fracture mechanics, HSLA steels, fracture toughness
Published: 10.07.2015; Views: 843; Downloads: 24
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5.
Nucleation and growth of a passive film on AISI 420 martensitic stainless steel under potentiostatic conditions
Regina Fuchs-Godec, Aljana Petek, Valter Doleček, 2002, original scientific article

Abstract: The kinetics of the early stage s of passive film formation on AISI stainless stell in mixtures of 0.1M ▫$H_2SO_4$▫ and 0.1M ▫$Na_2SO_4$▫, with pH-values of 2.42, 2.85 and 3.33, were studied at different anodic potentials. The potentiostatic step method was used as an electrochemical technique in which the anodic current density was measured as a function of time. For analysis of the measured data, the theory of "topochemical reaction" was applied for the charcterization of the exponent n in that part where the steepest current decay was observed. Through this theory, which includes the Erofeev equation, the number of conversion steps could be obtained, as well as the number of directions in which the nuclei grow. It was found that this theory can be successfully applied to the passivation process of AISI 420 stainles steel.
Keywords: corrosion, corrision resistance, martensitic stainless steels, passive films, potentiostatic step method, topochemical reactions
Published: 10.07.2015; Views: 983; Downloads: 64
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6.
The influence of copper on the decarburization and recrystallization of Fe-Si-Al alloys
Darja Steiner Petrovič, Monika Jenko, Valter Doleček, 2006, original scientific article

Abstract: The decarburization and recrystallization of Fe-Si-Al alloys containing copper was investigated. The decarburization annealing of non-oriented electrical steel sheets produced from Fe-Si-Al alloys depends on the chemical reactions between the gas mixture and the carbon at the steel's surface. The carbon diffusion, the temperature of decarburization annealing, the composition of the gas mixture and the chemical composition of the steel are the influencing parameters that determine the kinetics and the mechanism of decarburization. The decarburization of Fe-Si-Al alloy with the mass fraction of 0.24% and 0.43% of copper was compared with the decarburization of an Fe-Si-Al alloy with a very small amount of copper (0.01%). The decarburization annealing was performed in a H2-H2O gas mixture at 840 °C. The residual carbon content was determined by analytical chemical method. The alloys were also recrystallized in hydrogen at 980 °C. Microstructure of samples after decarburization and recrystallization annealing was investigated with optical microscopy.
Keywords: alloys, recrystallization, decraburization, non-oriented electrical sheet steels, copper, carbon
Published: 10.07.2015; Views: 675; Downloads: 60
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7.
Vloga in nastanek mikrostrukturnih sestavin M-A v zvarnih spojih maloogljičnih visokotrdnostnih konstrukcijskih jekel
Zdravko Praunseis, Masao Toyoda, Alojz Križman, Mitsuru Ohata, 2001, review article

Abstract: The existence of martensite-austenite constituents in the weld metal and heat-affected zone seriously reduces the fracture toughness of the welded joint. Therefore, we have investigated the formation of the martensite-austenite constituents when high-strength low-alloy steel is welded with a high heat input or using multi-pass welding. This paper deals with the effects of martensite-austenite constituents on the fracture toughness, the metallurgical features of the martensite-austenite constituents, and the prevention and elimination of the martensite-austenite constituents in the welded joints.
Keywords: arc welding, high-strength low-alloy steels, microstructure, martensite-austenite constituents, weld metal, heat-affected zone, cooling rate
Published: 01.06.2012; Views: 1429; Downloads: 89
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8.
The fracture behaviour of global/local mis-matched weld joints provided on HSLA steels
Inoslav Rak, Nenad Gubeljak, Zdravko Praunseis, 2001, original scientific article

Abstract: 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.
Keywords: welding, welded joints, strength mismatching, fracture toughness, CTOD, hardness, impact toughness, HSLA steels
Published: 01.06.2012; Views: 1470; Downloads: 101
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9.
Tensile test models for low-carbon microalloyed steels with high niobium contents
Marcos Pérez-Bahillo, Nenad Gubeljak, David A. Porter, Beatriz López, Jožef Predan, Antonio Martín-Meizoso, 2011, original scientific article

Abstract: In the present investigation, the effect of both: rolling parameters (2 reduction rates and 3 cooling rates) and chemical elements such as: C, Mn, Nb,Ti, Mo, Ni, Cr, Cu and B, has been studied in relation to strength properties in low-carbon microalloyed steels with high niobium contents (up to 0,12 wt. % Nb). For this purpose, an experimental set-up was designed based on an intelligent design of experiments (DoE), resulting in 26 casts (laboratory casts).Acombination of metallography, Electron Back-Scattered Diffraction (EBSD) and tensile tests have been performed to study how processing parameters and chemical composition affect the strength. The results, where the proof stress, tensile strength, uniform and fracture elongations are the response variables, have been analysed statistically by means of multiple linear regression technique, leading to response equations. From the results, it was found that the effectiveness of niobium increasing the strength is reduced as carbon content increases.
Keywords: microalloyed steels, mechanical properties, niobium
Published: 01.06.2012; Views: 1190; Downloads: 80
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10.
Some factors affecting fatigue resistance of welds
Vladimir Gliha, Zijah Burzić, Tomaž Vuherer, 2010, published scientific conference contribution

Abstract: The fatigue strength of polycrystalline metals is hardness and defect size dependent. The fatigue strength of welds depends on the size of grains and actual local mean stress, too. Local mean stress is influenced by the global R-ratio and static preloading. The welds in the as-welded condition are pre-stressed due to the existence of welding residual stresses. The sign and magnitude of residual stresses depend on the welding conditions. Changes of residual stresses, hardness and defect size are experimentally determined in the present work. Samples of studied metals are prepared by using either thermal cycle simulator or laboratory furnace and water quenching. The methods of microstructure preparation and type of load result in actual local R-ratio at the used weld toe models. Specimens are cyclic loaded in the similar way as steel at the weld toe. The bottom of the notch is either defect-free or defected by Vickers indentation. Final results show that coarser grain and higher local R-ratios lower the fatigue strength of welds.
Keywords: CrNiMo steels, weld, fatigue resistance, heat-affected zone, small weld defects
Published: 31.05.2012; Views: 1178; Downloads: 17
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