The effect of heat input on the ferrite modification in weld metal of low-carbon steels

U ovom radu je prikazano kako količina unete toplote pri zavarivanju utiče na mikrostrukturu metala šava dva toplo valjana mikrolegirana čelika, zavarena elektrolučnim postupkom u zaštiti mešavine gasova (Ar + 5% CO2 + 0,91% O2). Posebna pažnja je posvećena morfologiji acikularnog ferita, koja značajno utiče na mehaničke osobine metala šava.This paper describes the influence of welding heat input on the weld metal microstructure of two hot rolled micro alloyed steels, welded by electric arc in shielding gases mixture (Ar + 5% CO2 + 0,91% O2). Morphology of acicular ferrite, which has a great effect on the weld metal mechanical properties, is also discussed

The effect of heat input on the ferrite modification in weld metal of low-carbon steels

U ovom radu je prikazano kako količina unete toplote pri zavarivanju utiče na mikrostrukturu metala šava dva toplo valjana mikrolegirana čelika, zavarena elektrolučnim postupkom u zaštiti mešavine gasova (Ar + 5% CO2 + 0,91% O2). Posebna pažnja je posvećena morfologiji acikularnog ferita, koja značajno utiče na mehaničke osobine metala šava.This paper describes the influence of welding heat input on the weld metal microstructure of two hot rolled micro alloyed steels, welded by electric arc in shielding gases mixture (Ar + 5% CO2 + 0,91% O2). Morphology of acicular ferrite, which has a great effect on the weld metal mechanical properties, is also discussed

Estimates of weldability and selection of the optimal procedure and technology for welding of high strength steels

High strength steels belong into a group of high quality steels, with exceptional mechanical properties, especially in regards to tensile strength. At the same time, as their deficiency is emphasized the limited and difficult weldability. In other words, some of those steels are weldable only with application of special measures related to controlled heat input. In that way, the favorable mechanical properties can be kept within the heat affected zone, with condition that the optimal welding technology is selected. Existing, very scarce and often unclear and insufficient recommendations for selection of the optimal welding technology are one of the causes of large number of flaws in welded joints. Mentioned problems, as well as others, can be successfully solved by proper selection of the procedure, filler metal and technology of welding, verified by experiments conducted in laboratory or in real operating conditions. Those experiments can not be performed in arbitrary conditions. Thus, partially due to results reported in this paper, technologists will obtain the possibility to predict in advance, in a very short time period, the mechanical and metallurgical properties of joints of this class of high strength steels. This will be possible without conducting the large number of practical tests or relying on personal experience of a designer

Učinak dipping profila gestacijske hipertenzije na majčine simptome i fizikalne nalaze, porođajnu težinu i prijevremeni porođaj

The study aimed to determine if the non-dipping pattern of blood pressure (BP) influences preterm delivery in gestational hypertension (GH), but also maternal clinical findings and birth weight. Sixty women with GH, i.e. 30 women with a dipping BP profile (control group) and 30 non-dippers (study group), were included in the study. Echocardiography was performed in all subjects, as well as ambulatory blood pressure monitoring (ABPM) during third trimester. ABPM was repeated 6-8 weeks after delivery. Thirteen women with preterm delivery were classified as non-dippers and only four as dippers (p=0.01). The average and peak systolic and diastolic night-time BP had negative linear correlation with birth weight (p<0.0005). Total vascular resistance (p<0.0005) and mass index (p=0.014) were significantly higher as compared with women with term delivery, while ejection fraction (EF) (p=0.007) and circumferential systolic velocity (p=0.042) were significantly reduced in the preterm delivery group. Multivariate binary logistic regression identified the average night-time systolic BP, left ventricular mass index and EF as independent predictors of preterm delivery. Study results suggested a relationship of the non-dipping BP pattern in GH with preterm delivery, birth weight, and maternal clinical findings.Cilj ovoga istraživanja bio je utvrditi povezanost non-dipping profila krvnog tlaka (KT) s prijevremenim porođajem, porođajnom težinom novorođenčeta te kliničkim i ehokardiografskim parametrima kod žena s gestacijskom hipertenzijom (GH). Istraživanje je obuhvatilo 60 žena s GH, 30 s dipping profilom KT (kontrolna skupina) i 30 non-dippera (ispitna skupina). Sve žene podvrgnute su kompletnoj ehokardiografiji i 24-satnom ambulantnom praćenju krvnog tlaka (ambulatory blood pressure monitoring, ABPM) tijekom trećeg trimestra, a ABPM je ponovljen 6-8 tjedana nakon porođaja. Ukupno 17 žena imalo je prijevremeni porođaj. Trinaest žena s prijevremenim porođajem imalo je non-dipping profil KT, dok su samo četiri žene imale dipping profil KT (0,01). Prosječni i maksimalni sistolički i dijastolički noćni KT imali su negativnu linearnu korelaciju s porođajnom težinom (p<0,0005). Ukupna vaskularna rezistencija (p<0,0005) i indeks mase miokarda lijeve klijetke (p=0,014) bili su znatno viši u skupini žena s prijevremenim porođajem, dok su parametri sistoličke funkcije, tj. ejekcijska frakcija (EF) (p=0,007) i brzina cirkumferentnog skraćenja miokarda lijevog ventrikla (p=0,042) bili statistički značajno sniženi u skupini žena s prijevremenim porođajem. Multivarijatna regresijska analiza pokazala je da su prosječni noćni sistolički KT, indeks mase lijevog ventrikla i EF identificirani kao nezavisni prediktori prijevremenog porođaja. Rezultati istraživanja pokazali su da postoji povezanost između non-dipping profila KT s prijevremenim porođajem, porođajnom težinom novorođenčeta i poremećajem hemodinamskog statusa majke u GH

Laser treatments of Nimonic 263 nickel-based superalloy

U ovom radu, proučavan je uticaj parametara određenih procesa laserske tehnike obrade materijala superlegure Nimonic 263 - bušenje, rezanje, zavarivanje i mehanička obrada laserom. Bušenje i zavarivanje su vršeni na laseru Nd:YAG laserom model HTS Mobile LS-P160. Prilikom bušenja rupa varirani su parametri frekvencije impulsa (5 Hz, 7Hz i 9 Hz) i dužine trajanja impulsa (1,8 ms do 3,6 ms). Ispitivana je mikrostruktura i određene su geometrijske i metalurške karakteristike rupa dobijenih ovim parametrima, na osnovu čega je izvršena optimizacija parametara obrade. Rezanje je izvedeno na laseru tipa Bistronic laser, (2000), BISTAR 3015. Varirani su parametri srednje snage lasera, brzina lasera, pritisak gasa i položaj fokusa. Na osnovu dobijenih geometrijskih karakteristika rezova i površinske morfologije diskutovani su i određeni optimalni parametri. Laserom zavareni spojevi limova legure Nimonik 263 su, osim mikroskopskih i profilometrijskih ispitivanja površina, ispitivani i metodom sa razaranjem. Prilikom laserskog deformacionog ojačavanja uzorci su bili izloženi laserskom svetlu na talasnoj dužini od 1064 nm i 532 nm, sa brojem akumuliranih impulsa: 50, 100 i 200. U svim delovima eksperimenta strukturna analiza superlegure Nimonic 263 izvedena je pomoću svetlosne mikroskopije (SM), skenirajuće elektronske mikroskopije (SEM) i EDS-analize. Merenja mikrotvrdoće vršena su pomoću metode Vikersa pod opterećenjem od 9,81N. Profilometrija je izvedena na beskontaktnom profilometru Zygo NewView 7100.In this paper, the influence of parameters of laser processing (drilling, cutting, welding and laser shock peening) on microstructure of superalloy Nimonic 263 are investigated. Drilling and welding process are carried out on the Nd: YAG laser model LS-HTS Mobile P160. When drilling the holes, the parameters of pulse frequency (5 Hz, 7 Hz and 9 Hz) and the pulses duration (1.8 ms to 3.6 ms) are varied. The microstructure is investigated and geometrical and metallurgical characteristics of the holes are determined.Cutting is carried out on the laser BISTRONIC, (2000), BISTAR 3015. The parameters that were varied are as follows: the average laser power, laser velocity, the pressure of the assisting gas and the focus position. Based on the geometrical characteristics of the cuts and surface morphology the optimal parameters are discussed and defined. The laser welded joints of Nimonic 263, in addition to microscopic examination and surface profilometry, were subjected to the destructive testing. During the laser shock peening, the samples were exposed to laser light at a wavelength of 1064 nm and 532 nm, with the number of accumulated pulses 50, 100 and 200. The operating laser was Nd: YAG EKSPLO, SL212P model. Structural analysis of Nimonic 263 was carried out using light microscopy, scanning electron microscopy and EDS analysis. Microhardness measurements were carried out using the Vickers method under load of 9,81N. Profilometry was performed on a contactless profilometer Zygo Newview 7100

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)

Old values for new times: Svetislav Stefanović, once and nowadays

After the fall of communism and the collapse of Yugoslavia, the ” new” Serbian elite made a demarcation towards the former state in all aspects, including its interpretation of the past. This phenomenon is especially present in reevaluations of the fascist ideology of 1930s which is often relativized to the point of unrecognizability by adducing positive facts. A characteristic example discussed in this paper is the defense of Dr Svetislav Stefanović’s ideological principles by his contemporary biographers

Activity of selenoenzymes GPx-1 and GPx-3 in the blood of working horses in the territory of Central Serbia

Glutathione peroxidase (GPx) is an enzyme that has 8 isoenzyme forms, of which GPx-1 is an obligatory intracellular enzyme, while GPx-3 is active in extracellular fluids, especially in blood plasma. The main role of GPx is the protection of cells from oxidative stress induced by free oxygen radicals. GPx activity is taken as a reliable indicator of selenium status in the human and animal organism. Selenium is introduced in organism mainly through the food chain. Ingested selenium is incorporated in the form of selenomethionine and selenocysteine into tissue proteins, i.e. enzymes. Detailed investigation related to the content of selenium in feed and domestic animals were carried out in Serbia, especially in economically significant species such as poultry, pigs, sheep and cattle. However, working coldblooded horses, especially those that are fed exclusively with locally grown feed, or are on pasture, have not been examined in detail so far. Due to their specific way of breeding, they are ideal indicators of the selenium status of monogastric herbivores in a given locality. The goal of our study was to determine the status of selenium based on the activity of GPx-1 and GPx-3 in blood samples of non-supplemented working horses in the territory of central Serbia. In our study, a total of 12 samples of horse blood taken from the localities of the municipalities of Kraljevo, Zaječar, Valjevo and Dimitrovgrad were tested as follows: 12 samples of blood plasma and 12 samples of washed erythrocytes. Measurement of GPx-3 and GPx-1 activity was carried out using the Guncler method at a wavelength of 366 nm. For each animal, during sampling, data on gender, age, vaccination and deworming, composition and origin of the given nutrients were recorded. The average activity of GPx-1 was 502.02 ± 91.77 μKat/l, and GPx-3 3.46 ± 1.02 μKat/l, which indicates the existence of a marginal selenium deficit in the population of unsupplemented working horses in the territory of central Serbia.Related to a Serbian-language version of the following article: [https://vet-erinar.vet.bg.ac.rs/handle/123456789/3373

Acicular ferrite in weld metal of low carbon steel

Ustanovljeno je da u metalu šava mikrolegiranih čelika dominira struktura ferita, koja se javlja u različitim morfološkim oblicima. Koji ce od njih biti najzastupljeniji u mikrostrukturi metala šava zavisi od velikog broja faktora. U ovom radu je opisan acikularni ferit kao morfološki oblik ferita koji se javlja u metalu šava mikrolegiranih čelika i doprinos čvrstoći i žilavosti metala šava.It has been established that in weld metal of micro- alloyed steel the ferritic structure dominates, occurring in different morphologic forms. The most dominating form in the weld metal depends on a significant number of factors. In this paper acicular ferrite as a morphologic form is described that occurs in weld metal of microalloyed steel and contributes to weld metal strength and toughness