Optimal welding technology of high strength steel S690QL

In this paper is presented the detailed procedure for defining the optimal technology for welding the structures made of the high strength steel S690QL. That steel belongs into a group of steels with exceptional mechanical properties. The most prominent properties are the high tensile strength and impact toughness, at room and at elevated temperatures, as well. However, this steel has a negative characteristic - proneness to appearance of cold cracks.  That impedes welding and makes as an imperative to study different aspects of this steel's properties as well as those of eventual filler metal. Selection and defining of the optimal welding technology of this high strength steel is done for the purpose of preserving the favorable mechanical properties once the welded joint is realized; properties of the welded metal and the melting zone, as well as in the heat affected zone, which is the most critical zone of the welded joint

Eksperimentalno modeliranje i numerička FE analiza procesa izvlačenja sa stanjenjem čeličnih traka

This paper deals with analysis of steel strip ironing using experimental modelling and numerical FE simulation. Since both approaches are complementary to each other, numerous results were obtained that enable complete analysis of the processes within deformation zone. Device for modelling of strip ironing has been developed for experimental testing. Die cone angle, holding force, contact friction conditions on the die and the punch side were varied, due to easily replaceable working elements of the device. Friction coefficient values used in numerical FE simulations were determined based on measured values of forces on die and punch, as well as forming load on machine. Experimentally obtained results were confirmed by FE analysis that provided additional information about physics of the process itself within deformation zone. Presented research results point to coherent influences of process factors on tensile wall stress values, which represents key indicator for efficiency of forming, resulting in recommendations for efficient process management.Rad se bavi analizom procesa izvlačenja sa stanjenjem čelične trake, primjenom eksperimentalnog modeliranja i numeričkih FE simulacija. Kako su oba pristupa komplementarna, dobiveno je mnoštvo rezultata za sveobuhvatnu analizu procesa u deformacijskoj zoni. Za potrebe eksperimentalnog modeliranja razvijen je uređaj za modeliranje procesa izvlačenja sa stanjenjem trake. Zahvaljujući lako izmjenjivim radnim elementima uređaja, varirane su vrijednosti kuta matrice, sile držanja, uvjeti kontaktnog trenja na strani izvlakača i matrice. Vrijednosti faktora trenja, korištenih u numeričkim FE simulacijama su određene na osnovu izmjerenih vrijednosti sila na matrici i izvlakaču, kao i ukupne sile na stroju. Eksperimentalno dobiveni rezultati potvrđeni su numeričkom FE analizom, pri čemu je ona dala dodatne informacije o samoj fizici procesa u deformacijskoj zoni. Prikazani rezultati istraživanja ukazuju na spregnute utjecaje analiziranih faktora procesa na iznos rasteznog naprezanja u stijenki matrice, koji predstavlja ključni pokazatelj uspješnosti obrade, iz kojih proizlaze preporuke za uspješno upravljanje procesom

Eenergetic analysis of hard facing and weld cladding of an air powered drop hammer damaged ram

This paper studies problems of hard facing of damaged and initially cracked mechanical engineering heavy parts of complex geometry such as large rams of air powered drop hammers. During long-term exploitation, these parts are subjected to thermal fatigue due to cyclic temperature changes and variable impact compression. Taking into consideration high ram costs and difficulties to purchase ram, the necessity of its reparation becomes obvious. The choices of the most suitable technologies of hard facing and welding of an initially cracked ram are also studied here. Besides the techno-economic analysis, an energetic analysis is performed as an additional criterion in assessment of the proposed technology

Theoretical-experimental determining of cooling time (t<inf>8/5</inf>) in hard facing of steels for forging dies

This paper investigates the accuracy of analytical, empirical, and numerical expressions, i. e. the most favourable methods for calculating the cooling time from 800 to 500 °C (t8/5). The degree of accuracy of time t8/5 is very significant, because it determines the cooling rate, and consequently the structural changes in heat affected zone for hard faced layers. Based on the presented results, one can conclude that the finite element method provides the best conformity with the experiment and among analytical and empirical formulas the same goes for the expression of Japanese authors, for the case of hard facing of plane and prismatic parts

Optimal welding technology of high strength steel S690QL

In this paper is presented the detailed procedure for defining the optimal technology for welding the structures made of the high strength steel S690QL. That steel belongs into a group of steels with exceptional mechanical properties. The most prominent properties are the high tensile strength and impact toughness, at room and at elevated temperatures, as well. However, this steel has a negative characteristic - proneness to appearance of cold cracks.  That impedes welding and makes as an imperative to study different aspects of this steel's properties as well as those of eventual filler metal. Selection and defining of the optimal welding technology of this high strength steel is done for the purpose of preserving the favorable mechanical properties once the welded joint is realized; properties of the welded metal and the melting zone, as well as in the heat affected zone, which is the most critical zone of the welded joint

Energetic analysis of hard facing and weld cladding of an air powered drop hammer damaged ram

This paper studies problems of hard facing of damaged and initially cracked mechanical engineering heavy parts of complex geometry such as large rams of air powered drop hammers. During long-term exploitation, these parts are subjected to thermal fatigue due to cyclic temperature changes and variable impact compression. Taking into consideration high ram costs and difficulties to purchase ram, the necessity of its reparation becomes obvious. The choices of the most suitable technologies of hard facing and welding of an initially cracked ram are also studied here. Besides the techno-economic analysis, an energetic analysis is performed as an additional criterion in assessment of the proposed technology