The 7th International Conference

Innovative Technologies for Joining Advanced Materials

June 19-20, 2014, Timişoara, Romania

With the support of

Sponsors

Abstracts

National R&D Institute for Welding and Material Testing – ISIM Timişoara

”Politehnica” University of Timișoara

Romanian Academy for Technical Sciences –Timişoara Subsidiary

ABSTRACTS Plenar Session

Enhanced Joint Properties by Magnetic Pulse Crimping with Filler Material CRAMER Heidi, MUELLER Marc, APPEL Ludwig Compared to conventional forming joining technics, e.q. mechanical crimping, the magnetic pulse crimping gives advantages because of a contact-free tooling, a symmetrical coaxial pressure and forming, as well as a low spring back after forming. Limitations of the general functionality of crimp joints also obtain for magnetic pulsed crimp joints: Leak-tightness, combined with corrosion resistance, and a partially Limitation of electrical conductivity (transition resistance). To improve and to extend the functionality of MP-crimp-joints different filler materials can be used. By environment of a public research project, adhesives, solder and metal coatings have been applied as filler materials to MP-crimping. Within the lecture the behavior of the filler materials under the influence of high speed forming, the suitable operating conditions and achieved joint properties will be described.

Session 1

Analysis of Current State and Integrity Evaluation for the Supply Tank of Generation Unit 6 of Thermal Power Plant Nikola Tesla ”A”, Obrenovac ARSIĆ Miodrag, BOŠNJAK Srđan, GRABULOV Vencislav, VELJOVIĆ Aleksandar, SAVIĆ Zoran Stable supply tank, with volume V = 250 m3 and operating pressure p = 1,5 MPa, of generation unit 6 at thermal power plant 'Nikola Tesla A' in Obrenovac, is designed for water-steam working fluid. It was made of steel Č 1204 as a single-part welded structure with a single wall. Cylindrical tank shell consists of 8 segments, while torispherical deep bottoms consist of 3 segments. The tank is in the horizontal position and it lays on 4 supports. There are five manometers installed at the tank for pressure control, as well as 5 spring-loaded safety valves. In this paper results of non-destructive tests performed on the tank are presented. Mechanical damages on parent material, up to 1.5 mm deep, were detected at the outer surface of the cylindrical section of the right bottom (as seen from the boiler) and on the inner surface of the shell, as well as sporadic pitting corrosion, up to 0.5 mm deep, and 2 mm misalignment of sheet metals in areas where shell segments are joined. Crack type linear indications were detected on the surface of welded joints through the use of magnetic particle testing. Through ultrasonic and radiographic testing it was determined that the homogeneity of welded joints is satisfactory. Hardness testing was performed on all segments of the tank, and obtained values were in the range between 118 and 130 HB. Metallographic examination, performed on specimens of all segments of the tank, showed that microstructure of material is either fine-grained or striped ferrite-pearlite. On the basis of test results the repair technology for shell and bottom segments was made, while on the basis of the analytical calculation of tank strength the integrity evaluation was carried out for the upcoming period of service, depending on the category of the vessel. Analyzing Properties of New Hard Coating Technologies for Increasing the Wear Resistance MILUTINOVIC Zlatan, RISTIC Marko, VASOVIC Ivana, PROKOLAB Milan, GLIGORIJEVIC Bojan The aim of this paper is improving the characteristic of Ventilation mill for grinding coal, which is one of the main parts of steam power plants in the system that makes a significant influence on the level of energy efficiency with its work. Working parts of the mill are dominantly exposed to intensive abrasive and erosive wear during exploitation. For solving the problem of increasing the wear resistance of transport parts and coal grinding in power plants, we need to investigate the optimal application of technology in hard coatings by different procedures, and filer materials. Hard coatings were carried out with cold (plasma and arc treatment) and hot metallization (with concurrent and subsequent drowning). The filler materials of different chemical composition and properties, based on Ni (NiCrBSi; NiCrBSiFe; NiCrBSi / WC) and Fe (FeCrCSiMo; FeCrCBSiTi; FeCrCBNiSi) has been used.

The main goal of this paper is to make the selection of optimal metalization procedures, group of filler materials and metalization technology definition, based on the results of structural and mechanical properties of samples, experimental model hardfacing. These were investigations of its structure, measurement and distribution of hardness in the samples, tribology characteristic samples with hard coatings. Based on the results of these tests, the filler materials and procedures for applying hard coatings were selected, which would be applied in the revitalization of parts in transport and at coal grinding.

Influence of Slag-Flux Mixture on the Properties of Welded Joints DOBRÁNSZKY János, NÉMETH Levente, BICZÓ Csaba Submerged arc welding (SAW) is one of the most versatile welding processes. All steel grades, from non- to high alloyed, including Ni-based alloys, can be welded with a combination of various techniques. The process became common worldwide for these properties, and shows a high degree of growth in countries with significant heavy industry. In the process, a large amount of slag is formed from the flux, which is treated as waste. The slag contains non-renewable raw materials, minerals. The mining, processing represents a significant environmental impact. Short life cycle of products from high-energy input is not compatible with the eco-thinking. That is why recycling of these materials is highly appropriate from environmental and economical aspects. The paper presents a method in which the slag can be used as a valuable flux component with significant cost- and waste reduction by ensuring no loss of mechanical properties.

Analysis of the Quality of the Weld Metal Obtained with Alloyed Flux-Cored Wire BAJIC Nikola, RAKIN Marko, VELJIĆ Darko, MRDAK Mihailo, STOJADINOVIC Slobodan, PEKEZ Jasmina The main aim of this paper is to assess the quality of newly produced, alloyed flux-cored wire with increased thickness of the steel cover compared to traditional according to ASTM, AWS A5.28 E110C-G, EN ISO 18276-A-T 69 6 Mn2.5Ni M M 3 H5 standard, alloyed with Ni and Mo, and designed for welding of fine-grained HSLA steel. Flux-cored wire was produced on a pilot production line that allows calibration of steel band of higher thickness and production of flux-cored wire. Quality assessment of the alloyed flux-cored wire was based on the analysis of the results of tests of mechanical properties and microstructure mainly of the weld metal. Variation of chemical composition and microstructure were analyzed along weld metal (for each welding pass) and heat affected zone (HAZ) using SEM and EDS. Based on the results of the quality assessment of flux-cored wire, the conclusions about the feasibility of industrial application of selected metallurgical grade of flux-cored wire designed for welding of fine-grain HSLA steel were presented.

Session 2

3D Simulation of Stress-Strain State of Plasma Arc Surfacing by CAD/CAE Software Sysweld DIMITROVA Rayna, NEDELCHEV Alexander, NIKOLOV Antonio The deformation process during the plasma arc surfacing is analyzed by CAD/CAE software SysWeld under Visual Environment using 3D simulation. The aim of simulation is visualization of a temperature field and a stress-strain state distribution as results of surfacing under typical technological parameters of plasma arc processing which could be used for education.

Ways of Numerical Prediction of Austenitic Grain Size in Heat-Affected Zone of Welds MORAVEC Jaromír, BRADÁČ Josef, NOVÁKOVÁ Iva In the present time there is a clear effort to achieve the most exact mathematical description of the behaviour of “Hi-tech” materials when exposed to temperature and stress loading. Besides the common numerically predicted values such as temperature, deformation and stress fields, or as the case may be structure changes during phase transformations, demands for prediction of the austenitic grain size in HAZ of welds become more and more frequent. That is why the present submission deals with the analysis of the determination of the grain size and grain growth kinetics of HR3C single-phase austenitic steel using the Monte Carlo Potts method. The procedure of obtaining the input data for

numerical simulations will be demonstrated on HR3C steel, including the determination of grain growth kinetics and definition of all the parameters needed for a computational model. Results from the numerical simulation in Sysweld program will be then compared against the real experiment for a multi-layered weld made on HR3C tube.

Stress State Arround the Imperfections in Welded Joints JOVIČIĆ Radomir, SEDMAK Simon, TATIĆ Uroš, LUKIĆ Uroš, PROKIĆ – CVETKOVIĆ Radica, POPOVIĆ Olivera, JOVIČIĆ Katarina Welded joints because of their geometry can cause a local increase of stress. In the presence of imperfections in welded joints the local stress additionaly increases and can lead to the formation of cracks. In this paper are presented cracks that were detected in the welded joint during testing of pressure equipment in service and the stress state around imperfection was analyzed by finite element method. It was concluded that even the imperfections that are acceptable for the highest level of quality, according to standard EN ISO 5817, causes significantly higher local stress than the stress predicted during design of structure.

Numerical Modeling and Initial Fatigue Life Estimations of Welded Structural Components VASOVIC Ivana, RISTIC Marko, RISTIC Slavica, MAKSIMOVIC Mirko, STAMENKOVIC Dragi Numerical simulations are powerful tool for analyzing and research in domain of mechanical constructions. In welded joints is very important to determine residual stresses and temperature distribution in sample, apropos, element of construction. For welded construction that are in exploitation is not possible doing experiments, so numerical simulations can give the required results and overview of stress state, residual stresses, critical areas, displacement, temperature distribution and other data is needed for analyzing and improvement of constructions or parts of constructions. This analysis includes finite element model for the thermal and mechanical welding simulation. Welding simulation was considered as a sequential coupled thermo-mechanical analysis. The residual stress distribution and magnitude in axial direction was obtained. Numerical methods are also used in order to predict the crack of specimen. In this paper is obtained good agreement of results between experiment and numerical simulations.

Repair Weld Simulation of Austenitic Steel Pipe BÉZI Zoltán, SZÁVAI Szabolcs In this study the repair weld simulation of an austenitic steel pipe is performed to measure the residual stresses caused by the welding. The simulation consists of three work tasks. First the girth welding of the pipe is performed on simplified geometries to decrease the calculation time. The next work task is the simulation of the machining of the repair weld excavation, performed in one simulation step. The last task is the simulation of the repair welding. Residual stress measurements are performed on weld repair to provide validation of the simulation performed on the model.

Application of Numerical Simulations at Welding Multilayer Welds from the Material X22CrMoV12-2 MORAVEC Jaromír, SLOVÁČEK Marek Heat-resisting martensitic steel X22CrMoV12-1 is suitable to be used particularly for steam turbine components (e.g. blades or action wheels of steam turbines) and as parts of airplanes structural devices. The aim of this paper is to show how numerical simulations can help to optimize welding procedure of this very hardly weldable material. On the real multilayer weld will be described how to arrange whole experiment in order to obtain not only relevant input data but also verification data. As a result it will be possible to set up the computational model for this type of steel and consequently to use it for simulation computations of welding and heat treatment of real structure components.

Development of a new generation of welding simulators for education and training. ENGH Erik During the years a number of different simulators have been developed for the welding community. These simulators have been targeted to different user groups and different technical level of the

group itself. The technological quality has mostly been on a professional level, although the user friendliness, we must admit, may have a wide interpretation of the word “friendliness”. The use of mobile devices, pads and so forth, with other interface methods than the keyboard, that has appeared over the last years have given us new opportunities to define user interfaces that are completely different from what was possible before. This paper will discuss a work in progress for a simulation project development related to education and training, in two different projects, IWSD (Leonardo da Vinci project) and Green Weld (EEA Grant project), currently running in Romania and in Bulgaria.

Session 3

Pulsed LASER-(micro)TIG Welding of Automotive Zn Coated Advanced High Strength Steels Thin Sheets in Overlap Configuration BÎRDEANU Aurel – Valentin The wider implementation into automotive sector of new materials categorized as Advanced High Strength Steels (AHSS) in order to reduce costs and weight require the development of appropriate joining technologies. The paper presents the results of applying of a new hybrid welding process, i.e. Pulsed LASER-(micro)TIG, for realizing overlap joints for Zn-coated AHSS materials. The statistical influence of main hybrid welding process parameters was investigated by means of factorial experimental design and weighted against the shear strength results of the realized joints. The influence of laser pulse peak power, the average welding TIG current and the joint gap was investigated for three types of Zn coated AHSS with different thicknesses. The results revealed that sane joints could be obtained with the new welding process and that the new process is fit to be applied for these materials. Each material did behave different in respect to the investigated process parameters and the results did reveal rather strong interaction between the influence factors (IF), however the joint gap does play an important role in respect to the maximum shear strength of the joint, which could be correlated to the specifics of the laser beam welding of Zn coated steels. The strong interaction between the studied IF imply further study of the new process by including other process parameters.

Joining of C/SiC Materials by Spark Plasma Sintering TSAKIRIS Violeta, KAPPEL Wilhelm, TALPEANU Dorinel, ALBU Florentina, PATROI Delia, MARINESCU Virgil High density graphite and silicon carbide powder (α - phase) were used to obtain joints by Spark Plasma Sintering (SPS) technique. The joining of C/SiC was performed both by direct bonding (DB) and with the aid of a ceramic powder mixture (SiC+5%wt.B4C) as intermediary joining material. The joints were performed in vacuum at 1900oC under 30 MPa with a dwell time of 3 minutes. The interface structures of the obtained joints were characterized from the structural and mechanical point of view. XRD analysis of both joints have shown only the presence of crystalline phases of SiC and C while the crystalline phase of B4C was not detected due to its low content (5 wt.%) with a higher degree of amorphization of 9.1% for the junction with interlayer than that of the corresponding junction obtained by DB (5.5%). Interface compositional analyses and SEM images have shown that the process of diffusion bonding was the mechanism both for joining by DB and with a SiC+5wt%B4C interlayer. The Vickers microhardness and Young Modulus values measured by nanoindentation evidenciated a strong increase of HV values (11 – 14 GPa) at interface for the junction with SiC+B4C intermediate layer and, as expected, the highest stiffness (180-197 GPa).

Lap Joint Laser Welding of Austenitic Stainless Steel Thin Sheets STANCIU Elena-Manuela, PASCU Alexandru, ROATĂ Ionuț-Claudiu This paper investigates the laser welding of AISI 304 stainless steel thin sheets. For the experimental procedure a 3,3 kW Nd:Yag laser was used. Nine samples were realised during this study and the influence of the process parameters on to the geometry and microstructure of the weld bead is analysed. The best result in case of 0,5 mm stainless steel laser welding are obtained by using a density power in the range of 700-850 kW/cm2 associated with a minimum spot diameter of 0,4 mm.

The weld bead compositional content was determined by an X ray dispersive field analyses. A decreasing of Mn and Si content into the weld zone was produced mainly by the burning and vaporization effects during the laser welding. Good tensile behaviour of the joints was obtained at all samples with fracture was produced at 600 MPa.

Research Regarding the Manufacture of Pipelines Through Automatic Tandem MAG Welding on Generators TOMA Cosmin, IOVANAS Radu, IOVANAS Daniela Maria The manufacture of pipelines is a complex technological process starting with laminates supply, joints cutting-processing, rolling, welding, calibration, control, packing, delivery. As a rule, the technological welding process is achieved by welding on generators through MAG and submerged arc welding, procedures which generally take place completely automatically, affecting the quality and cost of products. Beside a series of advantages, submerged arc welding also has disadvantages; it does not eliminate the operator’s intervention and implies some high linear energies with implications on the mechanical-metallurgical characteristics of the welded joints. In this paper we present the preliminary results of the experiments which have been carried out on welded joints on X52 steel plate, g = 12 mm, through classical MAG welding, with one wire - filler material on the first layer, and the filling beads through tandem MAG welding, with two wires. We should mention that the plates had a V(30°) joint and the welding was executed unilaterally, horizontally, the wire - filler material being of the same quality G42 4 M G3 SI1 ( EN ISO 14341) and diameter (1.2 mm), and EN ISO 14175 protection gas. The entire technological welding process was carried out in laboratory conditions, fully robotized, using a QIROX-315 welding robot fitted with QUINTO-GLC 603-type tandem MAG welding installations, owned by ICDT-PRO-DD C12 “Advanced welding eco-technologies”, belonging to Transylvania University of Braşov.

Lead-Free Alloys for Ecological Solders Manufacturing KOSTOV Ana, MILOSAVLJEVIC Aleksandra, TODOROVIC Radisa, GOMIDZELOVIC Lidija Although the European Union’s directive about environment protection as WEEE and RoHS have been carried out in 2003, led solders are still in used in Serbia. In the aim to respect the European and world directives and laws, it is necessary to reduce a quantity of toxic element and to establish lead and cadmium free solders in production. In this paper it was presented lead-free alloys, which are used for ecological solders manufacturing and various applications.

Composite Rods for Brazing BINCHICIU Emilia, FLESER Traian, VOICULESCU Ionelia The paper presents research conducted for the development of precursors and wrapped rods for brazing, that deposit, through melting, two different alloys, with respect to the level of silver alloying and the melting temperature. The alloy with the high silver content is introduced under the form of powder, in the coating of the brazing rods, in a participation proportion that assures a buffer layer, with advance proprieties of diffusion in the base metal and in the core alloy of the coated rod. The participation ratio of the silver rich powder alloy is established within the following limits 8-12%, depending on their melting point, the grinding degree and mixing with the deoxidizer coat. The development of the precursors was made by homogeneous melting and spraying on a oblique plan, the grains obtained were grounded, the grist obtained is considered optimum to be introduced in the coating mixture after it successfully passed through a sieve with a mesh of 0.1 mm. The alloyed precursors with 45% silver, grounded between the above mentioned limits, were introduced in the deoxidizer coat mixture of the bare rods, type Ag30, according to SR EN 1044/1999. The resulted mixture was used to manufacture experimental lots of covered rods for brazing, which were used for testing, in order to achieve highly important joints. The melting temperature of the precursors was established through micro-alloying so that it will be 10-150C higher than that of the deoxidizer coat, which in turn has a lower melting temperature, by 56-60˚C, than the melting temperature of the core alloy. The deoxidizer coat is usually fluoroboric type, conforming to SR EN 1045/2001.

Representative joints made with the new experimental rods, after testing, presented results consistent with the requirements, which allowed the authors to appreciate this method as appropriate for cost reduction with brazing materials in the use of composite coated rods.

Nanostructured Materials for Cladding by Welding TIHANOV-TĂNĂSACHE Daniel, FLOREA Carmen, BINCHICIU Emilia, GEANTA Victor The rigorous stress conditions of active surfaces, from the components of magmatic rock processing equipment of surface pits, required finding new materials and system processes that achieve a major impact on wear processes, in the sense of decreasing them. Conducted research with classic cladding by welding materials showed a high importance of the chromium carbides in deposits, in the fight against wear. From manufacturing considerations, the participation of chromium carbides in the deposits made with traditional welding materials is 35%, which required finding new ways to obtain superior performances. The group of authors considered the nanostructure method to be convenient, hence of finishing the deposition structure, by introducing in the cladding, welding material composition centers of crystallization with colloidal size and superior temperatures, compared to the molten through welding bath temperatures. In order to achieve a new generation of cladding by welding materials, we proceeded to develop, on the above mentioned principle, rods that deposit by welding alloys like Fe-20%Cr-4%W-1%Ti, nanostructure with melted tungsten carbides and colloidal grinded. The rods thus obtained were used for cladding active surfaces of general purpose extraction and processing machines for basaltic rocks, to achieve highways. Results obtained confirm theoretical assumptions, which led to the implementation of new products in industrial production.

New Ecological Technique for Soldering of Metallic Materials COJOCARU Radu, BOȚILĂ Lia, VERBIȚCHI Victor, CIUCĂ Cristian The performances, qualities and extraordinary development potential of the friction stir welding process (FSW) are well known in the world, both in the scientific and industrial areas. The innovative technical developments, based on the principle of the FSW process, conducted at ISIM Timisoara, as well as the results obtained so far have put the foundation for initiating a new method for bonding of materials, namely friction stir soldering. The principle of the new soldering process is based on important features of the FSW process. The paper presents the results of a program of experiments, which had as its main objective checking whether the new proposed soldering process is viable and applicable. Positive results were obtained by the soldering tests of copper (Cu99), brass (CuZn39Pb2) and steel (S235). Promoting this new environmentally friendly process of soldering is beneficial, because it complies with the current trends worldwide regarding both the environment and health.

Session 4

Methodology for Reparation of Damaged Sleeves and Welded Shield Sections of Guide Vanes at Hydropower Plant DJERDAP 1 ARSIĆ Miodrag, VISTAĆ Brane, BOŠNJAK Srđan, GRABULOV Vencislav, SAVIĆ Zoran Vertical Kaplan turbines, manufactured in Russia and with nominal power of 200 MW, have been installed in 6 hydroelectric generating units at ’Djerdap 1’. During the refurbishment of hydropower plant experimental non-destructive tests were performed in order to determine the state of turbine components. During the course of testing damage was detected at sleeves and welded shields of guide vanes, which occurred as a consequence of turbine shaft vibrations. 1782 mm long guide vane sleeves were made of cast steel 25L (GOST standard), 260 mm long sleeve was made of forged steel St 25 (GOST standard), while welded shields of guide vanes were made of austenitic steel 08X18H10T (GOST standard). Results of experimental tests and methodology for reparation of damaged surfaces of sleeves and welded shields of guide vanes are presented in this paper. It was necessary, due to the structural solution used for the design of guide vanes and their function during service, to define a large number of details, carefully reconsider them and carry out all activities with extreme care in order to enable the safe operation and continuous use of vanes through the use of reparation

methodology for welding/surface welding of sleeves and welded shields. Overlooking, underestimation or incorrect perception of important details could cause significant problems during turbine operation.

Research on argon protection when using WIG welding ŢUNEA Daniel, BURCĂ Mircea The paper presents the theoretical bases of gas flow, as drowned jets, the device used for viewing the pure gas cone (argon) using a smoke screen infused on the edge of the argon jet and then the results of researches carried out on four sizes of nozzles often used in TIG welding. On each type of nozzle the argon flow parameter was varied and the height of the cone of pure argon was photographed and measured. The paper ends with the mathematical correlations that allow us to maximize the height of pure cone argon in relation to its flow.

Reconditioning by Welding of Rims Manufactured from Nonferrous Alloys BULARDA Nicoleta, HEPUT Teodor At present, in the automotive industry, the trend on the world plane is to fit on the wheels with rims made from nonferrous alloys, based on aluminum, magnesium or titanium. These rims have the advantage that they are lighter than the same rims made from steel, reducing the unsprung mass of the vehicle, and increasing the vehicle performances, that lead to the better handling, the faster braking and the better acceleration. Also, by using the rims made from nonferrous alloys, the increasing of the fuel consumption efficiency and the reducing of the carbon monoxide (CO) emission are obtained. During the traffic, the wheels (rim + tyre) can be subjected to accidental collisions, such as the impact with the pavement, leading to damages of the rims, which must be reconditioned. The paper presents the results of structural examinations and mechanical tests, made on car rims made from nonferrous alloys, degraded and reconditioned by specific welding technologies. The structural and mechanical characteristics determined in the zones reconditioned by welding are at the level of the base metals used to made the investigated rims, that confirm the adequate quality of them, and a low risc to cracking.

Estimating the Reliability for Asphalt Milling Machines Teeth Manufactured by Claddings Processes IOVANAS Razvan Florin, IOVANAS Daniela Maria, DUMITRASCU Adela-Eliza The issues from the last decades related to the crisis of natural resources, raw materials, equipment, energy etc., gave rise to a new concept, namely sustainable development. The theory of sustainable development focuses on the development of quality products to provide trust and confidence, so as reliable. On this line the paper presents an approach on assessing the reliability and non-reliability of the milling teeth for asphalt machines classic manufactured and those manufactured by welding load, which give them self wear protection systems and self-lock at rotation. So in this sense there are presented comparative estimates regarding to the operating lifetime of the four batches of milling teeth for asphalt, 41Cr4 mark steel (EN 10083-1) the classic version and 3 groups of teeth load by weld on their working surface(wear) by different welding methods, namely: WIG - with filler material type tubular wire FILEUR DUR 606B, WIG – filler material with tubular type VT2, 5CrTiD rods, and MIG/MAG (CMT), the tubular wire filler material type FILEUR DUR. So, asphalt milling machines were stripped with 4 groups of teeth in order to track the behaviour during exploitation of each batch. Assuming that the product specifications properly respond customers' requirements, the level of reliability can be measured accurately by the fraction of delivered units that meet the specifications. On this line for estimating the reliability the Monte Carlo simulation method was used, which is suitable for analyzing the products that are designed to provide superior quality.

The Influence of Vibration on the Microstructure of the Wear-Resistant Layer Made with the Welding Wire MSG-6-GZ-C-60G LUCA Mihai Alexandru, PISU MACHEDON Teodor In the production of steel parts exigent of high durability to abrasive wear at high temperatures and / or corrosive environment, the method is used for the deposition welding with the addition material MSG-6-GZ-C-60G. With this material layer it is made of 55-60 HRC hardness, corrosion and wear resistant, with properties that are kept up to temperatures of 500 ⁰C. There can be manufactured new parts (pressure casting forms, components for dies, molds, etc.), or dynamically and abrasion-torn reconditioned parts may be required. Deposits have been made with wear-resistant layer on the steel 42CrMo4, with and without the generation of vibration during welding. For the samples swing, a device was used with an electrodynamic exciter to generate vibrations with frequencies up to 20 kHz. Vibration tests were performed at a frequency of 50 Hz, because the frequency can be applied in industrial conditions, by means of excitation of electromagnetic or vibration driven motor. There have been registered horizontal and vertical accelerations which lead to changes in the conditions of crystallisation of the melt, respectively the formation of a microstructure with superior features. Microstructures and hardness recorded on specimens welded with and without vibration are comparatively presented. Micrographs which were made demonstrate the favourable influence of the vibration on the quality of the deposited layer and the base material. Whith the vibration with accelerations of ax = 55 m/s2 and az = 70 m/s2 resulted: much lower deformation of the base material, HAZ - a lower content of residual austenite, in the TZ there was a great interlock of the two materials, in the deposited material the dendritic crystals strongly fragmented and the grain was finished.

Corrective Solutions for the Shaft with Flange Used for Fixing the Blade on a 5 kW Wind Turbine to Withstand Extreme Weather Conditions BĂDĂRĂU Rodica, MILOŞ Teodor, BORDEAŞU Ilare, BEJ Adrian The paper presents a case study on the original solution of a flange shaft as part of the root area of a 5 kW wind turbine blade. There were analyzed the causes that led to the shaft breakage under wind loadings in extreme weather conditions, and consequently technical solutions have been searched in order to improve the shaft design making it more reliable as mechanical strength at extreme wind loadings. The flange shaft is a welded subassembly that keeps the blades attached to the rotor hub. The first part of the paper consists in an analysis referring the loading status, the materials used for blade manufacturing, the identification of critical areas where the breaking was initiated and also the causes for which the materials assumed and specified in the technical design and manufacturing technology failed under loading at wind gusts of about 30 m/sec. Based on this preliminary analysis, the second part of the paper presents the technical solutions which were considered in reference to the materials and the improved design concept aiming to provide the right mechanical strength necessary to withstand specific wind loadings in extreme weather conditions.

Cold Metal Transfer Welding of Aluminum 5456 Thin Sheets ROATA Ionut-Claudiu, PASCU Alexandru, STANCIU Elena-Manuela, POP Mihai Alin This study aims to determine the optimal parameters for cold metal transfer MIG welding of aluminum thin sheets. Starting from this perspective, the filler material of AlMg5 full wire type and a synergic regime of welding with a low linear energy were used. The characterization of welded joints was achieved by macro – microscopic analyses, mechanical tests (microhardness and tensile) aiming to lower the thermo - mechanically affected zone. The results highlight the major influence of the welding parameters over the weld bead geometry and tensile behaviour of the joint.

Refining the Welding Technique for Nuclear Fuel Elements at INR Pitesti TRUTA Calin-Stefan, DEACONU Viorel, GONDAC Cristian Sealing of nuclear fuel material inside the fuel element clad must create a leak-tight "safety barrier" to prevent the release of radioactive products to environment. High quality welds are mandatory to withstand harsh conditions (radiation, pressure, temperature, corrosion) making possible the safe

operation of nuclear reactors. The joint design, material selection and welding technique must be combined by smartly balancing possible technological options to yield the best attainable quality for the intended purpose; these choices are discussed in the paper. For thin-walled clad to end-plug welding, heat flow pattern as determined by joint design and fitting accuracy proved to be crucial for the fusion boundary shape and moreover for the success rate in automate welding. Consequently, Finite Element Analysis of the transient thermal field during welding was performed, in order to determine the best compromise with reasonable machining precision for parts. The main features of the developed thermal model and some results illustrating its good predictions vs. actual welds are also presented. Helium-shielded pulsed welding was initially preferred to minimize HAZ, distortion and porosity but unfortunately important cast-to-cast variation in penetration was observed with Inconel-600 plugs, due to Marangoni effect. Extensive work was done to overcome this, mainly through variation of pulsing and of the shielding gas; depth-to-width ratio can be noticeably improved with no material addition. Out of welding classic cladding materials, studies were initiated at INR on joining oxide-dispersion strengthened (ODS) alloys and specialty austenitic formulations (e.g. 15/15Ti) since they are candidate materials of great interest for the next generation of nuclear reactors.

Session 5

Determination of some Mechanical Properties of Welded Reinforcing Steel with Self-shielded Wires by Vibration Tests BERETEU Liviu, BURCĂ Mircea, MOISA Raul, SIMOIU Dorin, DRĂGĂNESCU Gheorghe, PAVEL Ştefănel, NEŞ Cristian Reinforced concrete is a material formed by pouring concrete over reinforcement steel bars and wires and sometimes by a polymer that turns by drying in a hard and rigid composite. Welding of steel reinforcement concrete is a relatively difficult operation and with a large amount of work, given by the large number of welds that are needed and when this work is make in site conditions. The most common method of steel reinforcement welding is manual welding with coated electrode. The major disadvantage of this process is low productivity in welding effects on execution time, and the cost of welding. An alternative to manual welding with coated electrode for steel reinforcement welding on site is the welding process with self-shielded tubular wires. The aim of this paper is to determine the mechanical properties of welded reinforcing steel PC 52 with self-shielded wires, using a vibroacustic technique. To validate this method, the results obtained by vibroacoustic signal processing are compared with those determined by the tensile stresses of the same samples.

The Effect of Water Pressure Variation on Cut Surfaces Quality during Abrasive Waterjet Cutting of Austenitic Steels PERIANU Ion Aurel, MITELEA Ion, ŞERBAN Viorel Aurel In this paper research elements regarding the effect of water pressure variation on cut surfaces quality are presented in the field of abrasive water jet cutting of materials hard to process by machining such as austenitic stainless steels, in this case with a thickness of 20 mm. Selection of the optimal cutting process based on technical and economic criteria takes into consideration the type and thickness of the targeted material and also the physical and geometrical quality requirements. The present paper contains experimental research results regarding abrasive water jet cutting of austenitic stainless steel EN 1.4306 (ASTM 304 L) at different values of water pressure. The abrasive material used is Garnet with particle granulation 80 Mesh. By making roughness measurements and hardness examinations of the cut surface an evaluation will be made of the surface quality defining the optimal pressure values.

Study Regarding the Cavitation Erosion Behaviour and Residual Stresses of Impact Resistant Hardfacing Materials SECOSAN Evelina Roxana, CIUBOTARIU Relu Costel, COJOCARU Vasile, FRUNZAVERDE Doina, CAMPIAN Constantin Viorel In the last twenty years the cavitation erosion resistance of various welded materials was subject of extensive studies. Despite these, the research field is still opened. The multitude of materials used for the fabrication of hydraulic equipment and the variety of the operating conditions in hydropower units require adapted solutions. This paper presents the investigations made on welded overlays realized using an impact resistant hardfacing alloy, recommended by manufacturers for protection against cavitation erosion. The material was characterized by metallographic investigations (light microscopy, scanning electron microscopy and EDX–analyse), Vickers micro hardness tests, residual stresses measurements carried out by the hole-drilling strain-gage method and cavitation erosion tests using the vibratory method. The results of the cavitation erosion tests were correlated to the behaviour of the martensitic stainless steel 1.4313 (grade X3CrNiMo13-4 corresponding to EN 10088-3) frequently used for the manufacturing of the hydraulic turbine components.

The Effect of Silicon Content into the Aluminum Matrix on the Microstructure and Mechanical Properties of TIG/FSW Welds GHEORGHIU Diana Antonia, TOMA Stefan Lucian, BEJINARIU Costica, BERNEVIG Mihai Aluminum silicon alloys, the 4xxx group of the aluminum alloys, are mostly processed into cast parts. As for other cast designated alloys, their weldability is often considered as an unimportant feature. The interest, if any, is almost completely related to the repair welding. The present work analyses how silicon particle dimensions, which depends mostly on the silicon content into the metallic matrix, affects the weld properties. Also it is revealed the HAZ metallographic aspect for two frequently welding processes used on aluminum alloys, TIG and FSW. Friction welds resistance is better than that of the TIG welds, associated with a lack of symmetry (retreating side versus advancing side). Silicon particles diminish their dimensions for hypo eutectic or eutectic concentrations; for hyper eutectic compositions the effect has an almost unimportant effect.

Evaluation of abrasive wear resistance of Fe-Cr-C hardfacing alloys deposited on active components of the agricultural components DOBRA Ramona Monica, FARBAS Nicolae, PASCU Doru Romulus In most of the engineering applications, such as mining, agriculture, metallurgy, the equipments fail due to abrasive wear. Hardfacing is one of the most economical and most widely used methods of improving surface characteristics of engineering equipments (wear, corrosion) without changing the bulk properties of the components. Fe-Cr-C hardfacing alloys are well known for their excellent performances under severe wear conditions. The wear behaviour of hardfacing alloys depends on their chemical composition, on the microstructure obtained after welding, of the welding technology, respectively the welding parameters which strongly influence, for example, the dilution with the base material or formation of precipitated hard phases. The aim of this study was to characterize the microstructure of Fe-Cr-C hardfacing alloys and to investigate their abrasive wear behaviour. The research has been carried out using four types of Fe-Cr-C hardfacing alloys (8, 12, 16 and 20 % Cr). The alloys were deposited on the low-carbon steel S355 JR by manual arc welding method. The abrasion wear testing was carried out using the Taber Rotary Abraser Equipment. The microstructure characterization and surface analysis were performed using optical microscopy and HV 10 hardness tests.

Characterization of Plasma Cut Surfaces with Water Bed Welding Metallic Materials MACHEDON PISU Teodor, LUCA Mihai, MACHEDON PISU Elena The purpose of this paper is to analyze the quality of cut surfaces with plasma in the free atmosphere and in the water bed of metallic materials being welded.

This process leads to savings in labor, materials, supplies and other costs of production, having as purpose the decrease in the cost of cutting the work piece and reducing deformation and heat affected zone in the piece cut, providing alternatives to processing cutting. It was designed and built a device cutting water bed that has been proven. In the macroscopic analysis reveals that the cutting in water bed slag layer is lower. After microhardness measurements (base material, heat affected zone, the cut) it is found that the cutting in water bed cut occurs on the surface microhardness increased by 36% .

Alternate Design Solutions for reduced Stress Concentration Factor (SCF) T Joints of Circular Hollow Structures DIMA Gabriel, MACHEDON - PISU Teodor, BALCU Ion Design for fatigue of lightweight welded tubular structures is a significant concern of development teams. Based on practical design experience, alternate T joint design to usual Circular Hollow Structures (CHS) T joins are proposed. Proposed designs employ formed members within relevant dimensions range. A method based on finite element analysis including weld modelling was used, with analytical calculation of weld toe stress. Stress concentration factors (SCF) are calculated for all proposed designs for all typical load cases. Best placement and dimensions of formed members is given, together with design recommendations.

Session 6

The Increasing of Corrosion Resistance of Low Alloy Carbon Steels Used in Petroleum Industry through Coating with Alloys Based On Fe-Ni-Cr by Thermal Spray TOMA Stefan Lucian, PENEOASU Margareta, BEJINARIU C., GHEORGHIU Diana Antonia, EVA Lucian, TOMA Bogdan The main objective of this paper is to evaluate the mechanical properties, chemical and corrosion resistance of four types of metallic coatings: FeCr, FeCoCr, and FeCoCrNi, FeCrNi sprayed through thermal spraying in electric arc on an anchor substrate type 95Ni5Al or 78.3Ni20Cr1. 4Si0.3Fe. The five layers tested were deposited on carbon steel support low alloyed and the obtained results have provided a picture regarding the possibilities of using of the deposits. Because these types of alloys are used to increase the wear resistance of tools, it is very important to know their behaviour is saline environment, because the contributions brought by this paper would increase the applicability domain of these materials (could be used to recondition by thermal spraying the tools used in naval and petroleum industry). The researches of the obtained deposits have been carried out through several methods to screen their performance. Therefore, there have been done investigations on the microstructural morphology of the deposit, by optical microscopy (OM) and scanning electron microscopy (SEM). The OM and SEM results have sought to determine the degree of uniformity of the deposits and the amount of pores and oxides in layer. The physical properties of coatings were also evaluated by adhesion and porosity quantification. The corrosion resistance was evaluated by exposing samples in saline fog chamber. The corrosion products formed on the surface layers were investigated by scanning electron microscopy (SEM) analysis of the SEM. The intermediate alloy 78.3Ni20Cr1.4Si0.3Fe used as anchoring layer allowed the reducing of the pores and micro cracks frequently found in the ordinary 95Ni5Al alloy. It has been observed that the deposits based on NiCrCo are good enough to be used as an efficient coating of carbon steel in aggressive marine environments.

Weldability of Magnesium and Aluminum Alloys using Nd-Yag Laser GEAMĂN Virgil, RADOMIR Irinel, POP Mihai Alin Weldability of magnesium alloy to aluminum alloy in laser weld bonded (LWB) joints are investigated. Results showed that magnesium/aluminum could be easily joined by LWB under proper technological parameters. The weld is characterized by complex vortex flow at the weld pool and there exist intermetallic compound layer between weld pool and lower sheet metal which is composed of the brittle phase of Al3Mg2.

The aim of this research is to evaluate the weldability using LWB process to join Mg/Al alloys using HLD 3504 – Laser Type Trumpf, to explain the experimental conditions and interpretation of results.

Defects Detection on the Welded Thin Steel Plates Using Vibroacustic Method BERETEU Liviu, VODĂ Mircea, MEDGYESI Tiberiu, DRĂGĂNESCU Gheorghe, SIMOIU Dorin The aim of this paper is the development and validation of a vibroacustic technique to welding defects detection, especially for welded thin plate structures. In welded structures subjected to dynamic cyclic loads may appear and propagate fatigue cracks due to local structural damage. These cracks may initiate due to the technological parameters used in welding process, or due to environmental operating conditions. By the means of Finite Element Method (FEM), the natural frequencies and shape modes of welded stainless steel specimens are determined. The analysis is carried out in undamaged condition as well as damaged one, after artificially induced damages. The experimental measurement of the vibroacustic response is carried out by using a condenser microphone, which is suitable for high-fidelity acoustic measurements in the frequency range of 40 – 18.000 Hz. The vibration responses of the welded specimens, in free-free conditions, are carried out using algorithms based on Fast Fourier Transform. The results are compared to modal parameters estimated using FE Analysis and with natural frequencies computed by Euler-Bernoulli theory.

Tenacity Evaluation of the Deposited Metals by Welding, Using 3Si-2 Wire of ø1.2 mm on S355J4 Steel PASCU Doru Romulus, DUMA Iuliana, DASCAU Horia The mechanical tenacity characterizes the materials behaviour to static and dynamic shocks, at the ambient and the negative temperatures. In the case of deposited metals by welding, the tenacity characterization is made by determining the impact energy, (KV), the crack back contraction, (CBC), the lateral expansion (EL), and the correlation between these characteristics. The paper presents the experimental results concerning the tenacity characteristics of the deposited metals by welding on S355J4 steel (SR EN 10025), using Si-2 wire of ø1.2 mm (SR EN ISO 14341). These characteristics have been determined by impact bending tests, at the testing temperatures of + 20ºC, -20ºC, -30ºC, and -40ºC. The characteristis of the deposited metals tenacity, experimental obtained, had high values at all the testing temperatures (KV = 96…208 J; CBC = 1.21…2.62 mm and EL = 1.65…3.57 mm), beeing more than the same characteristics corresponding to S355J4 steel. So, it means that the deposited metals by welding using Si-2 wire of ø1.2 mm are not susceptible to the embrittlement-cracking phenomena.

Research on the Influence of Artificial Ageing on the Tensile Properties of Plastic Coated Composites with Fabric Inserts, in the Presence of Simulated Welding Defects KUN Lorand, MURARIU Alin Constantin An experimental research regarding the effects of artificial ageing by UV exposure on the tensile properties of a plastic coated composite material with fabric inserts, used mainly in the production of truck covers is presented in this paper. For the purpose of artificial ageing, the authors designed and built at ISIM Timisoara an original equipment with high performance UV lamps, adjustable geometry and forced cooling system. Defects of different sized were created in the aged and not aged specimens in order to simulate potential defects that appear during the joining process of these materials. The influence of artificial ageing with 24h and 48h exposure and defect size is highlighted by comparative analysis of the results obtained from the tensile tests that were carried out on all specimens. The results are further compared to the tensile properties of aged and not aged welded specimens, obtained using the high frequency current and hot air welding methods. The results show clear correlation between the defect size and the maximum tensile force and the elongation at break respectively. It is concluded however that further testing is necessary in the specially built equipment in order to properly describe the effect of accelerated artificial ageing by UV exposure on the tensile properties of plastic coated composite materials with fabric inserts.

Reconditioning by Metal Deposition Technology. Temperature Finite Element Modeling NITOI Dan Florin, DUMITRU Marius Gabriel, DUMITRU Bogdan, MIHAILESCU Alexandru, CISMAS Suzana Carmen This article presents finite element modeling for temperature as a result of the metal deposition technology. In such cases, this is the only research method to offer reliable information, taking into account the totally unfavorable working conditions for stress and strain gauges. By selecting the most appropriate initial condition, the output data come very close to the real result. In the paper, the temperature behavior is modeled because it influences the structural transformation and the stress, which can cause problems under the circumstances of improper working technologies.

Structural Integrity of Welded Structures Selected,  peer  reviewed  papers  from  the  10th  International  Conference  on Structural  Integrity of Welded Structures  (ISCS13),  July 11­12, 2013, Timisoara, Romania 

The conference takes place every two years and is traditionally organized by the  National  R&D  Institute  of Welding  and Material  Testing,  ISIM  Timisoara  in cooperation  with  the  “Politehnica”  University  of  Timisoara  and  the  Timisoara Branch of the Romanian Academy of Technical Sciences. 

The  volume  includes  33  papers  selected  from  the  55  papers  that  were submitted.  The  authors  highlighted  the  results  of  their  own  research  and development activity carried out  in the frame of their  institutes and universities from Romania, Germany, Hungary, Kazakhstan and Serbia.

Copyright © 2013 Trans Tech Publications Ltd, Switzerland Volume 814 of Advanced Materials Research ISSN print 1022‐6680 ISSN cd 1022‐6680 ISSN web 1662‐8 

Editor General Manager of  National R&D Institute of Welding and Materials Testing ‐ ISIM Timisoara Dr. Ing. Alin Constantin Murariu 

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Full text available online at http://www.scientific.net/AMR.814 

WELDING & MATERIAL TESTING

Publisher: National R&D Institute for Welding and Material Testing - ISIM TIMIŞOARA (Romania)

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field of welding and material testing Language: English Publishing papers: free of charge Category: B+ Frequency: 4 issues per year

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