Advanced Materials Research Vol. 1029

Abstract: 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 resul ts of surfacing under typical technological parameters of plasma arc processing which could be used for education. Key w ords : CAD/CAE simulation , plasma arc surfacing , stress-strain state

Abstract: Normal 0 false false false MicrosoftInternetExplorer4 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. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}

Abstract: 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.

Abstract: 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. Keywords: TIG welding, Pure argon cone

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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% .