Papers by Keyword: Weld Penetration

Abstract: The idea of using electrical pulse current at manual arc welding with coated electrode starts from the observation of frequency influence, unchanging in manual TIG welding with filler materials, on weld pool volume, by partial solidification of the weld pool in base time of the pulse current, thus being able to control its volume.This paper presents for the first time this new challenge of inverter modern sources: manual metal arc welding using pulsed current.Experimental research findings highlight the technological aspects when using pulsed current in manual metal arc welding, using STEL welding equipment that has this option. The application - concerns the establishment the lack of fusion welded joints in fillet positions. It highlights the beneficial effect of pulsed current, in particular by the joint penetration.Experiments have pursued highlighting of welding pulsed current and frequency of the pulses by the appearance of the joint and the influence by weld geometry for lack of fusion fillet joint. Also, the influence of frequency pulsed current by arc stability, sprays, etc. compared with standard welding was observed.

Abstract: AC A-TIG welding on 5052 aluminum alloy was investigated. The single component of oxide TiO₂, SiO₂, Cr₂O₃, V₂O₅ and halide CaF₂ was served as activating fluxes to study the effect on weld penetration and weld forming. The experimental results show that weld penetration can be increased and welding productivity can be improved in A-TIG welding. Activating fluxes, especially TiO₂ and SiO₂, have more significant effect on weld penetration than conventional TIG welding, moreover the better weld shape formed after coating activating flux is obtained, weld width has slight decrease that makes HAZ of A-TIG welding smaller.

Abstract: This paper reports the results of experimental research concerning the connection between the deck plate and the web of the longitudinal stiffeners in an orthotropic plated bridge deck on a microscopic scale. An important number of test specimens of a weld are studied with the help of a video microscope, to detect the efficiency of the root of the weld. The second part of the paper is concerned with parametric analysis of the lack of weld penetration by using accurate finite element modeling. The results demonstrate that the weld quality often required cannot always be assured, which surely has important consequence on the stresses in the weld and the fatigue resistance.

Abstract: The purpose of this work was to investigate the effect of activating fluxes and welding parameter to the penetration and depth-to-width ratio (DWR) of 6061 aluminum alloy welds. Bead-on-plate argon gas tungsten arc (GTA) welding process was made on 6061 aluminum alloy of plate without filling metals. The activating fluxes used in the experiment were CaO, ZnO, SiO₂, TiO₂, Al₂O₃, Cr₂O₃, CaF₂ and Na₂CO₃. Based on the higher penetration of weld bead and welding arc voltage, four fluxes were selected to create three new mixtures using 50% of each original fluxes. The mixed fluxes were used to investigate the effect to the welding penetration. Finally, The Taguchi method was employed to achieve optimal DWR of weld bead and investigate the welding parameters that significantly affect welding quality. The experimental procedure of GTA welding with activating flux via the Taguchi method produced full penetration of weld bead on a 6.35 mm thickness of 6061 aluminum alloy plate with single pass weld.

Abstract: The main objective of this study is to generate new understanding and improve computational method for optimization design on the parameters of double ellipsoid welding heat source. On the basis of Infrared measurement (IR), two optimization design methods, the zero-order method and first-order method, were combined to confirm the heat source parameters. The simulated thermal cycles, the weld penetration and the weld width were consistent to the experimental results with such corrected parameters. The effects of the parameters were analyzed by gradient evaluation method. It presents that as each of the parameters increasing, the peak temperature in the thermal cycle declines. Of all the three parameters, the sensitivities of the weld penetration and width with parameter c are great.

Abstract: Based on the bead on plate test and the effects of heat input on weld penetration, the equivalence between 2 kW CW (Continuous Wave) Nd:YAG laser power and pulsed GMA(Gas Metal Arc) power and the effect of welding speed on their equivalent ratios in welding carbon steel and Al alloy were studied. The studied results show that 9.8 kW pulsed GMA power is needed to reach the same weld penetration depth with 2 kW CW Nd:YAG laser power for welding of low carbon steel at v=1.2 m/min; for Al alloy, it is 3.92 kW pulsed GMA power. The equivalent ratios of 2 kW Nd:YAG laser power and pulsed GMA power are 4.9~6.4 and 1.85~2.1 times at different welding speed for low carbon steel and Al alloy, respectively. But their equivalent ratios have different variations with welding speed; at which the equivalent ratio of low carbon steel increases with welding speed and that of Al alloy decreases. The studied results offer the experimental boundary of heat input for analyzing the effect of Nd:YAG laser power and pulsed GMA power on laser+pulsed GMA hybrid welding process.

Abstract: A spacer grid assembly, which is an interconnected array of slotted grid straps welded at the intersections to form an egg crate structure, is one of the core structural components of the nuclear fuel assemblies of a Pressurized light Water Reactor (PWR). The spacer grid assembly is structurally required to have enough buckling strength under lateral loads so that the nuclear fuel rods are maintained in a coolable geometry, and that control rods are able to be inserted. The ability of a spacer grid assembly to resist lateral loads is usually characterized in terms of its dynamic and static crush strengths. Since the crush strengths of a spacer grid assembly are known to depend on the weld qualities at the intersections of the slotted grid straps, high-tech welding methods, such as a TIG welding, LASER beam welding or Electron beam welding method, have been used recently in the nuclear fuel manufacturing fields. In this study, to meet the above requirements, two kinds of researches were carried out. First, by adjusting the LASER beam welding parameters, an optimum welding combination of the LASER beam welding parameters was obtained for welding a spacer grid assembly. Second, a new LASER beam welding technique was proposed to obtain a longer weld line and a smaller weld bead size by tilting the LASER beam. The buckling strength of the spacer grid welded by the new LASER beam welding technique was enhanced by up to 30 % when compared to that by the conventional LASER beam welding method.