Papers by Keyword: Filler Wire

Abstract: Additive technologies, in particular, wire-feed laser deposition, can significantly reduce the production cycle of manufacturing large-sized parts or parts of complex shape due to partial or complete elimination of technological operations such as casting, machining and welding. The aim of the work is to develop an analytical model of heating and melting of the filler wire during wire-feed laser deposition. The heat conduction problem was solved by the functional-analytical methods. The practical effectiveness of the functional-analytical methods with respect to computational time is several orders of magnitude higher than numerical ones. Obtained analytical solution made it possible to determine the temperature field for heat flux arbitrarily distributed on the filler wire surface. It is established that at a higher feed rate, the wire tip is completely melted at a greater distance from the laser axis. The shape of the melting surface also depends on the feed rate. At a slow feed rate, a more uniform heating of the wire over the cross section occurs. The melting surface has a small angle of inclination.

Abstract: The urgency of the development of mathematical modeling tools that allow calculating the shape of free surface of the melt during the analysis of surfacing processes, introduced in additive production, is shown. A mathematical formulation of the problem is presented, which corresponds to Lagrangian description of liquid medium. It includes equation of motion and energy equation. A numerical algorithm for solving this problem is described, based on Smoothed Particle Hydrodynamics method, and the corresponding equations are given. The analysis of the results of solution of test problems is carried out and comparison of experimental results of the process with well-known data and physical representations is given. The conclusion is made about the possibility of applying this modeling method for development of additive production and creation of automatic control systems for the processes of shaping.

Abstract: Multi-pass laser and laser-arc narrow-gap welding make it possible to obtain high-quality butt joints of large-thickness pipe steels with hardness up to 2600...2800 MPa and toughness close to the base metal toughness at a temperature of 20°C. When multi-pass welding methods are used, the subsequent pass makes heat treatment of the previous ones, and reduces the rate of their cooling yet. This allows excluding heat treatment of the joint after welding, which significantly reduces the time and costs for manufacturing large-sized structures.

Abstract: Compared to steel, the required amount of energy for conventional welding of copper is higher, due to its higher thermal conductivity. This problem is mainly solved by preheating the work pieces or welding processes with high intensities such as laser beam welding. As the absorption of copper for infrared wavelengths, which are commonly used in industrial applications today, is typically low, the energy efficiency of the laser welding process is low. Besides this, if filler wires are used in order to increase the bridgeable width of joining gaps, the energy consumption of the process is further increased due to the additional amount of energy required to melt the filler material.As roughened surfaces of copper parts are known to increase absorption and consequently energy efficiency of laser beam welding without filler wires, this paper investigates the influence of surface structured filler wires on laser beam welding of copper alloys. Thus, the correlation between knurling geometries, absorption, molten volume and the welding result is investigated. For this reason, the welding result is evaluated by means of geometrical, electrical and mechanical weld seam properties e.g. seam width, weld reinforcement, area of cross-section, electrical resistance, tensile strength and strain.

Abstract: The CW CO2 laser weldability of various Al-Mg alloys was investigated in terms of weld strength, ductility, Vickers hardness, formability and solidification cracking tendency when both autogenous and wire feed welding were made. Tensile strength of the laser welds was lower than that of the corresponding base metals, and it was linearly proportional to the Mg content of the weld metal. Formability and ductility of Al-Mg alloy laser welds were lower than those of corresponding base alloys as well. As for the weld solidification structure, as the Mg content increased in the weld metal, more equiaxed grains developed. Hence, softening of weld metal and solidification cracking were decreased in the weld metal containing higher Mg. Solidification cracking of Al-Mg alloy laser welds showed the highest susceptibility at 1.6 to 1.9wt.% Mg, and it decreased with further increase of Mg content.

Abstract: Magnesium alloys are becoming important material for light weight car body, due to their low specific density but high specific strength. However they have a poor weldability, caused by high oxidization tendency and low vapour temperature. In this study, the welding performance of magnesium alloy was investigated for automobile application. The material was rolled magnesium alloy sheet contains 3wt%Al, 1wt%Zn and Mg balance. The effects of filler wire addition was investigated on 2kW Nd:YAG laser welding. For the results, the mechanical properties of welded specimen were similar with base metal in laser welding with and without filler wire. The bridging ability was improved with filler wire without weld properties deterioration on laser welding of magnesium alloy.

Abstract: This paper renders research into the fundamentals governing the melt pool dynamics of a hybrid bifocal laser welding system consisting of an Nd:YAG and a high power diode laser (HPDL). The resulting superposition of keyhole by heat conduction mode welding is assayed for extruded aluminum. In particular the diffusion of the surface oxygen layer is considered. By comparing the results attainable by bifocal laser hybrid welding to the constituent laser processes synergetic effects of the laser hybrid can be demonstrated. These are namely the doubling of the welding speed from 2.0 min-1 to 4.0 m min-1, the reduction of the roughness of the weld surface from 60 om to approximately 10 om and an increase in energy transfer efficiency. The experimental investigations verifying these synergies are outlined and discussed.