Conventional Welding Technologies Research Articles

An Inherent Strain Method Using Progressive Element Activation for Fast Distortion Calculation in Directed Energy Deposition

The finite element analysis (FEA) simulation of directed energy deposition (DED) processes offers many potential cost savings during the build job optimization process, through, e.g., distortion predictions. However, the biggest challenge is the long calculation time, frequently exceeding the actual build time. One way of simplifying the simulation with the aim of reducing the calculation times is the inherent strain method. While this method is already used commercially in the simulation of powder bed-based processes and conventional welding technologies, its use in DED is still the subject of research. In this work, an inverse determination of an inherent strain is carried out on a 20-layer-high, single-track-wide wall, common theories are reviewed, and an approach based on thermal strain is introduced. As a result, the calculation time could be reduced by 83% and the accuracy remained at 92%.

Evaluating edge joint preparation impact on penetration depth in laser-arc hybrid welding

Nowadays, conventional welding technologies such as submerged arc welding (SAW) are still used in most heavy-steel industries. This type of traditional technology means that welding takes up a large part of the productive time. As a solution to this problem, there are welding methods, such as Laser-Arc Hybrid Welding (LAHW), that have the potential to reduce the cost of manufacturing large steel structures. This is possible due to the reduced number of weld passes required to join thicker steel sections, as large thicknesses can be welded in one or a few passes.A problem with LAHW is achieving satisfactory quality. For this reason, it is essential to study the starting conditions, e.g. edge joint preparation. The target of this research work is to find out the relationship between the penetration value of the weld bead obtained and the edge joint preparation. The evolution of the molten pool and the behavior of the molten material in the joint is discussed for the different edge joint preparation configurations. The effect of the roughness is that it affects the wetting of the molten material in the joint, which would affect the penetration result, together with the gap and air volume gap used in the joint. Cut-wire is also used in the research, in samples that presented a larger air volume gap. The behavior of the molten metal inside the joint in this case is also discussed. In addition, the quality of the weld beads has also been determined by making macrographs, microstructural analysis, X-ray, microhardness profiles, tensile test and Charpy test. Some pores and cracks have been found, although destructive tests show adequate behavior of the weld bead. It is possible to elucidate from the findings that as the roughness, gap and/or air volume gap of the edge joint increases, the penetration value obtained increases. Cut-wire samples obtained full penetration.

Evaluation on the performance of sustainable wire arc additive manufacturing using micro plasma arc welding

Metal additive manufacturing has gained popularity due to its significant advancement in minimising waste. The product design using additive manufacturing (AM) does not require mould and less material required, which is less waste. In this way, AM has the potential to transform the manufacturing industries towards greater sustainability. Besides, AM allow more complex designs and shape than conventional manufacturing. Wire arc additive manufacturing (WAAM) is one of the most popular metal AM that has received significant attention due to its usefulness for localising, repairing, and modifying instead of discarding and replacing entire components. However, conventional welding technology faced the issue of significant heat input, low surface quality, and low dimensional accuracy of WAAM components. Micro-plasma arc welding (MPAW) is a new alternative to the WAAM process. The speciality of MPAW is low current provided of 1A to 25A current range, leading to low heat input and energy-efficient manufacturing. The present study shows various metallic structures developed using an MPAW-based WAAM system, and the relative error between the CAD model and four different structures was determined. Overall, the study outcome shows the geometric uniformity of parts produced with an MPAW-based WAAM system and demonstrates smooth surface finish can be obtained.

Determining the technological parameters of electron-beam welding of high-strength titanium alloys

It is usually quite difficult to carry out deep penetration of thick-walled products from titanium alloys using conventional welding technologies. In this study, it was proposed to use electron beam welding under high vacuum conditions for the realization of 40 mm thick melting of VT23, VT3-1 alloys. This paper considers the possibility of obtaining high-quality welded joints from high-strength titanium alloys having (a+β) two-phase structures. For the implementation of research works, samples were made from selected materials, samples were welded according to the specified modes, metallographic analysis was performed, and the level of mechanical properties was determined. The research results were verified under laboratory conditions. The technological features of the processes of electron-beam welding of products with a thickness of 40 mm were considered; the parameters affecting the weldability of titanium alloys and their structure were determined. The welded samples were checked by X-ray non-destructive testing, the microstructure of the welds was studied, and the physical and mechanical properties of the welded joints were checked. It was established that a feature of titanium alloys VT3-1, VT23 is the need for heat treatment after welding under the base metal regimes to improve the characteristics of the welded joint. The resulting strength limit of the alloys after heat treatment reached values of 1250 MPa and more, while the impact toughness was at the level of 48–50 J·cm-2. Modeling the welding process has made it possible to ensure the reproducibility of the characteristics of the welded joint at a level close to that of the base metal, to increase the quality indicators of welded joints, and to reduce the time required to test the technology. The studies of simulator samples showed compliance of the quality of welded joints with the predefined parameters.

Rotary Friction Welding and Dissimilar Metal Joining of Aluminium and Stainless Steel Alloys

Friction welding (FW) is cost-effective, efficient, occupational safer and also eco-friendly in the absence of pollution, smoke, fume, and IR radiation during welding than conventional welding technologies. In this paper, the joining of aluminium AA6063 and steel SS304 dissimilar metal is explained with different faying surfaces and their SEM images of weld interface (WI), joint quality, tensile and yield strength, and the axial shortening are evaluated and compared. The joint quality factor of the experiment faying surface modification ‘E3’ was the maximum and about >100% with 236 MPa strength. The axial shortening was also less than 27 mm. The joint with hemispherical faying surface showed ‘U’ shaped WI and the joint with taper faying surface showed ‘V’ shape WI. So, the cross-sectional area of WI can be increased and the strength also increased. FW yields very high strength, low-stress weld with no weld defects such as porosity, voids etc. Here, in most cases, the joint strength is equal to base metal strength and it can avoid fastening to join two metals. FW has a minimal and narrow heat-affected zone (HAZ) of few microns size that differentiates FW from other welding techniques. The grain size of HAZ is directly proportional to the heat input during welding. During fusion welding of dissimilar materials, a lot of intermetallic compounds are formed at the weld interface and that will lead to poor strength of the welding because they have different chemical and mechanical qualities; therefore FW is a good choice for joining dissimilar metal rods as the intermetallic compounds can be reduced by FW.

Experimental and numerical investigations on built-up cold-formed steel beams using resistance spot welding

The lightweight steel structural systems such as trusses or built-up beams, consisting of thin gage steel elements, are highly efficient and have the advantages in ease of handling and construction. The major concern relates to the joining technique between each part of the element. Commonly, the connection between thin-walled elements is performed by self-drilling screws but the quantity of time and manpower necessary for a large number of connections, demands an improved solution. Conventional welding technology is not appropriate for connecting thin sheets, such those of 0.4 mm–1.0 mm, to thicker ones of 1.0 mm–3.5 mm. The electric resistance spot or seam welding are widely used in the automotive industry to connect thin-to-thin metal materials. These technologies can be applied in case of thin-walled cold-formed construction, too. The paper presents a study on a new technical solution for lightweight cold-formed steel beams made of corrugated sheet web and built-up steel profiles for the flanges, connected by spot welding. Starting from the investigations on simple lap joint specimens tested under tensile-shear loading for various thicknesses combinations, the research concerns also metallographic aspects and investigates the response of the full-scale beams subjected to bending. Based on the obtained results, the study intends to demonstrate the feasibility and advantages of this solution compared to self-drilling screw solution. Particularly, besides the structural performance, the spot-welding solution increase significantly the work productivity and enables for automated fabrication in order to develop the mass production of these types of beams.

Laser Multi-Pass Narrow-Gap Welding – A Promising Technology for Joining Thick-Walled Components of Future Power Plants

Today, the average worldwide efficiency of coal-fired power plants stands at about 33 percent. The consistent use of state of the art technologies would enable an increase of the average efficiency of up to 47 percent and thus a sharp reduction of greenhouse gas emissions. The importance of improvements in this field becomes apparent when reviewing e.g. plans in Europe in 2017 for new power plants to be built across the continent. About 44 percent of the envisaged 153 gigawatts are still to be generated by fossil-fuel power plants [1]. One technical solution is to increase the steam turbine inlet temperature to 700°C. This, however, requires the use of nickel-based superalloys. Only these alloys satisfy all the requirements with regard to high-temperature, corrosion and oxidation resistance and creep behavior [2], [3]. Due to their relatively poor machinability, forgeability and high material costs compared to the steel-based alloys they are to replace, a more effective welding technology is needed to overcome the disadvantages of conventional welding technologies, i.e. large quantities of filler metal required and high energy input per unit length resulting in distortion and the potential reduction of high-temperature properties.

Integrating Fiber Fabry-Perot Cavity Sensor Into 3-D Printed Metal Components for Extreme High-Temperature Monitoring Applications

This paper reports the methods of embedding into 3-D printed metal components a fused silica capillary designed to accept an in-fiber Fabry–Perot cavity-based extreme high-temperature sensor. The components are manufactured in stainless steel (SS316) by additive manufacturing using selective laser melting (SLM). The temperature sensor consists of a standard single-mode optical fiber with the F-P sensor located at the distal end of the fiber with the fiber being inserted into the capillary. The capillary is either directly embedded into the structure during the SLM build process or brazed into the structure in between the SLM build process, and the advantages and disadvantages of these two manufacturing approaches are discussed. Temperature sensing of up to 1000 °C inside the metal with an accuracy better than ±10 °C is reported. The capillary can be directly embedded in the component, which needs to be monitored, or it can be embedded in a metal coupon, which can be attached to a component by conventional welding technology, including the use of laser metal deposition (LMD). In the case of LMD, the sensor coupon can also be fully encapsulated by over cladding the coupon.

Influence of Process Temperature on Hardness of Friction Stir Welded High Strength Aluminum Alloys for Aerospace Applications

The increasing application of innovative materials, such as high strength aluminum alloys, is challenging the manufacturing processes of the Aerospace and Aeronautics Industries. Despite this challenge the processes need to comply with high requirements regarding the reproducibility and the quality of the products. For this reason the adaption of conventional welding technologies to the new materials is considered to be difficult. Therefore, innovative welding technologies such as Friction Stir Welding (FSW) have been developed [1].This paper deals with the implementation of FSW into a new production process for lightweight dome structures of fuel tanks: Starting at temper condition O two AA 2219 plates are joined using FSW technology to form a larger blank. After that, the blanks are formed to shape using spinforming technology. The manufacturing process is accompanied by several steps of heat treatment to accomplish a finished tank-dome in temper condition T8.The studies presented in this paper aimed on finding a correlation between the process parameters and the properties of the welding seam, which are essential for the following spinforming process. For this purpose the experiments were conducted using design of experiments (DoE). The resulting hardness increase of the welding seam was chosen as target variable. Based on the acquired data a regression model was established and used to estimate optimal parameters for dome production.

Laser-Hybrid welding, an innovative technology to join automotive body parts

The design of Tail lamps has been changed dramatically since cars built. At modern lamps, the lenses are absolutely transparent and allow a direct view onto the weld seam. Conventional welding technologies, such as vibration and hot plate welding cannot compete with this demand. Focused on this targeted application, LPKF Laser & Electronics AG has developed in cooperation with the Bavarian Laser Centre a unique Laser welding technology called hybrid welding.

Preparation of graded multilayer materials and evaluation of residual stresses

It is generally difficult to join ceramics to alloys by conventional welding technologies to fabricate graded multilayer materials with various excellent engineering properties. In this study, MoSi 2 and 316L stainless steel are chosen a typical example and are joined together using the spark plasma sintering technique. To evaluate the joint quality, the interlayer system of the graded material is characterized using analysis of the residual stress by the finite element ANSYS code. The results show that dense uniformed joints can be achieved with such graded inter-layers because the coefficient of thermal expansion (CTE) of each interlayer closely matched over a wide temperature range. Such a compatibility between the graded inter-layers prevents MoSi 2 with low toughness from the occurrence of microcracks resulted from the residual stresses formed during cooling of the joint. Further theoretical analysis indicates that with the increase in the compositional distribution exponent ( P), maximum radial and axial residual tensile stress first increases and then decreases. In addition, with the increase in the number ( n) of graded layer, maximum radial and axial residual tensile stress decreases gradually.

Development of residual stress and surface cracks in laser treated low carbon steel

Scripta ME?~LLJR3iCA Vol. 25, pp. 779-784, 199! Pergamon Press plc et M.~,e~AL[A Printed in the U.S.A. All rights reserved DEVELOPMENT OF RESIDUAL STRESS AND SURFACE CRACKS IN LASER TREATED LOW CARBON STEEL B.A. Van Bmssel, H.J. Hegge and J.Th.M. De Hosson Department of Applied Physics, Materials Science Centre, University of Groningen, Nijenborgh 18, 9747 AG Groningen, The Netherlands R. Delhez, Th.H. de Keijser, N.M. Van der Pers Laboratory of Metallurgy, Rotterdamseweg 137, 2628 AL Delft, The Netherlands (Received January 17, 1991) Introduction Laser surface melting is a powerful technique to produce wear resistant layers. It combines the advantages of local hardening, alloying and high quench rates. The latter may result in new metastable phases with novel tribological properties. Despite these advantages laser melting may produce residual stresses in the surface layer which may affect the wear performance and the sensitivity to fatigue and fracture. As is known from conventional welding technologies [ 11, local heating may cause detrimental stresses. During a laser treatment a similar situation is created and consequently residual stresses are being detected [2,3,41. In former studies however average stress intensities are measured over a laser track. Here results of measurements will be reported which present a better insight in stress variations within and in the neighbourhood of a laser pass. Another aspect of a laser treatment is the occurrence of some cracks in the surface. In principle cracks are preferential sites for fatigue or corrosion fracture [5,6,7]. Here the main interest concentrates on the residual stresses produces by a continuous COz laser treatment and effects on fracture in a low carbon steel CK 22. With respect to cooling rate and heat input a continuous laser can be placed in between a short pulse laser and electric arc welding. Applying a short pulse laser it is possible to produce a shock wave. By rapid heating plastic deformation occurs and even evaporation of a thin surface layer [8,91. Although the interaction time of a continuous laser beam is larger, deformation effects may be expected as is confirmed by the residual stresses found. In welding heat is maintained during a time lapse which is long enough to anneal a large amount of the defects. In contrast to this, the thermal cycle of a laser treatment is much shorter, which may prevent annealing effects. Experiment