Welding Energy Research Articles

Investigations of properties in hybrid welds at 40-mm sheet thickness

Laser gas metal arc hybrid welding (laser-GMA hybrid welding) offers capabilities for improving the economy of welding in comparison to conventional welding processes due to characteristics concerning material and seam design. Research into this process was restricted to a sheet thickness range of between 6 and 12 mm for steel. However, for steel, container, vehicle or ship engineering in particular, structures (components) with large wall thicknesses are of special interest. These structures are currently welded by using the submerged arc welding process, which requires a high input of energy, welding material and working time. The objective of this project was to determine the influence of the reduction of the weld volume and energy per unit length of weld on the formation of residual stresses and their effects on the fatigue strength of hybrid welded sheets with large wall thicknesses. As a result, better qualities with regard to fatigue strength and toughness have been achieved for hybrid welded joints in comparison to submerged arc-welded joints for wall thicknesses of 40 mm.

Ultrasonic spot welding of Al/Mg/Al tri-layered clad sheets

Solid-state ultrasonic spot welding (USW) was used to join Al/Mg/Al tri-layered clad sheets, aiming at exploring weldability and identifying failure mode in relation to the welding energy. It was observed that the application of a low welding energy of 100J was able to achieve the optimal welding condition during USW at a very short welding time of 0.1s for the tri-layered clad sheets. The optimal lap shear failure load obtained was equivalent to that of the as-received Al/Mg/Al tri-layered clad sheets. With increasing welding energy, the lap shear failure load initially increased and then decreased after reaching a maximum value. At a welding energy of 25J, failure occurred in the mode of interfacial failure along the center Al/Al weld interface due to insufficient bonding. At a welding energy of 50J, 75J and 100J, failure was also characterized by the interfacial failure mode, but it occurred along the Al/Mg clad interface rather than the center Al/Al weld interface, suggesting stronger bonding of the Al/Al weld interface than that of the Al/Mg clad interface. The overall weld strength of the Al/Mg/Al tri-layered clad sheets was thus governed by the Al/Mg clad interface strength. At a welding energy of 125J and 150J, thinning of weld nugget and extensive deformation at the edge of welding tip caused failure at the edge of nugget region, leading to a lower lap shear failure load.

Fatigue life estimation of ultrasonic spot welded Mg alloy joints

Lightweight magnesium alloys are increasingly used in automotive and other transportation industries for weight reduction and fuel efficiency improvement. The structural application of magnesium components requires proper welding and fatigue resistance to guarantee their durability and safety. The objective of this investigation was to identify failure mode and estimate fatigue life of ultrasonic spot welded (USWed) lap joints of an AZ31B-H24 magnesium alloy. It was observed that the solid-state USWed joints exhibited a superior fatigue life compared with other welding processes. Fatigue failure mode changed from interfacial failure to transverse-through-thickness crack growth with decreasing cyclic load level, depending on the welding energy. Fatigue crack initiation and propagation occurred from both the notch tip inside the faying surface and the edge of sonotrode indentation-footprints due to the presence of stress concentration. A life prediction model for the spot welded lap joints developed by Newman and Dowling was adopted to estimate the fatigue lives of the USWed magnesium alloy joints. The fatigue life estimation, based on the fatigue crack growth model with the global and local stress intensity factors as a function of kink length and the experimentally determined kink angle, agreed fairly well with the obtained experimental results.

Energy and bond strength development during ultrasonic consolidation

A process model was developed that couples the effects of the three adjustable ultrasonic consolidation (UC) process parameters (amplitude, force and speed) into a single term – thermal weld energy due to frictional and volumetric heat generation. Infrared thermography was used to evaluate weld energy during UC and a relationship was established between weld energy and the peel strength of ultrasonically consolidated aluminum. An optimum processing widow was identified for bonding Al 1100-0 and Al 3003-H14 based on UC processing temperature and weld time. Bonding occurred well below the material melting temperatures, confirming that thermal softening in the bulk of the material or melting are not the bonding mechanisms and that bonding takes place in the solid-state.

Characterization of ultrasonic spot welded joints of Mg-to-galvanized and ungalvanized steel with a tin interlayer

Ultrasonic spot welded (USWed) Mg-to-bare steel, Mg-to-galvanized steel and Mg-to-bare steel with Sn interlayer (placed in-between Mg and bare steel) were studied. Weak joining occurred in the USWed Mg-to-bare steel, since Mg and Fe do not react with each other. The intermetallic compounds (IMCs) of Mg7Zn3 and Mg2Zn11, which led to the failure of the joint, were largely present in the USWed Mg-to-galvanized steel joint. The introduction of a Sn interlayer in the USWed Mg-to-bare steel actively worked as an intermediate medium to join Mg to Fe, and led to the presence of a distinctive composite-like Sn and Mg2Sn eutectic structure. The lap shear strength of Mg-to-bare steel with Sn interlayer joint was significantly higher than that of the Mg-to-bare steel and Mg-to-galvanized steel joints. Failure during the tensile lap shear tests occurred mainly in the partial nugget pull-out mode in the dissimilar joints of Mg-to-bare steel with Sn interlayer. All the joints of Mg-to-galvanized steel failed from the interface (cohesive failure). The addition of Sn interlayer resulted in energy saving since the welding energy required to achieve the maximum strength decreased from 1750 to 1500J in the Mg-to-steel joints.

STRENGTH AND FRACTURE TOUGHNESS OF THE WELDED JOINTS MADE OF HIGH-STRENGTH FERRITIC STEEL

Abstract The paper presents experimental results of the characteristics of strength and fracture toughness of the material from the different zones of welded joints made of different participation of the linear welding energy. Strength characteristics and fracture toughness were determined in the weld material, in the area of fusion line, in the material of the heat affected zone and in the base material

Vibrational energy loss analysis in battery tab ultrasonic welding

In ultrasonic metal welding processes, high-frequency ultrasonic energy is used to generate friction and heat at the interface between weld parts to produce solid-state bonds. It has been observed that sufficient energy is required to produce proper bonding, while excessive energy can cause such quality issues as weld fracture and perforation. Therefore, it is important to have a product/process design in ultrasonic welding to ensure efficient energy conversion from ultrasonics to welding energy, minimizing energy loss in the process. In this work, vibrational energy loss associated with the longitudinal and flexural vibrations of the Cu coupon during ultrasonic welding is studied by applying one-dimensional continuous vibration models. To facilitate our modeling, experimental results from the free response of Cu coupon were obtained to determine the damping characteristics of the Cu coupon in the welding process. Our analysis shows that substantial energy loss can occur during welding due to the flexural vibration of the Cu coupon, especially when the overhang (the upper part of the Cu coupon extended from the anvil) of the Cu coupon resonates at or close to the welding frequency (about 20kHz), degrading the weld quality of battery tabs. This study contributes to understanding the fundamental dynamics of the Cu coupon during ultrasonic welding and its impact on weld quality.

Ultrasonic Welding Simulations for Multiple Layers of Lithium-Ion Battery Tabs

Ultrasonic welding is a solid-state bond created using ultrasonic energy. It has been used in the semiconductor industry for several decades, and more recently, in the automotive industry such as for lithium-ion battery welding. Although there existed numerical simulations for ultrasonic welding, the models were limited to two-layer and like materials stackups. In this study, finite element theories are introduced and simulation procedure is established for multiple sheets and dissimilar metal ultrasonic welding. The procedures require both abaqus/Standard and abaqus/Explicit to simulate the coupled mechanical-thermal phenomena over the entire weld duration with moderate computational cost. The procedure is verified and used to simulate selected specific cases involving multiple sheets and dissimilar materials, i.e., copper and aluminum. The simulation procedure demonstrates its capability to predict welding energy, distortion, and temperature distribution of the workpieces. Case studies of ultrasonic welding simulations for multiple layers of lithium-ion battery tabs are presented. The prediction leads to several innovative ultrasonic welding process designs for improved welding quality.

Trends in Joining Dissimilar Metals by Welding

The welding of dissimilar materials finds a wide variety of applications in the fields of industrial construction and manufacturing, where the characteristic features of the different materials are optimized for the desired application to result in cost effectiveness and value addition. Non-fusion welding methods such as solid state welding and high energy beam welding are more popular for welding dissimilar metal combinations, due to fewer complications, than fusion welding, which melts the base metal and forms brittle intermetallic compounds (IMCs) that may lead to failure. Various factors have to be considered when assessing the feasibility of welding dissimilar metals and producing a sound weld joint. This paper presents a broad classification of the most commonly used welding processes for dissimilar materials, discusses some of the commonly used welding processes with examples of some common material combinations, critical factors for good welding, and practical difficulties arising from the physical and chemical properties of materials. From the findings, it can be inferred that continuous improvement and research is still required in the field of dissimilar metal welding, particularly in the light of increasing demand for tailored material for modern engineering and industrial applications.

State of the art of electromagnetic energy for welding and powder compaction

The innovation of advanced materials and their application to engineering structures can be related to their ease of fabricating defect-free parts. The identification of various energy sources has resulted in various new processing techniques in manufacturing and electromagnetic energy is one which offers promising qualities for high-velocity forming, welding, and compaction of metals. Bimetallic joint designs were proposed in automobiles to reduce the weight and to take advantage of properties of different metals in the same construction. Joining by fusion is impossible in certain cases due to huge differences in melting point, thermal conductivity, volumetric specific heat, and coefficient of thermal expansion. In the present study, magnetic-pulse welding of a Cu/Al joint and an ODS alloy is investigated. The formation of intermetallic phases and interface morphology is presented along with a quantitative analysis for temperature in the Al/Cu joint. Also, initial investigations on the application of electromagnetic energy for compaction of aluminum powders are reported.

Effect of welding energy on interface zone of Al–Cu ultrasonic welded joint

Ultrasonic welding is attracting increasing attentions in joining of dissimilar materials. The effect of welding energy on joint strength, failure behaviour and microstructure of Al–Cu ultrasonic welded joint has been experimentally investigated. The results showed that joint strength increased with welding energy initially and reached its maximum at 1000 J, then dropped significantly instead. Meanwhile, the failure mode changed from interfacial debonding to nugget pullout, and then back to cleavage failure. Various microstructures with different morphologies and properties were also observed at the interfacial region. At lower energy, the joint was only partly bonded by numbers of dispersed microbonds. A swirl-like structure appeared at the weld interface and led to a mechanical interlocking between the materials at higher energies (∼1000 J). However, cavity defects and intermetallic compound (IMC) were more likely to form under excessively high energies. A 0·5 μm thick IMC layer with dominant phase of Al4Cu9 was found in 2000 J joint.

An analysis of the welding-induced deformation of ship panels using a statistical tool

Abstract This paper proposes a practical way to predict the welding-induced deformation of 5-mm-thick steel ship panels prefabricated in a Polish shipyard, developed by means of a number of experiments and a body of data collected on the butt welding line using the submerged arc welding technique. The program of the experiments was so designed as to test different welding energy conditions as well as pressure values generated by the devices used during the welding. Subsequently, different welding trials were carefully carried out and data collected to find the most important parameters which contribute to welding deformation. The data obtained were analysed using the Design-ExpertR statistical software, and consideration was given to the data arrangement method that would allow for the most appropriate description of the welding deformation. As a result of the foregoing efforts, an approach to predicting the welding deformation, based on a numerical equation including the main welding parameters, was developed. The accuracy of the equation was partially evaluated and the results turned out to be satisfactory, as the actual and the predicted values were comparable. Another important advantage achieved was the arrangement of data used to compute the welding deformation.

Avaliação do campo de tensões residuais por difração de raios - X utilizando o método do sen²ψ em revestimentos metálicos do aço inoxidável E308-L

A aplicação por soldagem de revestimentos metálicos de aços e ligas nobres resistentes à corrosão é uma alternativa bastante razoável economicamente frente à fabricação de componentes maciços nestas ligas. Entretanto há uma carência de informações sobre as alterações mecânico/metalúrgicas causadas pelos ciclos térmicos de soldagem quando da aplicação destes revestimentos, principalmente sobre a influência sobre o nível de tensões residuais , que é mister no entendimento do fenômeno da corrosão assistida por tensão. O objetivo deste trabalho foi avaliar o nível de tensões residuais superficiais em revestimentos do aço inoxidável AWS E308-L T-1 aplicados pelo processo de soldagem ao Arco Elétrico com Arame Tubular sobre chapas do aço ASTM A36. As medições das tensões residuais foram realizadas por um difratômetro portátil de raios - X na superfície dos revestimentos e os principais resultados obtidos foram que a natureza das tensões residuais na superfície dos revestimentos sempre se apresentou compressivas e não observou-se uma linearidade da magnitude das tensões residuais em função da energia de soldagem.

Ultrasonic spot welded AZ31 magnesium alloy: Microstructure, texture, and lap shear strength

The structural application of ultra-lightweight magnesium alloys inevitably involves welding and joining. A solid-state welding – ultrasonic spot welding (USW) – was conducted on AZ31B-H24 Mg alloy sheet by varying a key parameter of welding energy in this study, aiming to identify the changes in the microstructure, crystallographic texture, and lap shear tensile strength. The grain size was observed to increase with increasing welding energy. Crystallographic texture determined via X-ray diffraction showed a significant change that corresponded well to the change in the deformation and recrystallization mechanisms of the Mg alloy. The lap shear strength first increased with increasing energy input, reached the maximum value at a welding energy of 2000J, then decreased. The welds generally fractured along the joint interface when the welding energy was lower than 2000J, while fracture occurred at the periphery of the joint (button pull-out) for the samples made with an energy input of higher than 2000J.

Influence of Surface Remelting Process on Corrosion Resistance of Welding Joints for SUS304 Stainless Steel by Electrode Arc Welding

The electrochemical corrosion tests of SUS304 stainless steel joint which was welded by electrode arc welding show that. The welding energy has obviously effect upon corrosion resistance of welding joints. The welding current directly influences the corrosion resistance of heat affected zone (HAZ) of welding joint. The Surface of joints was remelted by the micro-plasma arc and argon arc process. It is suggested that corrosion resistance of welding joint was improved obviously after remelting. The main reasons for improving the corrosion resistance of welding joint may be that grain refined, chromium oxidation film formed and elements diffusion inhibited by arc-remelting process.

Significance of electrode stick-out when welding with flux-cored wires

Electrode stick-out is a parameter which makes it possible to change welding energy without changing the quantity of deposited metal delivered to a welding puddle. It is particularly important when welding with flux-cored wires. Knowledge of its impact on welding parameters and formation of weld geometry is very useful when making fillet welds of small thicknesses. Understanding the mechanism of electrode stick-out's impact on weld geometry helps to avoid many problems when welding.

Energy Analysis in TIG Welding Process

Abstract An analysis of energy utilization during TIG welding process has been reported in this paper. Fifteen samples of three different diameters of pipe pieces of ASTM A 106 Gr. B, seamless type and API 5LS Gr. B, spirally welded type, are selected for experimentation. The temperatures on the external surface at different locations on each of these seamless pipes (of different diameters) during welding have been measured with the help of electronic pyrometers. The amount of total electrical energy input during welding has been recorded in the wattmeter. The convection and radiation energy losses, that take place from the surface of the pipe piece, have also been determined by using suitable mathematical expressions developed for the purpose. An overall energy balance is carried out taking into account the convection heat loss, the radiation heat loss and the unaccounted loss, for each sample. Then the variation of the ratio of the percentage of unaccounted energy loss to total weld energy input against total weld energy input has been plotted. From the graphs it is seen that with increase in diameter of the pipe and with rise in total weld energy input, the percentage unaccounted energy loss gradually decreases.

Study on Squitter Pulsed Welding Repairing Technology of ZL105 Alloys

An experimental investigation of ac pulsed argon arc welding of the ZL105 alloy was carried out under the condition of existed the defects of the high temperature, the thermal deformation. The surface morphology, microstructure and temperature field of the surfacing layers were investigated. The results showed that the heat accumulation of squitter pulsed welding was less, and with smaller HAZ, crystal grains were thinner in the same conditions. Compared with argon arc welding, the energy of squitter pulse argon arc welding acted on the matrix was less but more centralized, the whole HAZ temperature raised slowly.

Improving weld strength of magnesium to aluminium dissimilar joints via tin interlayer during ultrasonic spot welding

Welding of magnesium to aluminium alloys is enormously challenging due to the formation of brittle Al12Mg17 intermetallic compounds (IMCs). This study was aimed at improving the strength of dissimilar joints of AZ31B-H24 magnesium alloy to 5754-O aluminium alloy by using a tin interlayer inserted in between the faying surfaces during ultrasonic spot welding. The addition of tin interlayer was observed to successfully eliminate the brittle Al12Mg17 IMCs, which were replaced by a layer of composite-like tin and Mg2Sn structure. Failure during the tensile lap shear tests occurred through the interior of the blended interlayer as revealed by X-ray diffraction and SEM observations. As a result, the addition of a tin interlayer resulted in a significant improvement in both joint strength and failure energy of magnesium to aluminium dissimilar joints and also led to an energy saving because the optimal welding energy required to achieve the highest strength decreased from ∼1250 to ∼1000 J.

The effect of high strain rate deformation on intermetallic reaction during ultrasonic welding aluminium to magnesium

High power ultrasonic spot welding (USW) is a low heat input solid-state joining process that may offer a solution for welding difficult dissimilar-material couples, like magnesium (Mg) to aluminium (Al) for automotive body applications. However, the high strain rate dynamic deformation in USW has been claimed to accelerate inter-diffusion rates in dissimilar joints. The interfacial reaction between Al, AA6111, and Mg AZ31 alloys has been studied as a function of welding energy. For the optimum welding condition of 600J (0.4s) the reaction layer thickness was already ∼5μm thick. Intermetallic reaction centres were found to nucleate within microwelds at the interface at very short welding times and spread and grow rapidly to form a continuous layer, composed of two sub-layers of Al12Mg17 and Al3Mg2. Interface liquation was also found for longer welding times at temperatures below the recognised lowest eutectic reaction temperature in the Al–Mg binary system. Modelling has been used to show that the solid state reaction kinetics were over twice the rate expected from parabolic growth predictions made using rate constants obtained under static test conditions. The reasons for this discrepancy and the depressed melting reaction are discussed.