Sheet Metal Welding Research Articles

Design and Development of a Portable Resistance Spot Welding Machine for Small-Scale Industries

Resistance spot welding (RSW) is a commonly used process in a variety of fields such as automotive, aerospace, household, furniture, and railway for welding sheet metal parts. These industries further demand a welding machine that is portable and versatile in terms of where it can be utilized, such as, among others, remote locations, and is cost and energy-efficient, reliable, and highly efficient performance-wise. With this aim, the work develops a portable spot-welding machine with specific specifications, of an electrode of 0.394 inches in diameter and 10 inches in length, made of copper, and transformer specifications of 6 V-1500 A with 7 variable current settings. This machine is designed to provide accurate, consistent, and reliable welding readings. Additionally, the machine works on an AC supply of 220 volts, making it easily usable. The machine is found to be cost-effective, with a development cost of only 6100 rupees. It has also been found to be reliable and effective in welding up to two 3 mm mild steel plates under different currents, resistivity, and voltage settings. The machine is simple to operate and user-friendly and with a compact and lightweight design, it is highly versatile and easy to operate for a wide range of welding applications.

Laser beam welding of high thickness sheet metal with highly dynamic beam shaping

Lasers with highly dynamic beam shaping have recently become available on the market. This article examines the question of whether it is possible to influence the welding result in terms of the weld seam formation (upper bead, root) and the microstructure with very high beam oscillation. Four different beam shapes are tested at different frequencies (up to 100 kHz) on material AH36 with a thickness of 8 mm.

Effect of placement configuration on the microstructure, porosity and mechanical performance of dissimilar remote laser welding of additive manufactured AlSi10Mg alloy and conventionally manufactured 1050 aluminium sheet

Additive manufacturing (AM) has gained significant attention in automotive applications, while the low weldability of AM material poses challenges when assembling AM materials with conventionally manufactured materials. This study investigated the laser welding of AM AlSi10Mg and AA1050 sheet metal in an overlap configuration, specifically focusing on the impact of placement configuration of two materials on weld properties. This aims to provide valuable insights for optimizing the localized geometry of AM components to enhance the joint performance. Results showed that positioning AM AlSi10Mg on top leads to a higher weld penetration and higher Si content within the molten pool, especially in the upper sheet. Additionally, weld zone grain structure was greatly influenced by alternating the placement configuration, where welds with AM AlSi10Mg on top exhibiting more equiaxed grains in the weld centre and refined columnar grains near the fusion boundary of upper sheet. Furthermore, significantly reduced weld porosity was determined by positioning AM AlSi10Mg at the bottom (3.2 ± 0.4 %∼7.1 ± 0.9 %) compared to placing it on top (16.9 ± 0.9 %∼20.1 ± 0.9 %) in all scenarios ranging from full penetration to partial penetration. This can be related to the fact that the hydrogen bubbles originating from AM AlSi10Mg experienced a shorter exposure in the molten pool, limiting the merging and growth of small bubbles. However, a slightly lower joint strength was determined in welds with AM AlSi10Mg at the bottom which may be due to the plastic deformation incompatibility between large columnar grains in the fusion zone and the fine grains in the as-printed material.

Study on mechanical and microstructural properties of advanced high-strength welded sheet metal

Continuous research is carried out in the automotive industry to decrease the weight of automobile bodies without reducing durability. For this purpose, the use of welding sheet metal is one of the successful techniques. Welded sheets are formed by combining two or more flat materials with different thicknesses and different mechanical properties, using the welding method, before being shaped in order to provide superior properties. This situation requires more attention during the shaping stages. It is important to calculate the pressures to be applied to the welding areas and to apply the shaping steps in a way that will not reduce the material strength. For this reason, the production stages of the dies to be used in the manufacture of these parts are just as important. In this study, an innovative die design is carried out for the production of welded sheet metal. The microstructure and mechanical properties of the welded sheet formed by the die were examined. The effect of the forces applied to the welding areas on the material and the mechanical properties of the materials of different thicknesses were determined. Within the scope of the study, microstructure analysis, hardness and tensile tests were carried out and the results were examined. When the results obtained were examined, it was seen that the strength and hardness values of the samples obtained from the welded area were higher than the other areas.

Design & manufacturing of cooled immersion tubes for divertor bolometry in Wendelstein 7-X

After the successful Operation phase 1.2b experimental campaign Wendelstein 7-X was upgraded for steady-state operation with pulse duration of 1800s and up to 18 GJ energy input. Heat management in steady-state requires active water-cooling of the in-vessel components, in particular if temperature-stable environments are required for diagnostics such as bolometry. Two new, actively cooled bolometer immersion tubes (IT) with two camera housings (5–7 detector heads each) have been designed and manufactured for W7-X. By installing the two IT in the same module viewing the poloidal plasma cross-section from opposite sides provides a complete coverage with lines of sight. This allows tomographic reconstruction of the plasma radiation, but make accurate knowledge of the diagnostic geometry essential. This makes accurate manufacturing and assembly essential.An additional design challenge in W7-X is the suppression of Electron Cyclotron Resonance Heating (ECRH) stray-radiation as well as undesired particle deposition from plasma deposition, dust and boronization in the interior of the IT. This was realized with a welded sheet metal shell and a shutter system for each IT. In the design of the cooling channel, a high degree of temperature stability in particular for the detector heads was required. This resulted in complex components that were challenging for conventional manufacturing approaches. Selective laser melting might be an improvement for future projects.

Optimization of Welding Parameters in MAG Lap Welding of DD13 Sheet Metal with Taguchi Method and FEM Analysis

In this study, DD13 sheet materials used in automobile swing manufacturing were welded with GMAW (Gas Metal Arc Welding) welding method with different parameters such as welding method, welding amperage, and welding speed. The optimized value of the welding parameters, which will give the lowest hardness value in the weld seam hardness, was calculated by the Taguchi method. In addition, the heat input values that are thought to affect the hardness change were calculated, and the results were used to interpret the hardness change and Taguchi optimization values. After the experimental studies, the optimized value was compared with the actual results, and the verification test was performed. As a result of the optimization process, the lowest hardness value was estimated as 172.98 HV0.1 in MAG welding performed at 420 min/mm welding speed, 290 A, and 33.6 V parameters. The validation test result was found to be consistent with 173.4 HV0.1. Based on these values, finite element analysis (FEM) was performed with Simufact Welding 8.0 software. As a result of the investigation, the weld macrostructure, thermal changes, and the amount of distortion were examined. The results obtained are in agreement with the validation experiments.

Comparing the sheet metal welding performance of different lasers

AbstractLaser technology has developed progressively over the last sixty years. It is commonly used for traditional processing applications, for example for cutting, marking and welding, especially in industries such as aerospace that are exploiting the use of advanced materials.

Emission of scattered radiation from the process zone of welding processes using high-power diode lasers

Highly efficient manufacturing processes in which innovative technologies are continuously integrated are essential for a globally competitive European maritime industry. Promising optimization potential lies in the welding of thick sheet metal. The use of new high-power diode lasers with output powers of up to 60 kilowatts can replace conventional welding processes and significantly improve welding quality and efficiency. In addition to the welding process development with extremely high laser powers, ensuring laser safety is a major challenge for adequate employees’ protection. This work aims to investigate the spatial distribution of laser radiation backscattered from the laser process zone into the hemisphere above the sheet metal. The results of the scattered radiation measurements performed are used to estimate the amount of thermal energy introduced from the laser process zone into a possible protective shielding against the scattered radiation. The derived maximum temperatures finally allow a suitable dimensioning of the shielding.

A mathematical model for thinning rate prediction of sheet double hydro-forming

Double sheet blank hydro-forming (DSBH) is a technology for forming hollow parts with complex shapes. The pair of workpieces is deformed and shaped by the high-pressure liquid inside. The material is thinned after hydraulic forming, which significantly affects the quality of the product, especially the fields with high requirements, such as the automotive and aerospace industry. The goal of optimizing input process parameters to ensure that the level of thinning into a product is within the allowable limit is posed by this study. This study considered blank holder force, forming fluid pressure, and relative thickness as candidate factors for optimization using Response Surface Method (RSM). The spherical parts were formed by the DSBH method of welding blank pairs of DC04 carbon steel material based on theoretical analysis, experiment solution, and experiment to verify the results. Experiments were performed with different combinations of parameters using the Box-Behnken design. This paper presented a mathematical model that helps determine material thinning rate according to these three process parameters in the hydro-forming of spherical parts from welded sheet metal pairs. The research results can be applied to control the input parameters in the DSBH to achieve the wall thickness of the spherical part as desired by the manufacturer.

Role of Welding Current on Mechanical Properties and Microstructural Characteristics of Resistance Spot Welded Dual Phase Steel Joints

Electrical Resistance Spot Welding (ERSW), an ideal sheet metal welding process for automotive applications due to the excellent reproducibility and weld integrity of the process. Dual-phase steels, the next-generation advanced high strength steel is utilized in white body applications. This paper discusses the effect of current on mechanical properties and microstructural features of the weld nugget. Macrostructure reveals the optimal welding current as 5.5 kA for decent nugget formation with maximum penetration and less heat-affected zone. The nugget microstructure consists of lath and needle-like martensite structure in the iron matrix. The shear fracture test revealed nugget pull-out failure at the periphery. The results concluded the role of current in the penetration and nugget formation along with the softening effect, which corresponds to the nugget failure.

CO2 laser spot welding of thin sheets AISI 321 austenitic stainless steel

Purpose: The present work aims to investigate the influence of CO2 laser spot welding (LSW) parameters on welding profile and mechanical properties of lap joint of AISI 321 thin sheet metals, and analyze the welding profile numerically by finite element (FE) method. Design/methodology/approach: The weld carried out using 150 W CO2 continues wave laser system. The impact of exposure time and laser power on the welding profile was investigated using an optical microscope. Microhardness and tensile strength tests were used to evaluate the mechanical properties of the joint. Ansys software was utilized to simulate the welding profile numerically. Findings: The results revealed that 2 s exposure time and 50 W power have led to uniform welding profile and highest shear force (340 N), lower hardness gradient across the heat affected zone (HAZ) and fusion zone (FZ). Finite element (FE) analysis of the welding profile showed good agreement with experimental analysis. Research limitations/implications: The selection of laser spot welding parameters for thin sheet metal was critical due to the probability of metal vaporisation with extra heat input during welding. Practical implications: Laser welding of AISI 321 steel is used in multiple industrial sectors such as power plants, petroleum refinement stations, pharmaceutical industry, and households. Thus, selecting the best welding parameters ensures high-quality joint. Originality/value: The use of CO2 laser in continuous wave (CW) mode instead of pulse mode for spot welding of thin sheet metal of AISI 321 austenitic stainless steel consider a real challenge because of the difficulty of control the heat input via proper selection of the welding parameters in order to not burn the processed target. Besides, the maintenance is easier and operation cost is lower in continuous CO2 than pulse mode.

Study of the Manufacturability of Production and Properties of Welding Wire from Alloy 1580

The results of studies on the production of welding wires with a diameter of 2.5 and 3.3 mm from alloy 1580 are presented. To compare the manufacturability of the processing, various methods were used to obtain billets for drawing with a diameter of 8-12 mm: the traditional method of direct hot extruding (discrete); combined rolling-extruding method; and ingotless rolling-extruding method (continuous). The developed modes of bar rolling, drawing and annealing made it possible to obtain prototypes of wire in laboratory and industrial conditions. It was found that alloy 1580 is highly manufacturable both with the traditional method of pressure treatment (extruding) and with combined rolling-extruding methods. It was revealed that the application of all methods makes it possible to obtain billets with the level of mechanical properties necessary for further multi-operation processing. Based on the results of research obtained in laboratory conditions, rational drawing modes for industrial wire production have been developed. As a result of bay drawing, pilot batches of welding wire with a diameter of 3.26 and 2.47 mm from alloy 1580 were obtained, which was successfully used for welding sheet metal.

A novel field shaper with slow-varying central hole for electromagnetic pulse welding of sheet metal

Electromagnetic pulse welding (EMPW) is a high-speed welding technology of solid state, which is of great significance to the welding of dissimilar metals. As a practical welding tool, the magnetic field shaper which is placed between the metal components and an electromagnetic coil has the function of concentrating the magnetic field, enhancing the electromagnetic force around the weld zone, and protecting the electromagnetic coil. However, there is a problem of insufficient welding area when using the traditional field shaper for welding. To overcome this issue, this paper carried out a numerical simulation of the principle of the field shaper for electromagnetic pulse welding of sheet metal by the method of joint simulation by ANSYS and COMSOL. The effects of diameter and configuration of the central hole of the field shaper on the peak value and distribution of the electromagnetic force upon the sheet metal were analyzed by simulation. Based on the results of the simulation, a novel field shaper with a slow-varying central hole was proposed, which can effectively improve the peak value and the uniformity of the distribution of the electromagnetic force. In the context, a new welding coefficient R is first proposed to evaluate the welding capability of the field shaper. On the basis of simulation, an electromagnetic welding platform was built for the welding of A1060 aluminum sheet to SS304 stainless steel plate both with a thickness of 1 mm. The experimental results show that the proposed field shaper can effectively improve the size of welding region.

Analysis of molten pool behavior with buttonhole formation in laser keyhole welding of sheet metal

A cavity, so-called buttonhole, was observed in the molten pool directly behind the oscillating laser beam and the supplied wire by means of suitable process control. A high seam surface quality was produced in the case with the buttonhole formation. A three-dimensional heat and mass transfer model was developed to understand the effect of the buttonhole in laser keyhole welding of sheet metal with a filler wire and one-dimensional laser beam oscillation. For a given welding condition, a stable catenoid-like buttonhole was shown which helped to reduce molten pool dynamics by its self-sustainability. The buttonhole formation was sensitive to the welding parameter of the air gap.

Cross-lines laser aided machine vision in tube-to-tubesheet welding for welding height control

Thermal distortion was a major issue in sheet metal welding. One particular issue to be addressed in this work for tube-to-tubesheet welding was the resultant variation in the welding torch to work distance, referred to as welding height hereafter, which can easily cause undercuts and burn-through. Unfortunately, efforts on control of welding height which was particularly critical for tube-to-tubesheet welding were limited. This paper thus introduced a machine vision system with a cross-line laser as the structured light to measure the welding height for adaptive correction and control. To extract the ICCL (intersection coordinate of cross-lines laser) which provided the variation in welding height, an image processing algorithm was proposed that segmented regions and extracted their centers. A linear relationship between WHVV (welding height variation value) and ICCL was established by least square method. Performance was tested experimentally for the experiment platform and it was found that the static and dynamic detection error were insignificant, no more than 0.007 and 0.016 mm respectively. When WHVV = 1 mm, the compensation error of 115 tubes varied from −0.037 to +0.028 mm.

Ocena bezpieczeństwa eksploatacji spawanego rusztu prasy mimośrodowej

The fatigue strength of welds of the press body for pressing car body sheets were analysed. The FEM models of the body were prepared taking into account welded sheet metal connections. Simulation, which took into account the damage of some welds, showed insufficient stiffness of the press grate, which in consequence caused a fatigue fracture of the eccentric press shaft.

Prediction and Control of Asymmetric Bead Shape in Laser-Arc Hybrid Fillet-Lap Joints in Sheet Metal Welds

The shape and size of a weld bead - consisting of outer weld surface and inner fusion boundary - are important quality and strength attributes in sheet metal welds. The asymmetricity coupled with additional controlling parameters makes it challenging to predict the bead shape in laser-arc hybrid fillet-lap joints with use of lower order nonlinear analytical mathematical functions. An artificial neural network is designed to address the challenge, considering the welding speed, wire feed speed, voltage, current, and laser power as inputs. The experimentally obtained weld bead profiles are digitized in polar coordinates (r, θ) and thereby many input-output pairs are made available for training even with a limited number of experiments. An optimized neural network topology is presented with an assessment of reliability of simulation results. A rational approach for determining the number of coordinate points needed to accurately map the weld bead profile is an important contribution from the present investigation. The parametric study elucidates the effects of input parameters on geometry of the weld beads. The neural network exhibits the capability of capturing the process physics - demonstrated through the analysis of the weld dilution obtained from the simulation results. The welding speed and wire feed speed signifyingly affect the bead shape while the laser power has a minor impact. The laser, even though with less power, improves the weld dilution due to preheating of the base plate and stabilization of the welding arc.

Numerical and experimental analysis of vibration damping performance of polyurethane adhesive in machine operations

Machining operations inherently cause structural vibrations of the work piece and machine involved, especially during roughening operations. This clearly adversely affects the surface roughness, tolerances and tooling lifetime. These effects are even more prominent in case the stiffness of the work piece to be machined is low and machining vibration excitation frequency range strongly overlaps the range of structural resonance frequencies of the work piece. This is typically the case for lightweight (sheet) metal structures. Additional fixation is costly, time-consuming and moreover it may induce structural loading and deformation which, after finishing, causes an out-of-tolerance work piece.This work presents an alternative approach which applies Polyurethane foam adhesive bonding as a temporary measure to reduce structural vibrations during milling operations of a large welded sheet metal construction.The first part of this work analyses the actual structural vibrations that occur during milling operations. Experimental and numerical modal analysis is carried out in order to determine the excitation and resonant vibration behaviour of the sheet metal structure. A dedicated Finite Element Model (FE – model) is set up which enables the necessary insights in where and how critical vibration levels may be reduced and how the work piece supports can be optimized. The second part of the work discusses the development and application of suitable vibration dampening supports applying Polyurethane foam adhesive. For this purpose, experiments are carried out to determine the vibration dampening performance of different foam layer thicknesses. These involve hammer excitation of dedicated small-scale adhesively bonded samples. FE modelling is applied to optimize the mounting of bonded Polyurethane dampers and to predict the effect on structural vibrations during milling operations. This part extensively outlines the specific experiments involved and the strategy for modelling the viscoelastic foam dampeners in the structural numerical model in a robust but effective way. The third part describes the validation measurement campaign and extensively compares structural vibration levels before and after providing the foam dampening measures. It concludes by showing that critical vibration levels may be reduced by over 58% with the method applied.

Friction Stir Spot Welding Applied to Weld Dissimilar Metals of AA1100 Al-alloy and C11000 Copper

Friction stir spot welding is a non-conventional joining process that use for welding sheet metal and alloy as solid state process which can be used instead of electric resistance spot welding process. In this project, AA1100 Al-alloy and C11000 copper with 3 mm thickness have welded by friction stir spot welding with tapper cylinder tool made fro m high speed steel materials with pin diameter of 3 mm and shoulder diameter of 10 mm. Manual and automatic friction welding process have been applied in drilling machine with different rotational speed of 760, 1065, 1445 and 2000 mm. Heat generation, dwell time and applied load have been measured during the welding process as well as tensile test and tool depth penetration with surface quality were evaluated. The result shows that heat generated equal to 50 °C in case of automatic process and 210 °C in case of manual process. However, the dwell time that’s required to complete the welding process in case of automatic process reduced to be 14% of the time that consume in the case of the manual welding process because applied load will be twice the time of manual applied load. Moreover, the maximum tensile strength of welded plates equal to 406 MPa at rotational speed of 1065 RPM.

Evaluation of Mechanical Properties of Tailor Welded Sheet Metal Blanks

A tailor welded blank consist of two or more sheet metals which are welded together prior to forming. The sheets which are welded together may be different in size, shape and even in thickness also. The blanks may be also differing in sense of coating and material grade also. This different blanks are welded together to form in to one continuous blank. In industries since last long years the materials which are used for preparing tailor welded blanks in general are combinations of mild steel to stainless steel with different grades. Also the common materials which are used for making tailor welded blanks are generally aluminium alloys with different grades or it may be combination of aluminium and steel alloy sheets. Most tailor welded blanks today embody a multiple thickness design in order to eliminate the use of extra reinforcing components. The advantages of using tailor welded blanks are numerous, they ensure that the components are light, stronger, and provide required functionality at lower cost than parts made from monolithic pressed sheets, as well as improving structural integrity, safety and corrosion resistance in specific areas. In an automotive application, Tailor welded blanks eliminate the need for reinforcement, resulting in an overall reduction in vehicle body weight. The use of different strength or thickness in a single part can simplify the whole structure of a vehicle. Low car weight means improved fuel economy that is very important to today’s energy consumption. Decrease of automobile parts number. This paper presents the tailor welded blanks of steel alloys tensile specimens are prepared and tested through uniaxial tensile test. Determined mechanical properties of tailor welded sheet metal blanks and also studies done on those properties.