Papers by Keyword: Welding Parameters

Abstract: Welding is a widely used and effective method of joining metals. However, serious challenges are often encountered in the process due to welding distortion. Distortions result from the thermal expansion and shrinkage of metals during the welding process. This review paper focuses on the mechanisms associated with welding distortion and various mitigation techniques adaptable by fabrication industries. Whereas full prevention of distortion is unattainable with a finite geometric accuracy, it can essentially be controlled to minimize the undesired impact of distortion on the geometric integrity, hence increasing the manufacturing efficiency and decreasing the production cost. This paper categorizes distortions into out-of-plane and in-plane deformation modes and describes the factors which influence distortions - welding parameters, sequences, and material properties. Furthermore, a review of traditional and novel mitigation strategies, such as the optimization of welding parameters and improved determination and prediction of the welding sequence schedule. In this review, based on the synthesis of current publications, efforts have been made to guide fabrication industries in determining appropriate procedures and parameters to be selected according to job requirements, with the sole aim of offering better weld quality and lowering of manufacturing cost.

Abstract: This research describes the numerical simulation of welding residual stresses (WRS)induced by Metal Inert Gas (MIG) welding, explicitly emphasizing the role of initial conditions. MIGwelding is a widely and commonly adopted process in different industries due to its strength andefficiency; however, it generates welding residual stresses that can influence welded components'structural integrity and performance. The numerical simulation calculates various initial conditions,such as pre-existing stresses, temperature variations, material characteristics, and so on, to model thewelding process accurately and with accurate results. By using finite element analysis or numericalsimulation, this study predicts and estimates the intensity and distribution of welding residual stressesin welded joints for optimizing welding parameters to reduce adverse effects on welded structures. Acomparison between non-destructive testing, such as X-ray diffraction (XRD) measurements andnumerical simulations, shows good agreement in assessing residual stresses and validating theaccuracy of the numerical model. Based on the numerical simulation software, the numericalcalculation and analysis of residual stress field under different preheating temperatures for pipewelding were carried out in this paper. The effects of different preheating temperatures on post-weldresidual stress were mainly studied. This approach enables comprehensive calculation of stressdistributions, including axial and hoop stresses across different weld pipes on the surface orientations,offering insights into critical stress areas and potential failure points. These findings demonstrate theutility of numerical simulations as an effective tool for enhancing welded structure design.

Abstract: Friction stir welding (FSW) refers to a solid-state welding method specifically used for joining low-melting-point metals that yields an exceptionally strong joint and low thermal distortion. There are various conditions and factors in FSW which have the effect on weld quality such as rotational speed and plunge rate. This research project is focused on determining the optimal parameters of the FSW process on aluminum sheets grade 6061-T6, using CNC as the main welding machine. The design of experiments employed the Taguchi method, using two essential welding parameters: rotation speed (RPM) and welding speed (mm/min). The ultimate tensile strength and microhardness values (Vickers) of a welding joint from each experiment were used to find the optimal welding conditions. The experimental results show that FSW of the two aluminum sheets with the rotational speed of 1750 RPM and welding speed of 900 mm/min yields the highest mechanical properties of the weldment having the ultimate tensile strength of 304.29 MPa and microhardness (Vickers) of 74.12 HV.

Abstract: In the field of metallurgy, joining dissimilar metals poses a significant challenge due to differences in their physical and chemical properties. One such combination that has gained attention is the joining of AISI 304 steel and Ti Grade 2. These two metals have unique characteristics that make them ideal for various applications, but their differences in thermal conductivity, melting points, and chemical reactivity make achieving a strong and durable joint challenging. Numerical simulations are currently widely used to predict the behaviour of materials during the joining process, as well as to optimize welding parameters in order to achieve a sound weld. In this study, the temperature fields during laser welding of 2 mm thick plates of AISI 304 steel and Ti Grade 2 were analysed based on the numerical simulations of the welding process using ANSYS software. A simulation model for the production of butt joints was developed to assess the impact of laser welding parameters, including laser power, welding speed, and laser beam offset towards the AISI 304 side, on the temperature distribution and weld-pool characteristics. The moving laser heat source was modelled using the conical model with a Gaussian distribution of the laser beam power. The material properties of AISI 304 steel and Ti Grade 2 were calculated as a function of temperature using JMatPro software. The cooling of welding plates by convection and radiation to the argon shielding gas and surrounding air was taken into account using a boundary condition of the third kind. Using the Design of Experiment (DoE) approach, the influence of technological parameters such as welding speed and power on the size of the molten zone on the top and root of the weld was analysed. An optimization of welding parameters was performed, resulting in a surface that represents a basic estimate of the location of admissible solutions in the design space. The results from the numerical simulation and the DoE experiment were compared, and then appropriate technological parameters were proposed for experimental laser welding of the considered dissimilar metals.

Abstract: Welding of dissimilar alloys, specifically that of titanium (Ti) and nickel (Ni), poses numerous challenges due to their significant differences in properties. This review paper aims to provide a comprehensive overview of the challenges associated with the welding of Ti alloys to Ni alloys and explore welding techniques, especially Tungsten Inert Gas (TIG) welding, Metal Inert Gas (MIG) welding, Laser beam welding, Laser-Arc hybrid welding and friction stir welding processes employed in this context. The challenges primarily involve the formation of brittle intermetallic phases, which can compromise joint quality. Additionally, issues such as thermal distortion, oxidation, and corrosion resistance further complicate the welding process. The paper also highlights recent advancements and innovations in dissimilar welding, such as the use of hybrid welding processes and advanced filler materials, to address the challenges and enhance joint performance. The knowledge shared in this review can guide future research and developmental efforts aimed at improving welding techniques, joint quality, and overall performance of Ti to Ni alloys welds.

Abstract: Resistance spot welding (RSW) is still the ideal joining method in the automotive industry. Mostly steel sheets are used in the car body, so overlap and layering are required for welding or riveting, as spot welding provides simultaneous clamping force with interfacial welding to ensure the required strength and quality. A fundamental understanding of heating and cooling rates in thermal distributions is essential for predicting microstructure formation in the weld and the heat-affected zones (HAZ) of RSW joints. The ability to measure the heat cycle in the RSW process can be valuable in weld control and welding parameter optimization. RSW parameters can be optimized through tensile shear tests and microscopic investigations. Heat cycle measurement (HCM) demonstrates the welding consequences in terms of the change in mechanical properties and microstructural formations. The accuracy of cooling rate measurements including t_8/5 cooling time is very important to predict the microstructural evolution in the HAZ, however, the thermocouple measurement raises numerous challenges due to the high temperature gradient and small weld and HAZ size. During our investigations heat cycle measurement has been conducted experimentally by a K-type thermocouple. The data logger is connected to the output of the thermocouple for recording the voltage to measure the temperature distributions as a function of both time and position during the welding process. Measurement results of 1 mm thick martensitic MS1400 steel overlapped RSW joints are discussed, and the HCM curve of heating and cooling rates of the spot-welding process is presented. The heat cycle during RSW was measured with two different welding parameter combinations. In addition to welding current, welding time, and electrode force, pulsation has shown disparate curves. Numerous experiments have been attempted to measure the heat cycle in HAZ sub-zones due to the difficulty of positioning the thermocouple accurately, uppercritical HAZ, intercritical HAZ, and subcritical HAZ were investigated and measured in both welding parameter combinations. Difficulties were encountered in the experimental work as a result of the instantaneous welding time and the vibration resulting from the passage of alternating electrical current between the two electrodes. A magnetic field is generated that affects the thermocouple measurement and appears as a noisy curve that is filtered out and smoothed. Joule heat, interfacial heat generation, and cooling effects of electrodes are also considered in the experiment.

Abstract: Resistance spot welding (RSW) is one of the most common welding methods for steel sheets, as it is mainly used to join the automotive body structure parts. Different types of ultra-high strength steels (UHSS) have become widely used in the automotive body to obtain the required demands such as lower car weight, improving crashworthiness behavior, and enhancing strength–ductility combination. Martensitic UHSS belong to the highest grades width their tensile strength above 1000 MPa. During the lifetime of the vehicle cyclic loading generally occurs, therefore the optimization of welding technology should be performed considering the fatigue resistance of the welded joints. In our research 1 mm thick standardized lap shear sheets of martensitic MS1400 steel were welded by a TECNA 8007 RSW equipment with two different welding parameter combinations. The idea was to analyze the effect of welding and pulsation parameters on joint properties under static and cyclic loading. The welding parameters have been calibrated to produce the same weld nugget size for both technological combinations. Macroscopic, hardness, and tensile-shear tests were carried out to determine the fundamental mechanical characteristics of the RSW joints. The relation between the weld nugget microstructure and mechanical properties was explored. The high cycle fatigue (HCF) tests were performed on an MTS 810.23 universal electro-hydraulic materials testing system. A statistical approach was applied during the preparation and evaluation of the investigations, which increased their reliability. Measured and analyzed data of the lap shear welded joints, prepared by different technological parameters, were compared and discussed. The parameters of the HCF experiments were calculated considering the Japanese testing method (JSME S 002-1981). In most of the samples it was observed from both welding parameter combinations that the fatigue cracks initiate and grow in curvature shape in the softened part of the heat-affected zone towards the base metals in both directions symmetrically. A slight difference was observed in the HCF resistance of the welded joints prepared by different welding parameters.

Abstract: Resistance Spot Welding (RSW) is widely employed in automotive, electronics, furniture, Coach building and package industries. Although various spot weld methods, such as Friction Stir Spot Welding, MIG Spot welding, Laser Spot welding and Ultrasonic Spot welding are in use, Resistance spot welding is a versatile and easy method to adopt in simple fabrication shop. It is well known that various factors significantly influence the spot size and its quality. Designers, while selecting RSW process are particularly interested in fixing the appropriate spot size and pitch distance for a specific application. Against the above background, this study has been carried out to arrive at desired spot size by varying the parameters using a simple shop-floor spot welder which is readily available in any fabrication shop. Three levels of power input, three levels of welding current time and many levels of weld cycle time have been adopted for 2mm thick low carbon steel sheet of IS 513 grade. A novel technique has been developed to apply adequate torque to shear the spot weld joint without any damage or distortion. Spot size has been determined by using vernier and profile projector. The nugget quality has been examined using optical microscope at different magnifications. The bond strength of the spot weld has been determined by tensile shear test. By adopting this simple technique, it is possible to achieve desired spot size which is defect free and having excellent penetration. Keywords: Low carbon steel sheet, Resistance Spot welding, Nugget size, welding parameters, macro & micro examination.

Abstract: In this study, MIG welding parameters were optimized by experts. The results showed that heat input affected the welding of all five specimens, and similar structural changes were observed. The part adjacent to the weld line, using low HI (BM) lower than the melting point, increased the grain size and decreased the average hardness (87 HV) at HAZ. In comparison, high HI (WZ) at melting point resulted in fine grain with a high hardness of 126.8 HV and tensile strength of 686 MPa. Nevertheless, fatigue testing revealed that the specimens suffered a brittle fracture under a slight load cycle of 104 N_f. Correlation analysis of HI, mechanical properties and optimization plot revealed the optimum HI of 363 J/mm, and the verification by fatigue testing showed the optimum load cycle of 106 N_f. However, the determination of maximum strength should be done using several techniques for more effective improvement of quality and yield using the research findings of this study.

Abstract: Reproducibility in respect to welded structures realization is one of the main requirements for a wide variety of industrial applications. One of the international tendencies regarding the use of the steel is the replacing, in critical areas, of structural steels with high performance steel, e.g. with HSLA steels. The paper presents the results of a factorial designed experimental program focused on determining mathematical correlations between the GMAW process parameters for T joints of 4mm thick steel plates of structural (S235JR+AR according to SR EN 10025-2) and hot-rolled, high-strength low-alloy (HSLA) steel plates (S420MC according to EN 10025-4), respectively. A comparison between the obtained mathematical correlations that connect the welding parameters and the main mechanical characteristics is presented. The correlations can be used for applying the optimal combination of welding process parameters for realizing the T-joints of welded products.