Showing papers on "Spot welding published in 2021"

Impact of process parameters of resistance spot welding on mechanical properties and micro hardness of stainless steel 304 weldments

Abstract: Resistance spot welding (RSW) is an essential process in the automobile sector to join the components. The steel is the principal material utilized in car generation because of its high obstruction against erosion, toughness, ease of support and its recuperation potential. Due to this, it was planned to study the mechanical properties, hardness and microstructure characteristics of RSW of Stainless steel 304.,In the present research, RSW of 304 stainless steel plates with 1 mm thickness and effect of current intensity, welding time, electrode pressure and holding time on nugget diameter, tensile strength microhardness and microstructure of the joints was investigated. The specimens were prepared according to the dimensions of 30 × 100 mm with 30 mm overlaps joint through the RSW machine. The tensile test of the specimen was carried out on a universal testing machine and microhardness of specimens measured using Vickers’s hardness tester. Taguchi L16 orthogonal array was used to scrutinize the significant parameters for each output.,It has been observed that the tensile strength of the specimen is affected by the current intensity and nugget diameter, and the weld time has a significant effect on the tensile strength. Microhardness is highly influenced by electrode pressure and holding time, as the increase in both these parameters resulted in the increase of microhardness. This is due to rapid cooling, which is done by the cooling water flowing through the copper electrodes.,This study was carried out using a copper electrode with a flat face with selected parameters and response factors. The study can be useful for researchers working on optimization of welding parameters on stainless steel.

Welding and processing of metallic materials by using friction stir technique: A review

Abstract: Friction stir technique played a vital role in recent industries as it has been utilized in welding and processing of metallic materials. Friction stir welding (FSW) is applied for joining the poorly weldable materials and enhancing the microstructure and the mechanical properties of the welded joints. Friction stir spot welding (FSSW), underwater friction stir welding (UFSW) and vertical compensation friction stir welding (VCFSW) are variants of FSW process. On the other hand, friction stir processing (FSP) is another method, whose basic principal originated from friction stirring technique, which can be utilized for manipulating the base materials by performing dynamic recrystallization on grains resulting in superior properties of the processed material. Friction stir alloying (FSA) is analogous to FSP with implanted reinforcement particles, producing surface composites. Like other fusion welding techniques, FSW process has its own defects which especially characterize the friction stir welded joints. Tunnels, voids, flash, lack of penetration, kissing bond and surface grooving are the common defects of FSW method. Since friction stirring action generates both thermal and mechanical loads beside the higher plastic deformation, finite element modeling (FEM) has been used in model and simulation this of the process. A few research gaps are pin pointed and some research recommendations are included.

Metallurgical and Mechanical Properties of Al–Cu Joint by Friction Stir Spot Welding and Modified Friction Stir Clinching

Abstract: Dissimilar joints of AA5083 and pure Cu joint are successfully produced and compared by friction stir spot welding and modified friction stir clinching with intermediate layer of Zn interlayer for the first time. Self-reacting behavior of Zn is observed to obtain sound welds resulted from intermixing in stir zone (in FSSW), refilled zone (in MFSC) and brazed zone (in both FSSW and MFSC). MFSC is used to fill the cavity of keyhole that in turn increased 40% strength of dissimilar Cu–Al joints. Presence of lamellar eutectics in brazed zone and intermetallic compounds such as Al2Cu, Al4Cu9, CuZn5 and Cu4Zn in weld zone are confirmed in Cu–Al MFSC joints.

The Role of HAZ Softening on Cross-Tension Mechanical Performance of Martensitic Advanced High Strength Steel Resistance Spot Welds

Abstract: Giga-grade martensitic advanced high-strength steels are prone to sub-critical heat-affected zone (SCHAZ) softening during resistance spot welding. The article aims at understanding the role of HAZ softening on the fracture mode, load-bearing capacity, and energy absorption capability of MS1400 resistance spot welds during the cross-tension test. The highest load-bearing capacity was obtained when pullout failure was initiated from the martensitic coarse-grained HAZ. However, more severe HAZ softening and formation of a wider softened zone, promoted at high heat input conditions, encourages strain localization in SCHAZ, promoting transition in failure location to sub-critical HAZ. This change in pullout failure location is responsible for the observed reduction in the weld peak load at high welding currents. Therefore, control of martensite tempering in the HAZ is critical to obtain strong and reliable resistance spot welds in martensitic advanced high-strength steel sheets. To preclude the detrimental effect of the martensite tempering on the weld strength, the minimum welding current, which enables pullout failure mode, should be used for resistance spot welding of MS1400 advanced martensitic steel.

Optimization of the cycle time of robotics resistance spot welding for automotive applications

Abstract: In the automobile manufacturing industry, resistance spot welding (RSW) is widely used, especially to build the car's body. The RSW is a standard and wide‐ranging joining technique in several assembling ventures, showing a wide range of possibilities for a competent procedure. Robots are commonly used for spot welding in various industrial applications. After completing assembling design, interest increases to improve the designed processes, cost‐reduction, environmental impact, and increase time productivity when all is said to be done. In this paper, the robot movement between two welding points, a path followed while spotting, gripping and payload‐carrying activities, numbers of holds, moves, and a possibility to enhance interaction between four Robots were analyzed using an offline Robot simulation software 'DELMIA‐V5'. The body shop assembly line of the SML ISUZU plant has four robots that perform about 209 welding spots in 532 sec. The optimal model reduced the whole welding cycle time by 68 sec, and after modification and proper sequencing, a12.7% reduction in cycle time was achieved. The offline Robot simulation software 'DELMIA‐V5' has good potential to produce optimal algorithms while saving precious time. It enables an organization to promote higher quality and to encourage meaningful creativity by reducing design flaws.

Optimization of postweld tempering pulse parameters for maximum load bearing and failure energy absorption in dual phase (DP590) steel resistance spot welds

Abstract: Resistance spot welds of dual phase (DP) steels are prone to low fracture toughness due to the formation of brittle martensitic structure in the fusion zone (FZ). In-process tempering of martensite via applying second pulse current is considered a new pathway to improve mechanical performance of the welds. The success of in-process tempering depends upon precise controlling the amount of heat input and uniform temperature distribution which in turn influenced by postweld tempering pulse parameters. This paper aims to investigate the effect of three postweld tempering pulse parameters such as welding current, welding time and cooling time applied after main pulse current on microstructure and mechanical properties of DP590 steel resistance spot weld. Mechanical properties in terms of peak load and failure energy were determined after performing cross tension (CT) test. Taguchi quality design based on L16 orthogonal array has been used to determine the optimum conditions for maximum peak load and failure energy. Moreover, microstructure-property relationship is also studied. The results show that at optimum conditions maximum improvement of 62% in peak load and 62.3% in failure energy is achieved in double pulse welds compared with conventional single pulse weld. It was found that improvement in peak load and failure energy resulted from (i) enhanced weld nugget size (WNS) and (ii) tempering of martensite in FZ and heat affected zone (HAZ). These factors are influenced by heat input (Q) during postweld heating cycle (PWHC) which in turn increased with increasing second pulse current and time.

High-strength Fe/Al dissimilar joint with uniform nanometer-sized intermetallic compound layer and mechanical interlock formed by adjustable probes during double-sided friction stir spot welding

Abstract: A high-strength Fe/Al dissimilar joint was successfully fabricated by double-sided friction stir spot welding (FSSW) with adjustable probes. By this technique, a flat surface on both sides of the joint can be obtained due to the double-sided shoulders and probes. Strong mechanical interlocks were introduced by the adjustable probes in the welding interface. In addition, a continuous and uniform IMC layer with a thickness as thin as about 30 nm was formed at an extremely low rotation speed due to the fresh surface induced by the adjustable probes. Consequently, a high-strength welded joint can be fabricated. Nano-beam diffraction results revealed that the 30 nm IMC layer was composed of a ternary phase of Al–Fe–Si. This novel technique was demonstrated to be effective and productive for joining dissimilar materials.

MCDM Optimization of Characteristics in Resistance Spot Welding for Dissimilar Materials Utilizing Advanced Hybrid Taguchi Method-Coupled CoCoSo, EDAS and WASPAS Method

Abstract: Resistance spot welding is the most noteworthy joining strategy used in various engineering applications, as automotive, boilers, vessels, etc, that are ordinarily subjected to variable tensile-shear forces because of the inadmissible utilization of the input spot welding factors, which chiefly cause the welded joints disappointment during the service life of the welded get together In this way, in order to avoid such failures, the welding quality of some materials like aluminum must be improved taking into consideration the performance and weight saving of the welded structure Thus, the need for optimizing the used welding parameter becomes essential for predicting a good welded joint Accordingly, this study aims at investigating the influence of the spot welding variables, including the squeeze time, welding time and current on the tensile-shear force of the similar and dissimilar lap joints for aluminum and steel sheets It was concluded that the use of Taguchi design can improve the welded joints strength through designing the experiments according to the used levels of the input parameters in order to obtain their optimal values that give the optimum tensile-shear force as the response Experimentation is planned as per Taguchi’s L9 orthogonal array Assumptions of ANOVA are discussed and carefully examined using analysis of residuals The various recent type of Hybrid Taguchi methods, ie, CoCoSo, WASPAS and EDAS-based Taguchi methods are applied to investigate the output responses of resistance spot welding operation The results revealed that the welding time and current are main affecting parameter of tensile-shear strength and nugget diameter Finally, experimental confirmation was carried out to identify the effectiveness of this proposed method Minitab 19 offer both mean analysis and S/N ratio base DOF by making suitable orthogonal array

FSSW process parameter optimization for AA2024 and AA7075 alloy

Abstract: The novelty of the present work is the investigation of friction stir spot welding between AA2024 and AA7075 aluminum plates performed by Box-Behnken technique of response surface methodology. The ...

A Comprehensive Review on Optimal Welding Conditions for Friction Stir Welding of Thermoplastic Polymers and Their Composites.

Abstract: Friction stir welding (FSW) and friction stir spot welding (FSSW) techniques are becoming widely popular joining techniques because of their increasing potential applications in automotive, aerospace, and other structural industries. These techniques have not only successfully joined similar and dissimilar metal and polymer parts but have also successfully developed polymer-metallic hybrid joints. This study classifies the literature available on the FSW and FSSW of thermoplastic polymers and polymer composites on the basis of joining materials (similar or dissimilar), joint configurations, tooling conditions, medium conditions, and study types. It provides a state-of-the-art and detailed review of the experimental studies available on the FSW and FSSW between similar thermoplastics. The mechanical properties of FSW (butt- and lap-joint configurations) and FSSW weld joints depend on various factors. These factors include the welding process parameters (tool rotational speed, tool traverse speed, tool tilt angle, etc.), base material, tool geometry (pin and shoulder size, pin profile, etc.) and tool material, and medium conditions (submerged, non-submerged, heat-assisted tooling, cooling-assisted tooling). Because of the dependence on many factors, it is difficult to optimize the welding conditions to obtain a high-quality weld joint with superior mechanical properties. The general guidelines are established by reviewing the available literature. These guidelines, if followed, will help to achieve high-quality weld joints with least defects and superior mechanical properties. Apart from parametric-based studies, the statistical-based studies (e.g., analysis of variance (ANOVA)-based studies) are covered, which helps with the determination of the influential parameters that affect the FSW and FSSW weld joint strength. Also, the optimal ranges of the most influential process parameters for different thermoplastic materials are established. The current work on the development of general guidelines and determination of influential parameters and their operating ranges from published literature can help with designing smart future experimental studies for obtaining the global optimum welding conditions. The gaps in the available literature and recommendations for future studies are also discussed.

Refill Friction Stir Spot Welding Al Alloy to Copper via Pure Metallurgical Joining Mechanism

Abstract: The current investigation of refill friction stir spot welding (refill FSSW) Al alloy to copper primarily involved plunging the tool into bottom copper sheet to achieve both metallurgical and mechanical interfacial bonding. Compared to conventional FSSW and pinless FSSW, weld strength can be significantly improved by using this method. Nevertheless, tool wear is a critical issue during refill FSSW. In this study, defect-free Al/copper dissimilar welds were successfully fabricated using refill FSSW by only plunging the tool into top Al alloy sheet. Overall, two types of continuous and ultra-thin intermetallic compounds (IMCs) layers were identified at the whole Al/copper interface. Also, strong evidence of melting and resolidification was observed in the localized region. The peak temperature obtained at the center of Al/copper interface was 591 °C, and the heating rate reached up to 916 °C/s during the sleeve penetration phase. A softened weld region was produced via refill FSSW process, the hardness profile exhibited a W-shaped appearance along middle thickness of top Al alloy. The weld lap shear load was insensitive to the welding condition, whose scatter was rather small. The fracture path exclusively propagated along the IMCs layer of Cu9Al4 under the external lap shear loadings, both CuAl2 and Cu9Al4 were detected on the fractured surface on the copper side. This research indicated that acceptable weld strength can be achieved via pure metallurgical joining mechanism, which has significant potential for the industrial applications.

Modeling of Phase Transformation Kinetics in Resistance Spot Welding and Investigation of Effect of Post Weld Heat Treatment on Weld Microstructure

Abstract: In recent years, the usage of dual phase (DP) steels, transformation induced plasticity (TRIP) steels and boron steels in some auto body parts has become a necessity because of their strength and lightweight. Resistance spot welding (RSW) being a process were steel is heated and cooled in a very short period of time, the resulting weld nugget is generally fully martensitic, especially in the case of DP, TRIP and boron steels but that also holds for plain carbon steels as AISI 1010 grade which is extensively used in auto body inner parts. Martensite in is turn must be avoided as much as possible when welding steel because it is the principal source of brittleness. Thus, this work aims in finding a mean to reduce martensite fraction and increase phase diversity in weld nugget. The prediction of phase transformation during RSW has been done. Simulations have been performed for 2 mm AISI 1010 sheets and results show that the application of post weld heat treatment leads to the reduction of martensite fraction, and formation of ferrite and bainite in the nugget. Welding experiments have been done in parallel and experimental weld nugget geometry is in good agreement with simulation results.

In-depth microscopic characterisation of the weld faying interface revealing stress-induced metallurgical transformations during friction stir spot welding

Abstract: Friction stir spot welding (FSSW) is a solid-state welding process, wherein the properties of a weld joint are influenced by the state of friction and localised thermodynamic conditions at the tool-workpiece interface. An issue well-known about FSSW joints is their lack of reliability since they abruptly delaminate at the weld-faying interface (WFI). This study explores the origins of the delamination of multiple lap welded aluminium alloy (AA 5754-H111) sheets joined by FSSW at different rotational speeds typically used in industry. Experimental techniques such as the small punch test (SPT), Vickers hardness test, Scanning Electron Microscopy (SEM), Scanning Acoustic Microscope (SAM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX) and Frequency-Modulated Kelvin Probe Force Microscopy (FM-KPFM) were employed. The experimental results revealed that a complex interplay of stress-assisted metallurgical transformations at the intersection of WFI and the recrystallised stir zone (RSZ) can trigger dynamic precipitation leading to the formation of Al3Mg2 intermetallic phase, while metallic oxides and nanopits remain entrapped in the WFI. These metallurgical transformations surrounded by pits, precipitates and oxides induces process instability which in turn paves way for fast fracture to become responsible for delamination.

Performance Analysis of Nano Silicon Carbide Reinforced Swept Friction Stir Spot Weld Joint in AA6061-T6 Alloy

Abstract: Swept friction stir spot welding (SFSSW) is one of the preferred welding methods used in joining metals. The application of this joining process is limited by path deviation, insufficient tool plunging and vibrations caused by high torque and force during the welding. In order to improve the weld strength and weld repeatability, the optimum process parameters of SFSSW of aluminium 6061-T6 alloy were investigated through Grey rational analysis. Initially, Taguchi L16 array consisting of diameter of guide hole, tool rotational and traverse speeds was developed and experiments were conducted by filling guide hole with Silicon Carbide nanoparticles. Grey relational analysis of the experiments reports that guide hole diameter = 3 mm, rotational speed = 1600 rpm and traverse speed = 20 mm/min are found to be optimal parameters for attaining the maximum lap shear strength and hardness. The cause-and-effect analysis of data reports that the amount of SiC added to the guide hole is the most significant factor influencing the weld strength. Furthermore, mechanical and metallurgical characterisation of weld samples prepared at optimum condition were compared with neat samples. The microstructural analysis of stir zone and the fractured area were also presented. The addition of nanoparticles and use of predicted optimum weld condition results homogeneous distribution, refined grains in the stir zone that causes a noteworthy increase in the weld strength.