Defect-free Welds Research Articles

Study on TIG welding parameters for joining different kind of aluminium tube with a tube plate

Welding is a vital metal joining technique with a wide range of industrial uses. In this study, numerous process factors such as current, feed rate, and distance between tube and work piece, among others, were used to investigate in Tungsten Inert Gas (TIG) welding. We used Aluminum 6063 tube to Aluminum 6061 tube plate for this TIG welding. After the welding is finished, a radiographic test is performed to show any welding faults that might lead to defect-free welds. The most critical control factors that would result in better joint strength were identified to use a Taguchi L9 orthogonal matrix. Furthermore, the most relevant process parameter was determined using quantitative independent test (ANOVA). In addition, the mechanical tests were performed to determine the welding strength. The value of the best welded connection strength for tubes with holes welded at interference was found to be 318.716 MPa.

Weld Strength of Friction Welding of Dissimilar Polymer Rods Fabricated by Fused Deposition Modeling.

Friction welding (FRW) is a promising method for joining cylindrical components of dissimilar and similar polymers or metals. In particular, FRW is capable of generating defect-free welds. Fused deposition modeling (FDM) has been widely employed in the automotive industry, ranging from lightweight tools, testing models, and functional parts. Conventionally, dissimilar parts fabricated by FDM are joined by glue. However, distinct disadvantages of this approach include both low joining strength and low joining efficiency. Hitherto, little has been reported on the characterizations of weld strength of FRW of dissimilar parts fabricated by FDM. In addition, FRW of dissimilar polymeric materials is a difficult task because different polymers have different physical, rheological, and mechanical properties. In this study, the effects of welding revolution on the weld strength of friction welding dissimilar parts fabricated by FDM are investigated experimentally. It was found that the average flexural strength of dissimilar polymer rods fabricated by FRW is about 1.52 times that of dissimilar polymer rods fabricated by gluing. The highest flexure strength can be obtained by FRW using polylactic acid (PLA) and PC (polycarbonate) rods. The average impact strength of dissimilar polymer rods fabricated by FRW is about 1.04 times that of dissimilar polymer rods joined by gluing. The highest impact strength can be obtained by FRW using PLA to PLA rods.

Multivariate optimization of mechanical and microstructural properties of welded joints by FSW method

This paper investigates the microstructural and mechanical properties in the joining of aluminum sheets using the friction stir welding (FSW) method. First, the microstructural properties are investigated, and then the effect of process parameters on the grain size, defect formation, microhardness, and fracture energy is discussed. The grain size in the stir zone is remarkably refined compared to the base metal, while the microhardness is reduced due to the annealing effects of the FSW. According to the findings, the material integrity in the stir zone is the most critical aspect in determining the value of absorbed energy in the fracture test. The existence of a cavity in the stir zone severely reduces the fracture energy, while the negative effects of the weld line remnant defect on the fracture energy are negligible. For each pin profile and rotational speed, the safe window of traverse speed for defect-free joint production is widened from the conical cylinder pin to the square pin and then to the threaded pin. The ratio of rotational speed to traverse speed (w/v) is the most important parameter in determining almost all characteristics of a joint produced by a specific tool. For each type of pin profile, there is a minimum amount for this ratio, below which the defect formation is very likely to the occurrence. The lowest w/v ratio required to generate a defect-free weld with the conical cylinder pin tool is nearly 2. While that is desirably lowered to 1.6 and 1.25 for square and threaded pin tools, respectively. For all three pin shapes, the hardness value is increased by increasing the traverse speed and decreasing the rotational speed. The grain size and Charpy impact fracture energy values are also reduced by decreasing the rotational speed and increasing the traverse speed. While, a power regression curve (that is very similar to the Hall-Petch relationship) is fitted well to describe the relationship between hardness and grain size, a second-order equation is fitted to the results of fracture energy vs. hardness and grain size. Furthermore, based on the obtained results, it can be concluded that the fracture energy value is more sensitive to the pin profile compared to other outputs of this research (i.e., hardness and grain size). Using the neural network, a relationship was obtained between the input parameters of the process, such as traverse speed, rotational speed, and tool shapes, with the mechanical and microstructural properties of the joints. This relationship was then used in a hybrid multiobjective optimization to find the optimal process parameters. As the best compromise option, hybrid multiobjective optimization proposes a traverse speed of 309 mm/min, a rotational speed of 495 rev/min, and a threaded cylinder pin shape.

Investigation on thermo-mechanical performances of friction stir welding of aluminum alloys (AA6063)

In this experimental study, aluminum alloy AA6063 plates are welded with a D2 steel tool shoulder and an HSS tool pin. Three-pin profiles were used to examine the optimum material flow, and three-pin lengths were utilized to determine the best pin length for joining a 6 mm plate. The four parameters, namely rotating tool speed, transverse tool speed, pin length, and pin profile, were analyzed to obtain the optimal bending, elongation%, and ultimate tensile strength (UTS). Mechanical parameters, such as UTS and elongation percentage are evaluated between heat-treated and non-heat-treated joints. It was observed that the cylindrical and threaded pins generated defect-free welding throughout the process. The finding initially produced voids due to excessive material loss upon entering the plate but later had defect-free welding. The temperature during welding is measured at eight separate sites (four on the advancing side and four on the retreating side) using a data logger to compare heat generation in different welding situations. The effect of the annealing process on the UTS (1.97%) and the elongation percentage (40.85%) have been examined for improved weld quality. The scanning electron microscopy (SEM) results revealed that the heat-treated sample possessed superior mechanical strength and a fine surface.

Studies on Bending Properties of AA 6061-T6 Aluminium Alloy Joined By Friction Stir Welding

Presently for various engineering applications AA6061-T6 aluminum-magnesium alloys are widely preferred, which is due to its light weight and superior properties as compared to other aluminum alloys. The metal joining process is most complex in various industrial applications like automobile, aerospace, railway and marine. The Friction Stir Welding (FSW) of AA6061-T6 alloy has influenced substantial scientific and industrial importance, because it has a potential to transform the welded product with a good quality joint. In the present work AA6061-T6 alloy joined using FSW process. Observation has been made about material flow behavior and effect of process parameters on various mechanical properties and associated defects during FSW. From experimental results it can be concluded that FSW can be used to produce defect free welds, with better bending properties as compared to the welds produced by other conventional welding process.

High speed friction stir welding of AA6063-T6 alloy in lightweight battery trays for EV industry: Influence of tool rotation speeds

Present work demonstrates high speed friction stir welding (HSFSW) of light weight battery trays assembly in electric vehicle (EV). Despite of solid-state and green nature of FSW, it suffers from the relatively low welding speed. With the help of suitable tool design and machine tool parameters, we successfully achieved defect-free welds at high welding speed of 4.0 and 4.5 m/min. Good quality welds are produced in 3 mm thick AA6063-T6 extruded aluminium alloy at such a high welding speeds by implementing violent material mixing i.e., higher tool rotation speeds (3500–4500 rpm) and plunge force (8.5–10.5 kN). The HSFSW cross-section registered curious hardness profile of ‘U’ shape. HSFSW resulted softening of weld stir zone (∼60 HV) along with HAZ (∼50 HV). The highest joint efficiency of 72 % was found for the weld produced at 4.0 m/min and 3500 rpm.

Numerical prediction of various defects and their formation mechanism during friction stir welding using coupled Eulerian-Lagrangian technique

Defective weld significantly hampers the quality of the weld and selection of optimum process parameter which produces defect-free weld is an experimental tedious task. A robust numerical model capable of predicting various types of defects is required to save cost and time. In the current work, a numerical model is developed based on coupled Eulerian-Lagrangian method and the concept of Volume of Fluid is incorporated to predict defects. It is the first attempt to numerically predict and analyze various types of defects such as tunnel, void, cavity, and root defects associated with friction stir welding. Defect formation is studied by varying tool rotation speed from 600 to 1500 rpm, welding speed from 30 to 180 mm/min, and tilt angle from 0 to 3°. The tilt angle of zero degree resulted in tunnel defect and one degree resulted in void and cavity. Tilt angle of two degree produced a defect-free weld. Also, parameters with a three-degree tilt angle yielded defective welds. The defect formation mechanism is correlated with temperature history, material flow, and axial force. A process parameter window is developed indicating the defective and non-defective weld conditions.

Influence of tool rotational speed on Microstructure and Mechanical Properties of Al-Li Alloy using Friction Stir Welding

Al-Li alloy is one of the suitable materials to be used in the aerospace industry due to its unique physical, mechanical, fatigue and corrosion resistance properties. The present study investigates the effect of rotational tool speed (TRS) on force and torque and its consequences on heat input, temperature, microstructure, and mechanical properties of a 5 mm thick 2050-T84 Al-Li alloy plates in square butt joint configuration. The investigation reveals defect-free welds at TRS ranging from 600 rpm to 1400 rpm. The grain size at nugget zone (NZ) and thermo-mechanically affected zone (TMAZ) increases (10.59 µm-16.79 µm; TMAZ-AS; 12.67µm-18.96 µm and TMAZ-RS; 12.22 µm-17.98 µm) with an increase in TRS (600–1400 rpm). The high ultimate tensile strength (UTS-410MPa) and % elongation (11.15%) was observed at 1400 rpm. With the help of scanning electron microscope (SEM) analysis of tensile fracture samples, the ductile nature of tensile fracture is observed.

Modeling and optimization of process parameters for friction stir welding of dissimilar aerospace alloys AA2014 and AA7075

Aluminum alloys possess a high strength-to-weight ratio and good corrosion resistance making them suitable for various structural parts and components used in the aerospace industry. However, the principal barrier restricting their use is their weldability. This experimental study addresses the issues in joining of dissimilar aerospace aluminum alloys. In this work, friction stir welding (FSW) of dissimilar high strength alloys AA2014 and AA7075 has been carried out and the effect of welding parameters has been studied to obtain defect-free high strength welds. Detailed statistical analysis was performed and suitable regression models were developed for prediction and optimization. Multi-objective optimization has been carried out by employing the desirability function to determine the optimal condition for defect-free welds with adequate mechanical properties. Microstructure and fracture surface of the optimum weld was also studied and compared with the lowest and highest heat input welded joints.

Influence of the incident angle on the OCT measurement during remote laser beam welding

In the field of remote laser beam welding, optical coherence tomography (OCT) is becoming increasingly important. OCT offers the possibility of generating information both during the welding process from the keyhole and outside the process, which is to be transferred into a holistic quality statement. In addition, OCT offers the potential to ensure the leak tightness of laser welding process and to realize new applications in the customer area using targeted welding into the lower sheet without recognizable seam root. Investigations in the field of body-in-white development validate this potential with a focus on welding depth measurement. Process-related and measurement-strategic investigations are carried out under variation of the processing and measurement angles. The generated measurement and metallographic results are processed and analyzed for validation of the OCT measurement and its stability during keyhole measuring. The findings derived from this, form the basis for detecting defect-free and defective welds and the development of future real-time repair strategies.

Electroslag surfacing of chromium cast irons in current-carrying mould

It is shown that electroslag surfacing of chromium cast irons can significantly improve their mechanical properties and obtain defect-free quality weld metal. The use of current-carrying mould expands the possibilities for using of different types of surfacing materials and regulating of the structure and properties of the deposited metal. Industrial experience of electroslag surfacing in the current-carrying mould of rolling rolls with chromium cast iron in the form of shot and liquid additive is presented. New direction in the development of surfacing work — obtaining of flat bimetallic billets designed for the hardening of wear surfaces is shown.

Friction stir welding of two major pin contours of AA2024 and AA6061

The research work deals with to join two dissimilar aluminum alloys by solid state welding process compared to fusion welding processes and compared with fusion welding process, fusion welds tend to produce more defects while joining dissimilar materials. The major problem of the two dissimilar metals involve in welding process have different mechanical properties and microstructures which in turn may affect welding parameters like weld current, hold time, weld force etc. In order to overcome these issues, Friction Stir Welding (FSW) can be used to get rid of defects since it uses a non-consumable tool and also produces defect free welds compared to other welding processes. This thesis work aims to joining an aluminum alloy of 2024 and aluminum alloy of 6061. The plates are joined by means of octagon probe tool made of high carbon high chromium steel (D2 tool steel). Other issues while welding dissimilar aluminum alloys are phase transformation change and selection of welding parameters (rotational speed, transvers speed, pin diameter, shoulder diameter, D/d ratio and etc.) From conducted trail experiment aluminum alloy of 2024 and aluminum alloy of 6061 by using octagon probe tool made by HC-HCR tool it was observed that a lower welding speed 500 rpm at starting stage lack of filling took place and after thermo-mechanical heating took place that produce better weld while compared to weld at higher speeds (710 rpm, and 1000 rpm) with same transvers speed of 20 mm/min.

Review of various methods of keyhole removal in friction stir welding sheets and pipes

Friction stir welding is preferred welding technique when compared to other fusion welding techniques due to its inherent advantages namely low work-piece distortion, good dimensional stability, repeatability and various other metallurgical, environmental and energy benefits. But friction stir welding is encompassed by various defects of which keyhole defect greatly affects the quality of weld. The goal of any welding process is to produce a defect free weld that could serve desired purpose. The keyhole produced at end of welding process is considered a defect. In this paper various methods used for keyhole removal which include filling keyhole directly or indirectly is done. General description of various methods of keyhole removal for both sheets and pipes have been made.

Effect of tool rotational speed on the friction stir welded aluminum alloys: A review

In contemporary world, leading industries such as automotive and aviation are using aluminium alloys due to its high strength to weight ratio. Conventional welding methods such as fusion arc welding causes solidification and liquid cracking in aluminium alloys. Friction Stir Welding (FSW), a solid state process has gained stupendous reputation in welding industry by successfully joining aluminium alloys with no obvious defects. The process parameters such as tool rotational speed, tool traverse speed and tool geometry plays a significant role in obtaining defect free welds and in increasing the joint efficiency. Tool rotational speed greatly influences the material movement and heat generation in FSW. This paper highlights the effect of rotational speed on mechanical and microstructural properties of the various aluminium alloys. The role of tool rotational speed in elimination of defects such as tunnel and kissing bond has also been discussed.

Metallographic analysis of in-house developed marine grade aluminum alloy AA5086friction stir welds

A friction stir welding (FSW) setup was developed and performed trial experiment on marine grade aluminum alloy 5086 in the present work. The input parameters were traverse speed (56 and 80 mm/min) and spindle speed (750 and 1000 rpm). From study it was observed that the spindle speed has an immense influenced on joint formation compared to feed speed. The rotational speed of 750 rpm produced defect joints due to inadequate welding heat generation and joints without defect were achieved at 1000 rpm spindle speed. The metallographic analysis and mechanical testing were conducted for the defect-free weld joints.

Microstructural and Process Parameters of aluminium alloys Using FSW

Friction stir welding (FSW) has become a popular method for connecting low weight metals. Material joining occurs in the solid state in FSW. Inserting a rotating tool travelling over the faying surfaces of the material to be bonded is used to complete the procedure. It produces practically defect-free welds with little distortion and a fine grain structure. However, the welding mechanism and process parametric combination for welds with consistent and dependable outcomes are not well understood. The thesis details the experimental efforts made to suggest an optimal combination of parameters with simple tool geometry for FSW at greater linear speeds. The materials for research were two precipitation hardenable aluminium alloys: 6mm thick 2219-T87 and 5083H321. The influence of process parameters on weld microstructural changes and defect development was also examined. The optimal combination of process parameters for the FSW of aluminium alloys was proposed, and the most relevant parameter for weld strength and quality was discovered.

Microstructure and mechanical properties of dissimilar friction stir welds of AA2014 and AA7075

This work investigates the effect of process parameters on microstructure, mechanical properties, and fracture behavior of friction stir welded high-strength aluminum alloys AA2014-T6 and AA7075-T6. Optical micrograph, tensile property, and hardness profile of each weld were determined for analysis, and the tensile fracture surfaces were studied by scanning electron microscope. Welds microstructure were heterogeneous and displayed structures comprising of both base metals and the onion rings were seen in all welds except for the lowest heat input weld. Grains in the weld nugget zone were more refined on the retreating side than the other side. Asymmetric hardness profile had a distinct softened zone on each side whose location and softening extent varied with the processing parameters. Welding speed had a more significant effect on tensile strength than rotary speed and, drastically decreased the same. Faster welding speed formed microscopic defects and changed the appearance of fractured surfaces from flat to zigzag. The welds underwent ductile and mixed-mode tensile failure on the advancing side. Attainment of optimum combination of process parameters is imperative to yield defect-free stronger dissimilar welds

Effect of Al2O3 nanoparticles on microstructure and mechanical properties of friction stir-welded dissimilar aluminum alloys AA7075-T6 and AA6061-T6

In this research, a defect-free dissimilar weld joint of AA7075-T6 and AA6061-T6 reinforced with Al2O3 nanoparticles was fabricated via friction stir welding (FSW). The influence of tool rotational speed (700, 900 and 1100 rpm), traverse speed (40, 50 and 60 mm/min) with varying volume fractions of Al2O3 nanoparticles (4%, 7% and 10%) on microstructural evolution and mechanical properties were investigated. The augmentation of various mechanical properties is based on the homogeneity of particle dispersion and grains refinement in the SZ of the FSWed joint. The findings revealed that the remarkable reduction in grain size in the SZ was observed owing to the incorporation of Al2O3 nanoparticles produces the pinning effect, which prevents the growth of grain boundaries by dynamic recrystallization (DRX). The increasing volume fraction of Al2O3 nanoparticles enhanced the mechanical properties such as tensile strength, % elongation and micro-hardness. Agglomeration of particles was observed in the SZ of the FSWed joints produced at lower tool rotational speed of 700 rpm and higher traverse speed of 60 mm/min due to unusual material flow. Homogenous particle dispersion and enhanced material mixing ensue at higher rotational speed of 1100 rpm and lower traverse speed of 40 mm/min exhibit higher tensile strength and micro-hardness.

Effects of sinusoidal oscillating laser beam on weld formation, melt flow and grain structure during aluminum alloys lap welding

A numerical model of 1.5 mm 6061/5182 aluminum alloys thin sheets lap joints under laser sinusoidal oscillation (sine) welding and laser welding (SLW) weld was developed to simulate temperature distribution and melt flow. Unlike the common energy distribution of SLW, the sinusoidal oscillation of laser beam greatly homogenized the energy distribution and reduced the energy peak. The energy peaks were located at both sides of the sine weld, resulting in the tooth-shaped sectional formation. This paper illustrated the effect of the temperature gradient (G) and solidification rate (R) on the solidification microstructure by simulation. Results indicated that the center of the sine weld had a wider area with low G/R, promoting the formation of a wider equiaxed grain zone, and the columnar grains were slenderer because of greater GR. The porosity-free and non-penetration welds were obtained by the laser sinusoidal oscillation. The reasons were that the molten pool volume was enlarged, the volume proportion of keyhole was reduced and the turbulence in the molten pool was gentled, which was observed by the high-speed imaging and simulation results of melt flow. The tensile test of both welds showed a tensile fracture form along the fusion line, and the tensile strength of sine weld was significantly better than that of the SLW weld. This was because that the wider equiaxed grain area reduced the tendency of cracks and the finer grain size close to the fracture location. Defect-free and excellent welds are of great significance to the new energy vehicles industry.

Establishing optimal friction stir welding parameters for AA2219-T87 Al-alloy using comprehensive RSM and GA approach

AA2219-T87 aluminium alloy has been used in aerospace applications because of its high strength, low density and resistance to corrosion. The copper in the alloy improves the hardness and lowers melting point, which makes two sections easily joined with a process called friction stir welding of aluminium alloy. In the present work, heat-treated AA2219 alloy was butt welded by solid-state friction stir welding process. This work aims to develop a suitable combination of welding parameters for producing defect-free weld joints of AA2219 alloy to improve tensile and corrosion properties. The most influencing control parameter for optimising the friction stir welding responses was determined using sophisticated design of experiments (DOE) techniques. Ultimate tensile strength and corrosion resistance are observed as responses in this study. To achieve the desired weld responses, a three-factor, three-level Box-behneken design was used. Analysis of Variance (ANOVA) was carried out to examine the interaction effect and significant welding parameter to set the optimal level of welding conditions. Multi-response regression equations have been developed using response surface methodology (RSM) to estimate the output characteristics of weld. The Genetic algorithm (GA) was used to optimise the predicted mathematical model under given optimization constraints. The results shown that the optimum responses are obtained at input factors rotational speed 300 rpm, welding speed 80 mm min−1, and axial force of 10kN.