Conventional Welding Techniques Research Articles

Study of the properties of high silicon aluminum alloy by laser welding

High silicon aluminum alloy is a kind of high-performance electronic packaging material, due to its excellent thermal conductivity, low thermal expansion coefficient, and low density. The heat affected zone (HAZ) of conventional welding techniques is too wide to weld the high silicon aluminum alloy, as wide HAZ will improve risk of cracking. Laser welding with narrow HAZ, high joint strength, and good morphology, has been considered as a promising method to weld high silicon aluminum alloy. Herein, the surface morphology, microstructure, and microhardness of laser welding joint between Al-50wt.%Si and Al-27wt.%Si alloys were investigated. It has been found that welding speed at 3 mm–5 mm/min can significantly reduce the hydrogen pores and cracks in laser welding joints. Also, the key paraments of laser welding to control the quality of joints are power and pulse width, while the former one is mainly controlling the joint width and the latter one is significantly changing the joint depth. Along the horizontal direction of laser welding joints, the microhardness increases firstly and then decreases, with the highest microhardness of 167 HV in the weld zone. Because the laser welding method could produce uniform microstructure of joints, the microhardness of joints is uniform along the longitudinal direction. The tensile properties of welding samples are almost the same with the properties of the Al-50wt.%Si base materials.

Transient liquid phase bonding technique for ultrahigh-vacuum compatible bimorph mirrors used in soft x-ray beamlines.

Bimorph mirrors place stringent requirements on the welding technology of silicon substrates and piezoelectric ceramics to ensure their ultrahigh-vacuum compatibility. Conventional welding techniques usually require high temperature and pressure, which have a high impact on the welding substrate, while the use of organic adhesives for bonding does not guarantee their stability in ultrahigh vacuum. Here, the transient liquid phase bonding technology based on an Au-In metal system was studied to meet the requirement for ultrahigh-vacuum application. The microstructure, chemical composition, and related mechanical properties of the bonding at different welding conditions were investigated. Meanwhile, the piezo ceramics and the bond were baked at 150 °C to test the stability. The results show that a stable bonding was achieved between centimeter-scaled single crystal silicon and lead zirconate titanate ceramics at 200 °C temperature and 2.5 MPa pressure, and the piezo ceramics and the bond are not damaged by baking to 150 °C for 48 h.

Development of novel welding techniques for dissimilar joining of 12 mm thick plates of AISI347H and IN625 for CSP power plants

• The study compares welding processes for joining AISI347H and IN625 for CSP plates. • The welding processes adopted are SP-MIG and DP-MIG. • DP-MIG has lower heat-input and residual stress than SP-MIG. • On comparing all the results, DP-MIG has better properties than SP-MIG. AISI347H and IN625 alloys are commonly used in for applications requiring higher strength at higher operating temperatures. However, the dissimilar joining of these materials is mostly used in fabrication of CSP energy storage tanks. While joining dissimilar metals, there are several practical challenges. The major concern regarding joining dissimilar materials is the selection of suitable welding techniques. Additionally, welding of thick sections requires more passes, which results in a higher heat-input, it will adversely affect the metallurgical and mechanical properties of the weldments. As a result, pulsed welding is a viable option for reducing overall heat input. In the present study two different pulsed current welding techniques namely, DP-MIG and SP-MIG welding were tried out successfully. It was observed that DP-MIG showed 27% reduction in the heat-input when compared to SP-MIG. Similarly, when DP-MIG was compared to SP-MIG, the residual stress was decreased by 75 MPa. In the fusion zone (FZ) micro segregation of alloying elements are lower to avoid secondary phase formation in DP-MIG technique. DP-MIG has better tensile strength and hardness than SP-MIG due to finer grain formation. The overall studies shows that DP-MIG shows better mechanical properties compared to conventional arc welding techniques.

Statistical Analysis of Friction-Stir Welding of Al- 6063 Alloys

Aluminum 6063 alloys are widely used in various engineering and industrial applications since they are highly corrosion resistant and exhibit superior mechanical properties. They are often used in extrusion projects because of their, weldability, moderate strength and good workability. These properties allow them to excel in architectural applications, piping, tubing, general extrusions for medical, automotive, parts profiling, building and construction, recreational equipment and furniture. Investigations revealed that joining of these alloys by conventional welding techniques has several limitations. Friction Stir Welding (FSW) is a highly efficient manufacturing process with improved safety due to absence of toxic fumes or molten spatters and also end products with reduced weld defects, better retention of mechanical properties, less distortion and less residual stress. The present work focuses mainly on the characterization of friction stir welded joints of Al 6063 alloys using reconfigured Vertical Milling Machine. Brinell Hardness, Impact strength & Fractography study of the weldments were carried out to analyze the hardness, impact strength and microstructure of the weld zone and heat affected zone. To justify the impact of contribution of input parameters over the process outcome, Minitab -17 statistical modeling analysis was carried out.

Computational investigation on transient thermal tensioning for mitigation of welding induced buckling by elastic FE method

Transient thermal tensioning (TTT) as an in-process technique is extensively used to mitigate welding induced buckling during the fabrication of thin plate welded structures, which drastically influences dimensional accuracy and manufacturing costs due to post-straightening work. In this study, the processes with conventional welding (CW) and TTT technique during the butt welding with thin plates were investigated by elastic FE method based on welding inherent deformation theory. In detail, thermal elastic plastic (TEP) FE analysis for the butt welded joint was validated, while the computed welding induced buckling and residual stress during CW process were in good agreement with experimental results. Then, TTT technique was implemented with above TEP FE analysis; it consists of two additional heat sources, which were symmetrically distributed and offset 150 mm with respect to the welding line. Moreover, the influence of energy intensity Q for additional heat sources on welding induced buckling mitigation was numerically examined. Elastic FE analyses during CW and TTT processes were carried out with welding inherent deformation evaluated by results of TEP FE analysis. The comparison between elastic FE analysis and TEP FE analysis suggests that the developed elastic FE analysis can accurately and efficiently represent welding distortion during CW and TTT processes with less than 5 % error. There is an appropriate interval of energy intensity Q during TTT process, which can significantly decrease relative displacement Urelative in the butt welded joint by up to 89.1 %. Furthermore, the reduction of tendon force and transverse inherent bending is the primary reason for welding buckling distortion mitigation during TTT process, and the decrease of tendon force is more critical.

Uniaxial and multiaxial fatigue behaviour of wire arc additively manufactured ER70S-6 low carbon steel components

Wire arc additive manufacturing (WAAM), also known as directed energy deposition (DED) process, is an efficient additive manufacturing technology, offers high potential to rapidly fabricate large-scale parts with complex geometries layer-by-layer. However, the fundamental understanding of the fatigue behaviour of such parts and the material requirements need to be significantly improved at all levels before this unique technology can be implemented for critical applications. This work aims to investigate the fatigue behaviour of WAAM built ER70S-6 steel under uniaxial, torsion and multiaxial loading conditions. Specimens were extracted in two different orientations: vertical and horizontal, to explore if the orientation direction has any effect on the fatigue results. Scanning Electron Microscopy (SEM) was conducted to examine the fracture surface of broken specimens and identify crack initiation regions and fracture mechanisms. The obtained results were compared with the fatigue data available in the literature on common structural steels fabricated using conventional welding and WAAM technique, showing similar fatigue behaviour with wrought S355 specimens. Moreover, the uniaxial data set on ER70S-6 WAAM specimens was evaluated according to the DNV RP-C203 standard for continuous welds, demonstrating advantageous fatigue resistance in the examined material.

Assessment of Optimum Mechanical Properties for Friction Stir Welding of Pure Copper and Aluminium Bronze

Joining Aluminium Bronze and copper alloys has more comprehensive applications like power distribution, marine and automotive sectors and conventional fusion welding techniques impairs the weld quality owing to the high temperatures required. Friction stir welding is a preferred technique for fusing these alloys. This process eliminates many common problems associated with fusion welding like oxidization of aluminium, porosity, hot cracking. In recent years, there has been a lot of research into employing friction stir welding to fuse incompatible metals and alloys. Mechanical parameters such as hardness, yield strength elongation and ultimate tensile strength in friction stir welded joints of pure copper and aluminium bronze are investigated in this study. Each of the parameters, such as axial force, tool rotational speed and traverse speed was varied three levels each. A mathematical model based on a face-centered central composite design was used to study the effect of welding parameters on output responses. The selected friction stir welding parameters have a considerable impact on the output responses that are measured. The optimum process parameters for increasing the mechanical characteristics of welded joints were determined to be 1000 rpm tool rotation speed, 30 mm/min traverse speed, and 4.5 kN axial force.

Influence of machine variables on the microstructure and mechanical properties of AA6061/TiO2 friction stir welds

ABSTRACT The present work explicates the joining of TiO2 (rutile) particles reinforced aluminium matrix composites (AMCs) through the friction stir welding (FSW) technique. Joining of AMCs using conventional fusion welding techniques faces a lot of challenges, which can be overcome by the FSW process. The effect of the two most critical process variables, welding speed, and tool rotational speed on the grain structure of the joint and on the mechanical behaviours was evaluated. The study revealed that machine variables regulate the quantity of heat input, heat exposure duration, and rate of cooling, thereby, significantly altering the grain size in the weld region and mechanical behaviour of the joint. The tool rotational speed had a substantial impact on the joint strength, whereas tool traverse speed facilitates homogeneous dispersion of reinforced particles in the matrix. The ‘W’-shaped hardness variation profile was observed across the weld zone, showing the highest hardness in the weld stir zone. The UTS of the welded specimen, measured across the joint was almost equal to the parent material with fracture occurring at the interface of the heat-affected and the thermo-mechanically affected zone which was the weakest point in the weld region.

Multi-Response Optimization of Friction Stir Welding of AA2050 Using Response Surface Methodology Coupled with Grey Relational Analysis and Principal Component Analysis

The third generation aluminium-lithium alloy AA2050 finds wide applications in defence and aircraft industries by virtue of its high strength-to-weight ratio and excellent corrosion resistance. Friction stir welding (FSW), relatively novel technique, is more suitable to join this alloy compared to other conventional fusion welding techniques. In this work, the overall quality of the weld joint was decided from the higher values of tensile strength, yield strength, percentage elongation, hardness of weld zone, hardness of heat affected zone, bending load and lower value of width of heat affected zone. The optimal (combined) design was used to design the experiments with four numeric factors (traverse speed, rotational speed, tilt angle and shoulder diameter) and a categoric factor (tool pin profile). The multi-response optimization problem was reduced into a single-response optimization problem using grey relational analysis (GRA); principal component analysis (PCA) was used to assign optimal weighting values for the responses in the process of dimensionality reduction. Mathematical model for the reduced single response, which can be perceived as overall weld quality, was developed by the response surface methodology (RSM) and the optimization of process parameters was also carried by the RSM. Analysis of variance (ANOVA) was carried to evaluate the significance of each parameter on the overall weld quality and the adequacy of the developed model. The confirmation tests conducted at optimum levels of parameters proved the effectiveness and robustness of the method.

Review on Vacuum Laser Beam Welding

Vacuum laser beam welding (VLBW) exhibits better welding characteristics, e.g., deep penetration, less pore, and spatter generation, compared with the conventional laser welding technique under atmospheric pressure. Low ambient pressure affects the vaporization temperature of the base material and the interaction between laser and plasma plume, which affects the behaviors of laser-induced plasma plume, keyhole, and weld pool flow. This review introduces improvements in welding characteristics such as penetration depth, pore, and spatter generation in the VLBW process. The effect of ambient pressure on welding characteristics was reviewed, and the behavior of laser-induced plume, keyhole, and molten pool under reduced ambient pressure was discussed to understand the mechanisms for enhanced weldability.

Effect of process parameters on friction stir welded joints of AA 7039

Friction Stir Welding is a new welding technique for joining high-strength aluminum alloys. In the recent years, the technology has already proved its presence in various industries like automobile, aviation, railways, marine, defense etc. Aluminum and its alloys are widely acceptable in structural applications, especially, AA 7039 is widely utilized in defense and marine industries. Friction Stir Welded joints usually does not exhibit the problems associated with the conventional welding techniques. The welding joints are highly influenced by the parameters involved in their fabrication. As a result, the purpose of this research is to investigate and characterize the influence of tool rotation speed and traverse speed (feed rate) on joining efficiency. Joint having weld configuration of 1000 RPM and 28 mm/min of feed rate shows highest tensile strength of 84.27% whereas lowest strength of 51.22% is recorded for the joint fabricated with 500 RPM and 56 mm of feed rate. Microhardness and microstructural features are investigated considering mechanical characteristics.

Friction based solid state welding – A review

The present paper aims to provide a review of an important class of welding process called friction based solid-state welding. Among many other advantages such as low heat input, shorter welding cycle friction based solid-state welding techniques are suitable for joining both similar and dissimilar materials and helps to eliminate the defects associated with the conventional fusion welding techniques and results in welds of high structural integrity. In this paper, two important friction based joining processes were reviewed namely rotatory friction welding (RFW) and linear friction welding (LFW). RFW is well established form of friction welding, while as, LFW is an emerging method of joining. In present article, the joining process is first described which is followed by the process parameters and their effect, finally the application of the process is introduced. In the end a conclusion section along with future outlook is introduced.

Friction stir welding of cast aluminum alloy (A319): Effect of process parameters

Due to their light weight and cast ability, cast aluminium alloys are gradually being used in aerospace and automotive applications. Welding aluminium castings together for variety of applications is very critical. Due to the existence of hot cracking, porosity and distortion, these alloys are difficult to fuse using conventional fusion welding techniques. Friction Stir Welding (FSW) is a revolutionary joining technology in solid state that does not require welded and melting the material, without the required for bulk melting, FSW forms the weld connection. Additionally, during dynamic recovery, the thermomechanical deformation refines the structure of the stir zone. As a result, FSW welds exhibit much superior mechanical properties compared to comparable fusion welds. As a result, the current inquiry will examine the outcome of FSW practice factors on the mechanical properties and metallurgical of cast aluminum–silicon alloys in a systematic manner. The effects of welding speed, rotation speed of tool, and axial force on the tensile strength, hardness, and microstructure of friction stir welding joints made of aluminum alloy are presented and discussed in this paper.

Mechanicalproperties of 304 stainless steel plates and friction stir welded Al 2219 alloy

The study examined the impact of different operating conditions of 2219 aluminium (Al) sheets and 304 stainless steel FSW. Recently, the FSW procedure has been utilised to fastening various materials as it was able for conventional fusion welding techniques to remove local casting errors. The microstructure and mechanical characteristics of the weld nugget depend primarily on several FSW parameters such as rotation of the instrument, feeding speed, offset and pin profile. The current paper examines and discusses the effects of instrument speed, feed rate, offset and the cleaning process for tensile behaviour. As demonstrated by the decrease in velocity from 710 to 500 rpm and the increase in feed rate from 40 to 80 mm/min, the joint was improved. Furthermore, by raising offset to 1.5 mm, the defect in the twisted area was reduced. The use of the ringing method also successfully enhanced the extension and tensile strength by 100% and 9%.

Numerical modeling of thermal field during friction stir welding using tool with polygonal pin profile

Friction stir welding produces better joint strength comparing with other conventional fusion welding techniques as the complete metal joining operation is executed in solid state itself. Even though the quality of weld is comparatively good, this joining technique has its own disadvantages. Improper material flow along the weld line may result in weld defects. Usage of polygonal pin geometry in tool pin rather than using conventional cylindrical pin geometry enhances flow of plasticized metal under the tool shoulder in the stir zone. Major problem associated with polygonal shaped tool pin is poor tool life. Yield strength of material under the tool shoulder creates opposing force for the movement of tool pin, which is submerged inside the workpiece for the entire joining process. Uneven stress distribution along the outer surface of the polygonal tool pin shape leads to premature tool failure. As the strength of material is a temperature dependent property, the heat input during the process has to be optimised with respect to the geometrical shape of the tool pin to improve tool life without compromising the weld quality a lot. In this paper, the variation in thermal field based on the geometrical shape of the tool pin was analysed using MATLAB based on the moving coordinate system. Rosenthal equation was used to estimate variation the peak temperature and temperature distribution with respect to pin shape in the view of optimising thermal environment towards better weld quality.

An experimental insight of friction stir welding of dissimilar AA 6061/Mg AZ 31 B joints

In the present scenario, aerospace and automobile industries depend on lightweight materials such as magnesium and aluminum alloys because of their great balance between mechanical properties and weight ratio. Despite these benefits during the joining process of these dissimilar materials by welding, many challenges arises. The prominent one is related to the low melting points of these lightweight metals which make it almost impossible the joining using conventional arc welding techniques. To tackle this challenge, Friction Stir Welding (FSW) can be considered as a promising candidate tool. In this study, to demonstrate the FSW performances of joining two dissimilar materials we have investigated the joining of AA 6061 and Mg AZ 31 B using a built-in house a modified milling machine. The dissimilar combinations of AA 6061 and Mg AZ 31 B joints were successfully joined by embedding different welding conditions and varying the offset distance. The mechanical performances were evaluated by conducting specific mechanical tests such as micro-hardness, tensile, and impact tests, respectively. To explain the mechanical results, we have applied optical microscopy observation on the microstructure associated with the bonding location. The results prove that the strength of the Friction Stir Welded joints is much higher as compared to other techniques especially in terms of dissimilar metals.

Thermal-induced Residual Stresses and Distortions in Friction Stir Welds - A Literature Review

Friction Stir Welding (FSW) is a solid-state welding technique that uses the heat generated from friction to assemble a wide variety of materials. Irrespective of having a lower heat input as compared to conventional welding techniques, friction stir welds are still prone to significant thermal-induced stresses and distortions owing to the uneven heating and cooling cycles that a weld goes through. Surprisingly, not several reviews have addressed both the residual stresses and distortions of friction stir welds despite their crucial impact on the weld performance. Therefore, the current paper reviews their development, their correlation with process parameters, and ways to reduce them. Moreover, it explains the current status of process modeling and research gaps in the area of interest.

Exploring the application domain of friction stir welding in aluminum and other alloys

Friction stir welding (FSW) is a new solid-state welding technique used to join similar and dissimilar materials, especially aluminium alloys. Friction stir (FS) welding proposes numerous benefits compared to conventional fusion welding techniques and can be successfully applied in shipbuilding, aerospace, automobile, and railway industries. This paper gives a comprehensive review of the FSW process and its technical aspects. The effects of tool pin profiles, feed rate, tool tilt angle and welding speed, etc., and mechanical and metallurgical behavior of FS welded joints have been reviewed in this article. In addition, this paper covers the literature review of friction stir welding of similar and dissimilar aluminum alloys (AA), optimization techniques, welding defects, and fatigue behavior of FS welded joints. Furthermore, a summarized report of work done by many researchers in friction stir welding is also presented. Finally, it also identifies the future scope, applications, and research gap.

Experience with advanced welding techniques (RMD & P-GMAW) with seamless metal cored wire for Oil & Gas pipeline industries

Regulated Metal Deposition (RMD™) process is a variant of Gas metal arc welding process (GMAW), which was developed with the aim to effectively control the metal transfer in the short-circuiting mode. The process is fundamentally a modified short-circuit GMAW process wherein a uniform droplet deposition, making it easier for the welder to control the puddle and hence achieve an enhanced quality of welded joints. In the present study, RMD technique has been established for API grade pipe (API 5L PSL2 X70 grade) particularly for depositing the root pass on 24” OD and 10.3 mm thick pipe. In addition to this, the RMD technique is tried for the first time with seamless metal cored wires (Megafill 240 M) in order to enhance the deposition rates in Indian Oil & Gas pipeline industry. The joint fill up is further attempted with pulsed GMAW technique using metal cored wires and further analysed. The weldments were tested by mechanical characterization. Mechanical characterization such as tensile properties, impact properties, bend test as well as all weld tensile properties of the weld joint were evaluated and found to be acceptable. A techno-commercial evaluation of the technique was carried out vis-à-vis conventional welding techniques such as SMAW process for root passes and Fill & Cap. It was found the proposed technique was cost effective as well as reliable. One of the inherent benefits of the RMD and Pulse GMAW technique is the reduction in the overall heat input of the welded joint imparting superior mechanical properties. The use of metal cored wires also established the proposed technique as a potential technique for heavy thick weldments by enhancing the overall productivity.

A Review on Heat Generation and Temperature Distribution Models in Friction stir Welding (FSW)

Nowadays the higher fuel efficiency is a major concern in every developing field of technology and it is also a cause for the development of lightweight materials. There are many applications in which it is required to join two dissimilar lightweight materials. Friction stir welding (FSW) is the most crucial development for such types of applications. This technique helps in overcoming the challenges raised during the joining of two dissimilar materials due to their incompatibility with conventional welding techniques. The lightweight materials developed with the help of friction stir welding (FSW) have applications in various industrial sectors like automotive, electronics, shipbuilding, railways, marine, and many others. It is inevitable in joining the different grades of materials like magnesium alloys, aluminum alloys, and low carbon steels without any weld defect. The thermal properties like heat generation and peak temperature also have a significant effect on the quality and strength of the weld joint. The thermal properties change the microstructure of the weld material and influence the mechanical properties of the welded material. This provides Temperature controlling methods so as to reduce the surface temperature and hence reduce the defects in the welded material. This present review article is based upon the summary of the work carried out by different researchers in the field of thermal modeling of the friction stir welding (FSW).