Solid State Welding Process Research Articles

Friction Spot Welding of Similar AA5754 to AA5754 Aluminum Alloys and Dissimilar AA5754 Aluminum to AZ31 Magnesium Alloys

Friction spot welding is a solid-state spot welding process developed and patented by Helmholtz-Zentrum Geesthacht, Germany. A non-consumable rotating tool consisting of two rotating parts, a pin and a sleeve, and one stationary clamping ring is used to join two or more similar/dissimilar sheets of materials in lap configuration. The result is a spot welded lap connection with minimal material loss and a flat surface without keyhole. The present work presents a summary of results from studies in similar AA5754 to AA5754 Al alloys and dissimilar AA5754 Al to AZ31 Mg alloys.

Effect of welding processes on mechanical and microstructural characteristics of high strength low alloy naval grade steel joints

Naval grade high strength low alloy (HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding (FSW). In this investigation, a comparative evaluation of mechanical (tensile, impact, hardness) properties and microstructural features of shielded metal arc (SMA), gas metal arc (GMA) and friction stir welded (FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.

Heat Reduction in a Tool Holder during Friction Stir Welding of Aluminium Alloy

Friction stir welding is a solid state welding process that uses a rotating tool to amalgamate two metals by the frictional heat generated. Recent developments in FSW of aluminium have been exploited in aerospace, marine and transport industries. The friction stir welding on aluminium metal generates heat which has detrimental effects on the system in the long run. The heat generated, due to the friction developed, has to be reduced to provide a constant thermal environment for the tool and the workpiece. This work focuses on the conception to develop a water cooled tool holder to reduce the excess temperature thereby protecting the spindle bearing. The current paper elucidates on the design and parameters of water cooled tool holder and spring loaded seal, its implementation and the results obtained by friction stir welding of aluminum.

Optimization of friction stir welding parameters for improved corrosion resistance of AA2219 aluminum alloy joints

Abstract The aluminium alloy AA2219 (Al–Cu–Mg alloy) is widely used in the fabrication of lightweight structures with high strength-to-weight ratio and good corrosion resistance. Welding is main fabrication method of AA2219 alloy for manufacturing various engineering components. Friction stir welding (FSW) is a recently developed solid state welding process to overcome the problems encountered in fusion welding. This process uses a non-consumable tool to generate frictional heat on the abutting surfaces. The welding parameters, such as tool pin profile, rotational speed, welding speed and axial force, play major role in determining the microstructure and corrosion resistance of welded joint. The main objective of this work is to develop a mathematical model to predict the corrosion resistance of friction stir welded AA2219 aluminium alloy by incorporating FSW process parameters. In this work a central composite design with four factors and five levels has been used to minimize the experimental conditions. Dynamic polarization testing was carried out to determine critical pitting potential in millivolt, which is a criteria for measuring corrosion resistance and the data was used in model. Further the response surface method (RSM) was used to develop the model. The developed mathematical model was optimized using the simulated annealing algorithm optimizing technique to maximize the corrosion resistance of the friction stir welded AA2219 aluminium alloy joints.

English

Welding is a process of joining similar metals by the application of heat and pressure. Welding process is used commonly to get the advanced properties of the metals like Mild steel, Aluminum, Copper, Magnesium etc. Among these metals Magnesium has the lowest density (1.78 g/cm3) and it has good mechanical properties like high strength to weight ratio, good damping capacity, and good corrosion resistant compared to Mild steel. But Magnesium is highly flammable which requires gas shielding to prevent the oxidation, which forms Magnesium oxide, an undesirable compound. Friction Stir Welding, a Solid State Welding process uses the heat developed by the rotating tool, due to the friction the heat developed is used to join the metals, where the weld zone temperature zone is comparatively lower than conventional welding .The retention of the mechanical characteristics is achieved in FSW process. But problems in FSW like Pin, Tunnel and Flash defects are produced in weld zone. These problems and Weld quality, microstructure, mechanical characteristics of the weld zone can be controlled by varying the FSW parameters such as Tool rotational speed, Tool traverse speed, Tool Axial force, Tool shoulder to tool pin diameter ratio, tool profile etc. In this project we are going to study the effects of these parameters in Friction Stir Welding of Magnesium alloys.

Friction stir welding of dissimilar aluminium–magnesium joints: sheet mutual position effects

Friction stir welding (FSW) is a solid state welding process used to weld difficult to be welded or unweldable materials as aluminium alloys. In the last years, other materials have been successfully tested as magnesium, titanium and nickel based alloys. Dissimilar joints can be obtained by FSW, but issues arise concerning the correct choice of the process parameters. In the paper, the results of an experimental and numerical campaign aimed to produce dissimilar AZ31-AA6016-T6 butt joints are presented. The effect of sheet mutual position and main process parameters was investigated. It was found that intermetallics are the main cause of the poor quality of the joints. Sound joints can be produced only if the magnesium alloy is in the advancing side.

High Cycle Fatigue Behaviour of Friction Stir Lap Welded 6061 Aluminium Alloy to Coated Steel Sheet Joint

Multi-material fabrication such as joining of steel and aluminium has become prominent now-a-days in automotive industries. Friction stir welding being a novel solid state welding process, has already established good joint strength between steel and aluminium; but fatigue strength of such dissimilar joint has not yet been explored. In the present study, the friction stir lap welding was performed at each rotation speed of 500, 1000, 1500 for two different travel speed i.e. 50 and 100 mm min−1 at a constant probe depth of 2.5 mm. Among the six different joints, joint strength achieved of maximum (5 kN) and minimum (2 kN) under two parameter combination i.e. 1000 rpm 50 mm min−1 and 500 rpm 100 mm min−1 respectively, have been exclusively characterized by high cycle fatigue at R ratio 0.1. Furthermore, R ratio has been varied from +0.5, +0.3 to −0.5, −0.3 at a particular load amplitude which shows the endurance limit (106 cycles) for both combination of parameters. The experimental results show that fatigue strength at 106 cycles for both the FS welded lap joint is about 20 % of their respective failure load. Thus better fatigue strength is associated with the lap joint performed with the joint of maximum load. The fatigue behaviour of two FS joints has been correlated with the thickness of intermetallic compound and accumulation of dislocations observed by TEM.

Investigation of aluminum-steel joint formed by explosion welding

Explosion welding is a solid state welding process that is used for the metallurgical joining of metals. Explosion cladding can be used to join a wide variety of dissimilar or similar metals [1]. This process uses the controlled detonation of explosives to accelerate one or both of the constituent metals into each other in such a manner as to cause the collision to fuse them together [2]. In this study, bonding ability of aluminum and steel with explosion welding was investigated. Experimental studies, microscopy, microhardness, tensile and bend test showed out that, aluminum and steel could be bonded with a good quality of bonding properties with explosion welding.

Review of magnetic pulse welding

Magnetic pulse welding(MPW) is a solid state welding process that is accomplished by a magnetic pulse causing a high-velocity impact on two materials, resulting in a true metallurgical bond. One of the great advantages of MPW is that it is suitable for joining dissimilar metals. No heat affected zones are created because of the negligible heating and the clean surfaces formation that is a consequence of the jet and the metal is not degraded. Also, compared to other general welding processes, this process leads to only a low formation of brittle intermetallic compounds However, although this process has many advantages its application to industrial fields has so far been very low. Therefore, in this study we are presenting the principles, apparatus and application of MPW for application the industrial fields.

Optimizing the Friction Welding Parameters to Maximize Tensile Strength of Sus 304HCu Austenitic Stainless Steel Tube Joints

The SUS 304HCu austenitic stainless steel is used in superheater / reheater of ultra super critical boilers for their high temperature oxidation and corrosion resistance. Cu addition to steels can have adverse effects on the mechanical properties during fusion welding as it can form low temperature eutectic phases that preferentially segregate to the grain boundaries and embrittle the alloy. Friction welding is a solid state welding process where the bonding takes place well below the melting temperature of the alloy, combined with the autogenous nature of this welding process minimizes the adverse effects of low temperature eutectics segregation. Hence, in this investigation an attempt has been made to develop an empirical relationship to predict the tensile strength of the friction welded SUS 304HCu tubes of 57.1 mm outer diameter and 3.5 mm thick using statistical tools such as design of experiments, analysis of variance and regression analysis. Response surface methodology was used to optimize the process variables and maximum joint efficiency of 99% was achieved using the optimized friction welding variables.

Experimental and Numerical Analysis of Microstructure Evolution during Linear Friction Welding of Ti6Al4V

Linear Friction Welding (LFW) is a solid state welding process used to joint bulk components. In the paper, an experimental and numerical study on LFW of Ti6Al4V titanium alloy is presented. A laboratory designed LFW machine has been used to weld the specimens with different contact pressure and oscillation frequency. The joint microstructure has been experimentally observed with SEM and EDS. A dedicated numerical model, able to predict temperature, strain and strain rate distribution as well as the phase volume fraction evolution, has been utilized to predict the final microstructure in the welded parts. It was found that complete transformation of the alpha phase into beta phase occurs during the process. After cool down, martensitic structure is obtained at the core of the weld due to high temperatures reached during the process and high cooling rates occurring at the end of the reciprocating motion. Microhardness measurements confirmed increased hardness in the Weld Zone with respect to the parent material

Investigation on strength of solid state Al6061/30%Al<SUB align="right">2O<SUB align="right">3 bonds for automotive applications using response surface methodology

Welding is an important joining operation with widespread applications in automotive components. Liquid state joining of aluminium-based composite materials in applications involving engine valve, drive shaft and axle was observed to create unnecessary metallurgical changes in the parent material, thereby reducing the joint strength. A solid state welding process could offer the required solution for this problem. Hence, the present work explores the possibility of obtaining strong joints with Al6061/30%Al2O3 composites by employing the process of friction welding (FW). The selection of proper levels of welding parameters like the rotational speed, burn-off length, frictional and upset pressure was essential to improve the strength of these bonds. Taguchi's L18 orthogonal array was used for conducting the experiments and the tensile strength of the bond was evaluated as the response. The response surface methodology (RSM) was used to form a quadratic model for the tensile strength and the prime welding condition for stronger joints was sorted out using the desirability analysis.

Effect of Heat Input on AA5052 Friction Stir Welds Characteristics

Friction Stir Welding (FSW) is a relatively novel solid state welding process that strong enhanced the welding of aluminum alloys for structural applications. In this process, the heat necessary for the required plastic flow of material is produced at the interfase tool-work piece, being affected by factors such as rotational speed, axial load and tool shoulder diameter, among others. The objective of this work was to study the effect of tool shoulder diameter on heat input during FSW of AA5052-H32 alloy and the resulting characteristics of the produced welded joints. Tools of 10, 12, 14 and 16mm shoulder diameter were constructed and used to butt weld plates of 3mm thick of AA5052-H32 aluminum alloy. Welds were made with 514rpm of rotational speed and 98mm/min of welding speed. Thermal cycles were acquired during welding using thermocouples. Macrostructural characterization and Vickers microhardness profiles were done on each welded sample. It was observed an increase in power with shoulder diameter, as well as a lower level of defects in the stirred zone, related with an improved plastic flow. Hardness also decreased with tool diameter, due to a higher thermal effect on the microstructure.

226 イナーシャ溶接プロセスの大変形熱弾塑性解析

Inertia friction welding is a solid state welding process with the small heat affected zone and the high joint quality and therefore expected to be a key manufacturing technology for the jet engine parts. However, development of welding process requires significant effort because it is a complicated thermo-mechanical phenomenon including the high speed friction and the large deformation at elevated temperature and difficult to understand. Simulation is expected as an effective tool in order to reduce long time and high cost experiments to find the process parameters. In this work, the simulation technology for inertia friction welding was developed by means of re-meshing techniques to avoid element distortion. A comparison with analytical result and experimental result was reported.

Wavelets Image Analysis for Friction Stir Processed TiNi Functional Behavior Characterization

A key topic regarding Ti Ni Shape Memory materials concerns the possibility to attain welded junctions that preserves the shape memory properties of material. Other research topic for SMAs regards the retention of the shape memory effect cyclic stability; in fact, good shape memory properties frequently decrease during SME cycling of material. A method able to improve the cyclic stability of TiNi shape memory effect is the grain refinement. Considering these above mentioned research topics, a solid state welding process, as the Friction Stir Welding, is thus attractive for SMA joining and it exhibits potentials for achieving welded joints affected by microstructural changes that preserve the shape memory properties and retain, furthermore, the cyclic stability of SME. The basic objective of this study was to investigate the feasibility of friction stir welding process to join TiNi shape memory alloy sheets flat memorized, preserving the TiNi shape memory behaviour. This aim has been pursued determining the influence of the thermomechanical modifications induced by Friction Stir Processing of TiNi sheets on the functional properties of material. Optical microscopic investigations of Friction Stir Processed material cross sections have been used to highlight the modified microstructure of processed zone. A proper image processing procedure has been performed in order to quantify the amount of martensitic phase and to detect its morphology modification along the processed region. Particularly each micrographic image at first has been denoised using the 2D Wavelet transform technique and successively a texture segmentation procedure allows evaluating the amount of the martensite and austenite phases and classifying the morphological changes of martensitic regions. The austenitic and martensitic transformation temperatures of material were investigated using a stress applied characterization method suitably set up to perform the whole stress-temperature material characterization.

The Effect of Tool Position for Aluminum and Copper at High Rotational Friction Stir Welding

Friction Stir Welding (FSW) is a solid state welding process used for welding similar and dissimilar materials. This welding technique allows welding of Aluminum alloys which present difficulties in fusion joining and allows different material couples to be welded continuously. In this study, 1050 aluminum alloy and commercially pure copper to increase heat input were produced at high rotation rate (2440 rev/min) with four different pin position (0-1-1.5-2 mm) and three different weld speeds (20-30-50 mm/min) by friction stir welding. The influence of welding parameters on microstructure and mechanical properties of the joints was investigated. Tensile and bending tests and microhardness measurements were used to determine of mechanical properties. Nugget zone microstructures were investigated by optical microscope and scanning electron microscope (SEM) and were analyzed in energy-dispersive X-ray spectroscopy (EDX). Depending on the XRD analysis results intermetallic phase was observed to form in the interfacial region. In the tensile test results, 83.55% weld performance was obtained in the friction stir welding merge of Al-Cu.

Joining sheet metals by electrically-assisted roll bonding

Roll bonding is a solid-state welding process performed by means of rolling. During the process, virgin metal is extruded to the surface from underneath the surface through micro cracks leading to the formation of new metallic bonds. Electrically-assisted roll bonding (EARB) was applied to roll bond 127μm aluminum sheet to 127μm aluminum or copper sheets. The quality of the bonds was examined through micrographs and peel tests. It was found that the Joule heating effect in EARB lowered rolling forces and increased the bond strengths of bonded sheets by as much as three times.

High Cycle Fatigue Behaviour of Friction Stir Lap Welded 6061 Aluminium Alloy to Coated Steel Sheet Joint

Multi-material fabrication such as joining of steel and aluminium has become prominent now-a-days in automotive industries. Friction stir welding being a novel solid state welding process, has already established good joint strength between steel and aluminium; but fatigue strength of such dissimilar joint has not yet been explored. In the present study, the friction stir lap welding was performed at each rotation speed of 500, 1000, 1500 for two different travel speed i.e. 50 and 100 mm min−1 at a constant probe depth of 2.5 mm. Among the six different joints, joint strength achieved of maximum (5 kN) and minimum (2 kN) under two parameter combination i.e. 1000 rpm 50 mm min−1 and 500 rpm 100 mm min−1 respectively, have been exclusively characterized by high cycle fatigue at R ratio 0.1. Furthermore, R ratio has been varied from +0.5, +0.3 to −0.5, −0.3 at a particular load amplitude which shows the endurance limit (106 cycles) for both combination of parameters. The experimental results show that fatigue strength at 106 cycles for both the FS welded lap joint is about 20 % of their respective failure load. Thus better fatigue strength is associated with the lap joint performed with the joint of maximum load. The fatigue behaviour of two FS joints has been correlated with the thickness of intermetallic compound and accumulation of dislocations observed by TEM.

Numerical Investigation on Dissimilar Friction Stir Welding of Aluminum and Magnesium Sheets

Friction Stir Welding (FSW) is a solid-state welding process used to weld difficult to be welded or unweldable materials as aluminum alloys. In the last years other materials have been successfully tested as magnesium, titanium and nickel based alloys. Mixed joints can be obtained by FSW but issues arise in the correct choice of the process parameters. In the paper a numerical model is presented for the prediction of the main field variables distribution and the occurring material flow in FSW of dissimilar AA6061 and AZ31 butt joints. Important insights are obtained on the effect of the mutual position of the two materials with respect to the advancing and retreating side of the joint has been highlighted.

Investigation of the effect of tool geometry on friction stir welding of 5083-O aluminum alloy

In this paper, effect of pin position (relative to tool shoulder position) on welded joint in friction stir welding (FSW) of aluminum 5083-O was investigated. FSW is a new solid-state welding process used to join metals and alloys (especially unweldable aluminums). To do this study, a FSW process was prepared by designing and fabricating tool and workpiece fixture and installing them on a milling machine. Then, some experiments were performed using the tool with a pin coaxial with the axis of tool shoulder. Hence, the tool enters edges of joint location and moves along joint line. Achieved results showed heat generation, severe plastic deformation, and material displacement in joint location which led to completeness of joint’s edges. It was also found that the tool temperature for tools with half pin and arched pin had a significant increase with the increase of rotational speed. Tools with more ability of mixing materials and forging of transferred material from the front of the pin to its back showed more ultimate tensile strength.