International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 4 Issue 03, March-2015 Influence of Green Joining Technique (FSW) on Microstructural and Mechanical Properties of Similar and Dissimilar Materials – An Overview Prashant S. H.¹, Dr. M S Ganesha Prasad² ¹Assistant Professor, ²Professor& Head, Dept. ofMechanical Engg., Sir M VIT, Dept. ofMechanical Engg., Bangalore – 562157 NHCE, Bangalore PiyushM³, Abhijit B³, Ashlesh³ and K H Amar³ ³UG Scholars, Dept. of Mechanical Engg. Sir M VIT, Bangalore – 562157 Abstract - Friction stir welding (FSW) is a relatively new solid- In late 1991, a very novel and potentially world beating state joining process which offers various advantages like low welding method was conceived and the process was duly distortion, absence of melt-related defects, high joint strength, named friction stir welding (FSW). Friction Stir Welding is etc. as compared to other conventional fusion welding the only solid state welding processes which do not have techniques. This joining technique is energy efficient, environment friendly and versatile.Joining of similar and drawbacks as other solid state welding processes and can dissimilar materials is a very important aspect of industrial be employed for butt welding and sheet welding of application. Especially joining of dissimilar materials is plates.The main advantage of FSW is that the original considered as a gateway for the implementation of lightweight material characteristic remains unchanged. materials in automobile and aerospace industries.In FSW, the FSW uses a rotating (non-consumable) cylindrical tool that technology diffusion has significantly outpaced the consists of a shoulder and a probe (Fig). The shoulder is fundamental understanding of microstructural evolution and pressed against the surface of the materials being welded, microstructure property relationships In this article, we are while the probe is forced between the two components by a going to study about different heat zones developed during downward force. The rotation of the tool under this force FSW process and its affect on microstructure and mechanical generates a frictional heat that decreases the resistance to properties on similar and dissimilar materials. plastic deformation of the material. The softened material Keywords – Dissimilar material, Process parameters, then easily moves behind the tool and forms a solid state Microstructure. weld as the stirred material is consolidated. FSW can be regarded as an autogenous keyhole joining technique I. INTRODUCTION Weldingis a process in which two metal pieces, similar or dissimilar may be joined by heating them to a temperature high enough to fuse the metal, with or without the application of pressure and with or without the aid of the filler materials. Welding is generally classified into two broadly categories: Fusion welding is achieved with a help of an intense heat source which leads to local melting and solidification removing the interface between the two base metals. Solid-state welding is achieved without exceeding the solidus temperature of the base metal. Hence the base metal Fig. 1.Friction Stir Welding remains in solid state. The manufacturers are under increasing pressure to produce In solid state welding, the cohesive force between the metal high strength and lighter products at the same time using atoms is utilized to join two metals. Solid state welding less energy, less environmentally harmful materials, at processes, like pressure welding, forge welding, ultrasonic lower cost in short time. FSW, being a solid-state, low- welding, role bonding and diffusion welding are time energy-input, repeatable mechanical process capable of consuming processes and require special surface producing very high-strength welds in a wide range of preparation. materials, offers a potentially lower-cost, environmentally safe solution to these challenges. IJERTV4IS030419 www.ijert.org 438 (This work is licensed under a Creative Commons Attribution 4.0 International License.) International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 4 Issue 03, March-2015 The weld-able materials using FSW are Aluminium (all Engine and chassis cradles alloys), Copper, Brass, Magnesium, Titanium, Steel Alloys, Stainless Steel, Tool Steel, Nickel, and Lead. Wheel rims FSW is emerging as a very effective solid-state Attachments to hydro formed tubes joining/processing technique. In a relatively short duration Space frames, e.g. welding extruded tubes to cast after invention, quite a few successful applications of FSW nodes have been demonstrated below. Truck bodies & tail lifts for lorries Shipbuilding and Marine Construction: The shipbuilding and marine industries are two of the first sectors that have Mobile cranes adopted the process for commercial applications. Armour plate vehicles The process is suitable for the following applications: Fuel tankers Panels for decks, sides, bulkheads and floors Caravans Hulls and superstructures Buses and airfield transportation vehicles Helicopter landing platforms II. STEPS INVOLVED IN FSW PROCESS Marine and transport structures The steps involved in process FSW are as follows: Masts and booms, e.g. for sailing boats A rotating FSW tool plunges into the joint line of the Refrigeration plant base material and moves forward. Aerospace Industry: At present the aerospace industry is When the rotating pin contacts the work surface, it welding prototype and production parts by friction stir rapidly friction heats the material at the point of welding. Opportunities exist to weld skins to spars, ribs, contact, thus lowering the materials mechanical and stringers for use in military and civilian aircraft. This strength. Under an applied force the pin forges and offers significant advantages compared to riveting and extrudes the material in its path, until the shoulder of machining from solid, such as reduced manufacturing costs the pin is in intimate contact with the work surface. and weight savings. Longitudinal butt welds in Al alloy Frictional heat caused by the rotating pin creates a fuel tanks for space vehicles have been friction stir welded plasticised region around the pin. and successfully used. The process could also be used to Pressure provided by the weld tool forces the increase the size of commercially available sheets by plasticised material behind the pin, cooling and welding them before forming. consolidating the weld. Stirring action takes place during a weld along the The friction stir welding process can be considered for: joint line of the plates. Wings, fuselages, empennages At the junction the friction heating, produced by the Cryogenic fuel tanks for space vehicles rotating shoulder and pin, produce a substantial plasticised layer of metal beneath the tool shoulder and about the pin. Aviation fuel tanks When the work-piece is moved against the pin or vice- versa, the plasticised material is mashed by the leading face External throw away tanks for military aircraft due to mechanical stirring and forging action imparted by Military and scientific rockets the pin profile and its direction of rotation. Repair of faulty MIG welds Consequently, as the stir welding tool proceeds down the joint line, it friction heats the abutting joint faces just ahead Railway Industry: The commercial production of high of the tool to a soft plastic state. It subsequently mashes the speed trains made from aluminium extrusions, which may joint line, breaking up the oxide film and stirs and be joined by friction stir welding, has been established. recombines the mashed material on the trailing side of the Applications include: tool where the material cools to form a solid phase weld. High speed trains III. PROCESS PARAMETERS In friction stir welding process, a number of process Rolling stock of railways, underground carriages, parameters have to be defined to get good, defect free trams joints. The important process parameters are: Railway tankers and goods wagons Tool geometry Container bodies Tool axial force Road Transportation: The friction stir welding process is Spindle speed currently being used commercially and is also being Tool transverse speed assessed by several automotive companies and suppliers. Tool tilt angle Feed rate Existing and potential applications include: Depth penetration IJERTV4IS030419 www.ijert.org 439 (This work is licensed under a Creative Commons Attribution 4.0 International License.) International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 4 Issue 03, March-2015 Tool geometryplays a very important role in obtaining good quality weld with sound mechanical properties. The tool comprises of shank, shoulder, and probe. The shoulder compresses the surface of the work piece and prevents the plasticize material from being expelled. The probe is to ensure sufficient working of material at the weld line and the control flow of the material around the tool to form weld of satisfactory quality as the weld progresses. Tool axial force is the force or load which is applied along Fig.2. Different Zones formation during FSW the tool axis and acts normal to the welding direction. Tool axial force is provided to initially plunge the probe and to The parent material(or base material) is the region which plasticize the material under the tool shoulder in the weld does not undergo deformation and the microstructure in region. this region is not affected by the heat produced during