Chapter 1

CHAPTER 1                                                                                            

INTRODUCTION  

                                 

1.1 Friction Stir Welding

In recent years, the friction stir welding process becomes advantageous due to its application to join aluminium alloys and dissimilar metals. The friction stir welding (FSW) process is initially explored by Wayne Thomas. In this welding process two dissimilar metal sheets are joined by passing rotating tool through adjoining edges of sheets. During passing of tool, the friction heat generation is responsible for welding. The key parameters in friction stir welding are speed of rotation of tool, tool shoulder diameter speed of welding, tool pin diameter, length of tool pin. Tool used in FSW have many geometries like hexagonal, square, rectangular and triangular shapes. If square shaped tool is used, then strength of weld will be we get a high strength weld. Different types of tests are employed on weld joint in order to calculate strength, % elongation, Vickers’s hardness, shear, tensile and yield strength of weld joint. Orthogonal array of Taguchi’s has been used to study the final experimental parameters. when a tool is rotated a two type of sides are there that is advancing side (AS) and retreating side (RS) and there exist a swirl. Friction stir welding can be performed on Pb, Cu, Ti, Mg, zirconium, hafnium and mild steel. The cons of friction stir welding are abstracted by study of tool material is rely on the material of specimen. [10]

1.2 Working Principle

In friction stir welding process, the non-consumable instrument is utilized with adjusted area, however towards the end where there is a strung test or more mind boggling woodwind, the convergence between the round and hollow part and the test is known as the shoulder the test invades the work piece however the shoulder rubs with the best surface. As appeared in schematic graph Figure1. At the point when a turning device which has a stick and bear and the stick is embedded in the little root hole between two aluminum plates. The turn of hardware warm is created in light of rubbing. It is known as the Solid state welding process because of moving erosion of hardware against the plates because of this liquefying of the plates happen just before the dissolving of purposes of its material and the joining procedure begins. The PC numerical controlled vertical processing machine is giving an exact outcome Various advantages of FWS are improved strength, no voids, joints are leakage proof with superior strength than other welded joints, improved repeatability, reduced distortion, quality and environment   aspects. The angle between the welding and direction of rolling is right angle to get a better result.

       

Figure1.1 Diagram of Friction Stir Welding

Friction stir welding was done using non-consumable tool consists of high chrome high carbon steel. Frictional heat is produced because of high normal pressure and shearing action of the shoulder. In this process heat makes the probe softened and this is controlled shoulder of tool. Tool is fitted a long

 line of joint. Whereas material is dissipated around the probe. This process makes high strains and strain rates which are higher than other processes. The friction stir welding process consists of deformation and thermal process.

 

1.3 FSW PROCESS PARAMETERS

In friction stir welding various input parameters are used by different research groups to investigate their effect on output characteristics. In this work input parameters like speed of welding, speed of tool rotation and profile of tool pin.

1. a) Tool pin profile– In literature different geometries of tool pin profile such as circular, hexagonal, square, triangular and hexagonal were used in FSW. Additionally, the effect of taper and cylindrical pin profile in FSW is reported in this study.
2. b) Tool rotational speed – Different joints characteristics are obtained by variation of tool rotational speed in friction stir welding.

(c) Welding Forces – In FSW there were many forces that act on tool like traverse and lateral.

 (1) Downward Force- is responsible for accurate position of tool while welding.

 (2) The force which acts in position parallel to welding axis is known as traverse force. This force occurs due to resistance caused by material to tool motion while welding.

 (3) The force which acts in direction perpendicular to tool movement is known as lateral force.

 (4) Torque is main factor responsible for tool rotation, its value is significantly affected by friction coefficient and flow strength of material.

 

1.4 Microstructural Features

FSW process is solid-state in nature, joined with its rounded section tool which brings about a deeply characteristic microstructure. There are some zones that are studied in microstructure:

• Stir Zone is known as nugget which contains large amount of deformed material. The morphology of stir zone grins is similar in nature but smaller in size than base material.

 

• Flow arm Zone is region includes metal of different nature. The surface of weld which includes material and which is pulled by shoulder to protect from the side of weld around the back of the tool.
• Thermo-Mechanically Affected Zone (TMAZ) is attached to stir zone. Due to lower effect of strain and temperature in this region, so the microstructure of welding samples is limited effected in this region.

 

                                      Figure1.2 Several zones around welded joint

(4) Heat-Affected Zone (HAZ) is region significantly affected by heat of welding process. With reference to TMAZ, the temperature in this region is lower. Moreover, the presence of age-hardened aluminum alloys is clear evidence of poor mechanical properties [15].

 

1.5 INDUSTRIAL APPLICATIONS OF FRICTION STIR WELDING

 (1)  Shipbuilding

The friction stir welding process are firstly used in marine and shipbuilding industries. The FSW is suitable for many applications like corrosion resisted panels, Offshore accommodation, sides, Boat sections, bulkheads and floors, panels for deck and wall construction, Helicopter landing platforms, freezer panels, honeycomb panels.

(2)  Aerospace Industry

The friction stir welding is used in welding sample parts in aerospace industry. There are many ways to weld such as ribs, spars and stringers. Also used in civilian and military aircraft. This offers huge favourable circumstances contrasted with riveting and maching from solid, for example, decreased cost of manufacturing and weight saving. There are many applications of FSW:

• Aeroplane Wings
• Aviation fuel tanks
• Cryogenic fuel tanks for space vehicles
• Scientific rockets and military rockets

(3)  Railway Industry

The high speed trains are manufactured from aluminium extrusions. All the joining processes can be accomplished by FSW. There are many applications which includes:

• High speed trains (bullet trains).
• Container bodies, railway tankers and wagons

(4)  Land Transportation

The FSW is mainly used to manufactured automobile parts by the automobile companies. There are many applications in industrial work:

• Wheel rims
• Engine parts
• Hydro formed tubes parts
• Welding of different sheet thicknesses like in tailored blanks

 (5)  Electrical Industry

The uses of friction stir welding in electrical industry shows rising interest for:

• Bus bars
• Electrical connectors
• Housings of Electric motor

 (6) 

Impressum

Verlag: BookRix GmbH & Co. KG

Tag der Veröffentlichung: 10.05.2018
ISBN: 978-3-7438-6825-0

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