A Dissertation Writing about Friction Stir Welding

General Introduction

• The two general categories in which all the types of welding can be divided is fusion welding and solid-state welding.
• During PhD Research Project, the fusion welding process involves chemical bonding of the metal in the molten stage and may need a filler material such as a consumable electrode or a spool of wire of the filler material.
• Examples of fusion welding are metal inert gas welding (MIG), tungsten inert gas welding (TIG), and laser welding.
• There are many disadvantages in the welding techniques where the metal is heated to its melting temperature and let it solidify to form the joint.
• The melting and solidification causes the mechanical properties of the weld to deteriorate such as low tensile strength, fatigue strength and ductility.
• The disadvantages also include porosity oxidation, micro segmentation, hot cracking and other micro structural defects in the joint.
• The solid-state welding is the process where coalescence is produced at the temperature below the melting temperatures of the base metal without any need for the filler material.
• Examples of solid-state welding are friction welding, explosion welding, forge welding, hot pressure welding and ultrasonic welding.
• The three important parameters time, temperature and pressure individually or in combination produce the joint in the base metal.
• Friction stir welding is also a solid-state welding process. Friction stir welding was invented by The Welding Institute (TWI) in December 1991.
• TWI filed successfully for patents in Europe, U.S., Japan, and Australia using various computer animation movies.
• FSW is used in research and production in many sectors, including aerospace, automotive, railway, shipbuilding, electronic housings, coolers, heat exchangers, and nuclear waste containers.
• FSW has been proven to be an effective process for welding aluminium, brass, copper, and other low-melting-temperature materials.

Working of FSW 

 

 

where A- During Plunging and B- During Welding

• In FSW, a cylindrical, shouldered tool with a profiled probe is rotated and slowly plunged into the weld joint between two pieces of sheet or plate material that are to be welded together.
• The side, on which tool rotation and travelling are in the same direction is known as advancing side.
• If they are in counter direction, then it is known as retreating side.
• Frictional heat is generated between the wear-resistant welding tool and the material of the workpieces. This heat causes the workpieces to soften without reaching the melting point and allows the tool to traverse along the weld line.
• The process originally was limited to low-melting-temperature.
• This problem was solved recently with the introduction of new tool material technologies such as polycrystalline cubic boron nitride (PCBN), tungsten rhenium, and ceramics using thesis writing services.