friction stir welding presentation
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16-02-2010, 12:55 PM
friction stir welding.ppt (Size: 7.18 MB / Downloads: 1,162)
FRICTION STIR WELDING
Â¢ Welding is a process of joining of different or similar material.
Economical, considerable freedom in designing, large no. of dissimilar or similar materials joined, weld as strong as the parent metal.
Different type of welding processes
1. Arc welding.
2. Oxy fuel gas welding.
3. Resistance welding
4. Solid state welding
Carbon arc welding
Electro gas welding
Gas metal arc welding
Gas tungsten arc welding
Plasma arc welding
Shielded metal arc welding
Submerged arc welding
2.Oxyfuel gas welding
Air acetylene welding
Oxy acetylene welding
Oxy hydrogen welding
Pressure gas welding
3. Resistance welding
Resistance seam welding
Resistance spot welding
4. Solid state welding
Hot pressure welding
Friction stir welding
Friction stir welding process
Â¢ Friction stir welding is a new solid state joining process.
Â¢ Here a cylindrical shouldered tool along with a profiled probe is rotated and fed at a constant traverse rate in to the joint.
Â¢ Frictional heat generated between the wear resistant welding tool and the workpiece along with mechanical mixing heat causes the stirred material to soften without reaching the melting point and allows the traversing of the tool along the weld line.
Â¢ The plasticised material is transferred from the leading edge of the tool to its trailing edge and is forged by the intimate contact of the tool shoulder and the pin profile thus leaving a solid bond between two phases
Materials and thickness
Friction stir welding can be used for joining
Â¢ 2000, 5000,6000,7000 series aluminium.
Â¢ Aluminium based metal matrix composites
Â¢ Copper and its alloys (up to 50mm in one pass).
Â¢ Titanium and its alloys.
Â¢ Zinc, plastic, stainless steel and nickel alloys.
Â¢ Low distortion, even in long welds.
Â¢ Excellent mechanical properties as proven by fatigue, tensile and bend tests.
Â¢ No arc, fume, spatter and porosity
Â¢ low shrinkage.
Â¢ Can operate in all positions.
Â¢ Non consumable tool.
Â¢ No filler wire, gas shielding.
Â¢ Can weld aluminium and copper of >50mm thickness on one pass
Applications of friction stir welding
1. Ship building and marine industries
â€œ Panels for decks, bulk heads and floors
â€œ Hulls and superstructures
â€œ Helicopter landing platforms
â€œ Mast and booms (sailing boat)
2. Aerospace industry
â€œ cryogenic fuel tank for space vehicles
â€œ Aviation fuel tanks
â€œ Military and scientific rockets
â€œ Various primary and secondary structural component
3. Railway and Land transport.
â€œ high speed trains
â€œ railway tankers and goods wagon
â€œ wheel rims
â€œ motor cycle and bicycle frames
Limitations of Friction stir welding
Â¢ Workpieces must be rigidly clamped
Â¢ Backing bar required (except for self reacting and directly opposed tools)
Â¢ Key holes at the end of each weld
Â¢ Cannot make joints that require metal deposition
Â¢ Less flexible than manual and arc processes
New technology with vital application in aerospace an marine
Presently limited to aluminium ,its alloys and related metals
FSW of steel and titanium alloys are developed and they are in the nascent stage
Will emerge as a better welding technology
Joined: Feb 2013
02-09-2013, 03:56 PM
Friction stir welding(FSW)
Friction stir .docx (Size: 1.08 MB / Downloads: 31)
Friction stir welding(FSW), a new solid state joining process combining deformation heating and mechanical work to obtain high quality, defect-free joints. Friction stir welding is well suited for joining aluminium alloys in a large range of plate thickness and has particular advantage over fusion welding when joining of highly alloyed aluminium is considered, high quality joints may even be made in discontinuously reinforced aluminium alloys. Because of the many demonstrated advantage of FSW over fusion welding techniques, the commercialization of friction stir welding is proceeding at a rapid pace. Current production application includes both large and small scale products.
In many industrial applications steels are readily replaced by nonferrous alloys, in most cases by aluminum alloys. Some of these materials combine mechanical strength comparable with structural steels and low weight, allowing for a significant reduction of weight. While production of components of aluminum alloys is not very complex, joining of these materials can sometimes cause serious problems. Lack of structural transformations in solid state and excellent thermal and electrical conductivity cause problems in fusion and resistance welding of aluminum alloys. That led to the development of Friction Stir Welding a solid state joining technique in which the joined material is plasticized by heat generated by friction between the surface of the plates and the contact surface of a special tool, composed of two main parts: shoulder and pin. Shoulder is responsible for the generation of heat and for containing the plasticized material in the weld zone, while pin mixes the material of the components to be welded,thus creating a joint. This allows for producing defect-free welds characterized by good mechanical properties.
Traditionally, friction welding is carried out by moving one component relative to the other along a common interface, while applying a compressive force across the joint. The friction heating generated at the interface softens both components, and when they
become plasticized the interface material is extruded out of the edges of the joint so that clean material from each component is left along the original interface. The relative motion is then stopped, and a higher final compressive force may be applied before the joint is allowed to cool. The key to friction welding is that no molten material is generated, the weld being formed in the solid state
FSW of aluminium
The most popular aluminum alloy contains about 8 wt% of silicon.
_ It therefore solidifies to primary aluminum-rich dendrites and a eutectic mixture of aluminum solid-solution and almost pure silicon.
_ The latter occurs as coarse silicon particles which tend to be brittle.
_ The cast alloy usually has some porosity.
_ Friction stir welding has the advantage that it breaks up the coarse silicon particles and heals any pores by the mechanical processing, as illustrated below.
1. Flow of material
Material motion occurs by two processes:
Material on the advancing front side of a weld enters into a zone that rotates and advances with the pin. This material was very highly deformed and sloughs off behind the pin to form arc-shaped features when viewed from above (i.e. down the tool axis). It was noted that the copper entered the rotational zone around the pin, where it was broken up into fragments. These fragments were only found in the arc shaped features of material behind the tool. The lighter material came from the retreating front side of the pin and was dragged around to the rear of the tool and filled in the gaps between the arcs of advancing side material. This material did not rotate around the pin and the lower level of deformation resulted in a larger grain size.
2.Generation and flow of heat
For any welding process it is, in general, desirable to increase the travel speed and minimize the heat input as this will increase productivity and possibly reduce the impact of welding on the mechanical properties of the weld. At the same time it is necessary to
ensure that the temperature around the tool is sufficiently high to permit adequate material flow and prevent flaws or tool fracture.
ADVANTAGES AND DISADVANTAGES
A number of potential advantages of FSW over conventional fusion-welding processes have been identified.
Good mechanical properties in the as welded condition.
Improved safety due to the absence of toxic fumes or the spatter of molten material.
No consumables - conventional steel tools can weld over 1000m of aluminium and no filler or gas shield is required for aluminium.
Easily automated on simple milling machines - lower setup costs and less training.
Can operate in all positions (horizontal, vertical, etc), as there is no weld pool.
Generally good weld appearance and minimal thickness under/over-matching, thus reducing the need for expensive machining after welding.
Low environmental impact.
CONCLUSION AND FUTURE SCOPE
FSW is the best process to welding Aluminum for long lengths with an excellent quality. Considerable effort is being made to weld higher temperature materials such as titanium and steels by using FSW. Take the process beyond its current use of mainly simple butt and lap joint configurations and make it a much more flexible fabrication
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