A Review of effect of different parameters in Friction Stir Welding

 

Jyotsna S. Rane¹, Deepak S. Patil¹, Vaibhav Mohale²

¹Asst. Professor, Dept. of Mechanical Engineering, Dr. D. Y. Patil College of Engineering, Akurdi,

Pune, Maharashtra (India) 411044

²Student, Dept. of Mechanical Engineering, Dr. D. Y. Patil College of Engineering, Akurdi,

 

ABSTRACT:

The comprehensive body of knowledge that has built up with respect to the friction stir welding (FSW) of aluminum alloys since the technique was invented in 1991 is reviewed on this paper. The basic principles of FSW are described, including metal flow and thermal history, before discussing how process parameters affect the weld microstructure and the likelihood of defects. Finally, the range of mechanical properties that can be achieved is discussed. It is demonstrated that FSW of aluminum is becoming an increasingly mature technology with numerous commercial applications.

 

 

INTRODUCTION:

Friction Stir Welding (FSW) was invented at The Welding Institute (TWI) of the United Kingdom(Cambridge) in 1991 as a solid state joining technique and was initially applied to Aluminum Alloys (Dawes C and Thomas W, TWI Bull, 1995; Thomas W M, etal., 1991). Friction Stir Welding is a solid state joining process combining deformation heating and mechanical work to obtain high quality, defect free joints. Friction Stir Welding is especially well suited to joining Aluminum Alloys in a large range of plate thickness and has particular advantages over fusion welding when joining of highly alloyed Aluminum is considered[1]. The heat input into the material and the resulting welding temperature can be controlled by adapting process parameters like the down-force, rotational speed or welding speed as shown in fig. 1

 

PRINCIPLE OF OPERATION:

 

 

Fig. 1 Principle drawing of the FSW process for overlap joints with indication of the main parameters

 

A non-consumable rotating tool with a specially designed pin and shoulder is inserted into the abutting edges of sheets or plates to be joined and subsequently traversed along the joint line. the FSW tool rotates in the counterclockwise direction and travels into the plunge (or left to right).The advancing side is on the right, where the tool rotation direction is the same as the tool travel direction (opposite the direction of metal flow), and the retreating side is on the left, where the tool rotation is opposite to the tool travel direction (parallel to the direction of metal flow) The tool serves three primary functions, that is, heating of the work piece, movement of material to produce the joint, and containment of the hot metal beneath the tool      shoulder [2].

 

Process parameter and their effect

The factors which influence on the friction stir welding are as follows

1. Rotational Speed

2. Welding Speed

3. Pressure on Tool (Down Force)

4. Tilting angle.

 

 

Tool material and design

Afterwards the selection of base material also the vital restriction in FSW process is selection of tool materials and shape of tool pin, shoulder. The tool produces the thermo mechanical deformation and work piece frictional heating necessary for friction stirring. When the down force is applied on tool then tool is introducing in the base materials. The friction stirring tool contains of a pin or probe, and shoulder. Contact of the pin with the work piece produces frictional and deformational heating and moderates the work piece material contacting the shoulder to the work piece increases the work piece heating, expands the zone of softened material, and constrains the deformed material.

 

Fig.2 various shapes of tool. a. cylindrical threaded; b. three flat threaded ; c. triangular; d. Trivex; e. threaded conical; f. schematic of a triflute

Microstructure studies

In the friction stir welding, mainly two-phase confluction is produced, Heat affected Zone (HAZ) and Thermo and Thermo mechanically affected zone (TMAZ). Affected thermally and mechanically at different degrees, microstructures in these two zones are composed of grains with different structures. The transition from the HAZ to the TMAZ is sharp. During the FSW process, the sub-size concave shoulder cause intense plastic material flow in the HAZ. The TMAZ is the result of the thermal effect and the plastic shear stress caused by the plastic material flow in the HAZ, thus grains in this zone are appreciably elongated along the direction of maximum shear stress. As HAZ is affected by both the sub-size concave shoulder and the rotating tool pin. Because of the experienced high temperature and intense plastic deformation, microstructures in the HAZ are characterized by fine and equaxied grains, which are formed according to the dynamic recrystallization mechanism. HAZ also experiences high temperature and intense plastic deformation caused by intense stirring effect of the rotating tool pin, and microstructures in this zone are also characterized by fine and equaxied grain structures owing to the dynamic recrystallization mechanism which is a usual phenomenon when affected by high temperature and intense plastic deformation[3].

 

Fig.3 Microstructural analysis

A. Unaffected material

B. Heat affected zone (HAZ)

C. Thermo-mechanically affected zone (TMAZ)

D. Weld nugget (stir zone)

 

 

Case Studies: Effect of Various Welding Parameters on FSW

Sr. no	Author Name	Substrate material	Parameter selected for study	Conclusion
1	Shashi Prakash Dwivedi [III]	A356/C355 Aluminum Alloy	Welding speed, tool speed, Axial force	It was found that the parameters which affect the tensile strength in descending order are as follows: tool rotational speed, axial force and welding speed.
2	Adil Sheikh, K.D. Bhatt, Alok B. Choudhary [VIII]	HDPE with 4% filler material	Rotational speed and welding speed	Although the tensile strength of the welded specimens was about 45MPa which is almost 80 % that of the base plate, the FSW process can be employed to weld HDPE plates with 4% filler minerals. Increasing the work linear speed from 14 to 56 mm/min had a decreasing effect on tensile strength
3	L. Suvarna Raju, DrAdepkumar, D P.Indrewaraiah [VII]	Cu plates of 200*100mm	Axial force, tool speed, Welding speed	Weldment made by FSW at the tool rotation speed of 900rpm and weld speed 40mm/min exhibited better mech properties. This is due to sufficient heat generation and proper mixing of material in the weld zone
4	P. Chandra Prasad P. Hema K. Ravindranath [I]	6.35 thick plate of Al Alloy	Axial force, tool speed, Welding speed	As the Tool Rotational Speed increases, effectively Hardness also increases, and in the same manner Axial Force also effects, if Welding Speed increases, effectively Hardness will be increases up to 60mm/min and slightly decreases at 72 mm/min
5	M.P.Meshram, Basantkumar,  [XII]	Austinitic stainless steel 120*80*4mm	tool speed, Welding speed	A defect free weld with parameters of 1100rpm and traverse speed 8mm/min showed tensile strength of Base material with 37% elongation
6	H. Ahmadi, N.B. Mostafa Arab F. Ashenai Ghasami [IV]	Plates of PP composites With 20% CF 100*50*4 mm	Welding speed, Rotational speed, Tilt angle	The welding speed was the most significant welding process parameter whereas the tilt angle was the least significant one affecting the tensile-shear strength
7	G. Elatharasan V.S. Senthil kumar [V]	AA6061-T6 And AA7056-T6	Welding speed, Rotational speed, Axial force	Ultimate tensile strength of FSW joints increases with increase in tool rotational speed and welding speed up to a max value and then decreases.

 

 

Advantages and disadvantages of FSW

FSW gives good mechanical properties in welded condition. It gives improved safety due to the absence of toxic fumes or the spatter of molten material. There are no consumables i.e. an threaded pin made of conventional tool steel e.g. hardened H13, can weld over 1 km (0.62 mi) of aluminium, and no filler or gas shield is required for aluminium. On simple milling machines this process is easily automated with lower setup costs and less training. FTW operate in all positions (horizontal, vertical, etc.), as there is no weld pool. Generally we get good weld appearance and minimal thickness under/over-matching in FSW, thus reducing the need for expensive machining after welding. The thinner materials can be used with same joint strength. This process gives low environmental impact. General performance and cost benefits are more when we switch from fusion to friction welding.

On the other hand there are some drawbacks like this process leaves exit hole, when the tool is withdrawn. Large down forces required with heavy-duty clamping necessary to hold the plates together. Less flexible than manual and arc processes (difficulties with thickness variations and non-linear welds).Often slower traverse rate than some fusion welding techniques, although this may be offset if fewer welding passes are required.

 

Applications

Friction stir welding and its variants friction stir spot welding and friction stir processing are used for the following industrial applications: shipbuilding and offshore, aerospace, automotive, rolling stock for railways, general fabrication, robotics, and computers.

 

Shipbuilding and offshore:

Two Scandinavian aluminium extrusion companies were the first to apply FSW commercially to the manufacture of fish freezer panels at Sapa in 1996, as well as deck panels and helicopter landing platforms at Marine Aluminium Aanensen. Marine Aluminium Aanensen subsequently merged with Hydro Aluminium Maritime to become Hydro Marine Aluminium. Some of these freezer panels are now produced by Riftec and Bayards. In 1997 two-dimensional friction stir welds in the hydrodynamically flared bow section of the hull of the ocean viewer vessel The Boss were produced at Research Foundation Institute with the first portable FSW machine. The Super Liner Ogasawara at Mitsui Engineering and Shipbuilding is the largest friction stir welded ship so far. The Sea Fighter of Nichols Bros and the Freedom class Littoral Combat Ships contain prefabricated panels by the FSW fabricators Advanced Technology and Friction Stir Link, Inc. respectively. The Houbei class missile boat has friction stir welded rocket launch containers of China Friction Stir Centre. HMNZS Rotoiti in New Zealand has FSW panels made by Donovans in a converted milling machine. Various companies apply FSW to armor plating for amphibious assault ships.

 

Aerospace:

 

Fig.5 Longitudinal and circumferential friction stir welds are used for the Falcon 9 rocket booster tank at the SpaceX factory

 

United Launch Alliance applies FSW to the Delta II, Delta IV, and Atlas V expendable launch vehicles, and the first of these with a friction stir welded Interstage module was launched in 1999. The process is also used for the Space Shuttle external tank, for Ares I and for the Orion Crew Vehicle test article at NASA as well as Falcon 1 and Falcon 9 rockets at SpaceX. The toe nails for ramp of Boeing C-17 Globemaster III cargo aircraft by Advanced Joining Technologies and the cargo barrier beams for the Boeing 747 Large Cargo Freighter were the first commercially produced aircraft parts. FAA approved wings and fuselage panels of the Eclipse 500 aircraft were made at Eclipse Aviation, and this company delivered 259 friction stir welded business jets, before they were forced into Chapter 7 liquidation. Floor panels for Airbus A400M military aircraft are now made by PfalzFlugzeugwerke and Embraer used FSW for the Legacy 450 and 500 Jets Friction stir welding also is employed for fuselage panels on the Airbus A380. BRÖTJE-Automation uses friction stir welding for gantry production machines developed for the aerospace sector as well as other industrial applications.

 

Automotive:

Aluminium engine cradles and suspension struts for stretched Lincoln Town Car were the first automotive parts that were friction stir at Tower Automotive, who use the process also for the engine tunnel of the Ford GT. A spin-off of this company is called Friction Stir Link, Inc. and successfully exploits the FSW process, e.g. for the flatbed trailer "Revolution" of Fontaine Trailers. In Japan FSW is applied to suspension struts at Showa Denko and for joining of aluminium sheets to galvanized steel brackets for the boot (trunk) lid of the Mazda MX-5. Friction stir spot welding is successfully used for the bonnet (hood) and rear doors of the Mazda RX-8 and the boot lid of the Toyota Prius. Wheels are friction stir welded at Simmons Wheels, UT Alloy Works and Fundo.Rear seats for the Volvo V70 are friction stir welded at Sapa, HVAC pistons at Halla Climate Control and exhaust gas recirculation coolers at Pierburg. Tailor welded blanksare friction stir welded for the Audi R8 at Riftec. The B-column of the Audi R8 Spider is friction stir welded from two extrusions at Hammerer Aluminium Industries in Austria.

 

Railways:

Since 1997 roof panels were made from aluminium extrusions at Hydro Marine Aluminium with a bespoke 25m long FSW machine, e.g. for DSB class SA-SD trains of Alstom LHB  Curved side and roof panels for the Victoria line trains of London Underground, side panels for Bombardier's Electrostar trains at Sapa Group and side panels for Alstom's British Rail Class 390 Pendolino trains are made at SapaGroup. Japanese commuter and express A-trains, and British Rail Class 395 trains are friction stir welded by Hitachi, while Kawasaki applies friction stir spot welding to roof panels and Sumitomo Light Metal produces Shinkansen floor panels. Innovative FSW floor panels are made by Hammerer Aluminium Industries in Austria for the Stadler KISS double decker rail cars, to obtain an internal height of 2 m on both floors and for the new car bodies of the Wuppertal Suspension Railway.

 

Heat sinks for cooling high-power electronics of locomotives are made at Sykatek, EBG, Austerlitz Electronics, EuroComposite, Sapa and Rapid Technic, and are the most common application of FSW due to the excellent heat transfer.

 

Fabrication:

 

Fig 8: The lids of 50-mm-thick copper canisters for nuclear waste are attached to the cylinder by friction stir welding at SKB

 

 

Façade panels and cathode sheets are friction stir welded at AMAG and Hammerer Aluminium Industries including friction stir lap welds of copper to aluminium. Bizerba meat slicers, Ökolüfter HVAC units and Siemens X-ray vacuum vessels are friction stir welded at Riftec. Vacuum valves and vessels are made by FSW at Japanese and Swiss companies. FSW is also used for the encapsulation of nuclear waste at SKB in 50-mm-thick copper canisters[ Pressure vessels from ø1m semispherical forgings of 38.1mm thick aluminum alloy 2219 at Advanced Joining Technologies and Lawrence Livermore Nat Lab. Friction stir processing is applied to ship propellers at Friction Stir Link, Inc. and to hunting knives by Diamond Blade. Bosch uses it in Worcester for the production of heat exchangers.

 

Robotics:

KUKA Robot Group has adapted its KR500-3MT heavy-duty robot for friction stir welding via the Delta NFS tool. The system made its first public appearance at the EuroBLECH show in November 2012.

 

Personal computers:

Apple applied friction stir welding on the 2012 iMac to effectively join the bottom to the back of the device.

 

REFERENCES:

1.     P. Jagadeesh Chandra Prasad, P Hema and K Ravindranath ‘Optimization of process parameters for friction stir welding of aluminum alloy aa6061 using square pin profile’ Vol. 3, No. 2, April, 2014.

2.     D. Raguraman, D. Muruganandam, L.A.Kumaraswamidhas ”Study of tool geometry on friction stir welding of aa 6061 and az61”  PP 63-69

3.     Shashi Prakash Dwivedi ” Effect of process parameters on tensile strength of friction stir welding A356/C355 aluminium alloys joint” PP 285~291 , 2014

4.     H. Ahmadi, N. B. Mostafa Arab and F. AshenaiGhasemi” Optimization of process parameters for friction stir lap welding of carbon fibre reinforced thermoplastic composites by Taguchi method” PP 279~284,2014

5.     G Elatharasan, V.S. Senthilkumar ”Modelling and optimization of dissimilar aluminium alloy using RSM” PP3477-3481, 2012

6.     H. Ahmadi, N. B. Mostafa Arab and F. AshenaiGhasemi” Optimization of process parameters for friction stir lap welding of carbon fibre reinforced thermoplastic composites by Taguchi method” PP279-284,2014

7.     L. Suvarna Raju, Dr. Adepu Kumar and Dr. P. Indreswaraiah“ Effect of Welding Speed on Mechanical Properties of Friction Stir Welded Copper” Vol. 4, No. 2, May 2014

8.     AdilShaikh, K.D. Bhatt, Alok B. Chaudhary“ Effect of friction stir welding process parameters on polymer weld” Volume 1, Issue 9, May-2014.

9.     Jeroen De Backer and Gunnar Bolmsjö and Anna-Karin Christiansson “Temperature control of robotic friction stir welding using the thermoelectric effect” PP 375–383, 2014

10.   I. Dinaharan, N. Murugan “Automation of friction stir welding process to join Aluminium Matrix Composites by Optimisation” PP 105-110, 2012

11.   Hyung-Suk Mun and Sung-Il Seo “Welding strain analysis of friction stir-welded aluminum alloy structures using inherent strain-based equivalent loads” PP 2775~2782, 2013

12.   Manish P. Meshram, BasanthkumarKodli, Suhash R. Dey “Friction Stir welding of Austinitic Stainless Steel by PCBN tool and its joint analyses” PP 135-139, 2014

13.   Sapa's Capabilities, Long length FSW — Max. length 26 m — Max. width 3,5 m — Double sided welding, Sapa company brochure.

14.   History, Principles and Advantages of FSW on Hitachi Transportation Systems Website. Hitachi-rail.com. Retrieved on 2012-01-03.

15.   Hitachi Class 395 Railway Strategies Live 2010. 23 June 2010, pp. 12–13. Retrieved on 2012-01-03.

16.   F. Ellermann, S. Pommer, G. Barth: Einsatz des Rührreibschweißens bei der Fertigung der Wagenkästen für die Schwebebahn Wuppertal. DVS Congress: Große Schweißtechnische Tagung, 15./16. September, Hotel Pullman Berlin Schweizerhof, Berlin.

 

 

 

Received on 12.04.2017                             Accepted on 18.05.2017        

©A&V Publications all right reserved