Friction welding

from Wikipedia, the free encyclopedia

The friction welding (EN ISO 4063: Process 42) is a welding process from the group of pressure welding . Two parts are moved relative to one another under pressure, the parts touching one another at the contact surfaces. The resulting friction causes the material to heat up and plasticize. At the end of the rubbing process, it is of crucial importance to correctly position the parts in relation to one another and to exert high pressure. The advantages of this process are that the so-called heat-affected zone is significantly smaller than with other welding processes and that there is no formation of melt in the joining zone. A variety of materials, such as aluminum and steel, can be welded together. The connection of metallic materials that do not form alloys is also possible in many cases.

Rotary friction welding

Flywheel friction welding

The rotary friction is a pressure welding process. At least one part to be joined in the joining zone must have a rotationally symmetrical shape. The energy supply is brought in exclusively by a relative movement of the parts to be joined under pressure. One part is stationary and the second part is set in rotation. It is widely used to weld connectors of different material quality to pipes (drill rods).

The process has been used in Germany since the 1970s. The most diverse material combinations are the great advantage of this process. Millions of exhaust valves for internal combustion engines are welded (high- temperature steel to hardenable steel) with cycle times of less than ten seconds.

The machines used are similar to lathes . They contain a rotating spindle and a non-rotating counterpart, which is clamped on an axially adjustable slide and pressed onto the rotating part. Depending on the dimensions, the axial forces can range from a few 100 N to over 10,000 kN (roughly equivalent to the weight force of 1000 t). The respective machines are then the size of a desk or a locomotive. Positioned friction welding is an (optional) special application and requires a special control and a special drive motor. Applications for this are cardan shafts, trailer axles and axle stabilizers.

Friction welding was first described in a patent application from James Bevington of Chicago in 1891.

Research and application of rotational friction welding

Russia

The industrial application of friction welding began in the context of a patent application by Al Khudikov. A scientific study by Vladim I. Vill in Russia in 1970 explained the underlying mechanisms of action and is still a standard work on this topic that is often cited worldwide. In 1961, more than 30 friction welding machines were in industrial use in Russia.

Germany

In the GDR , developments in friction welding began in 1967 at the Technical University of Karl-Marx-Stadt in what is now Chemnitz , which from 1967 worked on research in the field of friction welding on behalf of the ZIS Halle . Research topics included:

  • Constructive and technological working documents for friction welding
  • Quality assurance in friction welding
  • Process control in friction welding
  • Calculation of friction weld connections
  • Influence of errors on the load-bearing capacity of friction-welded connections

From 1968 the industrial use in the GDR took place first in the tool industry for drill blanks (material combination high speed steel / C60). From around 1970 in other branches of industry, such as turbine construction, shipbuilding, clutch and engine construction, rail vehicle construction, cardan shaft production, agricultural machinery construction, motorcycle production and much more. From 1970 there was also a friction welding working group within the framework of the Chamber of Technology. Members of this working group were representatives of the companies using friction welding. Twice a year, there was a lively exchange of experiences in corresponding meetings.

In the GDR there was no machine manufacturer, therefore machines were developed and built in various branches of industry, e.g. B. in the tool industry the friction welding machines RSA 20 and RSA 39 and in agricultural machinery the RSM 50, which works with a vertical spindle. The SR 100 was developed in cooperation with 10 companies and assembled by a machine tool manufacturer. In the Council for Mutual Economic Aid, there was cooperation, in particular on technological developments in friction welding, between the VNIIESO Leningrad (USSR), IS Gliwice (Poland), VUZ Bratislava (Czechoslovakia), MTI Budapest (Hungary), ISIM Timișoara ( ro ) ( Romania) and the TU Karl-Marx-Stadt. In 1985 around 45 friction welding machines were in industrial use in the GDR, in addition to the self-made machines mentioned, there were also some machines from Poland and France.

The friction welding process in Germany is now being scientifically investigated and further developed in the following institutions: Forschungszentrum Jülich , Institute for Machine Tools and Industrial Management of the Technical University of Munich (iwb) and Magdeburg-Stendal University . In Germany, the German Association for Welding Technology and the SLV Munich have been taking care of standardization and the exchange of experience in this area since 1983 .

The most important German friction welding machine manufacturers are: H&B ​​Omega, Harms & Wende, GS-Steuerungstechnik and Kuka . Rotary friction welding is mainly used by automobile manufacturers and their suppliers, including Daimler and IFA . The process is used for Liebherr hydraulic excavators and MTU Aero Engines , among others . In the oil and gas industry, UGS Mittenwalde uses the process for welding pipes. In Germany there are several companies that specialize in friction welding and serve various industrial sectors: AluStir, ITM Zschaler, Raiser and Schnabel.

Great Britain

In Great Britain The Welding Institute developed parameters for the industrial application of rotary friction welding as well as numerous process variants. The most important British friction welding machine manufacturers are: Blacks Equipment, British Federal, MTI and Thompson.

United States

The Edison Welding Institute is significantly driving the development of the process. The company Caterpillar , Rockwell International and American Manufacturing and Foundry developed the first friction welding machines. Today, MTI is regarded as the leading machine manufacturer.

Orbital friction welding

Orbital friction welding according to ISO 15620 is a friction welding process. In contrast to the related rotational friction welding, the parts here do not have to be rotationally symmetrical. The energy supply is introduced under pressure by means of a circular oscillating motion of the parts to be joined - similar to an orbital sander. The alignment of the axes remains the same. In multi-orbital friction welding, both components vibrate, in contrast to orbital friction welding, which is therefore called "single orbital friction welding".

Friction stir welding

Principle of friction stir welding:
1 Immerse the rotating tool 2 Dwell to generate heat 3 Process 4 Stop the movement 5 Pull out the tool 6 Inspect the finished weld seam

The friction stir welding (English: friction stir welding , FSW, 4063 EN ISO: Process 43) in many cases also, friction stir welding called, was founded in 1991 by Wayne Thomas invented by TWI ( The Welding Institute ) in Great Britain patent protected. With friction stir welding, the frictional energy is not generated by the relative movement of the two joining partners, but by a wear-resistant rotating tool.

The process flow is essentially divided into six steps. In the first step, a rotating tool is pressed with high force into the joint gap until the tool shoulder comes into contact with the component surface. During the second step, the rotating tool remains at the immersion point for a few seconds. Due to the friction between the tool shoulder and the joining partner, the material under the shoulder heats up to just below the melting point. This rise in temperature results in a drop in strength, which plasticizes the material and allows the joining zone to mix. The third step begins with the onset of the feed movement, in which the rotating tool is moved along the joining line with high pressure. The pressure gradient between the front and back of the tool and its rotational movement caused by the feed movement cause the plasticized material to be transported around the tool, which mixes there and forms the seam. In the fourth step, the movement is stopped at the end of the seam. In the fifth step, the rotating tool is pulled out of the joining zone again. In the sixth step, the finished weld is examined visually or examined using non-destructive testing methods .

Due to the characteristic process sequence of friction stir welding, the process is particularly suitable for aluminum alloys. Problems that are caused by the phase transition during fusion welding of aluminum alloys, such as hot cracking and pore formation, do not occur during friction stir welding due to the absence of a liquid or vapor phase.

A rotating, wear-resistant, slightly inclined friction stir welding tool is pressed into the joint gap and moved from right to left
Friction stir welding tool tacking a tank for the space shuttle

In terms of process technology, there is a connection with forging and extrusion, on the one hand the material is compressed by a force directed vertically to the workpiece surface with the introduction of heat and on the other hand the partially plastic material is pressed down by turbulence due to the geometry of the rotating tool. An extrusion channel is created that extends to the root of the seam (also called a weld nugget ). The workpieces to be joined stand still. A special shape of the seam before welding is not necessary.

The tool consists of a shoulder that is perpendicular to the pin and has a larger diameter than the pin itself. The shoulder can be imagined as a half-shell that is supposed to isolate the ambient air from the weld seam. The pin is responsible for swirling the material. The inclination of the tool to the workpiece surface is about 2 ° to 3 ° in a piercing arrangement. The tool itself has little wear and tear; to maintain quality, it must be replaced after about 3 km of weld seam.

Advantages of friction stir welding

  • Additional materials not necessary
  • high achievable seam strengths
  • no protective gas required
  • relatively simple process flow
  • wide range of mixed connections possible
  • relatively low temperatures (in aluminum approx. 550 ° C on the weld seam surface) and thus little distortion

The process is also used to improve local properties and to close pores in cast structures. The term FSP (English: friction stir processing ) is often used instead of FSW (English: friction stir welding ).

Challenge when using friction stir welding

  • Relatively high process forces, depending on the alloy and component thickness from 1 kN to well over 20 kN
  • Limited 3D capability due to the necessary contact from shoulder to component
  • End crater at the end of the weld seam due to the exit of the tool. A solution was found for this by means of an automatically retractable pin tool , RPT, RPT technology.

Friction stir welding can be used to join sheets of different materials with a depth of more than 30 mm. The achievable welding depths and welding speeds depend heavily on the material to be joined and generally decrease with increasing strength and hardness. The process forces increase sharply with increasing strength and hardness of the material. The process is therefore mainly used for aluminum. It is also possible to join metal foams and mixed aluminum-steel joints.

The FSW is mainly used for welding large components. Application examples here are the aircraft industry, aerospace, shipbuilding, rail vehicle construction, as well as automobile construction, but now also increasingly smaller batch sizes in container construction or medical technology.

Another example is the back doors of the Mazda RX-8 . There is no continuous seam here, only points are welded. This is also called friction stir spot welding (English: friction stir spot welding, FSSW ). The tool usually only performs a vertical movement here.

Conventionally, special machines are used for the FSW, which have been specially designed or converted to meet the requirements of this process. Tricept robot systems are also used occasionally. Conventional production tools are now also being used for the FSW in order to reduce costs and increase flexibility. For example, the FSW process has meanwhile been implemented on machine tools or standard industrial robots.

A hybrid variant of friction stir welding is LAFSW welding ( laser assisted friction stir welding ). In this variant, additional thermal energy is introduced by a laser beam that runs directly ahead of the rotating tool. Among other things, this is intended to reduce the vertical force when inserting the FSW tool into the workpiece and to increase the welding speed. Because of the laser, this process variant leads to increased machine investment costs.

literature

  • Specialist group for welding engineering training: joining technology welding technology. 6., revised. Edition. DVS Verlag, Düsseldorf 2004, ISBN 3-87155-786-2 .
  • U. Dilthey, A. Brandenburg: Welding manufacturing processes. Volume 3: Design and strength of welded structures. 2nd Edition. Springer Verlag, 2001, ISBN 3-540-62661-1 .
  • K.-J. Matthes, E. Richter: Welding technology. Fachbuchverlag Leipzig in Carl Hanser Verlag, 2002, ISBN 3-446-40568-2 .

Web links

Commons : welding  - album with pictures, videos and audio files
Wiktionary: Friction welding  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Gerd Witt among others: Pocket book of manufacturing technology. Carl Hanser Verlag, Munich 2006, ISBN 3-446-22540-4 ( limited preview in the Google book search).
  2. ↑ James H. Bevington: Spinning tubes mode of welding the ends of wire, rods, etc, and mode of making tubes. US Patent No. 463134, 1891.
  3. ↑ AI Chudikov: Friction Welding . Russian patent No. RU106270 dated February 16, 1956.
  4. ↑ VI Vill: Svarka metallov treniem. UPP Lensovnarkkhoz, Leningrad, June 25, 1959. And Friction Welding of Metals (translated from Russian), American Welding Society and Reinhold Publishing, February 1962.
  5. ^ KJ Matthes and W. Schneider: Welding technology - welding of metallic materials. 6th updated edition, Fachbuchverlag Leipzig in Carl Hanser Verlag Munich, 2016. ISBN 978-3-446-44561-1 , e-book ISBN 978-3-446-44554-3 .
  6. ↑ a b c Dietmar Schober with the collaboration of Alexis Neumann: Friction welding of metals: construction, technology, quality assurance. DVS reference book series welding technology, Volume 107, 1991, ISBN 3-87155-124-4
  7. ↑ Marc Lotz: Increasing the manufacturing accuracy in flywheel friction welding through model-based control processes Herbert Utz Verlag, 2012.
  8. ↑ a b c DVS - German Association for Welding and Allied Processes e. V. - Committee for technology: Joint committee DVS / DIN AG V 11.1 / NA 092-00-24 AA “Friction welding”.
  9. ^ Ludwig Appel (GSI mbH, SLV Munich branch): Current information on friction welding. In: 23. Exchange of experience on friction welding. SLV Munich, March 12, 2019.
  10. ↑ Flash butt and friction welding. Lectures at the special conference of the same name in Braunschweig, 8. – 9. March 1983. DVS reports Volume 77, ISBN 3-87155-382-4 .
  11. ↑ Flash butt and friction welding with related processes. Lectures at the 3rd international DVS conference in Stuttgart on April 5–6. December 1991. DVS reports Volume 139, ISBN 3-87155-444-8 .
  12. ↑ Till Maier (KUKA Deutschland GmbH, Augsburg): KUKA SmartConnect.frictionwelding - Industry 4.0 solutions from KUKA for friction welding machines. In: 23. Exchange of experience on friction welding. SLV Munich, March 12, 2019.
  13. ↑ David Schmicker (IFA Rotorion Powertrain GmbH, Haldensleben): Product development of cardan shaft components . In: 23. Exchange of experience on friction welding. SLV Munich, March 12, 2019.
  14. ↑ Thomas Faber (UGS Geotechnologie-Systeme GmbH, Mittenwalde): Friction welding of pipes for deep drilling applications. In: 23. Exchange of experience on friction welding. SLV Munich, March 12, 2019.
  15. ↑ AluStir: rotational friction welding .
  16. ↑ Bavarian Research Foundation : Orbital friction welding - a new key technology for joining metallic materials
  17. ↑ patent WO9310935 : Improvements Relating to friction welding. Registered on November 27, 1982 , inventors: WM Thomas, ED Nicholas, JC Needham, MG Murch, CJ Dawes. ‌
  18. ↑ Göttmann et al .: Properties of Friction Stir Welded Blanks Made from DC04 Mild Steel and Aluminum AA6016 .
  19. ↑ Official website. (Flash) (No longer available online.) Eclipse Aviation Corporation, archived from the original on October 18, 2009 ; accessed on January 29, 2008 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.aws.org
  20. ↑ Friction Stir Welding ( Memento from January 20, 2012 in the web archive archive.today ) (English).
  21. ↑ J. Przydatek: A ship classification view of friction stir welding. In: Proceedings of 1st Internation Friction Stir Welding Symposium. Thousand Oaks (USA) 14.-16. June 1999.
  22. ↑ Fred Delany, Stephan W Kallee, Mike J Russell: Friction Stir Welding of Aluminum Ships. TWI Ltd, accessed May 1, 2014 .
  23. ^ Stephan W. Kallee, John Davenport, E. Dave Nicholas: Railway Manufacturers Implement Friction Stir Welding. (No longer available online.) American Welding Society, archived from the original October 18, 2009 ; accessed on January 29, 2008 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.aws.org
  24. ↑ Robot-assisted friction stir welding. (Project description) (No longer available online.) Archived from the original on June 30, 2008 ; Retrieved January 29, 2008 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.iwb.tum.de
  25. ↑ Georg Völlner: Friction stir welding with heavy-duty industrial robots. Herbert Utz Verlag, Munich 2010, ISBN 978-3-8316-0955-0 ( limited preview in the Google book search).