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  • Spin Welding- "Four different phases can be distinguished in the vibration welding process; the solid friction phase, the transient phase, the steady-state phase and the cooling phase.


In the solid friction phase, heat is generated as a result of the friction between the two surfaces. This causes the polymer material to heat up until the melting point is reached. The heat generated is dependent on the applied tangential velocity and the pressure.

In the second phase, a thin molten polymer layer is formed which grows as a result of the ongoing heat generation. In this stage heat is generated by viscous dissipation. At first only a thin molten layer exists and consequently the shear-rate and viscous heating contributions are large. As the thickness of the molten layer increases the degree of viscous heating decreases.

Thereafter, (start of third phase) the melting rate equals the outward flow rate (steady state). As soon as this phase has been reached, the thickness of the molten layer is constant. The steady-state is maintained until a certain "melt down depth" has been reached at which point the rotation is stopped.

At this point (phase 4) the polymer melt cools and solidification starts, while film drainage still occurs since the welding pressure remains. After all the material has solidified, drainage stops and the joint is formed."

Process of spin welding

  • Linear Friction Welding - "Linear Friction Welding (LFW) is seen a key technology for the aerospace industry as it enables the joining of difficult to bond materials, can be used as a repair process, and to build the complex structures required for today's gas turbines. Essentially, it is a non-melting fusion process producing high integrity welds with little prior surface preparation required.

    • As the parts to be welded are forced into intimate contact, a fully reversed motion is imposed on part of the system. This generates frictional heat in the immediate region about the weld plane, thereby softening a finite volume of material. As the weld proceeds, a portion of this visco-plastic layer is extruded at the periphery of the weld interface, in rippled sheets of metal known as flash. This should ensure that any interfacial contaminant is expelled. The combination of fast joining times of the order of a few seconds, and the direct heat input at the weld interface, gives rise to relatively small heat affected zones. This, by judicious selection of components geometry, this also limits process induced distortions.


To this date, precious little research has been done in the area of LFW. It is generally accepted that friction welding can be separated into (i) a dry friction stage, followed by (ii) an increased asperity contact, and (iii) some sort of steady state once the relatively high weld temperature has been acquired. It is not clear how the surface contaminants are removed - especially from the mid-point of the weld."

Linear Friction Welding

  • Friction Surfacing - "Friction Surfacing is a process derived from friction welding whereby a coating material, in rod form (termed the MechtrodeTM) is rotated under pressure, generating a plasticised layer in the rod at the interface with the substrate. By moving a substrate across the face of the rotating rod a plasticised layer between 0.2-2.5mm thick is deposited (depending on mechtrode diameter and coating material). The resulting composite material is created to provide the characteristics demanded by any given application.


During the coating process, the applied layer of metal reaches a temperature near the melting point whilst simultaneously undergoing plastic deformation. The coating is thus the product of a hot forging action, as opposed to the casting mechanism inherent in welding and spraying processes. This important difference means that many of the defects commonly associated with these techniques are avoided."

What is Friction Surfacing technology?

  • Friction Stud Welding - "In early 1998, friction stud welding was performed commercially at a depth of 1,300 feet (394m) and involved the friction welding of anode continuity tails to riser base piles using a work-class ROV. The friction welding equipment used was a Circle Technologies HMS 3000, which is hydraulically-driven, electronically-controlled, and rated to a depth of 3,000 feet (910m).


Based on this concept, the Naval Sea Systems Command (NAVSEA) initiated another program to evaluate underwater friction stud welding for use in submarine rescue. The program required interfacing the HMS 3000 friction stud welder with the Navy's atmospheric diving suit (ADS), rated to 2,000 feet (606m). The feasibility of this concept was demonstrated in 2001 by Oceaneering International using their WASP ADS and the HMS 3000 friction stud welding system.

Friction stud welding provides the capability to weld a pattern of studs to the hull of a disable submarine, to which a pad-eye can be attached for the SRC haul-down cable and life support gas can be provided by means of a hot tap process using hollow studs. Combined with an ADS, the system provides rescue capabilities well beyond 300 feet (91m).

Concurrent with the Navy's application for underwater friction stud welding for submarine rescue, Oceaneering pursued the application commercially for offshore platform repairs. However, initial research showed that there was a limited amount of accurate public information on the mechanical properties of underwater friction stud welding. As such, the use of this process for any offshore repair without a full evaluation for mechanical, corrosion, and fatigue would not be acceptable."

Underwater Friction Stud Welding for Military and Commercial Use

  • Friction Stir Welding - "Friction stir welding (FSW) is a novel welding technique invented by The Welding Institute (TWI) in 1991. FSW is actually a solid-state joining process that is a combination of extruding and forging and is not a true welding process. Since the process occurs at a temperature below the melting point of the work piece material, FSW has several advantages over fusion welding. Some of the process advantages are given in the following list.


FSW is energy efficient
FSW requires minimal, if any, consumables.
FSW produces desirable microstructures in the weld and heat-affected zones
FSW is environmentally "friendly" (no fumes, noise, or sparks)
FSW can successfully join materials that are "unweldable" by fusion welding methods.
FSW produces less distortion than fusion welding techniques.
Friction stir welding uses a cylindrical, shouldered tool with a profiled pin that is rotated and slowly plunged into the joint line between two pieces of sheet or plate material, which are butted together. Frictional heat is generated between the wear resistant welding tool and the work piece. This heat causes the work piece material to soften without reaching the melting point and allows the tool to traverse the weld line. As it does, the plasticized material is transferred from the leading edge of the tool to the trailing edge of the tool shoulder and pin. It leaves a solid phase bond between the two work pieces."

Intelligent Stir Welding for Industry and Research - ISTIR
FSW Process Experience at MTS

''Suggested Additional Reading:''

American Welding Society, Welding Handbook, Volume 2 (8th ed.)

All the above infomation was taken from the various web sites. These sites can be viewed, and there addresses follow there extracts. Thanks to the various people for their hard work in their various fields.