Friction welding is a solid-state mechanical welding process where the heat needed for welding & joining the metals by creating a metallurgical bond is provided by rubbing or rotating the parts to be joined together under axial pressure. One part is fixed, the other is rotated, either linear or rotating (the most used), when the temperature is reached due to the friction between both parts, an additional forging force is applied on the welding joint.
This simple and fast process makes it possible to obtain metallurgical bonds with a relatively narrow thermally affected zone (Heat affected zone), because the welding zone does not go through the liquid state (solid-liquid-solidification) and welding is completed in solid state.
Types of Friction Welding
There are 3 main types of Friction Welding techniques:
- Linear Friction Welding (LFW), obtained by a linear round-trip movement.
- Rotary Friction welding, obtained by relative rotation of the two parts.
- Friction Stir Welding (FSW).
Friction Stir Welding (FSW)
Friction Stir welding consists of making a junction between two components in the solid state, jointly exerting intense pressure and friction at the point of contact between two adjacent surfaces. The specific tool used to do this, by its rotary movement, creates a heating that “plasticizes” the material in the welding axis, and then mixes the interfaces.
However, the heat is particularly controlled and relatively well defined in the weld area. Indeed, during welding, the melting temperature of the welded metal is not reached but remains at 60-80% compared to the melting threshold.
As shown in below figure, friction stir welding (FSW) welding is carried out by the action of a rotating tool following the joint of two parts to be welded.
The role of this is to preheat the material by friction, until obtaining an elastic state of the material to form an elastic weld pool.
Friction Welding Parameters
|Rotational speed||50 to 80,000 rpm|
|Axial pressure||15 to 400 MN/m2|
|Diameter range||1 to 150 mm|
|Cycle time||5 to 500 s|
|Implementation||Standard welding machine with special tools|
|Equipment Portability||Generally fixed in the workshop|
No welding consumable is required for Friction Welding.
Practically all materials and thermoplastics, and dissimilar metals can be welded with Friction Welding.
Applications of Friction Welding
Friction Welding is used in automotive, aeronautics, rail, general mechanics, electricity, public works equipment, engine valves, transmission components, air bag cartridges, car bridges, tractor and truck trailer bridges, hydraulic cylinder rods, ball joint axles, track bearings, small electrical connectors, drill pipes.
Advantages of Friction Welding
The advantages of friction welding are high-quality assemblies, the speed of the process compared to conventional welding processes and the possibility of complete automation of the process in such a way that consistent quality is guaranteed.
The main Advantages of Friction Welding are:
- Quality welding joint execution,
- No inclusion,
- Little deformation after welding due to short welding times and low maximum temperatures,
- Controlled welding cycle,
- Dissimilar materials can be joined together, such as aluminum or copper, to steel,
- Allows to obtain a fine-grained microstructure in the welding area,
- High productivity,
- High welding Speed for large surfaces,
- Automation possible,
- Mechanical, robust and simple equipment,
- No consumables: filler metal, shielding gas,
- No high energy consumption.
- Environmentally friendly: no shielding gases, no welding fumes or radiation.
- Less noise: welds do not need to be ground
- No need for certified welders.
Disadvantages of Friction Welding
Disadvantages of Friction Welding are:
- Limitation of the process by rotating one of the components,
- high precision of the axial alignment of the welded joint.
- Large investment,
- significant clamping effort,
- Limited welding joint types,
Health and safety in Friction Welding
No radiation, no electrical risk, no smoke and splashes, risks of rotating machine tools.