Benefits
Micro friction welding can produce simple weld geometries at high speed without the use of external heating and usually without fluxes.
Technology
The basic principle of friction welding is rotation under an axial force of the faces of one or both of the components to generate heat and deformation. If the rotational speed and force are correct, the interfaces will be heated by friction and the contaminated interface surfaces will be plastically extruded laterally to form an upset or weld flash. After a short time rotation is arrested and the weld is consolidated by the axial force.
The controlling parameters in miniature friction welding are the peripheral speed and the applied pressure. The speed required to weld most materials is between 250 and 350 m/min, which creates difficulties when applying the process to small diameter components. The required rotational speed of a 0.8mm diameter rod, to reach 250m/min is 37,000rpm has resulted in the use of low torque, high speed air motors.
A wide range of dissimilar and metallurgically incompatible materials can be joined, e.g. Aluminium to Alumina ceramic, but it is restricted in terms of component geometry, e.g:
- Rod to rod
- Tube to tube
- Rod or tube to plate
Expertise
The Microtechnology Section of TWI has expertise in:
- Material selection
- Tooling design
- Process development and optimisation
Equipment
TWI has a bespoke micro friction welder capable of welding rods up to a maximum diameter of 3mm. The maximum speed achievable is 100 000 rpm which, depending on the material type means that rods smaller than 1mm in diameter could be welded.
Project Work
Project work has included process development for dry cell current collector manufacture and feasibility studies for a wide range of material combinations.
If you require further information or if you want to discuss your application, please email to micro@twi.co.uk.
Copyright © 2008 TWI Ltd